Import bytes-0.5.4

* Add OWNERS and Android.bp Bug: 143953733 Test: make Change-Id: Ica69d7252abb1c2967f2c0e11a62d0bd83192fb3
author: Chih-Hung Hsieh <chh@google.com> 2020-06-10 20:15:59 -0700
committer: Chih-Hung Hsieh <chh@google.com> 2020-06-10 20:15:59 -0700
commit: 01ae379526218e7f6ca28510b6c06098419b7380 (patch)
tree: ded7cfd36c57807924e0b2e62439a8df9f6d32c1
parent: 7457df12a2eb70afcfa283968f7d1fadf123b0a1 (diff)
download: bytes-01ae379526218e7f6ca28510b6c06098419b7380.tar.gz
53 files changed, 8712 insertions, 0 deletions
diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..c9be272
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+  "git": {
+    "sha1": "fe6e67386451715c5d609c90a41e98ef80f0e1d1"
+  }
+}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..4fffb2f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+/Cargo.lock
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..624e6c9
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,12 @@
+// This file is generated by cargo2android.py --run --dependencies.
+
+rust_library_host_rlib {
+    name: "libbytes",
+    crate_name: "bytes",
+    srcs: ["src/lib.rs"],
+    edition: "2018",
+    features: [
+        "default",
+        "std",
+    ],
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..21a51ab
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,150 @@
+# 0.5.4 (January 23, 2020)
+
+### Added
+- Make `Bytes::new` a `const fn`.
+- Add `From<BytesMut>` for `Bytes`.
+
+### Fix
+- Fix reversed arguments in `PartialOrd` for `Bytes`.
+- Fix `Bytes::truncate` losing original capacity when repr is an unshared `Vec`.
+- Fix `Bytes::from(Vec)` when allocator gave `Vec` a pointer with LSB set.
+- Fix panic in `Bytes::slice_ref` if argument is an empty slice.
+
+# 0.5.3 (December 12, 2019)
+
+### Added
+- `must_use` attributes to `split`, `split_off`, and `split_to` methods (#337).
+
+### Fix
+- Potential freeing of a null pointer in `Bytes` when constructed with an empty `Vec<u8>` (#341, #342).
+- Calling `Bytes::truncate` with a size large than the length will no longer clear the `Bytes` (#333).
+
+# 0.5.2 (November 27, 2019)
+
+### Added
+- `Limit` methods `into_inner`, `get_ref`, `get_mut`, `limit`, and `set_limit` (#325).
+
+# 0.5.1 (November 25, 2019)
+
+### Fix
+- Growth documentation for `BytesMut` (#321)
+
+# 0.5.0 (November 25, 2019)
+
+### Fix
+- Potential overflow in `copy_to_slice`
+
+### Changed
+- Increased minimum supported Rust version to 1.39.
+- `Bytes` is now a "trait object", allowing for custom allocation strategies (#298)
+- `BytesMut` implicitly grows internal storage. `remaining_mut()` returns
+  `usize::MAX` (#316).
+- `BufMut::bytes_mut` returns `&mut [MaybeUninit<u8>]` to reflect the unknown
+  initialization state (#305).
+- `Buf` / `BufMut` implementations for `&[u8]` and `&mut [u8]`
+  respectively (#261).
+- Move `Buf` / `BufMut` "extra" functions to an extension trait (#306).
+- `BufMutExt::limit` (#309).
+- `Bytes::slice` takes a `RangeBounds` argument (#265).
+- `Bytes::from_static` is now a `const fn` (#311).
+- A multitude of smaller performance optimizations.
+
+### Added
+- `no_std` support (#281).
+- `get_*`, `put_*`, `get_*_le`, and `put_*le` accessors for handling byte order.
+- `BorrowMut` implementation for `BytesMut` (#185).
+
+### Removed
+- `IntoBuf` (#288).
+- `Buf` implementation for `&str` (#301).
+- `byteorder` dependency (#280).
+- `iovec` dependency, use `std::IoSlice` instead (#263).
+- optional `either` dependency (#315).
+- optional `i128` feature -- now available on stable. (#276).
+
+# 0.4.12 (March 6, 2019)
+
+### Added
+- Implement `FromIterator<&'a u8>` for `BytesMut`/`Bytes` (#244).
+- Implement `Buf` for `VecDeque` (#249).
+
+# 0.4.11 (November 17, 2018)
+
+* Use raw pointers for potentially racy loads (#233).
+* Implement `BufRead` for `buf::Reader` (#232).
+* Documentation tweaks (#234).
+
+# 0.4.10 (September 4, 2018)
+
+* impl `Buf` and `BufMut` for `Either` (#225).
+* Add `Bytes::slice_ref` (#208).
+
+# 0.4.9 (July 12, 2018)
+
+* Add 128 bit number support behind a feature flag (#209).
+* Implement `IntoBuf` for `&mut [u8]`
+
+# 0.4.8 (May 25, 2018)
+
+* Fix panic in `BytesMut` `FromIterator` implementation.
+* Bytes: Recycle space when reserving space in vec mode (#197).
+* Bytes: Add resize fn (#203).
+
+# 0.4.7 (April 27, 2018)
+
+* Make `Buf` and `BufMut` usable as trait objects (#186).
+* impl BorrowMut for BytesMut (#185).
+* Improve accessor performance (#195).
+
+# 0.4.6 (Janary 8, 2018)
+
+* Implement FromIterator for Bytes/BytesMut (#148).
+* Add `advance` fn to Bytes/BytesMut (#166).
+* Add `unsplit` fn to `BytesMut` (#162, #173).
+* Improvements to Bytes split fns (#92).
+
+# 0.4.5 (August 12, 2017)
+
+* Fix range bug in `Take::bytes`
+* Misc performance improvements
+* Add extra `PartialEq` implementations.
+* Add `Bytes::with_capacity`
+* Implement `AsMut[u8]` for `BytesMut`
+
+# 0.4.4 (May 26, 2017)
+
+* Add serde support behind feature flag
+* Add `extend_from_slice` on `Bytes` and `BytesMut`
+* Add `truncate` and `clear` on `Bytes`
+* Misc additional std trait implementations
+* Misc performance improvements
+
+# 0.4.3 (April 30, 2017)
+
+* Fix Vec::advance_mut bug
+* Bump minimum Rust version to 1.15
+* Misc performance tweaks
+
+# 0.4.2 (April 5, 2017)
+
+* Misc performance tweaks
+* Improved `Debug` implementation for `Bytes`
+* Avoid some incorrect assert panics
+
+# 0.4.1 (March 15, 2017)
+
+* Expose `buf` module and have most types available from there vs. root.
+* Implement `IntoBuf` for `T: Buf`.
+* Add `FromBuf` and `Buf::collect`.
+* Add iterator adapter for `Buf`.
+* Add scatter/gather support to `Buf` and `BufMut`.
+* Add `Buf::chain`.
+* Reduce allocations on repeated calls to `BytesMut::reserve`.
+* Implement `Debug` for more types.
+* Remove `Source` in favor of `IntoBuf`.
+* Implement `Extend` for `BytesMut`.
+
+
+# 0.4.0 (February 24, 2017)
+
+* Initial release
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..6a4393f
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,35 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+edition = "2018"
+name = "bytes"
+version = "0.5.4"
+authors = ["Carl Lerche <me@carllerche.com>", "Sean McArthur <sean@seanmonstar.com>"]
+description = "Types and traits for working with bytes"
+documentation = "https://docs.rs/bytes"
+readme = "README.md"
+keywords = ["buffers", "zero-copy", "io"]
+categories = ["network-programming", "data-structures"]
+license = "MIT"
+repository = "https://github.com/tokio-rs/bytes"
+[dependencies.serde]
+version = "1.0"
+optional = true
+[dev-dependencies.serde_test]
+version = "1.0"
+
+[features]
+default = ["std"]
+std = []
+[target."cfg(not(windows))".dev-dependencies.loom]
+version = "0.2.13"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..257e788
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,36 @@
+[package]
+
+name = "bytes"
+# When releasing to crates.io:
+# - Update html_root_url.
+# - Update CHANGELOG.md.
+# - Update doc URL.
+# - Create "v0.5.x" git tag.
+version = "0.5.4"
+license = "MIT"
+authors = [
+    "Carl Lerche <me@carllerche.com>",
+    "Sean McArthur <sean@seanmonstar.com>",
+]
+description = "Types and traits for working with bytes"
+documentation = "https://docs.rs/bytes"
+repository = "https://github.com/tokio-rs/bytes"
+readme = "README.md"
+keywords = ["buffers", "zero-copy", "io"]
+categories = ["network-programming", "data-structures"]
+edition = "2018"
+
+[features]
+default = ["std"]
+std = []
+
+[dependencies]
+serde = { version = "1.0", optional = true }
+
+[dev-dependencies]
+serde_test = "1.0"
+
+# loom is currently not compiling on windows.
+# See: https://github.com/Xudong-Huang/generator-rs/issues/19
+[target.'cfg(not(windows))'.dev-dependencies]
+loom = "0.2.13"
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..58fb29a
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,25 @@
+Copyright (c) 2018 Carl Lerche
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..e6f674c
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,19 @@
+name: "bytes"
+description: "Types and traits for working with bytes"
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/bytes"
+  }
+  url {
+    type: GIT
+    value: "https://github.com/tokio-rs/bytes"
+  }
+  version: "0.5.4"
+  license_type: NOTICE
+  last_upgrade_date {
+    year: 2020
+    month: 6
+    day: 3
+  }
+}
diff --git a/MODULE_LICENSE_BSD_LIKE b/MODULE_LICENSE_BSD_LIKE
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_BSD_LIKE
diff --git a/NOTICE b/NOTICE
new file mode 120000
index 0000000..7a694c9
--- /dev/null
+++ b/NOTICE
@@ -0,0 +1 @@
+LICENSE
+\ No newline at end of file
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..46fc303
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..afc2ed2
--- /dev/null
+++ b/README.md
@@ -0,0 +1,48 @@
+# Bytes
+
+A utility library for working with bytes.
+
+[![Crates.io][crates-badge]][crates-url]
+[![Build Status][azure-badge]][azure-url]
+
+[crates-badge]: https://img.shields.io/crates/v/bytes.svg
+[crates-url]: https://crates.io/crates/bytes
+[azure-badge]: https://dev.azure.com/tokio-rs/bytes/_apis/build/status/tokio-rs.bytes?branchName=master
+[azure-url]: https://dev.azure.com/tokio-rs/bytes/_build/latest?definitionId=3&branchName=master
+
+[Documentation](https://docs.rs/bytes)
+
+## Usage
+
+To use `bytes`, first add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+bytes = "0.5"
+```
+
+Next, add this to your crate:
+
+```rust
+use bytes::{Bytes, BytesMut, Buf, BufMut};
+```
+
+## Serde support
+
+Serde support is optional and disabled by default. To enable use the feature `serde`.
+
+```toml
+[dependencies]
+bytes = { version = "0.5", features = ["serde"] }
+```
+
+## License
+
+This project is licensed under the [MIT license](LICENSE).
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in `bytes` by you, shall be licensed as MIT, without any additional
+terms or conditions.
+
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
new file mode 100644
index 0000000..18b5974
--- /dev/null
+++ b/azure-pipelines.yml
@@ -0,0 +1,68 @@
+trigger: ["master"]
+pr: ["master"]
+
+jobs:
+# Check formatting
+# - template: ci/azure-rustfmt.yml
+#   parameters:
+#     name: rustfmt
+
+# Apply clippy lints
+# - template: ci/azure-clippy.yml
+#   parameters:
+#     name: clippy
+
+# This represents the minimum Rust version supported by
+# Bytes. Updating this should be done in a dedicated PR.
+#
+# Tests are not run as tests may require newer versions of
+# rust.
+- template: ci/azure-test-stable.yml
+  parameters:
+    name: minrust
+    rust_version: 1.39.0
+    cmd: check
+
+# Stable
+- template: ci/azure-test-stable.yml
+  parameters:
+    name: stable
+    cross: true
+    features:
+      - serde
+
+# Nightly
+- template: ci/azure-test-stable.yml
+  parameters:
+    name: nightly
+    # Pin nightly to avoid being impacted by breakage
+    rust_version: nightly-2019-09-25
+    benches: true
+
+# Run tests on some extra platforms
+- template: ci/azure-cross-compile.yml
+  parameters:
+    name: cross
+
+# Sanitizers
+- template: ci/azure-tsan.yml
+  parameters:
+    name: tsan
+    rust_version: nightly
+
+# Loom
+- template: ci/azure-loom.yml
+  parameters:
+    name: loom
+    rust_version: stable
+
+
+- template: ci/azure-deploy-docs.yml
+  parameters:
+    dependsOn:
+      # - rustfmt
+      # - clippy
+      - stable
+      - nightly
+      - minrust
+      - cross
diff --git a/benches/buf.rs b/benches/buf.rs
new file mode 100644
index 0000000..0c9a1d9
--- /dev/null
+++ b/benches/buf.rs
@@ -0,0 +1,187 @@
+#![feature(test)]
+#![deny(warnings, rust_2018_idioms)]
+
+extern crate test;
+
+use test::Bencher;
+use bytes::Buf;
+
+/// Dummy Buf implementation
+struct TestBuf {
+    buf: &'static [u8],
+    readlens: &'static [usize],
+    init_pos: usize,
+    pos: usize,
+    readlen_pos: usize,
+    readlen: usize,
+}
+impl TestBuf {
+    fn new(buf: &'static [u8], readlens: &'static [usize], init_pos: usize) -> TestBuf {
+        let mut buf = TestBuf {
+            buf,
+            readlens,
+            init_pos,
+            pos: 0,
+            readlen_pos: 0,
+            readlen: 0,
+        };
+        buf.reset();
+        buf
+    }
+    fn reset(&mut self) {
+        self.pos = self.init_pos;
+        self.readlen_pos = 0;
+        self.next_readlen();
+    }
+    /// Compute the length of the next read :
+    /// - use the next value specified in readlens (capped by remaining) if any
+    /// - else the remaining
+    fn next_readlen(&mut self) {
+        self.readlen = self.buf.len() - self.pos;
+        if let Some(readlen) = self.readlens.get(self.readlen_pos) {
+            self.readlen = std::cmp::min(self.readlen, *readlen);
+            self.readlen_pos += 1;
+        }
+    }
+}
+impl Buf for TestBuf {
+    fn remaining(&self) -> usize {
+        return self.buf.len() - self.pos;
+    }
+    fn advance(&mut self, cnt: usize) {
+        self.pos += cnt;
+        assert!(self.pos <= self.buf.len());
+        self.next_readlen();
+    }
+    fn bytes(&self) -> &[u8] {
+        if self.readlen == 0 {
+            Default::default()
+        } else {
+            &self.buf[self.pos..self.pos + self.readlen]
+        }
+    }
+}
+
+/// Dummy Buf implementation
+///  version with methods forced to not be inlined (to simulate costly calls)
+struct TestBufC {
+    inner: TestBuf,
+}
+impl TestBufC {
+    fn new(buf: &'static [u8], readlens: &'static [usize], init_pos: usize) -> TestBufC {
+        TestBufC {
+            inner: TestBuf::new(buf, readlens, init_pos),
+        }
+    }
+    fn reset(&mut self) {
+        self.inner.reset()
+    }
+}
+impl Buf for TestBufC {
+    #[inline(never)]
+    fn remaining(&self) -> usize {
+        self.inner.remaining()
+    }
+    #[inline(never)]
+    fn advance(&mut self, cnt: usize) {
+        self.inner.advance(cnt)
+    }
+    #[inline(never)]
+    fn bytes(&self) -> &[u8] {
+        self.inner.bytes()
+    }
+}
+
+macro_rules! bench {
+    ($fname:ident, testbuf $testbuf:ident $readlens:expr, $method:ident $(,$arg:expr)*) => (
+        #[bench]
+        fn $fname(b: &mut Bencher) {
+            let mut bufs = [
+                $testbuf::new(&[1u8; 8+0], $readlens, 0),
+                $testbuf::new(&[1u8; 8+1], $readlens, 1),
+                $testbuf::new(&[1u8; 8+2], $readlens, 2),
+                $testbuf::new(&[1u8; 8+3], $readlens, 3),
+                $testbuf::new(&[1u8; 8+4], $readlens, 4),
+                $testbuf::new(&[1u8; 8+5], $readlens, 5),
+                $testbuf::new(&[1u8; 8+6], $readlens, 6),
+                $testbuf::new(&[1u8; 8+7], $readlens, 7),
+            ];
+            b.iter(|| {
+                for i in 0..8 {
+                    bufs[i].reset();
+                    let buf: &mut dyn Buf =  &mut bufs[i]; // type erasure
+                    test::black_box(buf.$method($($arg,)*));
+                }
+            })
+        }
+    );
+    ($fname:ident, slice, $method:ident $(,$arg:expr)*) => (
+        #[bench]
+        fn $fname(b: &mut Bencher) {
+            // buf must be long enough for one read of 8 bytes starting at pos 7
+            let arr = [1u8; 8+7];
+            b.iter(|| {
+                for i in 0..8 {
+                    let mut buf = &arr[i..];
+                    let buf = &mut buf as &mut dyn Buf; // type erasure
+                    test::black_box(buf.$method($($arg,)*));
+                }
+            })
+        }
+    );
+    ($fname:ident, option) => (
+        #[bench]
+        fn $fname(b: &mut Bencher) {
+            let data = [1u8; 1];
+            b.iter(|| {
+                for _ in 0..8 {
+                    let mut buf = Some(data);
+                    let buf = &mut buf as &mut dyn Buf; // type erasure
+                    test::black_box(buf.get_u8());
+                }
+            })
+        }
+    );
+}
+
+macro_rules! bench_group {
+    ($method:ident $(,$arg:expr)*) => (
+        bench!(slice, slice, $method $(,$arg)*);
+        bench!(tbuf_1,        testbuf TestBuf  &[],  $method $(,$arg)*);
+        bench!(tbuf_1_costly, testbuf TestBufC &[],  $method $(,$arg)*);
+        bench!(tbuf_2,        testbuf TestBuf  &[1], $method $(,$arg)*);
+        bench!(tbuf_2_costly, testbuf TestBufC &[1], $method $(,$arg)*);
+        // bench!(tbuf_onebyone,        testbuf TestBuf  &[1,1,1,1,1,1,1,1], $method $(,$arg)*);
+        // bench!(tbuf_onebyone_costly, testbuf TestBufC &[1,1,1,1,1,1,1,1], $method $(,$arg)*);
+    );
+}
+
+mod get_u8 {
+    use super::*;
+    bench_group!(get_u8);
+    bench!(option, option);
+}
+mod get_u16 {
+    use super::*;
+    bench_group!(get_u16);
+}
+mod get_u32 {
+    use super::*;
+    bench_group!(get_u32);
+}
+mod get_u64 {
+    use super::*;
+    bench_group!(get_u64);
+}
+mod get_f32 {
+    use super::*;
+    bench_group!(get_f32);
+}
+mod get_f64 {
+    use super::*;
+    bench_group!(get_f64);
+}
+mod get_uint24 {
+    use super::*;
+    bench_group!(get_uint, 3);
+}
diff --git a/benches/bytes.rs b/benches/bytes.rs
new file mode 100644
index 0000000..9c36e60
--- /dev/null
+++ b/benches/bytes.rs
@@ -0,0 +1,118 @@
+#![feature(test)]
+#![deny(warnings, rust_2018_idioms)]
+
+extern crate test;
+
+use test::Bencher;
+use bytes::Bytes;
+
+#[bench]
+fn deref_unique(b: &mut Bencher) {
+    let buf = Bytes::from(vec![0; 1024]);
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_shared(b: &mut Bencher) {
+    let buf = Bytes::from(vec![0; 1024]);
+    let _b2 = buf.clone();
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_static(b: &mut Bencher) {
+    let buf = Bytes::from_static(b"hello world");
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn clone_static(b: &mut Bencher) {
+    let bytes = Bytes::from_static("hello world 1234567890 and have a good byte 0987654321".as_bytes());
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&bytes.clone());
+        }
+    })
+}
+
+#[bench]
+fn clone_shared(b: &mut Bencher) {
+    let bytes = Bytes::from(b"hello world 1234567890 and have a good byte 0987654321".to_vec());
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&bytes.clone());
+        }
+    })
+}
+
+#[bench]
+fn clone_arc_vec(b: &mut Bencher) {
+    use std::sync::Arc;
+    let bytes = Arc::new(b"hello world 1234567890 and have a good byte 0987654321".to_vec());
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&bytes.clone());
+        }
+    })
+}
+
+#[bench]
+fn from_long_slice(b: &mut Bencher) {
+    let data = [0u8; 128];
+    b.bytes = data.len() as u64;
+    b.iter(|| {
+        let buf = Bytes::copy_from_slice(&data[..]);
+        test::black_box(buf);
+    })
+}
+
+#[bench]
+fn slice_empty(b: &mut Bencher) {
+    b.iter(|| {
+        let b = Bytes::from(vec![17; 1024]).clone();
+        for i in 0..1000 {
+            test::black_box(b.slice(i % 100..i % 100));
+        }
+    })
+}
+
+#[bench]
+fn slice_short_from_arc(b: &mut Bencher) {
+    b.iter(|| {
+        // `clone` is to convert to ARC
+        let b = Bytes::from(vec![17; 1024]).clone();
+        for i in 0..1000 {
+            test::black_box(b.slice(1..2 + i % 10));
+        }
+    })
+}
+
+#[bench]
+fn split_off_and_drop(b: &mut Bencher) {
+    b.iter(|| {
+        for _ in 0..1024 {
+            let v = vec![10; 200];
+            let mut b = Bytes::from(v);
+            test::black_box(b.split_off(100));
+            test::black_box(b);
+        }
+    })
+}
diff --git a/benches/bytes_mut.rs b/benches/bytes_mut.rs
new file mode 100644
index 0000000..ded1d14
--- /dev/null
+++ b/benches/bytes_mut.rs
@@ -0,0 +1,249 @@
+#![feature(test)]
+#![deny(warnings, rust_2018_idioms)]
+
+extern crate test;
+
+use test::Bencher;
+use bytes::{BufMut, BytesMut};
+
+#[bench]
+fn alloc_small(b: &mut Bencher) {
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(BytesMut::with_capacity(12));
+        }
+    })
+}
+
+#[bench]
+fn alloc_mid(b: &mut Bencher) {
+    b.iter(|| {
+        test::black_box(BytesMut::with_capacity(128));
+    })
+}
+
+#[bench]
+fn alloc_big(b: &mut Bencher) {
+    b.iter(|| {
+        test::black_box(BytesMut::with_capacity(4096));
+    })
+}
+
+
+#[bench]
+fn deref_unique(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(4096);
+    buf.put(&[0u8; 1024][..]);
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_unique_unroll(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(4096);
+    buf.put(&[0u8; 1024][..]);
+
+    b.iter(|| {
+        for _ in 0..128 {
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_shared(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(4096);
+    buf.put(&[0u8; 1024][..]);
+    let _b2 = buf.split_off(1024);
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&buf[..]);
+        }
+    })
+}
+
+#[bench]
+fn deref_two(b: &mut Bencher) {
+    let mut buf1 = BytesMut::with_capacity(8);
+    buf1.put(&[0u8; 8][..]);
+
+    let mut buf2 = BytesMut::with_capacity(4096);
+    buf2.put(&[0u8; 1024][..]);
+
+    b.iter(|| {
+        for _ in 0..512 {
+            test::black_box(&buf1[..]);
+            test::black_box(&buf2[..]);
+        }
+    })
+}
+
+#[bench]
+fn clone_frozen(b: &mut Bencher) {
+    let bytes = BytesMut::from(&b"hello world 1234567890 and have a good byte 0987654321"[..]).split().freeze();
+
+    b.iter(|| {
+        for _ in 0..1024 {
+            test::black_box(&bytes.clone());
+        }
+    })
+}
+
+#[bench]
+fn alloc_write_split_to_mid(b: &mut Bencher) {
+    b.iter(|| {
+        let mut buf = BytesMut::with_capacity(128);
+        buf.put_slice(&[0u8; 64]);
+        test::black_box(buf.split_to(64));
+    })
+}
+
+#[bench]
+fn drain_write_drain(b: &mut Bencher) {
+    let data = [0u8; 128];
+
+    b.iter(|| {
+        let mut buf = BytesMut::with_capacity(1024);
+        let mut parts = Vec::with_capacity(8);
+
+        for _ in 0..8 {
+            buf.put(&data[..]);
+            parts.push(buf.split_to(128));
+        }
+
+        test::black_box(parts);
+    })
+}
+
+#[bench]
+fn fmt_write(b: &mut Bencher) {
+    use std::fmt::Write;
+    let mut buf = BytesMut::with_capacity(128);
+    let s = "foo bar baz quux lorem ipsum dolor et";
+
+    b.bytes = s.len() as u64;
+    b.iter(|| {
+        let _ = write!(buf, "{}", s);
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    })
+}
+
+#[bench]
+fn bytes_mut_extend(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(256);
+    let data = [33u8; 32];
+
+    b.bytes = data.len() as u64 * 4;
+    b.iter(|| {
+        for _ in 0..4 {
+            buf.extend(&data);
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
+
+// BufMut for BytesMut vs Vec<u8>
+
+#[bench]
+fn put_slice_bytes_mut(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(256);
+    let data = [33u8; 32];
+
+    b.bytes = data.len() as u64 * 4;
+    b.iter(|| {
+        for _ in 0..4 {
+            buf.put_slice(&data);
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
+
+#[bench]
+fn put_u8_bytes_mut(b: &mut Bencher) {
+    let mut buf = BytesMut::with_capacity(256);
+    let cnt = 128;
+
+    b.bytes = cnt as u64;
+    b.iter(|| {
+        for _ in 0..cnt {
+            buf.put_u8(b'x');
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
+
+#[bench]
+fn put_slice_vec(b: &mut Bencher) {
+    let mut buf = Vec::<u8>::with_capacity(256);
+    let data = [33u8; 32];
+
+    b.bytes = data.len() as u64 * 4;
+    b.iter(|| {
+        for _ in 0..4 {
+            buf.put_slice(&data);
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
+
+#[bench]
+fn put_u8_vec(b: &mut Bencher) {
+    let mut buf = Vec::<u8>::with_capacity(256);
+    let cnt = 128;
+
+    b.bytes = cnt as u64;
+    b.iter(|| {
+        for _ in 0..cnt {
+            buf.put_u8(b'x');
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
+
+#[bench]
+fn put_slice_vec_extend(b: &mut Bencher) {
+    let mut buf = Vec::<u8>::with_capacity(256);
+    let data = [33u8; 32];
+
+    b.bytes = data.len() as u64 * 4;
+    b.iter(|| {
+        for _ in 0..4 {
+            buf.extend_from_slice(&data);
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
+
+#[bench]
+fn put_u8_vec_push(b: &mut Bencher) {
+    let mut buf = Vec::<u8>::with_capacity(256);
+    let cnt = 128;
+
+    b.bytes = cnt as u64;
+    b.iter(|| {
+        for _ in 0..cnt {
+            buf.push(b'x');
+        }
+        test::black_box(&buf);
+        unsafe { buf.set_len(0); }
+    });
+}
diff --git a/ci/azure-cross-compile.yml b/ci/azure-cross-compile.yml
new file mode 100644
index 0000000..be46ca3
--- /dev/null
+++ b/ci/azure-cross-compile.yml
@@ -0,0 +1,46 @@
+parameters:
+  cmd: build
+  rust_version: stable
+
+jobs:
+- job: ${{ parameters.name }}
+  displayName: Cross
+  strategy:
+    matrix:
+      i686:
+        vmImage: ubuntu-16.04
+        target: i686-unknown-linux-gnu
+      armv7:
+        vmImage: ubuntu-16.04
+        target: armv7-unknown-linux-gnueabihf
+      powerpc:
+        vmImage: ubuntu-16.04
+        target: powerpc-unknown-linux-gnu
+      powerpc64:
+        vmImage: ubuntu-16.04
+        target: powerpc64-unknown-linux-gnu
+      wasm:
+        vmImage: ubuntu-16.04
+        target: wasm32-unknown-unknown
+  pool:
+    vmImage: $(vmImage)
+
+  steps:
+    - template: azure-install-rust.yml
+      parameters:
+        rust_version: ${{parameters.rust_version}}
+
+    - script: cargo install cross
+      displayName: Install cross
+      condition: not(eq(variables['target'], 'wasm32-unknown-unknown'))
+
+    - script: cross ${{ parameters.cmd }} --target $(target)
+      displayName: cross ${{ parameters.cmd }} --target $(target)
+      condition: not(eq(variables['target'], 'wasm32-unknown-unknown'))
+
+    # WASM support
+    - script: |
+        rustup target add $(target)
+        cargo build --target $(target)
+      displayName: cargo build --target $(target)
+      condition: eq(variables['target'], 'wasm32-unknown-unknown')
diff --git a/ci/azure-deploy-docs.yml b/ci/azure-deploy-docs.yml
new file mode 100644
index 0000000..52ac48f
--- /dev/null
+++ b/ci/azure-deploy-docs.yml
@@ -0,0 +1,39 @@
+parameters:
+  dependsOn: []
+
+jobs:
+- job: documentation
+  displayName: 'Deploy API Documentation'
+  condition: and(succeeded(), eq(variables['Build.SourceBranch'], 'refs/heads/master'))
+  pool:
+    vmImage: 'Ubuntu 16.04'
+  dependsOn:
+    - ${{ parameters.dependsOn }}
+  steps:
+  - template: azure-install-rust.yml
+    parameters:
+      rust_version: stable
+  - script: |
+      cargo doc --no-deps
+      cp -R target/doc '$(Build.BinariesDirectory)'
+    displayName: 'Generate Documentation'
+  - script: |
+      set -e
+
+      git --version
+      ls -la
+      git init
+      git config user.name 'Deployment Bot (from Azure Pipelines)'
+      git config user.email 'deploy@tokio-rs.com'
+      git config --global credential.helper 'store --file ~/.my-credentials'
+      printf "protocol=https\nhost=github.com\nusername=carllerche\npassword=%s\n\n" "$GITHUB_TOKEN" | git credential-store --file ~/.my-credentials store
+      git remote add origin https://github.com/tokio-rs/bytes
+      git checkout -b gh-pages
+      git add .
+      git commit -m 'Deploy Bytes API documentation'
+      git push -f origin gh-pages
+    env:
+      GITHUB_TOKEN: $(githubPersonalToken)
+    workingDirectory: '$(Build.BinariesDirectory)'
+    displayName: 'Deploy Documentation'
+
diff --git a/ci/azure-install-rust.yml b/ci/azure-install-rust.yml
new file mode 100644
index 0000000..0217659
--- /dev/null
+++ b/ci/azure-install-rust.yml
@@ -0,0 +1,33 @@
+steps:
+  # Linux and macOS.
+  - script: |
+      set -e
+      curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain none
+      export PATH=$PATH:$HOME/.cargo/bin
+      rustup toolchain install $RUSTUP_TOOLCHAIN
+      rustup default $RUSTUP_TOOLCHAIN
+      echo "##vso[task.setvariable variable=PATH;]$PATH:$HOME/.cargo/bin"
+    env:
+      RUSTUP_TOOLCHAIN: ${{parameters.rust_version}}
+    displayName: "Install rust (*nix)"
+    condition: not(eq(variables['Agent.OS'], 'Windows_NT'))
+
+  # Windows.
+  - script: |
+      curl -sSf -o rustup-init.exe https://win.rustup.rs
+      rustup-init.exe -y --default-toolchain none
+      set PATH=%PATH%;%USERPROFILE%\.cargo\bin
+      rustup toolchain install %RUSTUP_TOOLCHAIN%
+      rustup default %RUSTUP_TOOLCHAIN%
+      echo "##vso[task.setvariable variable=PATH;]%PATH%;%USERPROFILE%\.cargo\bin"
+    env:
+      RUSTUP_TOOLCHAIN: ${{parameters.rust_version}}
+    displayName: "Install rust (windows)"
+    condition: eq(variables['Agent.OS'], 'Windows_NT')
+
+  # All platforms.
+  - script: |
+        rustup toolchain list
+        rustc -Vv
+        cargo -V
+    displayName: Query rust and cargo versions
diff --git a/ci/azure-loom.yml b/ci/azure-loom.yml
new file mode 100644
index 0000000..1db9c3a
--- /dev/null
+++ b/ci/azure-loom.yml
@@ -0,0 +1,15 @@
+jobs:
+- job: ${{parameters.name}}
+  displayName: Loom tests
+  pool:
+    vmImage: ubuntu-16.04
+
+  steps:
+  - template: azure-install-rust.yml
+    parameters:
+      rust_version: ${{parameters.rust_version}}
+
+  - script: RUSTFLAGS="--cfg loom" cargo test --lib
+    displayName: RUSTFLAGS="--cfg loom" cargo test --lib
+
+
diff --git a/ci/azure-test-stable.yml b/ci/azure-test-stable.yml
new file mode 100644
index 0000000..e543eee
--- /dev/null
+++ b/ci/azure-test-stable.yml
@@ -0,0 +1,50 @@
+parameters:
+  cmd: test
+  rust_version: stable
+  features: []
+
+jobs:
+- job: ${{ parameters.name }}
+  displayName: ${{ parameters.displayName }}
+  strategy:
+    matrix:
+      Linux:
+        vmImage: ubuntu-16.04
+
+      ${{ if parameters.cross }}:
+        MacOS:
+          vmImage: macOS-10.13
+        Windows:
+          vmImage: vs2017-win2016
+  pool:
+    vmImage: $(vmImage)
+
+  steps:
+  - template: azure-install-rust.yml
+    parameters:
+      rust_version: ${{parameters.rust_version}}
+
+  # Run with default crate features
+  - script: cargo ${{ parameters.cmd }}
+    displayName: cargo ${{ parameters.cmd }}
+
+  # Run with each specified feature
+  - ${{ each feature in parameters.features }}:
+    - script: cargo ${{ parameters.cmd }} --features ${{ feature }}
+      displayName: cargo ${{ parameters.cmd }} --features ${{ feature }}
+
+  - ${{ if eq(parameters.cmd, 'test') }}:
+    - script: cargo doc --no-deps
+      displayName: cargo doc --no-deps
+
+  - ${{ if parameters.benches }}:
+    - script: cargo check --benches
+      displayName: Check benchmarks
+
+  # Run with all features
+  - script: cargo ${{ parameters.cmd }} --all-features
+    displayName: cargo ${{ parameters.cmd }} --all-features
+
+  # Run with no default features
+  - script: cargo check --no-default-features
+    displayName: cargo check --no-default-features
diff --git a/ci/azure-tsan.yml b/ci/azure-tsan.yml
new file mode 100644
index 0000000..198b187
--- /dev/null
+++ b/ci/azure-tsan.yml
@@ -0,0 +1,26 @@
+jobs:
+- job: ${{ parameters.name }}
+  displayName: TSAN
+  pool:
+    vmImage: ubuntu-16.04
+
+  steps:
+  - template: azure-install-rust.yml
+    parameters:
+      rust_version: ${{ parameters.rust_version }}
+
+  - script: |
+      set -e
+
+      export RUST_TEST_THREADS=1
+      export ASAN_OPTIONS="detect_odr_violation=0 detect_leaks=0"
+      export TSAN_OPTIONS="suppressions=`pwd`/ci/tsan"
+
+      # Run address sanitizer
+      RUSTFLAGS="-Z sanitizer=address" \
+      cargo test --target x86_64-unknown-linux-gnu --test test_bytes --test test_buf --test test_buf_mut
+
+      # Run thread sanitizer
+      RUSTFLAGS="-Z sanitizer=thread" \
+      cargo test --target x86_64-unknown-linux-gnu --test test_bytes --test test_buf --test test_buf_mut
+    displayName: TSAN / MSAN
diff --git a/ci/tsan b/ci/tsan
new file mode 100644
index 0000000..e53f9b8
--- /dev/null
+++ b/ci/tsan
@@ -0,0 +1,24 @@
+# TSAN suppressions file for `bytes`
+
+# TSAN does not understand fences and `Arc::drop` is implemented using a fence.
+# This causes many false positives.
+race:Arc*drop
+race:arc*Weak*drop
+
+# `std` mpsc is not used in any Bytes code base. This race is triggered by some
+# rust runtime logic.
+race:std*mpsc_queue
+
+# Some test runtime races. Allocation should be race free
+race:alloc::alloc
+
+# Not sure why this is warning, but it is in the test harness and not the library.
+race:TestEvent*clone
+race:test::run_tests_console::*closure
+
+# Probably more fences in std.
+race:__call_tls_dtors
+
+# This ignores a false positive caused by `thread::park()`/`thread::unpark()`.
+# See: https://github.com/rust-lang/rust/pull/54806#issuecomment-436193353
+race:pthread_cond_destroy
diff --git a/src/buf/buf_impl.rs b/src/buf/buf_impl.rs
new file mode 100644
index 0000000..843db71
--- /dev/null
+++ b/src/buf/buf_impl.rs
@@ -0,0 +1,1006 @@
+use core::{cmp, ptr, mem};
+
+#[cfg(feature = "std")]
+use std::io::IoSlice;
+
+use alloc::{boxed::Box};
+
+macro_rules! buf_get_impl {
+    ($this:ident, $typ:tt::$conv:tt) => ({
+        const SIZE: usize = mem::size_of::<$typ>();
+         // try to convert directly from the bytes
+         // this Option<ret> trick is to avoid keeping a borrow on self
+         // when advance() is called (mut borrow) and to call bytes() only once
+        let ret =  $this.bytes().get(..SIZE).map(|src| unsafe {
+            $typ::$conv(*(src as *const _ as *const [_; SIZE]))
+        });
+
+        if let Some(ret) = ret {
+             // if the direct conversion was possible, advance and return
+            $this.advance(SIZE);
+            return ret;
+        } else {
+            // if not we copy the bytes in a temp buffer then convert
+            let mut buf = [0; SIZE];
+            $this.copy_to_slice(&mut buf); // (do the advance)
+            return $typ::$conv(buf);
+        }
+    });
+    (le => $this:ident, $typ:tt, $len_to_read:expr) => ({
+        debug_assert!(mem::size_of::<$typ>() >= $len_to_read);
+
+        // The same trick as above does not improve the best case speed.
+        // It seems to be linked to the way the method is optimised by the compiler
+        let mut buf = [0; (mem::size_of::<$typ>())];
+        $this.copy_to_slice(&mut buf[..($len_to_read)]);
+        return $typ::from_le_bytes(buf);
+    });
+    (be => $this:ident, $typ:tt, $len_to_read:expr) => {{
+        debug_assert!(mem::size_of::<$typ>() >= $len_to_read);
+
+        let mut buf = [0; (mem::size_of::<$typ>())];
+        $this.copy_to_slice(&mut buf[mem::size_of::<$typ>()-($len_to_read)..]);
+        return $typ::from_be_bytes(buf);
+    }};
+}
+
+/// Read bytes from a buffer.
+///
+/// A buffer stores bytes in memory such that read operations are infallible.
+/// The underlying storage may or may not be in contiguous memory. A `Buf` value
+/// is a cursor into the buffer. Reading from `Buf` advances the cursor
+/// position. It can be thought of as an efficient `Iterator` for collections of
+/// bytes.
+///
+/// The simplest `Buf` is a `&[u8]`.
+///
+/// ```
+/// use bytes::Buf;
+///
+/// let mut buf = &b"hello world"[..];
+///
+/// assert_eq!(b'h', buf.get_u8());
+/// assert_eq!(b'e', buf.get_u8());
+/// assert_eq!(b'l', buf.get_u8());
+///
+/// let mut rest = [0; 8];
+/// buf.copy_to_slice(&mut rest);
+///
+/// assert_eq!(&rest[..], &b"lo world"[..]);
+/// ```
+pub trait Buf {
+    /// Returns the number of bytes between the current position and the end of
+    /// the buffer.
+    ///
+    /// This value is greater than or equal to the length of the slice returned
+    /// by `bytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"hello world"[..];
+    ///
+    /// assert_eq!(buf.remaining(), 11);
+    ///
+    /// buf.get_u8();
+    ///
+    /// assert_eq!(buf.remaining(), 10);
+    /// ```
+    ///
+    /// # Implementer notes
+    ///
+    /// Implementations of `remaining` should ensure that the return value does
+    /// not change unless a call is made to `advance` or any other function that
+    /// is documented to change the `Buf`'s current position.
+    fn remaining(&self) -> usize;
+
+    /// Returns a slice starting at the current position and of length between 0
+    /// and `Buf::remaining()`. Note that this *can* return shorter slice (this allows
+    /// non-continuous internal representation).
+    ///
+    /// This is a lower level function. Most operations are done with other
+    /// functions.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"hello world"[..];
+    ///
+    /// assert_eq!(buf.bytes(), &b"hello world"[..]);
+    ///
+    /// buf.advance(6);
+    ///
+    /// assert_eq!(buf.bytes(), &b"world"[..]);
+    /// ```
+    ///
+    /// # Implementer notes
+    ///
+    /// This function should never panic. Once the end of the buffer is reached,
+    /// i.e., `Buf::remaining` returns 0, calls to `bytes` should return an
+    /// empty slice.
+    fn bytes(&self) -> &[u8];
+
+    /// Fills `dst` with potentially multiple slices starting at `self`'s
+    /// current position.
+    ///
+    /// If the `Buf` is backed by disjoint slices of bytes, `bytes_vectored` enables
+    /// fetching more than one slice at once. `dst` is a slice of `IoSlice`
+    /// references, enabling the slice to be directly used with [`writev`]
+    /// without any further conversion. The sum of the lengths of all the
+    /// buffers in `dst` will be less than or equal to `Buf::remaining()`.
+    ///
+    /// The entries in `dst` will be overwritten, but the data **contained** by
+    /// the slices **will not** be modified. If `bytes_vectored` does not fill every
+    /// entry in `dst`, then `dst` is guaranteed to contain all remaining slices
+    /// in `self.
+    ///
+    /// This is a lower level function. Most operations are done with other
+    /// functions.
+    ///
+    /// # Implementer notes
+    ///
+    /// This function should never panic. Once the end of the buffer is reached,
+    /// i.e., `Buf::remaining` returns 0, calls to `bytes_vectored` must return 0
+    /// without mutating `dst`.
+    ///
+    /// Implementations should also take care to properly handle being called
+    /// with `dst` being a zero length slice.
+    ///
+    /// [`writev`]: http://man7.org/linux/man-pages/man2/readv.2.html
+    #[cfg(feature = "std")]
+    fn bytes_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
+        if dst.is_empty() {
+            return 0;
+        }
+
+        if self.has_remaining() {
+            dst[0] = IoSlice::new(self.bytes());
+            1
+        } else {
+            0
+        }
+    }
+
+    /// Advance the internal cursor of the Buf
+    ///
+    /// The next call to `bytes` will return a slice starting `cnt` bytes
+    /// further into the underlying buffer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"hello world"[..];
+    ///
+    /// assert_eq!(buf.bytes(), &b"hello world"[..]);
+    ///
+    /// buf.advance(6);
+    ///
+    /// assert_eq!(buf.bytes(), &b"world"[..]);
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function **may** panic if `cnt > self.remaining()`.
+    ///
+    /// # Implementer notes
+    ///
+    /// It is recommended for implementations of `advance` to panic if `cnt >
+    /// self.remaining()`. If the implementation does not panic, the call must
+    /// behave as if `cnt == self.remaining()`.
+    ///
+    /// A call with `cnt == 0` should never panic and be a no-op.
+    fn advance(&mut self, cnt: usize);
+
+    /// Returns true if there are any more bytes to consume
+    ///
+    /// This is equivalent to `self.remaining() != 0`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"a"[..];
+    ///
+    /// assert!(buf.has_remaining());
+    ///
+    /// buf.get_u8();
+    ///
+    /// assert!(!buf.has_remaining());
+    /// ```
+    fn has_remaining(&self) -> bool {
+        self.remaining() > 0
+    }
+
+    /// Copies bytes from `self` into `dst`.
+    ///
+    /// The cursor is advanced by the number of bytes copied. `self` must have
+    /// enough remaining bytes to fill `dst`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"hello world"[..];
+    /// let mut dst = [0; 5];
+    ///
+    /// buf.copy_to_slice(&mut dst);
+    /// assert_eq!(&b"hello"[..], &dst);
+    /// assert_eq!(6, buf.remaining());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if `self.remaining() < dst.len()`
+    fn copy_to_slice(&mut self, dst: &mut [u8]) {
+        let mut off = 0;
+
+        assert!(self.remaining() >= dst.len());
+
+        while off < dst.len() {
+            let cnt;
+
+            unsafe {
+                let src = self.bytes();
+                cnt = cmp::min(src.len(), dst.len() - off);
+
+                ptr::copy_nonoverlapping(
+                    src.as_ptr(), dst[off..].as_mut_ptr(), cnt);
+
+                off += cnt;
+            }
+
+            self.advance(cnt);
+        }
+    }
+
+    /// Gets an unsigned 8 bit integer from `self`.
+    ///
+    /// The current position is advanced by 1.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08 hello"[..];
+    /// assert_eq!(8, buf.get_u8());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is no more remaining data in `self`.
+    fn get_u8(&mut self) -> u8 {
+        assert!(self.remaining() >= 1);
+        let ret = self.bytes()[0];
+        self.advance(1);
+        ret
+    }
+
+    /// Gets a signed 8 bit integer from `self`.
+    ///
+    /// The current position is advanced by 1.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08 hello"[..];
+    /// assert_eq!(8, buf.get_i8());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is no more remaining data in `self`.
+    fn get_i8(&mut self) -> i8 {
+        assert!(self.remaining() >= 1);
+        let ret = self.bytes()[0] as i8;
+        self.advance(1);
+        ret
+    }
+
+    /// Gets an unsigned 16 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08\x09 hello"[..];
+    /// assert_eq!(0x0809, buf.get_u16());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u16(&mut self) -> u16 {
+        buf_get_impl!(self, u16::from_be_bytes);
+    }
+
+    /// Gets an unsigned 16 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x09\x08 hello"[..];
+    /// assert_eq!(0x0809, buf.get_u16_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u16_le(&mut self) -> u16 {
+        buf_get_impl!(self, u16::from_le_bytes);
+    }
+
+    /// Gets a signed 16 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08\x09 hello"[..];
+    /// assert_eq!(0x0809, buf.get_i16());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i16(&mut self) -> i16 {
+        buf_get_impl!(self, i16::from_be_bytes);
+    }
+
+    /// Gets a signed 16 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x09\x08 hello"[..];
+    /// assert_eq!(0x0809, buf.get_i16_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i16_le(&mut self) -> i16 {
+        buf_get_impl!(self, i16::from_le_bytes);
+    }
+
+    /// Gets an unsigned 32 bit integer from `self` in the big-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08\x09\xA0\xA1 hello"[..];
+    /// assert_eq!(0x0809A0A1, buf.get_u32());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u32(&mut self) -> u32 {
+        buf_get_impl!(self, u32::from_be_bytes);
+    }
+
+    /// Gets an unsigned 32 bit integer from `self` in the little-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\xA1\xA0\x09\x08 hello"[..];
+    /// assert_eq!(0x0809A0A1, buf.get_u32_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u32_le(&mut self) -> u32 {
+        buf_get_impl!(self, u32::from_le_bytes);
+    }
+
+    /// Gets a signed 32 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08\x09\xA0\xA1 hello"[..];
+    /// assert_eq!(0x0809A0A1, buf.get_i32());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i32(&mut self) -> i32 {
+        buf_get_impl!(self, i32::from_be_bytes);
+    }
+
+    /// Gets a signed 32 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\xA1\xA0\x09\x08 hello"[..];
+    /// assert_eq!(0x0809A0A1, buf.get_i32_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i32_le(&mut self) -> i32 {
+        buf_get_impl!(self, i32::from_le_bytes);
+    }
+
+    /// Gets an unsigned 64 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x01\x02\x03\x04\x05\x06\x07\x08 hello"[..];
+    /// assert_eq!(0x0102030405060708, buf.get_u64());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u64(&mut self) -> u64 {
+        buf_get_impl!(self, u64::from_be_bytes);
+    }
+
+    /// Gets an unsigned 64 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08\x07\x06\x05\x04\x03\x02\x01 hello"[..];
+    /// assert_eq!(0x0102030405060708, buf.get_u64_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u64_le(&mut self) -> u64 {
+        buf_get_impl!(self, u64::from_le_bytes);
+    }
+
+    /// Gets a signed 64 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x01\x02\x03\x04\x05\x06\x07\x08 hello"[..];
+    /// assert_eq!(0x0102030405060708, buf.get_i64());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i64(&mut self) -> i64 {
+        buf_get_impl!(self, i64::from_be_bytes);
+    }
+
+    /// Gets a signed 64 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x08\x07\x06\x05\x04\x03\x02\x01 hello"[..];
+    /// assert_eq!(0x0102030405060708, buf.get_i64_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i64_le(&mut self) -> i64 {
+        buf_get_impl!(self, i64::from_le_bytes);
+    }
+
+    /// Gets an unsigned 128 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16 hello"[..];
+    /// assert_eq!(0x01020304050607080910111213141516, buf.get_u128());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u128(&mut self) -> u128 {
+        buf_get_impl!(self, u128::from_be_bytes);
+    }
+
+    /// Gets an unsigned 128 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x16\x15\x14\x13\x12\x11\x10\x09\x08\x07\x06\x05\x04\x03\x02\x01 hello"[..];
+    /// assert_eq!(0x01020304050607080910111213141516, buf.get_u128_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u128_le(&mut self) -> u128 {
+        buf_get_impl!(self, u128::from_le_bytes);
+    }
+
+    /// Gets a signed 128 bit integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16 hello"[..];
+    /// assert_eq!(0x01020304050607080910111213141516, buf.get_i128());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i128(&mut self) -> i128 {
+        buf_get_impl!(self, i128::from_be_bytes);
+    }
+
+    /// Gets a signed 128 bit integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x16\x15\x14\x13\x12\x11\x10\x09\x08\x07\x06\x05\x04\x03\x02\x01 hello"[..];
+    /// assert_eq!(0x01020304050607080910111213141516, buf.get_i128_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i128_le(&mut self) -> i128 {
+        buf_get_impl!(self, i128::from_le_bytes);
+    }
+
+    /// Gets an unsigned n-byte integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x01\x02\x03 hello"[..];
+    /// assert_eq!(0x010203, buf.get_uint(3));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_uint(&mut self, nbytes: usize) -> u64 {
+        buf_get_impl!(be => self, u64, nbytes);
+    }
+
+    /// Gets an unsigned n-byte integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x03\x02\x01 hello"[..];
+    /// assert_eq!(0x010203, buf.get_uint_le(3));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_uint_le(&mut self, nbytes: usize) -> u64 {
+        buf_get_impl!(le => self, u64, nbytes);
+    }
+
+    /// Gets a signed n-byte integer from `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x01\x02\x03 hello"[..];
+    /// assert_eq!(0x010203, buf.get_int(3));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_int(&mut self, nbytes: usize) -> i64 {
+        buf_get_impl!(be => self, i64, nbytes);
+    }
+
+    /// Gets a signed n-byte integer from `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x03\x02\x01 hello"[..];
+    /// assert_eq!(0x010203, buf.get_int_le(3));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_int_le(&mut self, nbytes: usize) -> i64 {
+        buf_get_impl!(le => self, i64, nbytes);
+    }
+
+    /// Gets an IEEE754 single-precision (4 bytes) floating point number from
+    /// `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x3F\x99\x99\x9A hello"[..];
+    /// assert_eq!(1.2f32, buf.get_f32());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_f32(&mut self) -> f32 {
+        f32::from_bits(Self::get_u32(self))
+    }
+
+    /// Gets an IEEE754 single-precision (4 bytes) floating point number from
+    /// `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x9A\x99\x99\x3F hello"[..];
+    /// assert_eq!(1.2f32, buf.get_f32_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_f32_le(&mut self) -> f32 {
+        f32::from_bits(Self::get_u32_le(self))
+    }
+
+    /// Gets an IEEE754 double-precision (8 bytes) floating point number from
+    /// `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x3F\xF3\x33\x33\x33\x33\x33\x33 hello"[..];
+    /// assert_eq!(1.2f64, buf.get_f64());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_f64(&mut self) -> f64 {
+        f64::from_bits(Self::get_u64(self))
+    }
+
+    /// Gets an IEEE754 double-precision (8 bytes) floating point number from
+    /// `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf = &b"\x33\x33\x33\x33\x33\x33\xF3\x3F hello"[..];
+    /// assert_eq!(1.2f64, buf.get_f64_le());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_f64_le(&mut self) -> f64 {
+        f64::from_bits(Self::get_u64_le(self))
+    }
+
+    /// Consumes remaining bytes inside self and returns new instance of `Bytes`
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let bytes = (&b"hello world"[..]).to_bytes();
+    /// assert_eq!(&bytes[..], &b"hello world"[..]);
+    /// ```
+    fn to_bytes(&mut self) -> crate::Bytes {
+        use super::BufMut;
+        let mut ret = crate::BytesMut::with_capacity(self.remaining());
+        ret.put(self);
+        ret.freeze()
+    }
+}
+
+macro_rules! deref_forward_buf {
+    () => (
+    fn remaining(&self) -> usize {
+        (**self).remaining()
+    }
+
+    fn bytes(&self) -> &[u8] {
+        (**self).bytes()
+    }
+
+    #[cfg(feature = "std")]
+    fn bytes_vectored<'b>(&'b self, dst: &mut [IoSlice<'b>]) -> usize {
+        (**self).bytes_vectored(dst)
+    }
+
+    fn advance(&mut self, cnt: usize) {
+        (**self).advance(cnt)
+    }
+
+    fn has_remaining(&self) -> bool {
+        (**self).has_remaining()
+    }
+
+    fn copy_to_slice(&mut self, dst: &mut [u8]) {
+        (**self).copy_to_slice(dst)
+    }
+
+    fn get_u8(&mut self) -> u8 {
+        (**self).get_u8()
+    }
+
+    fn get_i8(&mut self) -> i8 {
+        (**self).get_i8()
+    }
+
+    fn get_u16(&mut self) -> u16 {
+        (**self).get_u16()
+    }
+
+    fn get_u16_le(&mut self) -> u16 {
+        (**self).get_u16_le()
+    }
+
+    fn get_i16(&mut self) -> i16 {
+        (**self).get_i16()
+    }
+
+    fn get_i16_le(&mut self) -> i16 {
+        (**self).get_i16_le()
+    }
+
+    fn get_u32(&mut self) -> u32 {
+        (**self).get_u32()
+    }
+
+    fn get_u32_le(&mut self) -> u32 {
+        (**self).get_u32_le()
+    }
+
+    fn get_i32(&mut self) -> i32 {
+        (**self).get_i32()
+    }
+
+    fn get_i32_le(&mut self) -> i32 {
+        (**self).get_i32_le()
+    }
+
+    fn get_u64(&mut self) -> u64 {
+        (**self).get_u64()
+    }
+
+    fn get_u64_le(&mut self) -> u64 {
+        (**self).get_u64_le()
+    }
+
+    fn get_i64(&mut self) -> i64 {
+        (**self).get_i64()
+    }
+
+    fn get_i64_le(&mut self) -> i64 {
+        (**self).get_i64_le()
+    }
+
+    fn get_uint(&mut self, nbytes: usize) -> u64 {
+        (**self).get_uint(nbytes)
+    }
+
+    fn get_uint_le(&mut self, nbytes: usize) -> u64 {
+        (**self).get_uint_le(nbytes)
+    }
+
+    fn get_int(&mut self, nbytes: usize) -> i64 {
+        (**self).get_int(nbytes)
+    }
+
+    fn get_int_le(&mut self, nbytes: usize) -> i64 {
+        (**self).get_int_le(nbytes)
+    }
+
+    fn to_bytes(&mut self) -> crate::Bytes {
+        (**self).to_bytes()
+    }
+
+    )
+}
+
+impl<T: Buf + ?Sized> Buf for &mut T {
+    deref_forward_buf!();
+}
+
+impl<T: Buf + ?Sized> Buf for Box<T> {
+    deref_forward_buf!();
+}
+
+impl Buf for &[u8] {
+    #[inline]
+    fn remaining(&self) -> usize {
+        self.len()
+    }
+
+    #[inline]
+    fn bytes(&self) -> &[u8] {
+        self
+    }
+
+    #[inline]
+    fn advance(&mut self, cnt: usize) {
+        *self = &self[cnt..];
+    }
+}
+
+impl Buf for Option<[u8; 1]> {
+    fn remaining(&self) -> usize {
+        if self.is_some() {
+            1
+        } else {
+            0
+        }
+    }
+
+    fn bytes(&self) -> &[u8] {
+        self.as_ref().map(AsRef::as_ref)
+            .unwrap_or(Default::default())
+    }
+
+    fn advance(&mut self, cnt: usize) {
+        if cnt == 0 {
+            return;
+        }
+
+        if self.is_none() {
+            panic!("overflow");
+        } else {
+            assert_eq!(1, cnt);
+            *self = None;
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl<T: AsRef<[u8]>> Buf for std::io::Cursor<T> {
+    fn remaining(&self) -> usize {
+        let len = self.get_ref().as_ref().len();
+        let pos = self.position();
+
+        if pos >= len as u64 {
+            return 0;
+        }
+
+        len - pos as usize
+    }
+
+    fn bytes(&self) -> &[u8] {
+        let len = self.get_ref().as_ref().len();
+        let pos = self.position();
+
+        if pos >= len as u64 {
+            return &[];
+        }
+
+        &self.get_ref().as_ref()[pos as usize..]
+    }
+
+    fn advance(&mut self, cnt: usize) {
+        let pos = (self.position() as usize)
+            .checked_add(cnt).expect("overflow");
+
+        assert!(pos <= self.get_ref().as_ref().len());
+        self.set_position(pos as u64);
+    }
+}
+
+// The existence of this function makes the compiler catch if the Buf
+// trait is "object-safe" or not.
+fn _assert_trait_object(_b: &dyn Buf) {}
diff --git a/src/buf/buf_mut.rs b/src/buf/buf_mut.rs
new file mode 100644
index 0000000..f5ed2a7
--- /dev/null
+++ b/src/buf/buf_mut.rs
@@ -0,0 +1,1088 @@
+use core::{cmp, mem::{self, MaybeUninit}, ptr, usize};
+
+#[cfg(feature = "std")]
+use std::fmt;
+
+use alloc::{vec::Vec, boxed::Box};
+
+/// A trait for values that provide sequential write access to bytes.
+///
+/// Write bytes to a buffer
+///
+/// A buffer stores bytes in memory such that write operations are infallible.
+/// The underlying storage may or may not be in contiguous memory. A `BufMut`
+/// value is a cursor into the buffer. Writing to `BufMut` advances the cursor
+/// position.
+///
+/// The simplest `BufMut` is a `Vec<u8>`.
+///
+/// ```
+/// use bytes::BufMut;
+///
+/// let mut buf = vec![];
+///
+/// buf.put(&b"hello world"[..]);
+///
+/// assert_eq!(buf, b"hello world");
+/// ```
+pub trait BufMut {
+    /// Returns the number of bytes that can be written from the current
+    /// position until the end of the buffer is reached.
+    ///
+    /// This value is greater than or equal to the length of the slice returned
+    /// by `bytes_mut`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut dst = [0; 10];
+    /// let mut buf = &mut dst[..];
+    ///
+    /// let original_remaining = buf.remaining_mut();
+    /// buf.put(&b"hello"[..]);
+    ///
+    /// assert_eq!(original_remaining - 5, buf.remaining_mut());
+    /// ```
+    ///
+    /// # Implementer notes
+    ///
+    /// Implementations of `remaining_mut` should ensure that the return value
+    /// does not change unless a call is made to `advance_mut` or any other
+    /// function that is documented to change the `BufMut`'s current position.
+    fn remaining_mut(&self) -> usize;
+
+    /// Advance the internal cursor of the BufMut
+    ///
+    /// The next call to `bytes_mut` will return a slice starting `cnt` bytes
+    /// further into the underlying buffer.
+    ///
+    /// This function is unsafe because there is no guarantee that the bytes
+    /// being advanced past have been initialized.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = Vec::with_capacity(16);
+    ///
+    /// unsafe {
+    ///     // MaybeUninit::as_mut_ptr
+    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'h');
+    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'e');
+    ///
+    ///     buf.advance_mut(2);
+    ///
+    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'l');
+    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'l');
+    ///     buf.bytes_mut()[2].as_mut_ptr().write(b'o');
+    ///
+    ///     buf.advance_mut(3);
+    /// }
+    ///
+    /// assert_eq!(5, buf.len());
+    /// assert_eq!(buf, b"hello");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function **may** panic if `cnt > self.remaining_mut()`.
+    ///
+    /// # Implementer notes
+    ///
+    /// It is recommended for implementations of `advance_mut` to panic if
+    /// `cnt > self.remaining_mut()`. If the implementation does not panic,
+    /// the call must behave as if `cnt == self.remaining_mut()`.
+    ///
+    /// A call with `cnt == 0` should never panic and be a no-op.
+    unsafe fn advance_mut(&mut self, cnt: usize);
+
+    /// Returns true if there is space in `self` for more bytes.
+    ///
+    /// This is equivalent to `self.remaining_mut() != 0`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut dst = [0; 5];
+    /// let mut buf = &mut dst[..];
+    ///
+    /// assert!(buf.has_remaining_mut());
+    ///
+    /// buf.put(&b"hello"[..]);
+    ///
+    /// assert!(!buf.has_remaining_mut());
+    /// ```
+    fn has_remaining_mut(&self) -> bool {
+        self.remaining_mut() > 0
+    }
+
+    /// Returns a mutable slice starting at the current BufMut position and of
+    /// length between 0 and `BufMut::remaining_mut()`. Note that this *can* be shorter than the
+    /// whole remainder of the buffer (this allows non-continuous implementation).
+    ///
+    /// This is a lower level function. Most operations are done with other
+    /// functions.
+    ///
+    /// The returned byte slice may represent uninitialized memory.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = Vec::with_capacity(16);
+    ///
+    /// unsafe {
+    ///     // MaybeUninit::as_mut_ptr
+    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'h');
+    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'e');
+    ///
+    ///     buf.advance_mut(2);
+    ///
+    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'l');
+    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'l');
+    ///     buf.bytes_mut()[2].as_mut_ptr().write(b'o');
+    ///
+    ///     buf.advance_mut(3);
+    /// }
+    ///
+    /// assert_eq!(5, buf.len());
+    /// assert_eq!(buf, b"hello");
+    /// ```
+    ///
+    /// # Implementer notes
+    ///
+    /// This function should never panic. `bytes_mut` should return an empty
+    /// slice **if and only if** `remaining_mut` returns 0. In other words,
+    /// `bytes_mut` returning an empty slice implies that `remaining_mut` will
+    /// return 0 and `remaining_mut` returning 0 implies that `bytes_mut` will
+    /// return an empty slice.
+    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>];
+
+    /// Fills `dst` with potentially multiple mutable slices starting at `self`'s
+    /// current position.
+    ///
+    /// If the `BufMut` is backed by disjoint slices of bytes, `bytes_vectored_mut`
+    /// enables fetching more than one slice at once. `dst` is a slice of
+    /// mutable `IoSliceMut` references, enabling the slice to be directly used with
+    /// [`readv`] without any further conversion. The sum of the lengths of all
+    /// the buffers in `dst` will be less than or equal to
+    /// `Buf::remaining_mut()`.
+    ///
+    /// The entries in `dst` will be overwritten, but the data **contained** by
+    /// the slices **will not** be modified. If `bytes_vectored_mut` does not fill every
+    /// entry in `dst`, then `dst` is guaranteed to contain all remaining slices
+    /// in `self.
+    ///
+    /// This is a lower level function. Most operations are done with other
+    /// functions.
+    ///
+    /// # Implementer notes
+    ///
+    /// This function should never panic. Once the end of the buffer is reached,
+    /// i.e., `BufMut::remaining_mut` returns 0, calls to `bytes_vectored_mut` must
+    /// return 0 without mutating `dst`.
+    ///
+    /// Implementations should also take care to properly handle being called
+    /// with `dst` being a zero length slice.
+    ///
+    /// [`readv`]: http://man7.org/linux/man-pages/man2/readv.2.html
+    #[cfg(feature = "std")]
+    fn bytes_vectored_mut<'a>(&'a mut self, dst: &mut [IoSliceMut<'a>]) -> usize {
+        if dst.is_empty() {
+            return 0;
+        }
+
+        if self.has_remaining_mut() {
+            dst[0] = IoSliceMut::from(self.bytes_mut());
+            1
+        } else {
+            0
+        }
+    }
+
+    /// Transfer bytes into `self` from `src` and advance the cursor by the
+    /// number of bytes written.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    ///
+    /// buf.put_u8(b'h');
+    /// buf.put(&b"ello"[..]);
+    /// buf.put(&b" world"[..]);
+    ///
+    /// assert_eq!(buf, b"hello world");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Panics if `self` does not have enough capacity to contain `src`.
+    fn put<T: super::Buf>(&mut self, mut src: T) where Self: Sized {
+        assert!(self.remaining_mut() >= src.remaining());
+
+        while src.has_remaining() {
+            let l;
+
+            unsafe {
+                let s = src.bytes();
+                let d = self.bytes_mut();
+                l = cmp::min(s.len(), d.len());
+
+                ptr::copy_nonoverlapping(
+                    s.as_ptr(),
+                    d.as_mut_ptr() as *mut u8,
+                    l);
+            }
+
+            src.advance(l);
+            unsafe { self.advance_mut(l); }
+        }
+    }
+
+    /// Transfer bytes into `self` from `src` and advance the cursor by the
+    /// number of bytes written.
+    ///
+    /// `self` must have enough remaining capacity to contain all of `src`.
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut dst = [0; 6];
+    ///
+    /// {
+    ///     let mut buf = &mut dst[..];
+    ///     buf.put_slice(b"hello");
+    ///
+    ///     assert_eq!(1, buf.remaining_mut());
+    /// }
+    ///
+    /// assert_eq!(b"hello\0", &dst);
+    /// ```
+    fn put_slice(&mut self, src: &[u8]) {
+        let mut off = 0;
+
+        assert!(self.remaining_mut() >= src.len(), "buffer overflow; remaining = {}; src = {}", self.remaining_mut(), src.len());
+
+        while off < src.len() {
+            let cnt;
+
+            unsafe {
+                let dst = self.bytes_mut();
+                cnt = cmp::min(dst.len(), src.len() - off);
+
+                ptr::copy_nonoverlapping(
+                    src[off..].as_ptr(),
+                    dst.as_mut_ptr() as *mut u8,
+                    cnt);
+
+                off += cnt;
+
+            }
+
+            unsafe { self.advance_mut(cnt); }
+        }
+    }
+
+    /// Writes an unsigned 8 bit integer to `self`.
+    ///
+    /// The current position is advanced by 1.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u8(0x01);
+    /// assert_eq!(buf, b"\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u8(&mut self, n: u8) {
+        let src = [n];
+        self.put_slice(&src);
+    }
+
+    /// Writes a signed 8 bit integer to `self`.
+    ///
+    /// The current position is advanced by 1.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i8(0x01);
+    /// assert_eq!(buf, b"\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i8(&mut self, n: i8) {
+        let src = [n as u8];
+        self.put_slice(&src)
+    }
+
+    /// Writes an unsigned 16 bit integer to `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u16(0x0809);
+    /// assert_eq!(buf, b"\x08\x09");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u16(&mut self, n: u16) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes an unsigned 16 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u16_le(0x0809);
+    /// assert_eq!(buf, b"\x09\x08");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u16_le(&mut self, n: u16) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes a signed 16 bit integer to `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i16(0x0809);
+    /// assert_eq!(buf, b"\x08\x09");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i16(&mut self, n: i16) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes a signed 16 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i16_le(0x0809);
+    /// assert_eq!(buf, b"\x09\x08");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i16_le(&mut self, n: i16) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes an unsigned 32 bit integer to `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u32(0x0809A0A1);
+    /// assert_eq!(buf, b"\x08\x09\xA0\xA1");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u32(&mut self, n: u32) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes an unsigned 32 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u32_le(0x0809A0A1);
+    /// assert_eq!(buf, b"\xA1\xA0\x09\x08");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u32_le(&mut self, n: u32) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes a signed 32 bit integer to `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i32(0x0809A0A1);
+    /// assert_eq!(buf, b"\x08\x09\xA0\xA1");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i32(&mut self, n: i32) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes a signed 32 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i32_le(0x0809A0A1);
+    /// assert_eq!(buf, b"\xA1\xA0\x09\x08");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i32_le(&mut self, n: i32) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes an unsigned 64 bit integer to `self` in the big-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u64(0x0102030405060708);
+    /// assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u64(&mut self, n: u64) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes an unsigned 64 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u64_le(0x0102030405060708);
+    /// assert_eq!(buf, b"\x08\x07\x06\x05\x04\x03\x02\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u64_le(&mut self, n: u64) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes a signed 64 bit integer to `self` in the big-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i64(0x0102030405060708);
+    /// assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i64(&mut self, n: i64) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes a signed 64 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i64_le(0x0102030405060708);
+    /// assert_eq!(buf, b"\x08\x07\x06\x05\x04\x03\x02\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i64_le(&mut self, n: i64) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes an unsigned 128 bit integer to `self` in the big-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u128(0x01020304050607080910111213141516);
+    /// assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u128(&mut self, n: u128) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes an unsigned 128 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u128_le(0x01020304050607080910111213141516);
+    /// assert_eq!(buf, b"\x16\x15\x14\x13\x12\x11\x10\x09\x08\x07\x06\x05\x04\x03\x02\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u128_le(&mut self, n: u128) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes a signed 128 bit integer to `self` in the big-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i128(0x01020304050607080910111213141516);
+    /// assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i128(&mut self, n: i128) {
+        self.put_slice(&n.to_be_bytes())
+    }
+
+    /// Writes a signed 128 bit integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i128_le(0x01020304050607080910111213141516);
+    /// assert_eq!(buf, b"\x16\x15\x14\x13\x12\x11\x10\x09\x08\x07\x06\x05\x04\x03\x02\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i128_le(&mut self, n: i128) {
+        self.put_slice(&n.to_le_bytes())
+    }
+
+    /// Writes an unsigned n-byte integer to `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_uint(0x010203, 3);
+    /// assert_eq!(buf, b"\x01\x02\x03");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_uint(&mut self, n: u64, nbytes: usize) {
+        self.put_slice(&n.to_be_bytes()[mem::size_of_val(&n) - nbytes..]);
+    }
+
+    /// Writes an unsigned n-byte integer to `self` in the little-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_uint_le(0x010203, 3);
+    /// assert_eq!(buf, b"\x03\x02\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_uint_le(&mut self, n: u64, nbytes: usize) {
+        self.put_slice(&n.to_le_bytes()[0..nbytes]);
+    }
+
+    /// Writes a signed n-byte integer to `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_int(0x010203, 3);
+    /// assert_eq!(buf, b"\x01\x02\x03");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_int(&mut self, n: i64, nbytes: usize) {
+        self.put_slice(&n.to_be_bytes()[mem::size_of_val(&n) - nbytes..]);
+    }
+
+    /// Writes a signed n-byte integer to `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_int_le(0x010203, 3);
+    /// assert_eq!(buf, b"\x03\x02\x01");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_int_le(&mut self, n: i64, nbytes: usize) {
+        self.put_slice(&n.to_le_bytes()[0..nbytes]);
+    }
+
+    /// Writes  an IEEE754 single-precision (4 bytes) floating point number to
+    /// `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_f32(1.2f32);
+    /// assert_eq!(buf, b"\x3F\x99\x99\x9A");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_f32(&mut self, n: f32) {
+        self.put_u32(n.to_bits());
+    }
+
+    /// Writes  an IEEE754 single-precision (4 bytes) floating point number to
+    /// `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_f32_le(1.2f32);
+    /// assert_eq!(buf, b"\x9A\x99\x99\x3F");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_f32_le(&mut self, n: f32) {
+        self.put_u32_le(n.to_bits());
+    }
+
+    /// Writes  an IEEE754 double-precision (8 bytes) floating point number to
+    /// `self` in big-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_f64(1.2f64);
+    /// assert_eq!(buf, b"\x3F\xF3\x33\x33\x33\x33\x33\x33");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_f64(&mut self, n: f64) {
+        self.put_u64(n.to_bits());
+    }
+
+    /// Writes  an IEEE754 double-precision (8 bytes) floating point number to
+    /// `self` in little-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_f64_le(1.2f64);
+    /// assert_eq!(buf, b"\x33\x33\x33\x33\x33\x33\xF3\x3F");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_f64_le(&mut self, n: f64) {
+        self.put_u64_le(n.to_bits());
+    }
+}
+
+macro_rules! deref_forward_bufmut {
+    () => (
+    fn remaining_mut(&self) -> usize {
+        (**self).remaining_mut()
+    }
+
+    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+        (**self).bytes_mut()
+    }
+
+    #[cfg(feature = "std")]
+    fn bytes_vectored_mut<'b>(&'b mut self, dst: &mut [IoSliceMut<'b>]) -> usize {
+        (**self).bytes_vectored_mut(dst)
+    }
+
+    unsafe fn advance_mut(&mut self, cnt: usize) {
+        (**self).advance_mut(cnt)
+    }
+
+    fn put_slice(&mut self, src: &[u8]) {
+        (**self).put_slice(src)
+    }
+
+    fn put_u8(&mut self, n: u8) {
+        (**self).put_u8(n)
+    }
+
+    fn put_i8(&mut self, n: i8) {
+        (**self).put_i8(n)
+    }
+
+    fn put_u16(&mut self, n: u16) {
+        (**self).put_u16(n)
+    }
+
+    fn put_u16_le(&mut self, n: u16) {
+        (**self).put_u16_le(n)
+    }
+
+    fn put_i16(&mut self, n: i16) {
+        (**self).put_i16(n)
+    }
+
+    fn put_i16_le(&mut self, n: i16) {
+        (**self).put_i16_le(n)
+    }
+
+    fn put_u32(&mut self, n: u32) {
+        (**self).put_u32(n)
+    }
+
+    fn put_u32_le(&mut self, n: u32) {
+        (**self).put_u32_le(n)
+    }
+
+    fn put_i32(&mut self, n: i32) {
+        (**self).put_i32(n)
+    }
+
+    fn put_i32_le(&mut self, n: i32) {
+        (**self).put_i32_le(n)
+    }
+
+    fn put_u64(&mut self, n: u64) {
+        (**self).put_u64(n)
+    }
+
+    fn put_u64_le(&mut self, n: u64) {
+        (**self).put_u64_le(n)
+    }
+
+    fn put_i64(&mut self, n: i64) {
+        (**self).put_i64(n)
+    }
+
+    fn put_i64_le(&mut self, n: i64) {
+        (**self).put_i64_le(n)
+    }
+    )
+}
+
+impl<T: BufMut + ?Sized> BufMut for &mut T {
+    deref_forward_bufmut!();
+}
+
+impl<T: BufMut + ?Sized> BufMut for Box<T> {
+    deref_forward_bufmut!();
+}
+
+impl BufMut for &mut [u8] {
+    #[inline]
+    fn remaining_mut(&self) -> usize {
+        self.len()
+    }
+
+    #[inline]
+    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+        // MaybeUninit is repr(transparent), so safe to transmute
+        unsafe { mem::transmute(&mut **self) }
+    }
+
+    #[inline]
+    unsafe fn advance_mut(&mut self, cnt: usize) {
+        // Lifetime dance taken from `impl Write for &mut [u8]`.
+        let (_, b) = core::mem::replace(self, &mut []).split_at_mut(cnt);
+        *self = b;
+    }
+}
+
+impl BufMut for Vec<u8> {
+    #[inline]
+    fn remaining_mut(&self) -> usize {
+        usize::MAX - self.len()
+    }
+
+    #[inline]
+    unsafe fn advance_mut(&mut self, cnt: usize) {
+        let len = self.len();
+        let remaining = self.capacity() - len;
+        if cnt > remaining {
+            // Reserve additional capacity, and ensure that the total length
+            // will not overflow usize.
+            self.reserve(cnt);
+        }
+
+        self.set_len(len + cnt);
+    }
+
+    #[inline]
+    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+        use core::slice;
+
+        if self.capacity() == self.len() {
+            self.reserve(64); // Grow the vec
+        }
+
+        let cap = self.capacity();
+        let len = self.len();
+
+        let ptr = self.as_mut_ptr() as *mut MaybeUninit<u8>;
+        unsafe {
+            &mut slice::from_raw_parts_mut(ptr, cap)[len..]
+        }
+    }
+
+    // Specialize these methods so they can skip checking `remaining_mut`
+    // and `advance_mut`.
+
+    fn put<T: super::Buf>(&mut self, mut src: T) where Self: Sized {
+        // In case the src isn't contiguous, reserve upfront
+        self.reserve(src.remaining());
+
+        while src.has_remaining() {
+            let l;
+
+            // a block to contain the src.bytes() borrow
+            {
+                let s = src.bytes();
+                l = s.len();
+                self.extend_from_slice(s);
+            }
+
+            src.advance(l);
+        }
+    }
+
+    fn put_slice(&mut self, src: &[u8]) {
+        self.extend_from_slice(src);
+    }
+}
+
+// The existence of this function makes the compiler catch if the BufMut
+// trait is "object-safe" or not.
+fn _assert_trait_object(_b: &dyn BufMut) {}
+
+// ===== impl IoSliceMut =====
+
+/// A buffer type used for `readv`.
+///
+/// This is a wrapper around an `std::io::IoSliceMut`, but does not expose
+/// the inner bytes in a safe API, as they may point at uninitialized memory.
+///
+/// This is `repr(transparent)` of the `std::io::IoSliceMut`, so it is valid to
+/// transmute them. However, as the memory might be uninitialized, care must be
+/// taken to not *read* the internal bytes, only *write* to them.
+#[repr(transparent)]
+#[cfg(feature = "std")]
+pub struct IoSliceMut<'a>(std::io::IoSliceMut<'a>);
+
+#[cfg(feature = "std")]
+impl fmt::Debug for IoSliceMut<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("IoSliceMut")
+            .field("len", &self.0.len())
+            .finish()
+    }
+}
+
+#[cfg(feature = "std")]
+impl<'a> From<&'a mut [u8]> for IoSliceMut<'a> {
+    fn from(buf: &'a mut [u8]) -> IoSliceMut<'a> {
+        IoSliceMut(std::io::IoSliceMut::new(buf))
+    }
+}
+
+#[cfg(feature = "std")]
+impl<'a> From<&'a mut [MaybeUninit<u8>]> for IoSliceMut<'a> {
+    fn from(buf: &'a mut [MaybeUninit<u8>]) -> IoSliceMut<'a> {
+        IoSliceMut(std::io::IoSliceMut::new(unsafe {
+            // We don't look at the contents, and `std::io::IoSliceMut`
+            // doesn't either.
+            mem::transmute::<&'a mut [MaybeUninit<u8>], &'a mut [u8]>(buf)
+        }))
+    }
+}
diff --git a/src/buf/ext/chain.rs b/src/buf/ext/chain.rs
new file mode 100644
index 0000000..a1ec597
--- /dev/null
+++ b/src/buf/ext/chain.rs
@@ -0,0 +1,234 @@
+use crate::{Buf, BufMut};
+use crate::buf::IntoIter;
+
+use core::mem::MaybeUninit;
+
+#[cfg(feature = "std")]
+use std::io::{IoSlice};
+#[cfg(feature = "std")]
+use crate::buf::IoSliceMut;
+
+/// A `Chain` sequences two buffers.
+///
+/// `Chain` is an adapter that links two underlying buffers and provides a
+/// continuous view across both buffers. It is able to sequence either immutable
+/// buffers ([`Buf`] values) or mutable buffers ([`BufMut`] values).
+///
+/// This struct is generally created by calling [`Buf::chain`]. Please see that
+/// function's documentation for more detail.
+///
+/// # Examples
+///
+/// ```
+/// use bytes::{Bytes, Buf, buf::BufExt};
+///
+/// let mut buf = (&b"hello "[..])
+///     .chain(&b"world"[..]);
+///
+/// let full: Bytes = buf.to_bytes();
+/// assert_eq!(full[..], b"hello world"[..]);
+/// ```
+///
+/// [`Buf::chain`]: trait.Buf.html#method.chain
+/// [`Buf`]: trait.Buf.html
+/// [`BufMut`]: trait.BufMut.html
+#[derive(Debug)]
+pub struct Chain<T, U> {
+    a: T,
+    b: U,
+}
+
+impl<T, U> Chain<T, U> {
+    /// Creates a new `Chain` sequencing the provided values.
+    pub fn new(a: T, b: U) -> Chain<T, U> {
+        Chain {
+            a,
+            b,
+        }
+    }
+
+    /// Gets a reference to the first underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::BufExt;
+    ///
+    /// let buf = (&b"hello"[..])
+    ///     .chain(&b"world"[..]);
+    ///
+    /// assert_eq!(buf.first_ref()[..], b"hello"[..]);
+    /// ```
+    pub fn first_ref(&self) -> &T {
+        &self.a
+    }
+
+    /// Gets a mutable reference to the first underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, buf::BufExt};
+    ///
+    /// let mut buf = (&b"hello"[..])
+    ///     .chain(&b"world"[..]);
+    ///
+    /// buf.first_mut().advance(1);
+    ///
+    /// let full = buf.to_bytes();
+    /// assert_eq!(full, b"elloworld"[..]);
+    /// ```
+    pub fn first_mut(&mut self) -> &mut T {
+        &mut self.a
+    }
+
+    /// Gets a reference to the last underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::BufExt;
+    ///
+    /// let buf = (&b"hello"[..])
+    ///     .chain(&b"world"[..]);
+    ///
+    /// assert_eq!(buf.last_ref()[..], b"world"[..]);
+    /// ```
+    pub fn last_ref(&self) -> &U {
+        &self.b
+    }
+
+    /// Gets a mutable reference to the last underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, buf::BufExt};
+    ///
+    /// let mut buf = (&b"hello "[..])
+    ///     .chain(&b"world"[..]);
+    ///
+    /// buf.last_mut().advance(1);
+    ///
+    /// let full = buf.to_bytes();
+    /// assert_eq!(full, b"hello orld"[..]);
+    /// ```
+    pub fn last_mut(&mut self) -> &mut U {
+        &mut self.b
+    }
+
+    /// Consumes this `Chain`, returning the underlying values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::BufExt;
+    ///
+    /// let chain = (&b"hello"[..])
+    ///     .chain(&b"world"[..]);
+    ///
+    /// let (first, last) = chain.into_inner();
+    /// assert_eq!(first[..], b"hello"[..]);
+    /// assert_eq!(last[..], b"world"[..]);
+    /// ```
+    pub fn into_inner(self) -> (T, U) {
+        (self.a, self.b)
+    }
+}
+
+impl<T, U> Buf for Chain<T, U>
+    where T: Buf,
+          U: Buf,
+{
+    fn remaining(&self) -> usize {
+        self.a.remaining() + self.b.remaining()
+    }
+
+    fn bytes(&self) -> &[u8] {
+        if self.a.has_remaining() {
+            self.a.bytes()
+        } else {
+            self.b.bytes()
+        }
+    }
+
+    fn advance(&mut self, mut cnt: usize) {
+        let a_rem = self.a.remaining();
+
+        if a_rem != 0 {
+            if a_rem >= cnt {
+                self.a.advance(cnt);
+                return;
+            }
+
+            // Consume what is left of a
+            self.a.advance(a_rem);
+
+            cnt -= a_rem;
+        }
+
+        self.b.advance(cnt);
+    }
+
+    #[cfg(feature = "std")]
+    fn bytes_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
+        let mut n = self.a.bytes_vectored(dst);
+        n += self.b.bytes_vectored(&mut dst[n..]);
+        n
+    }
+}
+
+impl<T, U> BufMut for Chain<T, U>
+    where T: BufMut,
+          U: BufMut,
+{
+    fn remaining_mut(&self) -> usize {
+        self.a.remaining_mut() + self.b.remaining_mut()
+    }
+
+    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+        if self.a.has_remaining_mut() {
+            self.a.bytes_mut()
+        } else {
+            self.b.bytes_mut()
+        }
+    }
+
+    unsafe fn advance_mut(&mut self, mut cnt: usize) {
+        let a_rem = self.a.remaining_mut();
+
+        if a_rem != 0 {
+            if a_rem >= cnt {
+                self.a.advance_mut(cnt);
+                return;
+            }
+
+            // Consume what is left of a
+            self.a.advance_mut(a_rem);
+
+            cnt -= a_rem;
+        }
+
+        self.b.advance_mut(cnt);
+    }
+
+    #[cfg(feature = "std")]
+    fn bytes_vectored_mut<'a>(&'a mut self, dst: &mut [IoSliceMut<'a>]) -> usize {
+        let mut n = self.a.bytes_vectored_mut(dst);
+        n += self.b.bytes_vectored_mut(&mut dst[n..]);
+        n
+    }
+}
+
+impl<T, U> IntoIterator for Chain<T, U>
+where
+    T: Buf,
+    U: Buf,
+{
+    type Item = u8;
+    type IntoIter = IntoIter<Chain<T, U>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        IntoIter::new(self)
+    }
+}
diff --git a/src/buf/ext/limit.rs b/src/buf/ext/limit.rs
new file mode 100644
index 0000000..f86e011
--- /dev/null
+++ b/src/buf/ext/limit.rs
@@ -0,0 +1,77 @@
+use crate::BufMut;
+
+use core::{cmp, mem::MaybeUninit};
+
+/// A `BufMut` adapter which limits the amount of bytes that can be written
+/// to an underlying buffer.
+#[derive(Debug)]
+pub struct Limit<T> {
+    inner: T,
+    limit: usize,
+}
+
+pub(super) fn new<T>(inner: T, limit: usize) -> Limit<T> {
+    Limit {
+        inner,
+        limit,
+    }
+}
+
+impl<T> Limit<T> {
+    /// Consumes this `Limit`, returning the underlying value.
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    /// Gets a reference to the underlying `BufMut`.
+    ///
+    /// It is inadvisable to directly write to the underlying `BufMut`.
+    pub fn get_ref(&self) -> &T {
+        &self.inner
+    }
+
+    /// Gets a mutable reference to the underlying `BufMut`.
+    ///
+    /// It is inadvisable to directly write to the underlying `BufMut`.
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+
+    /// Returns the maximum number of bytes that can be written
+    ///
+    /// # Note
+    ///
+    /// If the inner `BufMut` has fewer bytes than indicated by this method then
+    /// that is the actual number of available bytes.
+    pub fn limit(&self) -> usize {
+        self.limit
+    }
+
+    /// Sets the maximum number of bytes that can be written.
+    ///
+    /// # Note
+    ///
+    /// If the inner `BufMut` has fewer bytes than `lim` then that is the actual
+    /// number of available bytes.
+    pub fn set_limit(&mut self, lim: usize) {
+        self.limit = lim
+    }
+}
+
+impl<T: BufMut> BufMut for Limit<T> {
+    fn remaining_mut(&self) -> usize {
+        cmp::min(self.inner.remaining_mut(), self.limit)
+    }
+
+    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+        let bytes = self.inner.bytes_mut();
+        let end = cmp::min(bytes.len(), self.limit);
+        &mut bytes[..end]
+    }
+
+    unsafe fn advance_mut(&mut self, cnt: usize) {
+        assert!(cnt <= self.limit);
+        self.inner.advance_mut(cnt);
+        self.limit -= cnt;
+    }
+}
diff --git a/src/buf/ext/mod.rs b/src/buf/ext/mod.rs
new file mode 100644
index 0000000..7b0bdab
--- /dev/null
+++ b/src/buf/ext/mod.rs
@@ -0,0 +1,176 @@
+//! Extra utilities for `Buf` and `BufMut` types.
+
+use super::{Buf, BufMut};
+
+mod chain;
+mod limit;
+#[cfg(feature = "std")]
+mod reader;
+mod take;
+#[cfg(feature = "std")]
+mod writer;
+
+pub use self::limit::Limit;
+pub use self::take::Take;
+pub use self::chain::Chain;
+
+#[cfg(feature = "std")]
+pub use self::{reader::Reader, writer::Writer};
+
+/// Extra methods for implementations of `Buf`.
+pub trait BufExt: Buf {
+    /// Creates an adaptor which will read at most `limit` bytes from `self`.
+    ///
+    /// This function returns a new instance of `Buf` which will read at most
+    /// `limit` bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, BufMut, buf::BufExt};
+    ///
+    /// let mut buf = b"hello world"[..].take(5);
+    /// let mut dst = vec![];
+    ///
+    /// dst.put(&mut buf);
+    /// assert_eq!(dst, b"hello");
+    ///
+    /// let mut buf = buf.into_inner();
+    /// dst.clear();
+    /// dst.put(&mut buf);
+    /// assert_eq!(dst, b" world");
+    /// ```
+    fn take(self, limit: usize) -> Take<Self>
+        where Self: Sized
+    {
+        take::new(self, limit)
+    }
+
+    /// Creates an adaptor which will chain this buffer with another.
+    ///
+    /// The returned `Buf` instance will first consume all bytes from `self`.
+    /// Afterwards the output is equivalent to the output of next.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, buf::BufExt};
+    ///
+    /// let mut chain = b"hello "[..].chain(&b"world"[..]);
+    ///
+    /// let full = chain.to_bytes();
+    /// assert_eq!(full.bytes(), b"hello world");
+    /// ```
+    fn chain<U: Buf>(self, next: U) -> Chain<Self, U>
+        where Self: Sized
+    {
+        Chain::new(self, next)
+    }
+
+    /// Creates an adaptor which implements the `Read` trait for `self`.
+    ///
+    /// This function returns a new value which implements `Read` by adapting
+    /// the `Read` trait functions to the `Buf` trait functions. Given that
+    /// `Buf` operations are infallible, none of the `Read` functions will
+    /// return with `Err`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, Bytes, buf::BufExt};
+    /// use std::io::Read;
+    ///
+    /// let buf = Bytes::from("hello world");
+    ///
+    /// let mut reader = buf.reader();
+    /// let mut dst = [0; 1024];
+    ///
+    /// let num = reader.read(&mut dst).unwrap();
+    ///
+    /// assert_eq!(11, num);
+    /// assert_eq!(&dst[..11], &b"hello world"[..]);
+    /// ```
+    #[cfg(feature = "std")]
+    fn reader(self) -> Reader<Self> where Self: Sized {
+        reader::new(self)
+    }
+}
+
+impl<B: Buf + ?Sized> BufExt for B {}
+
+/// Extra methods for implementations of `BufMut`.
+pub trait BufMutExt: BufMut {
+    /// Creates an adaptor which can write at most `limit` bytes to `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BufMut, buf::BufMutExt};
+    ///
+    /// let arr = &mut [0u8; 128][..];
+    /// assert_eq!(arr.remaining_mut(), 128);
+    ///
+    /// let dst = arr.limit(10);
+    /// assert_eq!(dst.remaining_mut(), 10);
+    /// ```
+    fn limit(self, limit: usize) -> Limit<Self>
+        where Self: Sized
+    {
+        limit::new(self, limit)
+    }
+
+    /// Creates an adaptor which implements the `Write` trait for `self`.
+    ///
+    /// This function returns a new value which implements `Write` by adapting
+    /// the `Write` trait functions to the `BufMut` trait functions. Given that
+    /// `BufMut` operations are infallible, none of the `Write` functions will
+    /// return with `Err`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BufMut, buf::BufMutExt};
+    /// use std::io::Write;
+    ///
+    /// let mut buf = vec![].writer();
+    ///
+    /// let num = buf.write(&b"hello world"[..]).unwrap();
+    /// assert_eq!(11, num);
+    ///
+    /// let buf = buf.into_inner();
+    ///
+    /// assert_eq!(*buf, b"hello world"[..]);
+    /// ```
+    #[cfg(feature = "std")]
+    fn writer(self) -> Writer<Self> where Self: Sized {
+        writer::new(self)
+    }
+
+    /// Creates an adapter which will chain this buffer with another.
+    ///
+    /// The returned `BufMut` instance will first write to all bytes from
+    /// `self`. Afterwards, it will write to `next`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BufMut, buf::BufMutExt};
+    ///
+    /// let mut a = [0u8; 5];
+    /// let mut b = [0u8; 6];
+    ///
+    /// let mut chain = (&mut a[..]).chain_mut(&mut b[..]);
+    ///
+    /// chain.put_slice(b"hello world");
+    ///
+    /// assert_eq!(&a[..], b"hello");
+    /// assert_eq!(&b[..], b" world");
+    /// ```
+    fn chain_mut<U: BufMut>(self, next: U) -> Chain<Self, U>
+        where Self: Sized
+    {
+        Chain::new(self, next)
+    }
+}
+
+impl<B: BufMut + ?Sized> BufMutExt for B {}
diff --git a/src/buf/ext/reader.rs b/src/buf/ext/reader.rs
new file mode 100644
index 0000000..e38103b
--- /dev/null
+++ b/src/buf/ext/reader.rs
@@ -0,0 +1,81 @@
+use crate::{Buf};
+
+use std::{cmp, io};
+
+/// A `Buf` adapter which implements `io::Read` for the inner value.
+///
+/// This struct is generally created by calling `reader()` on `Buf`. See
+/// documentation of [`reader()`](trait.Buf.html#method.reader) for more
+/// details.
+#[derive(Debug)]
+pub struct Reader<B> {
+    buf: B,
+}
+
+pub fn new<B>(buf: B) -> Reader<B> {
+    Reader { buf }
+}
+
+impl<B: Buf> Reader<B> {
+    /// Gets a reference to the underlying `Buf`.
+    ///
+    /// It is inadvisable to directly read from the underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::buf::BufExt;
+    ///
+    /// let mut buf = b"hello world".reader();
+    ///
+    /// assert_eq!(b"hello world", buf.get_ref());
+    /// ```
+    pub fn get_ref(&self) -> &B {
+        &self.buf
+    }
+
+    /// Gets a mutable reference to the underlying `Buf`.
+    ///
+    /// It is inadvisable to directly read from the underlying `Buf`.
+    pub fn get_mut(&mut self) -> &mut B {
+        &mut self.buf
+    }
+
+    /// Consumes this `Reader`, returning the underlying value.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, buf::BufExt};
+    /// use std::io;
+    ///
+    /// let mut buf = b"hello world".reader();
+    /// let mut dst = vec![];
+    ///
+    /// io::copy(&mut buf, &mut dst).unwrap();
+    ///
+    /// let buf = buf.into_inner();
+    /// assert_eq!(0, buf.remaining());
+    /// ```
+    pub fn into_inner(self) -> B {
+        self.buf
+    }
+}
+
+impl<B: Buf + Sized> io::Read for Reader<B> {
+    fn read(&mut self, dst: &mut [u8]) -> io::Result<usize> {
+        let len = cmp::min(self.buf.remaining(), dst.len());
+
+        Buf::copy_to_slice(&mut self.buf, &mut dst[0..len]);
+        Ok(len)
+    }
+}
+
+impl<B: Buf + Sized> io::BufRead for Reader<B> {
+    fn fill_buf(&mut self) -> io::Result<&[u8]> {
+        Ok(self.buf.bytes())
+    }
+    fn consume(&mut self, amt: usize) {
+        self.buf.advance(amt)
+    }
+}
diff --git a/src/buf/ext/take.rs b/src/buf/ext/take.rs
new file mode 100644
index 0000000..6fc4ffc
--- /dev/null
+++ b/src/buf/ext/take.rs
@@ -0,0 +1,150 @@
+use crate::Buf;
+
+use core::cmp;
+
+/// A `Buf` adapter which limits the bytes read from an underlying buffer.
+///
+/// This struct is generally created by calling `take()` on `Buf`. See
+/// documentation of [`take()`](trait.Buf.html#method.take) for more details.
+#[derive(Debug)]
+pub struct Take<T> {
+    inner: T,
+    limit: usize,
+}
+
+pub fn new<T>(inner: T, limit: usize) -> Take<T> {
+    Take {
+        inner,
+        limit,
+    }
+}
+
+impl<T> Take<T> {
+    /// Consumes this `Take`, returning the underlying value.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::buf::{Buf, BufMut, BufExt};
+    ///
+    /// let mut buf = b"hello world".take(2);
+    /// let mut dst = vec![];
+    ///
+    /// dst.put(&mut buf);
+    /// assert_eq!(*dst, b"he"[..]);
+    ///
+    /// let mut buf = buf.into_inner();
+    ///
+    /// dst.clear();
+    /// dst.put(&mut buf);
+    /// assert_eq!(*dst, b"llo world"[..]);
+    /// ```
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    /// Gets a reference to the underlying `Buf`.
+    ///
+    /// It is inadvisable to directly read from the underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, buf::BufExt};
+    ///
+    /// let mut buf = b"hello world".take(2);
+    ///
+    /// assert_eq!(11, buf.get_ref().remaining());
+    /// ```
+    pub fn get_ref(&self) -> &T {
+        &self.inner
+    }
+
+    /// Gets a mutable reference to the underlying `Buf`.
+    ///
+    /// It is inadvisable to directly read from the underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, BufMut, buf::BufExt};
+    ///
+    /// let mut buf = b"hello world".take(2);
+    /// let mut dst = vec![];
+    ///
+    /// buf.get_mut().advance(2);
+    ///
+    /// dst.put(&mut buf);
+    /// assert_eq!(*dst, b"ll"[..]);
+    /// ```
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+
+    /// Returns the maximum number of bytes that can be read.
+    ///
+    /// # Note
+    ///
+    /// If the inner `Buf` has fewer bytes than indicated by this method then
+    /// that is the actual number of available bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, buf::BufExt};
+    ///
+    /// let mut buf = b"hello world".take(2);
+    ///
+    /// assert_eq!(2, buf.limit());
+    /// assert_eq!(b'h', buf.get_u8());
+    /// assert_eq!(1, buf.limit());
+    /// ```
+    pub fn limit(&self) -> usize {
+        self.limit
+    }
+
+    /// Sets the maximum number of bytes that can be read.
+    ///
+    /// # Note
+    ///
+    /// If the inner `Buf` has fewer bytes than `lim` then that is the actual
+    /// number of available bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, BufMut, buf::BufExt};
+    ///
+    /// let mut buf = b"hello world".take(2);
+    /// let mut dst = vec![];
+    ///
+    /// dst.put(&mut buf);
+    /// assert_eq!(*dst, b"he"[..]);
+    ///
+    /// dst.clear();
+    ///
+    /// buf.set_limit(3);
+    /// dst.put(&mut buf);
+    /// assert_eq!(*dst, b"llo"[..]);
+    /// ```
+    pub fn set_limit(&mut self, lim: usize) {
+        self.limit = lim
+    }
+}
+
+impl<T: Buf> Buf for Take<T> {
+    fn remaining(&self) -> usize {
+        cmp::min(self.inner.remaining(), self.limit)
+    }
+
+    fn bytes(&self) -> &[u8] {
+        let bytes = self.inner.bytes();
+        &bytes[..cmp::min(bytes.len(), self.limit)]
+    }
+
+    fn advance(&mut self, cnt: usize) {
+        assert!(cnt <= self.limit);
+        self.inner.advance(cnt);
+        self.limit -= cnt;
+    }
+}
diff --git a/src/buf/ext/writer.rs b/src/buf/ext/writer.rs
new file mode 100644
index 0000000..1418418
--- /dev/null
+++ b/src/buf/ext/writer.rs
@@ -0,0 +1,88 @@
+use crate::BufMut;
+
+use std::{cmp, io};
+
+/// A `BufMut` adapter which implements `io::Write` for the inner value.
+///
+/// This struct is generally created by calling `writer()` on `BufMut`. See
+/// documentation of [`writer()`](trait.BufMut.html#method.writer) for more
+/// details.
+#[derive(Debug)]
+pub struct Writer<B> {
+    buf: B,
+}
+
+pub fn new<B>(buf: B) -> Writer<B> {
+    Writer { buf }
+}
+
+impl<B: BufMut> Writer<B> {
+    /// Gets a reference to the underlying `BufMut`.
+    ///
+    /// It is inadvisable to directly write to the underlying `BufMut`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::buf::BufMutExt;
+    ///
+    /// let mut buf = Vec::with_capacity(1024).writer();
+    ///
+    /// assert_eq!(1024, buf.get_ref().capacity());
+    /// ```
+    pub fn get_ref(&self) -> &B {
+        &self.buf
+    }
+
+    /// Gets a mutable reference to the underlying `BufMut`.
+    ///
+    /// It is inadvisable to directly write to the underlying `BufMut`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::buf::BufMutExt;
+    ///
+    /// let mut buf = vec![].writer();
+    ///
+    /// buf.get_mut().reserve(1024);
+    ///
+    /// assert_eq!(1024, buf.get_ref().capacity());
+    /// ```
+    pub fn get_mut(&mut self) -> &mut B {
+        &mut self.buf
+    }
+
+    /// Consumes this `Writer`, returning the underlying value.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::buf::BufMutExt;
+    /// use std::io;
+    ///
+    /// let mut buf = vec![].writer();
+    /// let mut src = &b"hello world"[..];
+    ///
+    /// io::copy(&mut src, &mut buf).unwrap();
+    ///
+    /// let buf = buf.into_inner();
+    /// assert_eq!(*buf, b"hello world"[..]);
+    /// ```
+    pub fn into_inner(self) -> B {
+        self.buf
+    }
+}
+
+impl<B: BufMut + Sized> io::Write for Writer<B> {
+    fn write(&mut self, src: &[u8]) -> io::Result<usize> {
+        let n = cmp::min(self.buf.remaining_mut(), src.len());
+
+        self.buf.put(&src[0..n]);
+        Ok(n)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
diff --git a/src/buf/iter.rs b/src/buf/iter.rs
new file mode 100644
index 0000000..1af421a
--- /dev/null
+++ b/src/buf/iter.rs
@@ -0,0 +1,133 @@
+use crate::Buf;
+
+/// Iterator over the bytes contained by the buffer.
+///
+/// This struct is created by the [`iter`] method on [`Buf`].
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use bytes::{Buf, Bytes};
+///
+/// let buf = Bytes::from(&b"abc"[..]);
+/// let mut iter = buf.into_iter();
+///
+/// assert_eq!(iter.next(), Some(b'a'));
+/// assert_eq!(iter.next(), Some(b'b'));
+/// assert_eq!(iter.next(), Some(b'c'));
+/// assert_eq!(iter.next(), None);
+/// ```
+///
+/// [`iter`]: trait.Buf.html#method.iter
+/// [`Buf`]: trait.Buf.html
+#[derive(Debug)]
+pub struct IntoIter<T> {
+    inner: T,
+}
+
+impl<T> IntoIter<T> {
+    /// Creates an iterator over the bytes contained by the buffer.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, Bytes};
+    /// use bytes::buf::IntoIter;
+    ///
+    /// let buf = Bytes::from_static(b"abc");
+    /// let mut iter = IntoIter::new(buf);
+    ///
+    /// assert_eq!(iter.next(), Some(b'a'));
+    /// assert_eq!(iter.next(), Some(b'b'));
+    /// assert_eq!(iter.next(), Some(b'c'));
+    /// assert_eq!(iter.next(), None);
+    /// ```
+    pub fn new(inner: T) -> IntoIter<T> {
+        IntoIter { inner }
+    }
+    /// Consumes this `IntoIter`, returning the underlying value.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, Bytes};
+    ///
+    /// let buf = Bytes::from(&b"abc"[..]);
+    /// let mut iter = buf.into_iter();
+    ///
+    /// assert_eq!(iter.next(), Some(b'a'));
+    ///
+    /// let buf = iter.into_inner();
+    /// assert_eq!(2, buf.remaining());
+    /// ```
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    /// Gets a reference to the underlying `Buf`.
+    ///
+    /// It is inadvisable to directly read from the underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, Bytes};
+    ///
+    /// let buf = Bytes::from(&b"abc"[..]);
+    /// let mut iter = buf.into_iter();
+    ///
+    /// assert_eq!(iter.next(), Some(b'a'));
+    ///
+    /// assert_eq!(2, iter.get_ref().remaining());
+    /// ```
+    pub fn get_ref(&self) -> &T {
+        &self.inner
+    }
+
+    /// Gets a mutable reference to the underlying `Buf`.
+    ///
+    /// It is inadvisable to directly read from the underlying `Buf`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use bytes::{Buf, BytesMut};
+    ///
+    /// let buf = BytesMut::from(&b"abc"[..]);
+    /// let mut iter = buf.into_iter();
+    ///
+    /// assert_eq!(iter.next(), Some(b'a'));
+    ///
+    /// iter.get_mut().advance(1);
+    ///
+    /// assert_eq!(iter.next(), Some(b'c'));
+    /// ```
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+}
+
+
+impl<T: Buf> Iterator for IntoIter<T> {
+    type Item = u8;
+
+    fn next(&mut self) -> Option<u8> {
+        if !self.inner.has_remaining() {
+            return None;
+        }
+
+        let b = self.inner.bytes()[0];
+        self.inner.advance(1);
+
+        Some(b)
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let rem = self.inner.remaining();
+        (rem, Some(rem))
+    }
+}
+
+impl<T: Buf> ExactSizeIterator for IntoIter<T> { }
diff --git a/src/buf/mod.rs b/src/buf/mod.rs
new file mode 100644
index 0000000..d4538f2
--- /dev/null
+++ b/src/buf/mod.rs
@@ -0,0 +1,31 @@
+//! Utilities for working with buffers.
+//!
+//! A buffer is any structure that contains a sequence of bytes. The bytes may
+//! or may not be stored in contiguous memory. This module contains traits used
+//! to abstract over buffers as well as utilities for working with buffer types.
+//!
+//! # `Buf`, `BufMut`
+//!
+//! These are the two foundational traits for abstractly working with buffers.
+//! They can be thought as iterators for byte structures. They offer additional
+//! performance over `Iterator` by providing an API optimized for byte slices.
+//!
+//! See [`Buf`] and [`BufMut`] for more details.
+//!
+//! [rope]: https://en.wikipedia.org/wiki/Rope_(data_structure)
+//! [`Buf`]: trait.Buf.html
+//! [`BufMut`]: trait.BufMut.html
+
+mod buf_impl;
+mod buf_mut;
+pub mod ext;
+mod iter;
+mod vec_deque;
+
+pub use self::buf_impl::Buf;
+pub use self::buf_mut::BufMut;
+pub use self::ext::{BufExt, BufMutExt};
+#[cfg(feature = "std")]
+pub use self::buf_mut::IoSliceMut;
+pub use self::iter::IntoIter;
+
diff --git a/src/buf/vec_deque.rs b/src/buf/vec_deque.rs
new file mode 100644
index 0000000..195e689
--- /dev/null
+++ b/src/buf/vec_deque.rs
@@ -0,0 +1,22 @@
+use alloc::collections::VecDeque;
+
+use super::Buf;
+
+impl Buf for VecDeque<u8> {
+    fn remaining(&self) -> usize {
+        self.len()
+    }
+
+    fn bytes(&self) -> &[u8] {
+        let (s1, s2) = self.as_slices();
+        if s1.is_empty() {
+            s2
+        } else {
+            s1
+        }
+    }
+
+    fn advance(&mut self, cnt: usize) {
+        self.drain(..cnt);
+    }
+}
diff --git a/src/bytes.rs b/src/bytes.rs
new file mode 100644
index 0000000..380b1c6
--- /dev/null
+++ b/src/bytes.rs
@@ -0,0 +1,1093 @@
+use core::{cmp, fmt, hash, mem, ptr, slice, usize};
+use core::iter::{FromIterator};
+use core::ops::{Deref, RangeBounds};
+
+use alloc::{vec::Vec, string::String, boxed::Box, borrow::Borrow};
+
+use crate::Buf;
+use crate::buf::IntoIter;
+use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+
+/// A reference counted contiguous slice of memory.
+///
+/// `Bytes` is an efficient container for storing and operating on contiguous
+/// slices of memory. It is intended for use primarily in networking code, but
+/// could have applications elsewhere as well.
+///
+/// `Bytes` values facilitate zero-copy network programming by allowing multiple
+/// `Bytes` objects to point to the same underlying memory. This is managed by
+/// using a reference count to track when the memory is no longer needed and can
+/// be freed.
+///
+/// ```
+/// use bytes::Bytes;
+///
+/// let mut mem = Bytes::from("Hello world");
+/// let a = mem.slice(0..5);
+///
+/// assert_eq!(a, "Hello");
+///
+/// let b = mem.split_to(6);
+///
+/// assert_eq!(mem, "world");
+/// assert_eq!(b, "Hello ");
+/// ```
+///
+/// # Memory layout
+///
+/// The `Bytes` struct itself is fairly small, limited to 4 `usize` fields used
+/// to track information about which segment of the underlying memory the
+/// `Bytes` handle has access to.
+///
+/// `Bytes` keeps both a pointer to the shared `Arc` containing the full memory
+/// slice and a pointer to the start of the region visible by the handle.
+/// `Bytes` also tracks the length of its view into the memory.
+///
+/// # Sharing
+///
+/// The memory itself is reference counted, and multiple `Bytes` objects may
+/// point to the same region. Each `Bytes` handle point to different sections within
+/// the memory region, and `Bytes` handle may or may not have overlapping views
+/// into the memory.
+///
+///
+/// ```text
+///
+///    Arc ptrs                   +---------+
+///    ________________________ / | Bytes 2 |
+///   /                           +---------+
+///  /          +-----------+     |         |
+/// |_________/ |  Bytes 1  |     |         |
+/// |           +-----------+     |         |
+/// |           |           | ___/ data     | tail
+/// |      data |      tail |/              |
+/// v           v           v               v
+/// +-----+---------------------------------+-----+
+/// | Arc |     |           |               |     |
+/// +-----+---------------------------------+-----+
+/// ```
+pub struct Bytes {
+    ptr: *const u8,
+    len: usize,
+    // inlined "trait object"
+    data: AtomicPtr<()>,
+    vtable: &'static Vtable,
+}
+
+pub(crate) struct Vtable {
+    /// fn(data, ptr, len)
+    pub clone: unsafe fn(&AtomicPtr<()>, *const u8, usize) -> Bytes,
+    /// fn(data, ptr, len)
+    pub drop: unsafe fn(&mut AtomicPtr<()>, *const u8, usize),
+}
+
+impl Bytes {
+    /// Creates a new empty `Bytes`.
+    ///
+    /// This will not allocate and the returned `Bytes` handle will be empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let b = Bytes::new();
+    /// assert_eq!(&b[..], b"");
+    /// ```
+    #[inline]
+    #[cfg(not(all(loom, test)))]
+    pub const fn new() -> Bytes {
+        // Make it a named const to work around
+        // "unsizing casts are not allowed in const fn"
+        const EMPTY: &[u8] = &[];
+        Bytes::from_static(EMPTY)
+    }
+
+    #[cfg(all(loom, test))]
+    pub fn new() -> Bytes {
+        const EMPTY: &[u8] = &[];
+        Bytes::from_static(EMPTY)
+    }
+
+    /// Creates a new `Bytes` from a static slice.
+    ///
+    /// The returned `Bytes` will point directly to the static slice. There is
+    /// no allocating or copying.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let b = Bytes::from_static(b"hello");
+    /// assert_eq!(&b[..], b"hello");
+    /// ```
+    #[inline]
+    #[cfg(not(all(loom, test)))]
+    pub const fn from_static(bytes: &'static [u8]) -> Bytes {
+        Bytes {
+            ptr: bytes.as_ptr(),
+            len: bytes.len(),
+            data: AtomicPtr::new(ptr::null_mut()),
+            vtable: &STATIC_VTABLE,
+        }
+    }
+
+    #[cfg(all(loom, test))]
+    pub fn from_static(bytes: &'static [u8]) -> Bytes {
+        Bytes {
+            ptr: bytes.as_ptr(),
+            len: bytes.len(),
+            data: AtomicPtr::new(ptr::null_mut()),
+            vtable: &STATIC_VTABLE,
+        }
+    }
+
+    /// Returns the number of bytes contained in this `Bytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let b = Bytes::from(&b"hello"[..]);
+    /// assert_eq!(b.len(), 5);
+    /// ```
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    /// Returns true if the `Bytes` has a length of 0.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let b = Bytes::new();
+    /// assert!(b.is_empty());
+    /// ```
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+
+    ///Creates `Bytes` instance from slice, by copying it.
+    pub fn copy_from_slice(data: &[u8]) -> Self {
+        data.to_vec().into()
+    }
+
+    /// Returns a slice of self for the provided range.
+    ///
+    /// This will increment the reference count for the underlying memory and
+    /// return a new `Bytes` handle set to the slice.
+    ///
+    /// This operation is `O(1)`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let a = Bytes::from(&b"hello world"[..]);
+    /// let b = a.slice(2..5);
+    ///
+    /// assert_eq!(&b[..], b"llo");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Requires that `begin <= end` and `end <= self.len()`, otherwise slicing
+    /// will panic.
+    pub fn slice(&self, range: impl RangeBounds<usize>) -> Bytes {
+        use core::ops::Bound;
+
+        let len = self.len();
+
+        let begin = match range.start_bound() {
+            Bound::Included(&n) => n,
+            Bound::Excluded(&n) => n + 1,
+            Bound::Unbounded => 0,
+        };
+
+        let end = match range.end_bound() {
+            Bound::Included(&n) => n + 1,
+            Bound::Excluded(&n) => n,
+            Bound::Unbounded => len,
+        };
+
+        assert!(
+            begin <= end,
+            "range start must not be greater than end: {:?} <= {:?}",
+            begin,
+            end,
+        );
+        assert!(
+            end <= len,
+            "range end out of bounds: {:?} <= {:?}",
+            end,
+            len,
+        );
+
+        if end == begin {
+            return Bytes::new();
+        }
+
+
+        let mut ret = self.clone();
+
+        ret.len = end - begin;
+        ret.ptr = unsafe { ret.ptr.offset(begin as isize) };
+
+        ret
+    }
+
+    /// Returns a slice of self that is equivalent to the given `subset`.
+    ///
+    /// When processing a `Bytes` buffer with other tools, one often gets a
+    /// `&[u8]` which is in fact a slice of the `Bytes`, i.e. a subset of it.
+    /// This function turns that `&[u8]` into another `Bytes`, as if one had
+    /// called `self.slice()` with the offsets that correspond to `subset`.
+    ///
+    /// This operation is `O(1)`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let bytes = Bytes::from(&b"012345678"[..]);
+    /// let as_slice = bytes.as_ref();
+    /// let subset = &as_slice[2..6];
+    /// let subslice = bytes.slice_ref(&subset);
+    /// assert_eq!(&subslice[..], b"2345");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Requires that the given `sub` slice is in fact contained within the
+    /// `Bytes` buffer; otherwise this function will panic.
+    pub fn slice_ref(&self, subset: &[u8]) -> Bytes {
+        // Empty slice and empty Bytes may have their pointers reset
+        // so explicitly allow empty slice to be a subslice of any slice.
+        if subset.is_empty() {
+            return Bytes::new();
+        }
+
+        let bytes_p = self.as_ptr() as usize;
+        let bytes_len = self.len();
+
+        let sub_p = subset.as_ptr() as usize;
+        let sub_len = subset.len();
+
+        assert!(
+            sub_p >= bytes_p,
+            "subset pointer ({:p}) is smaller than self pointer ({:p})",
+            sub_p as *const u8,
+            bytes_p as *const u8,
+        );
+        assert!(
+            sub_p + sub_len <= bytes_p + bytes_len,
+            "subset is out of bounds: self = ({:p}, {}), subset = ({:p}, {})",
+            bytes_p as *const u8,
+            bytes_len,
+            sub_p as *const u8,
+            sub_len,
+        );
+
+        let sub_offset = sub_p - bytes_p;
+
+        self.slice(sub_offset..(sub_offset + sub_len))
+    }
+
+    /// Splits the bytes into two at the given index.
+    ///
+    /// Afterwards `self` contains elements `[0, at)`, and the returned `Bytes`
+    /// contains elements `[at, len)`.
+    ///
+    /// This is an `O(1)` operation that just increases the reference count and
+    /// sets a few indices.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let mut a = Bytes::from(&b"hello world"[..]);
+    /// let b = a.split_off(5);
+    ///
+    /// assert_eq!(&a[..], b"hello");
+    /// assert_eq!(&b[..], b" world");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Panics if `at > len`.
+    #[must_use = "consider Bytes::truncate if you don't need the other half"]
+    pub fn split_off(&mut self, at: usize) -> Bytes {
+        assert!(
+            at <= self.len(),
+            "split_off out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
+
+        if at == self.len() {
+            return Bytes::new();
+        }
+
+        if at == 0 {
+            return mem::replace(self, Bytes::new());
+        }
+
+        let mut ret = self.clone();
+
+        self.len = at;
+
+        unsafe { ret.inc_start(at) };
+
+        ret
+    }
+
+    /// Splits the bytes into two at the given index.
+    ///
+    /// Afterwards `self` contains elements `[at, len)`, and the returned
+    /// `Bytes` contains elements `[0, at)`.
+    ///
+    /// This is an `O(1)` operation that just increases the reference count and
+    /// sets a few indices.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let mut a = Bytes::from(&b"hello world"[..]);
+    /// let b = a.split_to(5);
+    ///
+    /// assert_eq!(&a[..], b" world");
+    /// assert_eq!(&b[..], b"hello");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Panics if `at > len`.
+    #[must_use = "consider Bytes::advance if you don't need the other half"]
+    pub fn split_to(&mut self, at: usize) -> Bytes {
+        assert!(
+            at <= self.len(),
+            "split_to out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
+
+        if at == self.len() {
+            return mem::replace(self, Bytes::new());
+        }
+
+        if at == 0 {
+            return Bytes::new();
+        }
+
+
+        let mut ret = self.clone();
+
+        unsafe { self.inc_start(at) };
+
+        ret.len = at;
+        ret
+    }
+
+    /// Shortens the buffer, keeping the first `len` bytes and dropping the
+    /// rest.
+    ///
+    /// If `len` is greater than the buffer's current length, this has no
+    /// effect.
+    ///
+    /// The [`split_off`] method can emulate `truncate`, but this causes the
+    /// excess bytes to be returned instead of dropped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let mut buf = Bytes::from(&b"hello world"[..]);
+    /// buf.truncate(5);
+    /// assert_eq!(buf, b"hello"[..]);
+    /// ```
+    ///
+    /// [`split_off`]: #method.split_off
+    #[inline]
+    pub fn truncate(&mut self, len: usize) {
+        if len < self.len {
+            // The Vec "promotable" vtables do not store the capacity,
+            // so we cannot truncate while using this repr. We *have* to
+            // promote using `split_off` so the capacity can be stored.
+            if self.vtable as *const Vtable == &PROMOTABLE_EVEN_VTABLE ||
+                self.vtable as *const Vtable == &PROMOTABLE_ODD_VTABLE {
+                drop(self.split_off(len));
+            } else {
+                self.len = len;
+            }
+        }
+    }
+
+    /// Clears the buffer, removing all data.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Bytes;
+    ///
+    /// let mut buf = Bytes::from(&b"hello world"[..]);
+    /// buf.clear();
+    /// assert!(buf.is_empty());
+    /// ```
+    #[inline]
+    pub fn clear(&mut self) {
+        self.truncate(0);
+    }
+
+    #[inline]
+    pub(crate) unsafe fn with_vtable(ptr: *const u8, len: usize, data: AtomicPtr<()>, vtable: &'static Vtable) -> Bytes {
+        Bytes {
+            ptr,
+            len,
+            data,
+            vtable,
+        }
+    }
+
+    // private
+
+    #[inline]
+    fn as_slice(&self) -> &[u8] {
+        unsafe {
+            slice::from_raw_parts(self.ptr, self.len)
+        }
+    }
+
+    #[inline]
+    unsafe fn inc_start(&mut self, by: usize) {
+        // should already be asserted, but debug assert for tests
+        debug_assert!(self.len >= by, "internal: inc_start out of bounds");
+        self.len -= by;
+        self.ptr = self.ptr.offset(by as isize);
+    }
+}
+
+// Vtable must enforce this behavior
+unsafe impl Send for Bytes {}
+unsafe impl Sync for Bytes {}
+
+impl Drop for Bytes {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            (self.vtable.drop)(&mut self.data, self.ptr, self.len)
+        }
+    }
+}
+
+impl Clone for Bytes {
+    #[inline]
+    fn clone(&self) -> Bytes {
+        unsafe {
+            (self.vtable.clone)(&self.data, self.ptr, self.len)
+        }
+    }
+}
+
+impl Buf for Bytes {
+    #[inline]
+    fn remaining(&self) -> usize {
+        self.len()
+    }
+
+    #[inline]
+    fn bytes(&self) -> &[u8] {
+        self.as_slice()
+    }
+
+    #[inline]
+    fn advance(&mut self, cnt: usize) {
+        assert!(
+            cnt <= self.len(),
+            "cannot advance past `remaining`: {:?} <= {:?}",
+            cnt,
+            self.len(),
+        );
+
+        unsafe {
+            self.inc_start(cnt);
+        }
+    }
+
+    fn to_bytes(&mut self) -> crate::Bytes {
+        core::mem::replace(self, Bytes::new())
+    }
+}
+
+impl Deref for Bytes {
+    type Target = [u8];
+
+    #[inline]
+    fn deref(&self) -> &[u8] {
+        self.as_slice()
+    }
+}
+
+impl AsRef<[u8]> for Bytes {
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.as_slice()
+    }
+}
+
+impl hash::Hash for Bytes {
+    fn hash<H>(&self, state: &mut H) where H: hash::Hasher {
+        self.as_slice().hash(state);
+    }
+}
+
+impl Borrow<[u8]> for Bytes {
+    fn borrow(&self) -> &[u8] {
+        self.as_slice()
+    }
+}
+
+impl IntoIterator for Bytes {
+    type Item = u8;
+    type IntoIter = IntoIter<Bytes>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        IntoIter::new(self)
+    }
+}
+
+impl<'a> IntoIterator for &'a Bytes {
+    type Item = &'a u8;
+    type IntoIter = core::slice::Iter<'a, u8>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.as_slice().into_iter()
+    }
+}
+
+impl FromIterator<u8> for Bytes {
+    fn from_iter<T: IntoIterator<Item = u8>>(into_iter: T) -> Self {
+        Vec::from_iter(into_iter).into()
+    }
+}
+
+// impl Eq
+
+impl PartialEq for Bytes {
+    fn eq(&self, other: &Bytes) -> bool {
+        self.as_slice() == other.as_slice()
+    }
+}
+
+impl PartialOrd for Bytes {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        self.as_slice().partial_cmp(other.as_slice())
+    }
+}
+
+impl Ord for Bytes {
+    fn cmp(&self, other: &Bytes) -> cmp::Ordering {
+        self.as_slice().cmp(other.as_slice())
+    }
+}
+
+impl Eq for Bytes {}
+
+impl PartialEq<[u8]> for Bytes {
+    fn eq(&self, other: &[u8]) -> bool {
+        self.as_slice() == other
+    }
+}
+
+impl PartialOrd<[u8]> for Bytes {
+    fn partial_cmp(&self, other: &[u8]) -> Option<cmp::Ordering> {
+        self.as_slice().partial_cmp(other)
+    }
+}
+
+impl PartialEq<Bytes> for [u8] {
+    fn eq(&self, other: &Bytes) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<Bytes> for [u8] {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
+    }
+}
+
+impl PartialEq<str> for Bytes {
+    fn eq(&self, other: &str) -> bool {
+        self.as_slice() == other.as_bytes()
+    }
+}
+
+impl PartialOrd<str> for Bytes {
+    fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
+        self.as_slice().partial_cmp(other.as_bytes())
+    }
+}
+
+impl PartialEq<Bytes> for str {
+    fn eq(&self, other: &Bytes) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<Bytes> for str {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
+    }
+}
+
+impl PartialEq<Vec<u8>> for Bytes {
+    fn eq(&self, other: &Vec<u8>) -> bool {
+        *self == &other[..]
+    }
+}
+
+impl PartialOrd<Vec<u8>> for Bytes {
+    fn partial_cmp(&self, other: &Vec<u8>) -> Option<cmp::Ordering> {
+        self.as_slice().partial_cmp(&other[..])
+    }
+}
+
+impl PartialEq<Bytes> for Vec<u8> {
+    fn eq(&self, other: &Bytes) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<Bytes> for Vec<u8> {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
+    }
+}
+
+impl PartialEq<String> for Bytes {
+    fn eq(&self, other: &String) -> bool {
+        *self == &other[..]
+    }
+}
+
+impl PartialOrd<String> for Bytes {
+    fn partial_cmp(&self, other: &String) -> Option<cmp::Ordering> {
+        self.as_slice().partial_cmp(other.as_bytes())
+    }
+}
+
+impl PartialEq<Bytes> for String {
+    fn eq(&self, other: &Bytes) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<Bytes> for String {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
+    }
+}
+
+impl PartialEq<Bytes> for &[u8] {
+    fn eq(&self, other: &Bytes) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<Bytes> for &[u8] {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
+    }
+}
+
+impl PartialEq<Bytes> for &str {
+    fn eq(&self, other: &Bytes) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<Bytes> for &str {
+    fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
+    }
+}
+
+impl<'a, T: ?Sized> PartialEq<&'a T> for Bytes
+    where Bytes: PartialEq<T>
+{
+    fn eq(&self, other: &&'a T) -> bool {
+        *self == **other
+    }
+}
+
+impl<'a, T: ?Sized> PartialOrd<&'a T> for Bytes
+    where Bytes: PartialOrd<T>
+{
+    fn partial_cmp(&self, other: &&'a T) -> Option<cmp::Ordering> {
+        self.partial_cmp(&**other)
+    }
+}
+
+// impl From
+
+impl Default for Bytes {
+    #[inline]
+    fn default() -> Bytes {
+        Bytes::new()
+    }
+}
+
+impl From<&'static [u8]> for Bytes {
+    fn from(slice: &'static [u8]) -> Bytes {
+        Bytes::from_static(slice)
+    }
+}
+
+impl From<&'static str> for Bytes {
+    fn from(slice: &'static str) -> Bytes {
+        Bytes::from_static(slice.as_bytes())
+    }
+}
+
+impl From<Vec<u8>> for Bytes {
+    fn from(vec: Vec<u8>) -> Bytes {
+        // into_boxed_slice doesn't return a heap allocation for empty vectors,
+        // so the pointer isn't aligned enough for the KIND_VEC stashing to
+        // work.
+        if vec.is_empty() {
+            return Bytes::new();
+        }
+
+        let slice = vec.into_boxed_slice();
+        let len = slice.len();
+        let ptr = slice.as_ptr();
+        drop(Box::into_raw(slice));
+
+        if ptr as usize & 0x1 == 0 {
+            let data = ptr as usize | KIND_VEC;
+            Bytes {
+                ptr,
+                len,
+                data: AtomicPtr::new(data as *mut _),
+                vtable: &PROMOTABLE_EVEN_VTABLE,
+            }
+        } else {
+            Bytes {
+                ptr,
+                len,
+                data: AtomicPtr::new(ptr as *mut _),
+                vtable: &PROMOTABLE_ODD_VTABLE,
+            }
+        }
+    }
+}
+
+impl From<String> for Bytes {
+    fn from(s: String) -> Bytes {
+        Bytes::from(s.into_bytes())
+    }
+}
+
+// ===== impl Vtable =====
+
+impl fmt::Debug for Vtable {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Vtable")
+            .field("clone", &(self.clone as *const ()))
+            .field("drop", &(self.drop as *const ()))
+            .finish()
+    }
+}
+
+// ===== impl StaticVtable =====
+
+const STATIC_VTABLE: Vtable = Vtable {
+    clone: static_clone,
+    drop: static_drop,
+};
+
+unsafe fn static_clone(_: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let slice = slice::from_raw_parts(ptr, len);
+    Bytes::from_static(slice)
+}
+
+unsafe fn static_drop(_: &mut AtomicPtr<()>, _: *const u8, _: usize) {
+    // nothing to drop for &'static [u8]
+}
+
+// ===== impl PromotableVtable =====
+
+static PROMOTABLE_EVEN_VTABLE: Vtable = Vtable {
+    clone: promotable_even_clone,
+    drop: promotable_even_drop,
+};
+
+static PROMOTABLE_ODD_VTABLE: Vtable = Vtable {
+    clone: promotable_odd_clone,
+    drop: promotable_odd_drop,
+};
+
+unsafe fn promotable_even_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let shared = data.load(Ordering::Acquire);
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        shallow_clone_arc(shared as _, ptr, len)
+    } else {
+        debug_assert_eq!(kind, KIND_VEC);
+        let buf = (shared as usize & !KIND_MASK) as *mut u8;
+        shallow_clone_vec(data, shared, buf, ptr, len)
+    }
+}
+
+unsafe fn promotable_even_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) {
+    let shared = *data.get_mut();
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        release_shared(shared as *mut Shared);
+    } else {
+        debug_assert_eq!(kind, KIND_VEC);
+        let buf = (shared as usize & !KIND_MASK) as *mut u8;
+        drop(rebuild_boxed_slice(buf, ptr, len));
+    }
+}
+
+unsafe fn promotable_odd_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let shared = data.load(Ordering::Acquire);
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        shallow_clone_arc(shared as _, ptr, len)
+    } else {
+        debug_assert_eq!(kind, KIND_VEC);
+        shallow_clone_vec(data, shared, shared as *mut u8, ptr, len)
+    }
+}
+
+unsafe fn promotable_odd_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) {
+    let shared = *data.get_mut();
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        release_shared(shared as *mut Shared);
+    } else {
+        debug_assert_eq!(kind, KIND_VEC);
+
+        drop(rebuild_boxed_slice(shared as *mut u8, ptr, len));
+    }
+}
+
+unsafe fn rebuild_boxed_slice(buf: *mut u8, offset: *const u8, len: usize) -> Box<[u8]> {
+    let cap = (offset as usize - buf as usize) + len;
+    Box::from_raw(slice::from_raw_parts_mut(buf, cap))
+}
+
+// ===== impl SharedVtable =====
+
+struct Shared {
+    // holds vec for drop, but otherwise doesnt access it
+    _vec: Vec<u8>,
+    ref_cnt: AtomicUsize,
+}
+
+// Assert that the alignment of `Shared` is divisible by 2.
+// This is a necessary invariant since we depend on allocating `Shared` a
+// shared object to implicitly carry the `KIND_ARC` flag in its pointer.
+// This flag is set when the LSB is 0.
+const _: [(); 0 - mem::align_of::<Shared>() % 2] = []; // Assert that the alignment of `Shared` is divisible by 2.
+
+static SHARED_VTABLE: Vtable = Vtable {
+    clone: shared_clone,
+    drop: shared_drop,
+};
+
+const KIND_ARC: usize = 0b0;
+const KIND_VEC: usize = 0b1;
+const KIND_MASK: usize = 0b1;
+
+unsafe fn shared_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let shared = data.load(Ordering::Acquire);
+    shallow_clone_arc(shared as _, ptr, len)
+}
+
+unsafe fn shared_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
+    let shared = *data.get_mut();
+    release_shared(shared as *mut Shared);
+}
+
+unsafe fn shallow_clone_arc(shared: *mut Shared, ptr: *const u8, len: usize) -> Bytes {
+    let old_size = (*shared).ref_cnt.fetch_add(1, Ordering::Relaxed);
+
+    if old_size > usize::MAX >> 1 {
+        crate::abort();
+    }
+
+    Bytes {
+        ptr,
+        len,
+        data: AtomicPtr::new(shared as _),
+        vtable: &SHARED_VTABLE,
+    }
+}
+
+#[cold]
+unsafe fn shallow_clone_vec(atom: &AtomicPtr<()>, ptr: *const (), buf: *mut u8, offset: *const u8, len: usize) -> Bytes {
+    // If  the buffer is still tracked in a `Vec<u8>`. It is time to
+    // promote the vec to an `Arc`. This could potentially be called
+    // concurrently, so some care must be taken.
+
+    // First, allocate a new `Shared` instance containing the
+    // `Vec` fields. It's important to note that `ptr`, `len`,
+    // and `cap` cannot be mutated without having `&mut self`.
+    // This means that these fields will not be concurrently
+    // updated and since the buffer hasn't been promoted to an
+    // `Arc`, those three fields still are the components of the
+    // vector.
+    let vec = rebuild_boxed_slice(buf, offset, len).into_vec();
+    let shared = Box::new(Shared {
+        _vec: vec,
+        // Initialize refcount to 2. One for this reference, and one
+        // for the new clone that will be returned from
+        // `shallow_clone`.
+        ref_cnt: AtomicUsize::new(2),
+    });
+
+    let shared = Box::into_raw(shared);
+
+    // The pointer should be aligned, so this assert should
+    // always succeed.
+    debug_assert!(
+        0 == (shared as usize & KIND_MASK),
+        "internal: Box<Shared> should have an aligned pointer",
+    );
+
+    // Try compare & swapping the pointer into the `arc` field.
+    // `Release` is used synchronize with other threads that
+    // will load the `arc` field.
+    //
+    // If the `compare_and_swap` fails, then the thread lost the
+    // race to promote the buffer to shared. The `Acquire`
+    // ordering will synchronize with the `compare_and_swap`
+    // that happened in the other thread and the `Shared`
+    // pointed to by `actual` will be visible.
+    let actual = atom.compare_and_swap(ptr as _, shared as _, Ordering::AcqRel);
+
+    if actual as usize == ptr as usize {
+        // The upgrade was successful, the new handle can be
+        // returned.
+        return Bytes {
+            ptr: offset,
+            len,
+            data: AtomicPtr::new(shared as _),
+            vtable: &SHARED_VTABLE,
+        };
+    }
+
+    // The upgrade failed, a concurrent clone happened. Release
+    // the allocation that was made in this thread, it will not
+    // be needed.
+    let shared = Box::from_raw(shared);
+    mem::forget(*shared);
+
+    // Buffer already promoted to shared storage, so increment ref
+    // count.
+    shallow_clone_arc(actual as _, offset, len)
+}
+
+unsafe fn release_shared(ptr: *mut Shared) {
+    // `Shared` storage... follow the drop steps from Arc.
+    if (*ptr).ref_cnt.fetch_sub(1, Ordering::Release) != 1 {
+        return;
+    }
+
+    // This fence is needed to prevent reordering of use of the data and
+    // deletion of the data.  Because it is marked `Release`, the decreasing
+    // of the reference count synchronizes with this `Acquire` fence. This
+    // means that use of the data happens before decreasing the reference
+    // count, which happens before this fence, which happens before the
+    // deletion of the data.
+    //
+    // As explained in the [Boost documentation][1],
+    //
+    // > It is important to enforce any possible access to the object in one
+    // > thread (through an existing reference) to *happen before* deleting
+    // > the object in a different thread. This is achieved by a "release"
+    // > operation after dropping a reference (any access to the object
+    // > through this reference must obviously happened before), and an
+    // > "acquire" operation before deleting the object.
+    //
+    // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
+    atomic::fence(Ordering::Acquire);
+
+    // Drop the data
+    Box::from_raw(ptr);
+}
+
+// compile-fails
+
+/// ```compile_fail
+/// use bytes::Bytes;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = Bytes::from("hello world");
+///     b1.split_to(6);
+/// }
+/// ```
+fn _split_to_must_use() {}
+
+/// ```compile_fail
+/// use bytes::Bytes;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = Bytes::from("hello world");
+///     b1.split_off(6);
+/// }
+/// ```
+fn _split_off_must_use() {}
+
+// fuzz tests
+#[cfg(all(test, loom))]
+mod fuzz {
+    use std::sync::Arc;
+    use loom::thread;
+
+    use super::Bytes;
+    #[test]
+    fn bytes_cloning_vec() {
+        loom::model(|| {
+            let a = Bytes::from(b"abcdefgh".to_vec());
+            let addr = a.as_ptr() as usize;
+
+            // test the Bytes::clone is Sync by putting it in an Arc
+            let a1 = Arc::new(a);
+            let a2 = a1.clone();
+
+            let t1 = thread::spawn(move || {
+                let b: Bytes = (*a1).clone();
+                assert_eq!(b.as_ptr() as usize, addr);
+            });
+
+            let t2 = thread::spawn(move || {
+                let b: Bytes = (*a2).clone();
+                assert_eq!(b.as_ptr() as usize, addr);
+            });
+
+            t1.join().unwrap();
+            t2.join().unwrap();
+        });
+    }
+}
diff --git a/src/bytes_mut.rs b/src/bytes_mut.rs
new file mode 100644
index 0000000..dc4e4b1
--- /dev/null
+++ b/src/bytes_mut.rs
@@ -0,0 +1,1552 @@
+use core::{cmp, fmt, hash, isize, slice, usize};
+use core::mem::{self, ManuallyDrop};
+use core::ops::{Deref, DerefMut};
+use core::ptr::{self, NonNull};
+use core::iter::{FromIterator, Iterator};
+
+use alloc::{vec::Vec, string::String, boxed::Box, borrow::{Borrow, BorrowMut}};
+
+use crate::{Bytes, Buf, BufMut};
+use crate::bytes::Vtable;
+use crate::buf::IntoIter;
+use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+
+/// A unique reference to a contiguous slice of memory.
+///
+/// `BytesMut` represents a unique view into a potentially shared memory region.
+/// Given the uniqueness guarantee, owners of `BytesMut` handles are able to
+/// mutate the memory. It is similar to a `Vec<u8>` but with less copies and
+/// allocations.
+///
+/// # Growth
+///
+/// `BytesMut`'s `BufMut` implementation will implicitly grow its buffer as
+/// necessary. However, explicitly reserving the required space up-front before
+/// a series of inserts will be more efficient.
+///
+/// # Examples
+///
+/// ```
+/// use bytes::{BytesMut, BufMut};
+///
+/// let mut buf = BytesMut::with_capacity(64);
+///
+/// buf.put_u8(b'h');
+/// buf.put_u8(b'e');
+/// buf.put(&b"llo"[..]);
+///
+/// assert_eq!(&buf[..], b"hello");
+///
+/// // Freeze the buffer so that it can be shared
+/// let a = buf.freeze();
+///
+/// // This does not allocate, instead `b` points to the same memory.
+/// let b = a.clone();
+///
+/// assert_eq!(&a[..], b"hello");
+/// assert_eq!(&b[..], b"hello");
+/// ```
+pub struct BytesMut {
+    ptr: NonNull<u8>,
+    len: usize,
+    cap: usize,
+    data: *mut Shared,
+}
+
+// Thread-safe reference-counted container for the shared storage. This mostly
+// the same as `core::sync::Arc` but without the weak counter. The ref counting
+// fns are based on the ones found in `std`.
+//
+// The main reason to use `Shared` instead of `core::sync::Arc` is that it ends
+// up making the overall code simpler and easier to reason about. This is due to
+// some of the logic around setting `Inner::arc` and other ways the `arc` field
+// is used. Using `Arc` ended up requiring a number of funky transmutes and
+// other shenanigans to make it work.
+struct Shared {
+    vec: Vec<u8>,
+    original_capacity_repr: usize,
+    ref_count: AtomicUsize,
+}
+
+// Buffer storage strategy flags.
+const KIND_ARC: usize = 0b0;
+const KIND_VEC: usize = 0b1;
+const KIND_MASK: usize = 0b1;
+
+// The max original capacity value. Any `Bytes` allocated with a greater initial
+// capacity will default to this.
+const MAX_ORIGINAL_CAPACITY_WIDTH: usize = 17;
+// The original capacity algorithm will not take effect unless the originally
+// allocated capacity was at least 1kb in size.
+const MIN_ORIGINAL_CAPACITY_WIDTH: usize = 10;
+// The original capacity is stored in powers of 2 starting at 1kb to a max of
+// 64kb. Representing it as such requires only 3 bits of storage.
+const ORIGINAL_CAPACITY_MASK: usize = 0b11100;
+const ORIGINAL_CAPACITY_OFFSET: usize = 2;
+
+// When the storage is in the `Vec` representation, the pointer can be advanced
+// at most this value. This is due to the amount of storage available to track
+// the offset is usize - number of KIND bits and number of ORIGINAL_CAPACITY
+// bits.
+const VEC_POS_OFFSET: usize = 5;
+const MAX_VEC_POS: usize = usize::MAX >> VEC_POS_OFFSET;
+const NOT_VEC_POS_MASK: usize = 0b11111;
+
+#[cfg(target_pointer_width = "64")]
+const PTR_WIDTH: usize = 64;
+#[cfg(target_pointer_width = "32")]
+const PTR_WIDTH: usize = 32;
+
+/*
+ *
+ * ===== BytesMut =====
+ *
+ */
+
+impl BytesMut {
+    /// Creates a new `BytesMut` with the specified capacity.
+    ///
+    /// The returned `BytesMut` will be able to hold at least `capacity` bytes
+    /// without reallocating. If `capacity` is under `4 * size_of::<usize>() - 1`,
+    /// then `BytesMut` will not allocate.
+    ///
+    /// It is important to note that this function does not specify the length
+    /// of the returned `BytesMut`, but only the capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BytesMut, BufMut};
+    ///
+    /// let mut bytes = BytesMut::with_capacity(64);
+    ///
+    /// // `bytes` contains no data, even though there is capacity
+    /// assert_eq!(bytes.len(), 0);
+    ///
+    /// bytes.put(&b"hello world"[..]);
+    ///
+    /// assert_eq!(&bytes[..], b"hello world");
+    /// ```
+    #[inline]
+    pub fn with_capacity(capacity: usize) -> BytesMut {
+        BytesMut::from_vec(Vec::with_capacity(capacity))
+    }
+
+    /// Creates a new `BytesMut` with default capacity.
+    ///
+    /// Resulting object has length 0 and unspecified capacity.
+    /// This function does not allocate.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BytesMut, BufMut};
+    ///
+    /// let mut bytes = BytesMut::new();
+    ///
+    /// assert_eq!(0, bytes.len());
+    ///
+    /// bytes.reserve(2);
+    /// bytes.put_slice(b"xy");
+    ///
+    /// assert_eq!(&b"xy"[..], &bytes[..]);
+    /// ```
+    #[inline]
+    pub fn new() -> BytesMut {
+        BytesMut::with_capacity(0)
+    }
+
+    /// Returns the number of bytes contained in this `BytesMut`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let b = BytesMut::from(&b"hello"[..]);
+    /// assert_eq!(b.len(), 5);
+    /// ```
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    /// Returns true if the `BytesMut` has a length of 0.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let b = BytesMut::with_capacity(64);
+    /// assert!(b.is_empty());
+    /// ```
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+    /// Returns the number of bytes the `BytesMut` can hold without reallocating.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let b = BytesMut::with_capacity(64);
+    /// assert_eq!(b.capacity(), 64);
+    /// ```
+    #[inline]
+    pub fn capacity(&self) -> usize {
+        self.cap
+    }
+
+    /// Converts `self` into an immutable `Bytes`.
+    ///
+    /// The conversion is zero cost and is used to indicate that the slice
+    /// referenced by the handle will no longer be mutated. Once the conversion
+    /// is done, the handle can be cloned and shared across threads.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BytesMut, BufMut};
+    /// use std::thread;
+    ///
+    /// let mut b = BytesMut::with_capacity(64);
+    /// b.put(&b"hello world"[..]);
+    /// let b1 = b.freeze();
+    /// let b2 = b1.clone();
+    ///
+    /// let th = thread::spawn(move || {
+    ///     assert_eq!(&b1[..], b"hello world");
+    /// });
+    ///
+    /// assert_eq!(&b2[..], b"hello world");
+    /// th.join().unwrap();
+    /// ```
+    #[inline]
+    pub fn freeze(mut self) -> Bytes {
+        if self.kind() == KIND_VEC {
+            // Just re-use `Bytes` internal Vec vtable
+            unsafe {
+                let (off, _) = self.get_vec_pos();
+                let vec = rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off);
+                mem::forget(self);
+                vec.into()
+            }
+        } else {
+            debug_assert_eq!(self.kind(), KIND_ARC);
+
+            let ptr = self.ptr.as_ptr();
+            let len = self.len;
+            let data = AtomicPtr::new(self.data as _);
+            mem::forget(self);
+            unsafe {
+                Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE)
+            }
+        }
+    }
+
+    /// Splits the bytes into two at the given index.
+    ///
+    /// Afterwards `self` contains elements `[0, at)`, and the returned
+    /// `BytesMut` contains elements `[at, capacity)`.
+    ///
+    /// This is an `O(1)` operation that just increases the reference count
+    /// and sets a few indices.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut a = BytesMut::from(&b"hello world"[..]);
+    /// let mut b = a.split_off(5);
+    ///
+    /// a[0] = b'j';
+    /// b[0] = b'!';
+    ///
+    /// assert_eq!(&a[..], b"jello");
+    /// assert_eq!(&b[..], b"!world");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Panics if `at > capacity`.
+    #[must_use = "consider BytesMut::truncate if you don't need the other half"]
+    pub fn split_off(&mut self, at: usize) -> BytesMut {
+        assert!(
+            at <= self.capacity(),
+            "split_off out of bounds: {:?} <= {:?}",
+            at,
+            self.capacity(),
+        );
+        unsafe {
+            let mut other = self.shallow_clone();
+            other.set_start(at);
+            self.set_end(at);
+            other
+        }
+    }
+
+    /// Removes the bytes from the current view, returning them in a new
+    /// `BytesMut` handle.
+    ///
+    /// Afterwards, `self` will be empty, but will retain any additional
+    /// capacity that it had before the operation. This is identical to
+    /// `self.split_to(self.len())`.
+    ///
+    /// This is an `O(1)` operation that just increases the reference count and
+    /// sets a few indices.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{BytesMut, BufMut};
+    ///
+    /// let mut buf = BytesMut::with_capacity(1024);
+    /// buf.put(&b"hello world"[..]);
+    ///
+    /// let other = buf.split();
+    ///
+    /// assert!(buf.is_empty());
+    /// assert_eq!(1013, buf.capacity());
+    ///
+    /// assert_eq!(other, b"hello world"[..]);
+    /// ```
+    #[must_use = "consider BytesMut::advance(len()) if you don't need the other half"]
+    pub fn split(&mut self) -> BytesMut {
+        let len = self.len();
+        self.split_to(len)
+    }
+
+    /// Splits the buffer into two at the given index.
+    ///
+    /// Afterwards `self` contains elements `[at, len)`, and the returned `BytesMut`
+    /// contains elements `[0, at)`.
+    ///
+    /// This is an `O(1)` operation that just increases the reference count and
+    /// sets a few indices.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut a = BytesMut::from(&b"hello world"[..]);
+    /// let mut b = a.split_to(5);
+    ///
+    /// a[0] = b'!';
+    /// b[0] = b'j';
+    ///
+    /// assert_eq!(&a[..], b"!world");
+    /// assert_eq!(&b[..], b"jello");
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Panics if `at > len`.
+    #[must_use = "consider BytesMut::advance if you don't need the other half"]
+    pub fn split_to(&mut self, at: usize) -> BytesMut {
+        assert!(
+            at <= self.len(),
+            "split_to out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
+
+        unsafe {
+            let mut other = self.shallow_clone();
+            other.set_end(at);
+            self.set_start(at);
+            other
+        }
+    }
+
+    /// Shortens the buffer, keeping the first `len` bytes and dropping the
+    /// rest.
+    ///
+    /// If `len` is greater than the buffer's current length, this has no
+    /// effect.
+    ///
+    /// The [`split_off`] method can emulate `truncate`, but this causes the
+    /// excess bytes to be returned instead of dropped.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut buf = BytesMut::from(&b"hello world"[..]);
+    /// buf.truncate(5);
+    /// assert_eq!(buf, b"hello"[..]);
+    /// ```
+    ///
+    /// [`split_off`]: #method.split_off
+    pub fn truncate(&mut self, len: usize) {
+        if len <= self.len() {
+            unsafe { self.set_len(len); }
+        }
+    }
+
+    /// Clears the buffer, removing all data.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut buf = BytesMut::from(&b"hello world"[..]);
+    /// buf.clear();
+    /// assert!(buf.is_empty());
+    /// ```
+    pub fn clear(&mut self) {
+        self.truncate(0);
+    }
+
+    /// Resizes the buffer so that `len` is equal to `new_len`.
+    ///
+    /// If `new_len` is greater than `len`, the buffer is extended by the
+    /// difference with each additional byte set to `value`. If `new_len` is
+    /// less than `len`, the buffer is simply truncated.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut buf = BytesMut::new();
+    ///
+    /// buf.resize(3, 0x1);
+    /// assert_eq!(&buf[..], &[0x1, 0x1, 0x1]);
+    ///
+    /// buf.resize(2, 0x2);
+    /// assert_eq!(&buf[..], &[0x1, 0x1]);
+    ///
+    /// buf.resize(4, 0x3);
+    /// assert_eq!(&buf[..], &[0x1, 0x1, 0x3, 0x3]);
+    /// ```
+    pub fn resize(&mut self, new_len: usize, value: u8) {
+        let len = self.len();
+        if new_len > len {
+            let additional = new_len - len;
+            self.reserve(additional);
+            unsafe {
+                let dst = self.bytes_mut().as_mut_ptr();
+                ptr::write_bytes(dst, value, additional);
+                self.set_len(new_len);
+            }
+        } else {
+            self.truncate(new_len);
+        }
+    }
+
+    /// Sets the length of the buffer.
+    ///
+    /// This will explicitly set the size of the buffer without actually
+    /// modifying the data, so it is up to the caller to ensure that the data
+    /// has been initialized.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut b = BytesMut::from(&b"hello world"[..]);
+    ///
+    /// unsafe {
+    ///     b.set_len(5);
+    /// }
+    ///
+    /// assert_eq!(&b[..], b"hello");
+    ///
+    /// unsafe {
+    ///     b.set_len(11);
+    /// }
+    ///
+    /// assert_eq!(&b[..], b"hello world");
+    /// ```
+    pub unsafe fn set_len(&mut self, len: usize) {
+        debug_assert!(len <= self.cap, "set_len out of bounds");
+        self.len = len;
+    }
+
+    /// Reserves capacity for at least `additional` more bytes to be inserted
+    /// into the given `BytesMut`.
+    ///
+    /// More than `additional` bytes may be reserved in order to avoid frequent
+    /// reallocations. A call to `reserve` may result in an allocation.
+    ///
+    /// Before allocating new buffer space, the function will attempt to reclaim
+    /// space in the existing buffer. If the current handle references a small
+    /// view in the original buffer and all other handles have been dropped,
+    /// and the requested capacity is less than or equal to the existing
+    /// buffer's capacity, then the current view will be copied to the front of
+    /// the buffer and the handle will take ownership of the full buffer.
+    ///
+    /// # Examples
+    ///
+    /// In the following example, a new buffer is allocated.
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut buf = BytesMut::from(&b"hello"[..]);
+    /// buf.reserve(64);
+    /// assert!(buf.capacity() >= 69);
+    /// ```
+    ///
+    /// In the following example, the existing buffer is reclaimed.
+    ///
+    /// ```
+    /// use bytes::{BytesMut, BufMut};
+    ///
+    /// let mut buf = BytesMut::with_capacity(128);
+    /// buf.put(&[0; 64][..]);
+    ///
+    /// let ptr = buf.as_ptr();
+    /// let other = buf.split();
+    ///
+    /// assert!(buf.is_empty());
+    /// assert_eq!(buf.capacity(), 64);
+    ///
+    /// drop(other);
+    /// buf.reserve(128);
+    ///
+    /// assert_eq!(buf.capacity(), 128);
+    /// assert_eq!(buf.as_ptr(), ptr);
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity overflows `usize`.
+    #[inline]
+    pub fn reserve(&mut self, additional: usize) {
+        let len = self.len();
+        let rem = self.capacity() - len;
+
+        if additional <= rem {
+            // The handle can already store at least `additional` more bytes, so
+            // there is no further work needed to be done.
+            return;
+        }
+
+        self.reserve_inner(additional);
+    }
+
+    // In separate function to allow the short-circuits in `reserve` to
+    // be inline-able. Significant helps performance.
+    fn reserve_inner(&mut self, additional: usize) {
+        let len = self.len();
+        let kind = self.kind();
+
+        if kind == KIND_VEC {
+            // If there's enough free space before the start of the buffer, then
+            // just copy the data backwards and reuse the already-allocated
+            // space.
+            //
+            // Otherwise, since backed by a vector, use `Vec::reserve`
+            unsafe {
+                let (off, prev) = self.get_vec_pos();
+
+                // Only reuse space if we stand to gain at least capacity/2
+                // bytes of space back
+                if off >= additional && off >= (self.cap / 2) {
+                    // There's space - reuse it
+                    //
+                    // Just move the pointer back to the start after copying
+                    // data back.
+                    let base_ptr = self.ptr.as_ptr().offset(-(off as isize));
+                    ptr::copy(self.ptr.as_ptr(), base_ptr, self.len);
+                    self.ptr = vptr(base_ptr);
+                    self.set_vec_pos(0, prev);
+
+                    // Length stays constant, but since we moved backwards we
+                    // can gain capacity back.
+                    self.cap += off;
+                } else {
+                    // No space - allocate more
+                    let mut v = ManuallyDrop::new(rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off));
+                    v.reserve(additional);
+
+                    // Update the info
+                    self.ptr = vptr(v.as_mut_ptr().offset(off as isize));
+                    self.len = v.len() - off;
+                    self.cap = v.capacity() - off;
+                }
+
+                return;
+            }
+        }
+
+        debug_assert_eq!(kind, KIND_ARC);
+        let shared: *mut Shared = self.data as _;
+
+
+        // Reserving involves abandoning the currently shared buffer and
+        // allocating a new vector with the requested capacity.
+        //
+        // Compute the new capacity
+        let mut new_cap = len.checked_add(additional).expect("overflow");
+
+        let original_capacity;
+        let original_capacity_repr;
+
+        unsafe {
+            original_capacity_repr = (*shared).original_capacity_repr;
+            original_capacity = original_capacity_from_repr(original_capacity_repr);
+
+            // First, try to reclaim the buffer. This is possible if the current
+            // handle is the only outstanding handle pointing to the buffer.
+            if (*shared).is_unique() {
+                // This is the only handle to the buffer. It can be reclaimed.
+                // However, before doing the work of copying data, check to make
+                // sure that the vector has enough capacity.
+                let v = &mut (*shared).vec;
+
+                if v.capacity() >= new_cap {
+                    // The capacity is sufficient, reclaim the buffer
+                    let ptr = v.as_mut_ptr();
+
+                    ptr::copy(self.ptr.as_ptr(), ptr, len);
+
+                    self.ptr = vptr(ptr);
+                    self.cap = v.capacity();
+
+                    return;
+                }
+
+                // The vector capacity is not sufficient. The reserve request is
+                // asking for more than the initial buffer capacity. Allocate more
+                // than requested if `new_cap` is not much bigger than the current
+                // capacity.
+                //
+                // There are some situations, using `reserve_exact` that the
+                // buffer capacity could be below `original_capacity`, so do a
+                // check.
+                let double = v.capacity().checked_shl(1).unwrap_or(new_cap);
+
+                new_cap = cmp::max(
+                    cmp::max(double, new_cap),
+                    original_capacity);
+            } else {
+                new_cap = cmp::max(new_cap, original_capacity);
+            }
+        }
+
+        // Create a new vector to store the data
+        let mut v = ManuallyDrop::new(Vec::with_capacity(new_cap));
+
+        // Copy the bytes
+        v.extend_from_slice(self.as_ref());
+
+        // Release the shared handle. This must be done *after* the bytes are
+        // copied.
+        unsafe { release_shared(shared) };
+
+        // Update self
+        let data = (original_capacity_repr << ORIGINAL_CAPACITY_OFFSET) | KIND_VEC;
+        self.data = data as _;
+        self.ptr = vptr(v.as_mut_ptr());
+        self.len = v.len();
+        self.cap = v.capacity();
+    }
+
+    /// Appends given bytes to this `BytesMut`.
+    ///
+    /// If this `BytesMut` object does not have enough capacity, it is resized
+    /// first.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut buf = BytesMut::with_capacity(0);
+    /// buf.extend_from_slice(b"aaabbb");
+    /// buf.extend_from_slice(b"cccddd");
+    ///
+    /// assert_eq!(b"aaabbbcccddd", &buf[..]);
+    /// ```
+    pub fn extend_from_slice(&mut self, extend: &[u8]) {
+        let cnt = extend.len();
+        self.reserve(cnt);
+
+        unsafe {
+            let dst = self.maybe_uninit_bytes();
+            // Reserved above
+            debug_assert!(dst.len() >= cnt);
+
+            ptr::copy_nonoverlapping(
+                extend.as_ptr(),
+                dst.as_mut_ptr() as *mut u8,
+                cnt);
+
+        }
+
+        unsafe { self.advance_mut(cnt); }
+    }
+
+    /// Absorbs a `BytesMut` that was previously split off.
+    ///
+    /// If the two `BytesMut` objects were previously contiguous, i.e., if
+    /// `other` was created by calling `split_off` on this `BytesMut`, then
+    /// this is an `O(1)` operation that just decreases a reference
+    /// count and sets a few indices. Otherwise this method degenerates to
+    /// `self.extend_from_slice(other.as_ref())`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let mut buf = BytesMut::with_capacity(64);
+    /// buf.extend_from_slice(b"aaabbbcccddd");
+    ///
+    /// let split = buf.split_off(6);
+    /// assert_eq!(b"aaabbb", &buf[..]);
+    /// assert_eq!(b"cccddd", &split[..]);
+    ///
+    /// buf.unsplit(split);
+    /// assert_eq!(b"aaabbbcccddd", &buf[..]);
+    /// ```
+    pub fn unsplit(&mut self, other: BytesMut) {
+        if self.is_empty() {
+            *self = other;
+            return;
+        }
+
+        if let Err(other) = self.try_unsplit(other) {
+            self.extend_from_slice(other.as_ref());
+        }
+    }
+
+    // private
+
+    // For now, use a `Vec` to manage the memory for us, but we may want to
+    // change that in the future to some alternate allocator strategy.
+    //
+    // Thus, we don't expose an easy way to construct from a `Vec` since an
+    // internal change could make a simple pattern (`BytesMut::from(vec)`)
+    // suddenly a lot more expensive.
+    #[inline]
+    pub(crate) fn from_vec(mut vec: Vec<u8>) -> BytesMut {
+        let ptr = vptr(vec.as_mut_ptr());
+        let len = vec.len();
+        let cap = vec.capacity();
+        mem::forget(vec);
+
+        let original_capacity_repr = original_capacity_to_repr(cap);
+        let data = (original_capacity_repr << ORIGINAL_CAPACITY_OFFSET) | KIND_VEC;
+
+        BytesMut {
+            ptr,
+            len,
+            cap,
+            data: data as *mut _,
+        }
+    }
+
+    #[inline]
+    fn as_slice(&self) -> &[u8] {
+        unsafe {
+            slice::from_raw_parts(self.ptr.as_ptr(), self.len)
+        }
+    }
+
+    #[inline]
+    fn as_slice_mut(&mut self) -> &mut [u8] {
+        unsafe {
+            slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
+        }
+    }
+
+    unsafe fn set_start(&mut self, start: usize) {
+        // Setting the start to 0 is a no-op, so return early if this is the
+        // case.
+        if start == 0 {
+            return;
+        }
+
+        debug_assert!(start <= self.cap, "internal: set_start out of bounds");
+
+        let kind = self.kind();
+
+        if kind == KIND_VEC {
+            // Setting the start when in vec representation is a little more
+            // complicated. First, we have to track how far ahead the
+            // "start" of the byte buffer from the beginning of the vec. We
+            // also have to ensure that we don't exceed the maximum shift.
+            let (mut pos, prev) = self.get_vec_pos();
+            pos += start;
+
+            if pos <= MAX_VEC_POS {
+                self.set_vec_pos(pos, prev);
+            } else {
+                // The repr must be upgraded to ARC. This will never happen
+                // on 64 bit systems and will only happen on 32 bit systems
+                // when shifting past 134,217,727 bytes. As such, we don't
+                // worry too much about performance here.
+                self.promote_to_shared(/*ref_count = */1);
+            }
+        }
+
+        // Updating the start of the view is setting `ptr` to point to the
+        // new start and updating the `len` field to reflect the new length
+        // of the view.
+        self.ptr = vptr(self.ptr.as_ptr().offset(start as isize));
+
+        if self.len >= start {
+            self.len -= start;
+        } else {
+            self.len = 0;
+        }
+
+        self.cap -= start;
+    }
+
+    unsafe fn set_end(&mut self, end: usize) {
+        debug_assert_eq!(self.kind(), KIND_ARC);
+        assert!(end <= self.cap, "set_end out of bounds");
+
+        self.cap = end;
+        self.len = cmp::min(self.len, end);
+    }
+
+    fn try_unsplit(&mut self, other: BytesMut) -> Result<(), BytesMut> {
+        if other.is_empty() {
+            return Ok(());
+        }
+
+        let ptr = unsafe { self.ptr.as_ptr().offset(self.len as isize) };
+        if ptr == other.ptr.as_ptr() &&
+           self.kind() == KIND_ARC &&
+           other.kind() == KIND_ARC &&
+           self.data == other.data
+        {
+            // Contiguous blocks, just combine directly
+            self.len += other.len;
+            self.cap += other.cap;
+            Ok(())
+        } else {
+            Err(other)
+        }
+    }
+
+    #[inline]
+    fn kind(&self) -> usize {
+        self.data as usize & KIND_MASK
+    }
+
+    unsafe fn promote_to_shared(&mut self, ref_cnt: usize) {
+        debug_assert_eq!(self.kind(), KIND_VEC);
+        debug_assert!(ref_cnt == 1 || ref_cnt == 2);
+
+        let original_capacity_repr =
+            (self.data as usize & ORIGINAL_CAPACITY_MASK) >> ORIGINAL_CAPACITY_OFFSET;
+
+        // The vec offset cannot be concurrently mutated, so there
+        // should be no danger reading it.
+        let off = (self.data as usize) >> VEC_POS_OFFSET;
+
+        // First, allocate a new `Shared` instance containing the
+        // `Vec` fields. It's important to note that `ptr`, `len`,
+        // and `cap` cannot be mutated without having `&mut self`.
+        // This means that these fields will not be concurrently
+        // updated and since the buffer hasn't been promoted to an
+        // `Arc`, those three fields still are the components of the
+        // vector.
+        let shared = Box::new(Shared {
+            vec: rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off),
+            original_capacity_repr,
+            ref_count: AtomicUsize::new(ref_cnt),
+        });
+
+        let shared = Box::into_raw(shared);
+
+        // The pointer should be aligned, so this assert should
+        // always succeed.
+        debug_assert_eq!(shared as usize & KIND_MASK, KIND_ARC);
+
+        self.data = shared as _;
+    }
+
+    /// Makes an exact shallow clone of `self`.
+    ///
+    /// The kind of `self` doesn't matter, but this is unsafe
+    /// because the clone will have the same offsets. You must
+    /// be sure the returned value to the user doesn't allow
+    /// two views into the same range.
+    #[inline]
+    unsafe fn shallow_clone(&mut self) -> BytesMut {
+        if self.kind() == KIND_ARC {
+            increment_shared(self.data);
+            ptr::read(self)
+        } else {
+            self.promote_to_shared(/*ref_count = */2);
+            ptr::read(self)
+        }
+    }
+
+    #[inline]
+    unsafe fn get_vec_pos(&mut self) -> (usize, usize) {
+        debug_assert_eq!(self.kind(), KIND_VEC);
+
+        let prev = self.data as usize;
+        (prev >> VEC_POS_OFFSET, prev)
+    }
+
+    #[inline]
+    unsafe fn set_vec_pos(&mut self, pos: usize, prev: usize) {
+        debug_assert_eq!(self.kind(), KIND_VEC);
+        debug_assert!(pos <= MAX_VEC_POS);
+
+        self.data = ((pos << VEC_POS_OFFSET) | (prev & NOT_VEC_POS_MASK)) as *mut _;
+    }
+
+    #[inline]
+    fn maybe_uninit_bytes(&mut self) -> &mut [mem::MaybeUninit<u8>] {
+        unsafe {
+            let ptr = self.ptr.as_ptr().offset(self.len as isize);
+            let len = self.cap - self.len;
+
+            slice::from_raw_parts_mut(ptr as *mut mem::MaybeUninit<u8>, len)
+        }
+    }
+}
+
+impl Drop for BytesMut {
+    fn drop(&mut self) {
+        let kind = self.kind();
+
+        if kind == KIND_VEC {
+            unsafe {
+                let (off, _) = self.get_vec_pos();
+
+                // Vector storage, free the vector
+                let _ = rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off);
+            }
+        } else if kind == KIND_ARC {
+            unsafe { release_shared(self.data as _) };
+        }
+    }
+}
+
+impl Buf for BytesMut {
+    #[inline]
+    fn remaining(&self) -> usize {
+        self.len()
+    }
+
+    #[inline]
+    fn bytes(&self) -> &[u8] {
+        self.as_slice()
+    }
+
+    #[inline]
+    fn advance(&mut self, cnt: usize) {
+        assert!(
+            cnt <= self.remaining(),
+            "cannot advance past `remaining`: {:?} <= {:?}",
+            cnt,
+            self.remaining(),
+        );
+        unsafe { self.set_start(cnt); }
+    }
+
+    fn to_bytes(&mut self) -> crate::Bytes {
+        self.split().freeze()
+    }
+}
+
+impl BufMut for BytesMut {
+    #[inline]
+    fn remaining_mut(&self) -> usize {
+        usize::MAX - self.len()
+    }
+
+    #[inline]
+    unsafe fn advance_mut(&mut self, cnt: usize) {
+        let new_len = self.len() + cnt;
+        assert!(new_len <= self.cap, "new_len = {}; capacity = {}", new_len, self.cap);
+        self.len = new_len;
+    }
+
+    #[inline]
+    fn bytes_mut(&mut self) -> &mut [mem::MaybeUninit<u8>] {
+        if self.capacity() == self.len() {
+            self.reserve(64);
+        }
+        self.maybe_uninit_bytes()
+    }
+
+    // Specialize these methods so they can skip checking `remaining_mut`
+    // and `advance_mut`.
+
+    fn put<T: crate::Buf>(&mut self, mut src: T) where Self: Sized {
+        while src.has_remaining() {
+            let s = src.bytes();
+            let l = s.len();
+            self.extend_from_slice(s);
+            src.advance(l);
+        }
+    }
+
+    fn put_slice(&mut self, src: &[u8]) {
+        self.extend_from_slice(src);
+    }
+}
+
+impl AsRef<[u8]> for BytesMut {
+    #[inline]
+    fn as_ref(&self) -> &[u8] {
+        self.as_slice()
+    }
+}
+
+impl Deref for BytesMut {
+    type Target = [u8];
+
+    #[inline]
+    fn deref(&self) -> &[u8] {
+        self.as_ref()
+    }
+}
+
+impl AsMut<[u8]> for BytesMut {
+    fn as_mut(&mut self) -> &mut [u8] {
+        self.as_slice_mut()
+    }
+}
+
+impl DerefMut for BytesMut {
+    #[inline]
+    fn deref_mut(&mut self) -> &mut [u8] {
+        self.as_mut()
+    }
+}
+
+impl<'a> From<&'a [u8]> for BytesMut {
+    fn from(src: &'a [u8]) -> BytesMut {
+        BytesMut::from_vec(src.to_vec())
+    }
+}
+
+impl<'a> From<&'a str> for BytesMut {
+    fn from(src: &'a str) -> BytesMut {
+        BytesMut::from(src.as_bytes())
+    }
+}
+
+impl From<BytesMut> for Bytes {
+    fn from(src: BytesMut) -> Bytes {
+        src.freeze()
+    }
+}
+
+impl PartialEq for BytesMut {
+    fn eq(&self, other: &BytesMut) -> bool {
+        self.as_slice() == other.as_slice()
+    }
+}
+
+impl PartialOrd for BytesMut {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        self.as_slice().partial_cmp(other.as_slice())
+    }
+}
+
+impl Ord for BytesMut {
+    fn cmp(&self, other: &BytesMut) -> cmp::Ordering {
+        self.as_slice().cmp(other.as_slice())
+    }
+}
+
+impl Eq for BytesMut {
+}
+
+impl Default for BytesMut {
+    #[inline]
+    fn default() -> BytesMut {
+        BytesMut::new()
+    }
+}
+
+impl hash::Hash for BytesMut {
+    fn hash<H>(&self, state: &mut H) where H: hash::Hasher {
+        let s: &[u8] = self.as_ref();
+        s.hash(state);
+    }
+}
+
+impl Borrow<[u8]> for BytesMut {
+    fn borrow(&self) -> &[u8] {
+        self.as_ref()
+    }
+}
+
+impl BorrowMut<[u8]> for BytesMut {
+    fn borrow_mut(&mut self) -> &mut [u8] {
+        self.as_mut()
+    }
+}
+
+impl fmt::Write for BytesMut {
+    #[inline]
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        if self.remaining_mut() >= s.len() {
+            self.put_slice(s.as_bytes());
+            Ok(())
+        } else {
+            Err(fmt::Error)
+        }
+    }
+
+    #[inline]
+    fn write_fmt(&mut self, args: fmt::Arguments<'_>) -> fmt::Result {
+        fmt::write(self, args)
+    }
+}
+
+impl Clone for BytesMut {
+    fn clone(&self) -> BytesMut {
+        BytesMut::from(&self[..])
+    }
+}
+
+impl IntoIterator for BytesMut {
+    type Item = u8;
+    type IntoIter = IntoIter<BytesMut>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        IntoIter::new(self)
+    }
+}
+
+impl<'a> IntoIterator for &'a BytesMut {
+    type Item = &'a u8;
+    type IntoIter = core::slice::Iter<'a, u8>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.as_ref().into_iter()
+    }
+}
+
+impl Extend<u8> for BytesMut {
+    fn extend<T>(&mut self, iter: T) where T: IntoIterator<Item = u8> {
+        let iter = iter.into_iter();
+
+        let (lower, _) = iter.size_hint();
+        self.reserve(lower);
+
+        // TODO: optimize
+        // 1. If self.kind() == KIND_VEC, use Vec::extend
+        // 2. Make `reserve` inline-able
+        for b in iter {
+            self.reserve(1);
+            self.put_u8(b);
+        }
+    }
+}
+
+impl<'a> Extend<&'a u8> for BytesMut {
+    fn extend<T>(&mut self, iter: T) where T: IntoIterator<Item = &'a u8> {
+        self.extend(iter.into_iter().map(|b| *b))
+    }
+}
+
+impl FromIterator<u8> for BytesMut {
+    fn from_iter<T: IntoIterator<Item = u8>>(into_iter: T) -> Self {
+        BytesMut::from_vec(Vec::from_iter(into_iter))
+    }
+}
+
+impl<'a> FromIterator<&'a u8> for BytesMut {
+    fn from_iter<T: IntoIterator<Item = &'a u8>>(into_iter: T) -> Self {
+        BytesMut::from_iter(into_iter.into_iter().map(|b| *b))
+    }
+}
+
+/*
+ *
+ * ===== Inner =====
+ *
+ */
+
+unsafe fn increment_shared(ptr: *mut Shared) {
+    let old_size = (*ptr).ref_count.fetch_add(1, Ordering::Relaxed);
+
+    if old_size > isize::MAX as usize {
+        crate::abort();
+    }
+}
+
+unsafe fn release_shared(ptr: *mut Shared) {
+    // `Shared` storage... follow the drop steps from Arc.
+    if (*ptr).ref_count.fetch_sub(1, Ordering::Release) != 1 {
+        return;
+    }
+
+    // This fence is needed to prevent reordering of use of the data and
+    // deletion of the data.  Because it is marked `Release`, the decreasing
+    // of the reference count synchronizes with this `Acquire` fence. This
+    // means that use of the data happens before decreasing the reference
+    // count, which happens before this fence, which happens before the
+    // deletion of the data.
+    //
+    // As explained in the [Boost documentation][1],
+    //
+    // > It is important to enforce any possible access to the object in one
+    // > thread (through an existing reference) to *happen before* deleting
+    // > the object in a different thread. This is achieved by a "release"
+    // > operation after dropping a reference (any access to the object
+    // > through this reference must obviously happened before), and an
+    // > "acquire" operation before deleting the object.
+    //
+    // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
+    atomic::fence(Ordering::Acquire);
+
+    // Drop the data
+    Box::from_raw(ptr);
+}
+
+impl Shared {
+    fn is_unique(&self) -> bool {
+        // The goal is to check if the current handle is the only handle
+        // that currently has access to the buffer. This is done by
+        // checking if the `ref_count` is currently 1.
+        //
+        // The `Acquire` ordering synchronizes with the `Release` as
+        // part of the `fetch_sub` in `release_shared`. The `fetch_sub`
+        // operation guarantees that any mutations done in other threads
+        // are ordered before the `ref_count` is decremented. As such,
+        // this `Acquire` will guarantee that those mutations are
+        // visible to the current thread.
+        self.ref_count.load(Ordering::Acquire) == 1
+    }
+}
+
+fn original_capacity_to_repr(cap: usize) -> usize {
+    let width = PTR_WIDTH - ((cap >> MIN_ORIGINAL_CAPACITY_WIDTH).leading_zeros() as usize);
+    cmp::min(width, MAX_ORIGINAL_CAPACITY_WIDTH - MIN_ORIGINAL_CAPACITY_WIDTH)
+}
+
+fn original_capacity_from_repr(repr: usize) -> usize {
+    if repr == 0 {
+        return 0;
+    }
+
+    1 << (repr + (MIN_ORIGINAL_CAPACITY_WIDTH - 1))
+}
+
+/*
+#[test]
+fn test_original_capacity_to_repr() {
+    assert_eq!(original_capacity_to_repr(0), 0);
+
+    let max_width = 32;
+
+    for width in 1..(max_width + 1) {
+        let cap = 1 << width - 1;
+
+        let expected = if width < MIN_ORIGINAL_CAPACITY_WIDTH {
+            0
+        } else if width < MAX_ORIGINAL_CAPACITY_WIDTH {
+            width - MIN_ORIGINAL_CAPACITY_WIDTH
+        } else {
+            MAX_ORIGINAL_CAPACITY_WIDTH - MIN_ORIGINAL_CAPACITY_WIDTH
+        };
+
+        assert_eq!(original_capacity_to_repr(cap), expected);
+
+        if width > 1 {
+            assert_eq!(original_capacity_to_repr(cap + 1), expected);
+        }
+
+        //  MIN_ORIGINAL_CAPACITY_WIDTH must be bigger than 7 to pass tests below
+        if width == MIN_ORIGINAL_CAPACITY_WIDTH + 1 {
+            assert_eq!(original_capacity_to_repr(cap - 24), expected - 1);
+            assert_eq!(original_capacity_to_repr(cap + 76), expected);
+        } else if width == MIN_ORIGINAL_CAPACITY_WIDTH + 2 {
+            assert_eq!(original_capacity_to_repr(cap - 1), expected - 1);
+            assert_eq!(original_capacity_to_repr(cap - 48), expected - 1);
+        }
+    }
+}
+
+#[test]
+fn test_original_capacity_from_repr() {
+    assert_eq!(0, original_capacity_from_repr(0));
+
+    let min_cap = 1 << MIN_ORIGINAL_CAPACITY_WIDTH;
+
+    assert_eq!(min_cap, original_capacity_from_repr(1));
+    assert_eq!(min_cap * 2, original_capacity_from_repr(2));
+    assert_eq!(min_cap * 4, original_capacity_from_repr(3));
+    assert_eq!(min_cap * 8, original_capacity_from_repr(4));
+    assert_eq!(min_cap * 16, original_capacity_from_repr(5));
+    assert_eq!(min_cap * 32, original_capacity_from_repr(6));
+    assert_eq!(min_cap * 64, original_capacity_from_repr(7));
+}
+*/
+
+unsafe impl Send for BytesMut {}
+unsafe impl Sync for BytesMut {}
+
+/*
+ *
+ * ===== PartialEq / PartialOrd =====
+ *
+ */
+
+impl PartialEq<[u8]> for BytesMut {
+    fn eq(&self, other: &[u8]) -> bool {
+        &**self == other
+    }
+}
+
+impl PartialOrd<[u8]> for BytesMut {
+    fn partial_cmp(&self, other: &[u8]) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(other)
+    }
+}
+
+impl PartialEq<BytesMut> for [u8] {
+    fn eq(&self, other: &BytesMut) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<BytesMut> for [u8] {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
+    }
+}
+
+impl PartialEq<str> for BytesMut {
+    fn eq(&self, other: &str) -> bool {
+        &**self == other.as_bytes()
+    }
+}
+
+impl PartialOrd<str> for BytesMut {
+    fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(other.as_bytes())
+    }
+}
+
+impl PartialEq<BytesMut> for str {
+    fn eq(&self, other: &BytesMut) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<BytesMut> for str {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
+    }
+}
+
+impl PartialEq<Vec<u8>> for BytesMut {
+    fn eq(&self, other: &Vec<u8>) -> bool {
+        *self == &other[..]
+    }
+}
+
+impl PartialOrd<Vec<u8>> for BytesMut {
+    fn partial_cmp(&self, other: &Vec<u8>) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(&other[..])
+    }
+}
+
+impl PartialEq<BytesMut> for Vec<u8> {
+    fn eq(&self, other: &BytesMut) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<BytesMut> for Vec<u8> {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        other.partial_cmp(self)
+    }
+}
+
+impl PartialEq<String> for BytesMut {
+    fn eq(&self, other: &String) -> bool {
+        *self == &other[..]
+    }
+}
+
+impl PartialOrd<String> for BytesMut {
+    fn partial_cmp(&self, other: &String) -> Option<cmp::Ordering> {
+        (**self).partial_cmp(other.as_bytes())
+    }
+}
+
+impl PartialEq<BytesMut> for String {
+    fn eq(&self, other: &BytesMut) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<BytesMut> for String {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
+    }
+}
+
+impl<'a, T: ?Sized> PartialEq<&'a T> for BytesMut
+    where BytesMut: PartialEq<T>
+{
+    fn eq(&self, other: &&'a T) -> bool {
+        *self == **other
+    }
+}
+
+impl<'a, T: ?Sized> PartialOrd<&'a T> for BytesMut
+    where BytesMut: PartialOrd<T>
+{
+    fn partial_cmp(&self, other: &&'a T) -> Option<cmp::Ordering> {
+        self.partial_cmp(*other)
+    }
+}
+
+impl PartialEq<BytesMut> for &[u8] {
+    fn eq(&self, other: &BytesMut) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<BytesMut> for &[u8] {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
+    }
+}
+
+impl PartialEq<BytesMut> for &str {
+    fn eq(&self, other: &BytesMut) -> bool {
+        *other == *self
+    }
+}
+
+impl PartialOrd<BytesMut> for &str {
+    fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
+        other.partial_cmp(self)
+    }
+}
+
+impl PartialEq<BytesMut> for Bytes {
+    fn eq(&self, other: &BytesMut) -> bool {
+        &other[..] == &self[..]
+    }
+}
+
+impl PartialEq<Bytes> for BytesMut {
+    fn eq(&self, other: &Bytes) -> bool {
+        &other[..] == &self[..]
+    }
+}
+
+fn vptr(ptr: *mut u8) -> NonNull<u8> {
+    if cfg!(debug_assertions) {
+        NonNull::new(ptr).expect("Vec pointer should be non-null")
+    } else {
+        unsafe { NonNull::new_unchecked(ptr) }
+    }
+}
+
+unsafe fn rebuild_vec(ptr: *mut u8, mut len: usize, mut cap: usize, off: usize) -> Vec<u8> {
+    let ptr = ptr.offset(-(off as isize));
+    len += off;
+    cap += off;
+
+    Vec::from_raw_parts(ptr, len, cap)
+}
+
+// ===== impl SharedVtable =====
+
+static SHARED_VTABLE: Vtable = Vtable {
+    clone: shared_v_clone,
+    drop: shared_v_drop,
+};
+
+unsafe fn shared_v_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let shared = data.load(Ordering::Acquire) as *mut Shared;
+    increment_shared(shared);
+
+    let data = AtomicPtr::new(shared as _);
+    Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE)
+}
+
+unsafe fn shared_v_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
+    let shared = (*data.get_mut()) as *mut Shared;
+    release_shared(shared as *mut Shared);
+}
+
+// compile-fails
+
+/// ```compile_fail
+/// use bytes::BytesMut;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = BytesMut::from("hello world");
+///     b1.split_to(6);
+/// }
+/// ```
+fn _split_to_must_use() {}
+
+/// ```compile_fail
+/// use bytes::BytesMut;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = BytesMut::from("hello world");
+///     b1.split_off(6);
+/// }
+/// ```
+fn _split_off_must_use() {}
+
+/// ```compile_fail
+/// use bytes::BytesMut;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = BytesMut::from("hello world");
+///     b1.split();
+/// }
+/// ```
+fn _split_must_use() {}
+
+// fuzz tests
+#[cfg(all(test, loom))]
+mod fuzz {
+    use std::sync::Arc;
+    use loom::thread;
+
+    use crate::Bytes;
+    use super::BytesMut;
+
+    #[test]
+    fn bytes_mut_cloning_frozen() {
+        loom::model(|| {
+            let a = BytesMut::from(&b"abcdefgh"[..]).split().freeze();
+            let addr = a.as_ptr() as usize;
+
+            // test the Bytes::clone is Sync by putting it in an Arc
+            let a1 = Arc::new(a);
+            let a2 = a1.clone();
+
+            let t1 = thread::spawn(move || {
+                let b: Bytes = (*a1).clone();
+                assert_eq!(b.as_ptr() as usize, addr);
+            });
+
+            let t2 = thread::spawn(move || {
+                let b: Bytes = (*a2).clone();
+                assert_eq!(b.as_ptr() as usize, addr);
+            });
+
+            t1.join().unwrap();
+            t2.join().unwrap();
+        });
+    }
+}
diff --git a/src/fmt/debug.rs b/src/fmt/debug.rs
new file mode 100644
index 0000000..f6a08b8
--- /dev/null
+++ b/src/fmt/debug.rs
@@ -0,0 +1,49 @@
+use core::fmt::{Debug, Formatter, Result};
+
+use crate::{Bytes, BytesMut};
+use super::BytesRef;
+
+/// Alternative implementation of `std::fmt::Debug` for byte slice.
+///
+/// Standard `Debug` implementation for `[u8]` is comma separated
+/// list of numbers. Since large amount of byte strings are in fact
+/// ASCII strings or contain a lot of ASCII strings (e. g. HTTP),
+/// it is convenient to print strings as ASCII when possible.
+impl Debug for BytesRef<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        write!(f, "b\"")?;
+        for &b in self.0 {
+            // https://doc.rust-lang.org/reference/tokens.html#byte-escapes
+            if b == b'\n' {
+                write!(f, "\\n")?;
+            } else if b == b'\r' {
+                write!(f, "\\r")?;
+            } else if b == b'\t' {
+                write!(f, "\\t")?;
+            } else if b == b'\\' || b == b'"' {
+                write!(f, "\\{}", b as char)?;
+            } else if b == b'\0' {
+                write!(f, "\\0")?;
+            // ASCII printable
+            } else if b >= 0x20 && b < 0x7f {
+                write!(f, "{}", b as char)?;
+            } else {
+                write!(f, "\\x{:02x}", b)?;
+            }
+        }
+        write!(f, "\"")?;
+        Ok(())
+    }
+}
+
+impl Debug for Bytes {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        Debug::fmt(&BytesRef(&self.as_ref()), f)
+    }
+}
+
+impl Debug for BytesMut {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        Debug::fmt(&BytesRef(&self.as_ref()), f)
+    }
+}
diff --git a/src/fmt/hex.rs b/src/fmt/hex.rs
new file mode 100644
index 0000000..09170ae
--- /dev/null
+++ b/src/fmt/hex.rs
@@ -0,0 +1,37 @@
+use core::fmt::{Formatter, LowerHex, Result, UpperHex};
+
+use crate::{Bytes, BytesMut};
+use super::BytesRef;
+
+impl LowerHex for BytesRef<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        for &b in self.0 {
+            write!(f, "{:02x}", b)?;
+        }
+        Ok(())
+    }
+}
+
+impl UpperHex for BytesRef<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        for &b in self.0 {
+            write!(f, "{:02X}", b)?;
+        }
+        Ok(())
+    }
+}
+
+macro_rules! hex_impl {
+    ($tr:ident, $ty:ty) => {
+        impl $tr for $ty {
+            fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+                $tr::fmt(&BytesRef(self.as_ref()), f)
+            }
+        }
+    };
+}
+
+hex_impl!(LowerHex, Bytes);
+hex_impl!(LowerHex, BytesMut);
+hex_impl!(UpperHex, Bytes);
+hex_impl!(UpperHex, BytesMut);
diff --git a/src/fmt/mod.rs b/src/fmt/mod.rs
new file mode 100644
index 0000000..676d15f
--- /dev/null
+++ b/src/fmt/mod.rs
@@ -0,0 +1,5 @@
+mod debug;
+mod hex;
+
+/// `BytesRef` is not a part of public API of bytes crate.
+struct BytesRef<'a>(&'a [u8]);
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..a61e347
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,117 @@
+#![deny(warnings, missing_docs, missing_debug_implementations, rust_2018_idioms)]
+#![doc(html_root_url = "https://docs.rs/bytes/0.5.4")]
+#![no_std]
+
+//! Provides abstractions for working with bytes.
+//!
+//! The `bytes` crate provides an efficient byte buffer structure
+//! ([`Bytes`](struct.Bytes.html)) and traits for working with buffer
+//! implementations ([`Buf`], [`BufMut`]).
+//!
+//! [`Buf`]: trait.Buf.html
+//! [`BufMut`]: trait.BufMut.html
+//!
+//! # `Bytes`
+//!
+//! `Bytes` is an efficient container for storing and operating on contiguous
+//! slices of memory. It is intended for use primarily in networking code, but
+//! could have applications elsewhere as well.
+//!
+//! `Bytes` values facilitate zero-copy network programming by allowing multiple
+//! `Bytes` objects to point to the same underlying memory. This is managed by
+//! using a reference count to track when the memory is no longer needed and can
+//! be freed.
+//!
+//! A `Bytes` handle can be created directly from an existing byte store (such as `&[u8]`
+//! or `Vec<u8>`), but usually a `BytesMut` is used first and written to. For
+//! example:
+//!
+//! ```rust
+//! use bytes::{BytesMut, BufMut};
+//!
+//! let mut buf = BytesMut::with_capacity(1024);
+//! buf.put(&b"hello world"[..]);
+//! buf.put_u16(1234);
+//!
+//! let a = buf.split();
+//! assert_eq!(a, b"hello world\x04\xD2"[..]);
+//!
+//! buf.put(&b"goodbye world"[..]);
+//!
+//! let b = buf.split();
+//! assert_eq!(b, b"goodbye world"[..]);
+//!
+//! assert_eq!(buf.capacity(), 998);
+//! ```
+//!
+//! In the above example, only a single buffer of 1024 is allocated. The handles
+//! `a` and `b` will share the underlying buffer and maintain indices tracking
+//! the view into the buffer represented by the handle.
+//!
+//! See the [struct docs] for more details.
+//!
+//! [struct docs]: struct.Bytes.html
+//!
+//! # `Buf`, `BufMut`
+//!
+//! These two traits provide read and write access to buffers. The underlying
+//! storage may or may not be in contiguous memory. For example, `Bytes` is a
+//! buffer that guarantees contiguous memory, but a [rope] stores the bytes in
+//! disjoint chunks. `Buf` and `BufMut` maintain cursors tracking the current
+//! position in the underlying byte storage. When bytes are read or written, the
+//! cursor is advanced.
+//!
+//! [rope]: https://en.wikipedia.org/wiki/Rope_(data_structure)
+//!
+//! ## Relation with `Read` and `Write`
+//!
+//! At first glance, it may seem that `Buf` and `BufMut` overlap in
+//! functionality with `std::io::Read` and `std::io::Write`. However, they
+//! serve different purposes. A buffer is the value that is provided as an
+//! argument to `Read::read` and `Write::write`. `Read` and `Write` may then
+//! perform a syscall, which has the potential of failing. Operations on `Buf`
+//! and `BufMut` are infallible.
+
+
+extern crate alloc;
+
+#[cfg(feature = "std")]
+extern crate std;
+
+pub mod buf;
+pub use crate::buf::{
+    Buf,
+    BufMut,
+};
+
+mod bytes_mut;
+mod bytes;
+mod fmt;
+mod loom;
+pub use crate::bytes_mut::BytesMut;
+pub use crate::bytes::Bytes;
+
+// Optional Serde support
+#[cfg(feature = "serde")]
+mod serde;
+
+#[inline(never)]
+#[cold]
+fn abort() -> ! {
+    #[cfg(feature = "std")]
+    {
+        std::process::abort();
+    }
+
+    #[cfg(not(feature = "std"))]
+    {
+        struct Abort;
+        impl Drop for Abort {
+            fn drop(&mut self) {
+                panic!();
+            }
+        }
+        let _a = Abort;
+        panic!("abort");
+    }
+}
diff --git a/src/loom.rs b/src/loom.rs
new file mode 100644
index 0000000..80947ac
--- /dev/null
+++ b/src/loom.rs
@@ -0,0 +1,9 @@
+#[cfg(not(all(test, loom)))]
+pub(crate) mod sync {
+    pub(crate) mod atomic {
+        pub(crate) use core::sync::atomic::{fence, AtomicPtr, AtomicUsize, Ordering};
+    }
+}
+
+#[cfg(all(test, loom))]
+pub(crate) use ::loom::sync;
diff --git a/src/serde.rs b/src/serde.rs
new file mode 100644
index 0000000..11020ae
--- /dev/null
+++ b/src/serde.rs
@@ -0,0 +1,82 @@
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::{cmp, fmt};
+use serde::{Serialize, Serializer, Deserialize, Deserializer, de};
+use super::{Bytes, BytesMut};
+
+macro_rules! serde_impl {
+    ($ty:ident, $visitor_ty:ident, $from_slice:ident, $from_vec:ident) => (
+        impl Serialize for $ty {
+            #[inline]
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+                where S: Serializer
+            {
+                serializer.serialize_bytes(&self)
+            }
+        }
+
+        struct $visitor_ty;
+
+        impl<'de> de::Visitor<'de> for $visitor_ty {
+            type Value = $ty;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+                formatter.write_str("byte array")
+            }
+
+            #[inline]
+            fn visit_seq<V>(self, mut seq: V) -> Result<Self::Value, V::Error>
+                where V: de::SeqAccess<'de>
+            {
+                let len = cmp::min(seq.size_hint().unwrap_or(0), 4096);
+                let mut values: Vec<u8> = Vec::with_capacity(len);
+
+                while let Some(value) = seq.next_element()? {
+                    values.push(value);
+                }
+
+                Ok($ty::$from_vec(values))
+            }
+
+            #[inline]
+            fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+                where E: de::Error
+            {
+                Ok($ty::$from_slice(v))
+            }
+
+            #[inline]
+            fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
+                where E: de::Error
+            {
+                Ok($ty::$from_vec(v))
+            }
+
+            #[inline]
+            fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+                where E: de::Error
+            {
+                Ok($ty::$from_slice(v.as_bytes()))
+            }
+
+            #[inline]
+            fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
+                where E: de::Error
+            {
+                Ok($ty::$from_vec(v.into_bytes()))
+            }
+        }
+
+        impl<'de> Deserialize<'de> for $ty {
+            #[inline]
+            fn deserialize<D>(deserializer: D) -> Result<$ty, D::Error>
+                where D: Deserializer<'de>
+            {
+                deserializer.deserialize_byte_buf($visitor_ty)
+            }
+        }
+    );
+}
+
+serde_impl!(Bytes, BytesVisitor, copy_from_slice, from);
+serde_impl!(BytesMut, BytesMutVisitor, from, from_vec);
diff --git a/tests/test_buf.rs b/tests/test_buf.rs
new file mode 100644
index 0000000..12b75a4
--- /dev/null
+++ b/tests/test_buf.rs
@@ -0,0 +1,101 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::Buf;
+use std::io::IoSlice;
+
+#[test]
+fn test_fresh_cursor_vec() {
+    let mut buf = &b"hello"[..];
+
+    assert_eq!(buf.remaining(), 5);
+    assert_eq!(buf.bytes(), b"hello");
+
+    buf.advance(2);
+
+    assert_eq!(buf.remaining(), 3);
+    assert_eq!(buf.bytes(), b"llo");
+
+    buf.advance(3);
+
+    assert_eq!(buf.remaining(), 0);
+    assert_eq!(buf.bytes(), b"");
+}
+
+#[test]
+fn test_get_u8() {
+    let mut buf = &b"\x21zomg"[..];
+    assert_eq!(0x21, buf.get_u8());
+}
+
+#[test]
+fn test_get_u16() {
+    let mut buf = &b"\x21\x54zomg"[..];
+    assert_eq!(0x2154, buf.get_u16());
+    let mut buf = &b"\x21\x54zomg"[..];
+    assert_eq!(0x5421, buf.get_u16_le());
+}
+
+#[test]
+#[should_panic]
+fn test_get_u16_buffer_underflow() {
+    let mut buf = &b"\x21"[..];
+    buf.get_u16();
+}
+
+#[test]
+fn test_bufs_vec() {
+    let buf = &b"hello world"[..];
+
+    let b1: &[u8] = &mut [];
+    let b2: &[u8] = &mut [];
+
+    let mut dst = [IoSlice::new(b1), IoSlice::new(b2)];
+
+    assert_eq!(1, buf.bytes_vectored(&mut dst[..]));
+}
+
+#[test]
+fn test_vec_deque() {
+    use std::collections::VecDeque;
+
+    let mut buffer: VecDeque<u8> = VecDeque::new();
+    buffer.extend(b"hello world");
+    assert_eq!(11, buffer.remaining());
+    assert_eq!(b"hello world", buffer.bytes());
+    buffer.advance(6);
+    assert_eq!(b"world", buffer.bytes());
+    buffer.extend(b" piece");
+    let mut out = [0; 11];
+    buffer.copy_to_slice(&mut out);
+    assert_eq!(b"world piece", &out[..]);
+}
+
+#[test]
+fn test_deref_buf_forwards() {
+    struct Special;
+
+    impl Buf for Special {
+        fn remaining(&self) -> usize {
+            unreachable!("remaining");
+        }
+
+        fn bytes(&self) -> &[u8] {
+            unreachable!("bytes");
+        }
+
+        fn advance(&mut self, _: usize) {
+            unreachable!("advance");
+        }
+
+        fn get_u8(&mut self) -> u8 {
+            // specialized!
+            b'x'
+        }
+    }
+
+    // these should all use the specialized method
+    assert_eq!(Special.get_u8(), b'x');
+    assert_eq!((&mut Special as &mut dyn Buf).get_u8(), b'x');
+    assert_eq!((Box::new(Special) as Box<dyn Buf>).get_u8(), b'x');
+    assert_eq!(Box::new(Special).get_u8(), b'x');
+}
diff --git a/tests/test_buf_mut.rs b/tests/test_buf_mut.rs
new file mode 100644
index 0000000..f002f7d
--- /dev/null
+++ b/tests/test_buf_mut.rs
@@ -0,0 +1,118 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::{buf::IoSliceMut, BufMut, BytesMut};
+use std::usize;
+use std::fmt::Write;
+
+#[test]
+fn test_vec_as_mut_buf() {
+    let mut buf = Vec::with_capacity(64);
+
+    assert_eq!(buf.remaining_mut(), usize::MAX);
+
+    assert!(buf.bytes_mut().len() >= 64);
+
+    buf.put(&b"zomg"[..]);
+
+    assert_eq!(&buf, b"zomg");
+
+    assert_eq!(buf.remaining_mut(), usize::MAX - 4);
+    assert_eq!(buf.capacity(), 64);
+
+    for _ in 0..16 {
+        buf.put(&b"zomg"[..]);
+    }
+
+    assert_eq!(buf.len(), 68);
+}
+
+#[test]
+fn test_put_u8() {
+    let mut buf = Vec::with_capacity(8);
+    buf.put_u8(33);
+    assert_eq!(b"\x21", &buf[..]);
+}
+
+#[test]
+fn test_put_u16() {
+    let mut buf = Vec::with_capacity(8);
+    buf.put_u16(8532);
+    assert_eq!(b"\x21\x54", &buf[..]);
+
+    buf.clear();
+    buf.put_u16_le(8532);
+    assert_eq!(b"\x54\x21", &buf[..]);
+}
+
+#[test]
+fn test_vec_advance_mut() {
+    // Regression test for carllerche/bytes#108.
+    let mut buf = Vec::with_capacity(8);
+    unsafe {
+        buf.advance_mut(12);
+        assert_eq!(buf.len(), 12);
+        assert!(buf.capacity() >= 12, "capacity: {}", buf.capacity());
+    }
+}
+
+#[test]
+fn test_clone() {
+    let mut buf = BytesMut::with_capacity(100);
+    buf.write_str("this is a test").unwrap();
+    let buf2 = buf.clone();
+
+    buf.write_str(" of our emergency broadcast system").unwrap();
+    assert!(buf != buf2);
+}
+
+#[test]
+fn test_bufs_vec_mut() {
+    let b1: &mut [u8] = &mut [];
+    let b2: &mut [u8] = &mut [];
+    let mut dst = [IoSliceMut::from(b1), IoSliceMut::from(b2)];
+
+    // with no capacity
+    let mut buf = BytesMut::new();
+    assert_eq!(buf.capacity(), 0);
+    assert_eq!(1, buf.bytes_vectored_mut(&mut dst[..]));
+
+    // with capacity
+    let mut buf = BytesMut::with_capacity(64);
+    assert_eq!(1, buf.bytes_vectored_mut(&mut dst[..]));
+}
+
+#[test]
+fn test_mut_slice() {
+    let mut v = vec![0, 0, 0, 0];
+    let mut s = &mut v[..];
+    s.put_u32(42);
+}
+
+#[test]
+fn test_deref_bufmut_forwards() {
+    struct Special;
+
+    impl BufMut for Special {
+        fn remaining_mut(&self) -> usize {
+            unreachable!("remaining_mut");
+        }
+
+        fn bytes_mut(&mut self) -> &mut [std::mem::MaybeUninit<u8>] {
+            unreachable!("bytes_mut");
+        }
+
+        unsafe fn advance_mut(&mut self, _: usize) {
+            unreachable!("advance");
+        }
+
+        fn put_u8(&mut self, _: u8) {
+            // specialized!
+        }
+    }
+
+    // these should all use the specialized method
+    Special.put_u8(b'x');
+    (&mut Special as &mut dyn BufMut).put_u8(b'x');
+    (Box::new(Special) as Box<dyn BufMut>).put_u8(b'x');
+    Box::new(Special).put_u8(b'x');
+}
diff --git a/tests/test_bytes.rs b/tests/test_bytes.rs
new file mode 100644
index 0000000..40fcae4
--- /dev/null
+++ b/tests/test_bytes.rs
@@ -0,0 +1,882 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::{Bytes, BytesMut, Buf, BufMut};
+
+use std::usize;
+
+const LONG: &'static [u8] = b"mary had a little lamb, little lamb, little lamb";
+const SHORT: &'static [u8] = b"hello world";
+
+fn is_sync<T: Sync>() {}
+fn is_send<T: Send>() {}
+
+#[test]
+fn test_bounds() {
+    is_sync::<Bytes>();
+    is_sync::<BytesMut>();
+    is_send::<Bytes>();
+    is_send::<BytesMut>();
+}
+
+#[test]
+fn test_layout() {
+    use std::mem;
+
+    assert_eq!(
+        mem::size_of::<Bytes>(),
+        mem::size_of::<usize>() * 4,
+        "Bytes size should be 4 words",
+    );
+    assert_eq!(
+        mem::size_of::<BytesMut>(),
+        mem::size_of::<usize>() * 4,
+        "BytesMut should be 4 words",
+    );
+
+    assert_eq!(
+        mem::size_of::<Bytes>(),
+        mem::size_of::<Option<Bytes>>(),
+        "Bytes should be same size as Option<Bytes>",
+    );
+
+    assert_eq!(
+        mem::size_of::<BytesMut>(),
+        mem::size_of::<Option<BytesMut>>(),
+        "BytesMut should be same size as Option<BytesMut>",
+    );
+
+}
+
+#[test]
+fn from_slice() {
+    let a = Bytes::from(&b"abcdefgh"[..]);
+    assert_eq!(a, b"abcdefgh"[..]);
+    assert_eq!(a, &b"abcdefgh"[..]);
+    assert_eq!(a, Vec::from(&b"abcdefgh"[..]));
+    assert_eq!(b"abcdefgh"[..], a);
+    assert_eq!(&b"abcdefgh"[..], a);
+    assert_eq!(Vec::from(&b"abcdefgh"[..]), a);
+
+    let a = BytesMut::from(&b"abcdefgh"[..]);
+    assert_eq!(a, b"abcdefgh"[..]);
+    assert_eq!(a, &b"abcdefgh"[..]);
+    assert_eq!(a, Vec::from(&b"abcdefgh"[..]));
+    assert_eq!(b"abcdefgh"[..], a);
+    assert_eq!(&b"abcdefgh"[..], a);
+    assert_eq!(Vec::from(&b"abcdefgh"[..]), a);
+}
+
+#[test]
+fn fmt() {
+    let a = format!("{:?}", Bytes::from(&b"abcdefg"[..]));
+    let b = "b\"abcdefg\"";
+
+    assert_eq!(a, b);
+
+    let a = format!("{:?}", BytesMut::from(&b"abcdefg"[..]));
+    assert_eq!(a, b);
+}
+
+#[test]
+fn fmt_write() {
+    use std::fmt::Write;
+    use std::iter::FromIterator;
+    let s = String::from_iter((0..10).map(|_| "abcdefg"));
+
+    let mut a = BytesMut::with_capacity(64);
+    write!(a, "{}", &s[..64]).unwrap();
+    assert_eq!(a, s[..64].as_bytes());
+
+
+    let mut b = BytesMut::with_capacity(64);
+    write!(b, "{}", &s[..32]).unwrap();
+    write!(b, "{}", &s[32..64]).unwrap();
+    assert_eq!(b, s[..64].as_bytes());
+
+
+    let mut c = BytesMut::with_capacity(64);
+    write!(c, "{}", s).unwrap();
+    assert_eq!(c, s[..].as_bytes());
+}
+
+#[test]
+fn len() {
+    let a = Bytes::from(&b"abcdefg"[..]);
+    assert_eq!(a.len(), 7);
+
+    let a = BytesMut::from(&b"abcdefg"[..]);
+    assert_eq!(a.len(), 7);
+
+    let a = Bytes::from(&b""[..]);
+    assert!(a.is_empty());
+
+    let a = BytesMut::from(&b""[..]);
+    assert!(a.is_empty());
+}
+
+#[test]
+fn index() {
+    let a = Bytes::from(&b"hello world"[..]);
+    assert_eq!(a[0..5], *b"hello");
+}
+
+#[test]
+fn slice() {
+    let a = Bytes::from(&b"hello world"[..]);
+
+    let b = a.slice(3..5);
+    assert_eq!(b, b"lo"[..]);
+
+    let b = a.slice(0..0);
+    assert_eq!(b, b""[..]);
+
+    let b = a.slice(3..3);
+    assert_eq!(b, b""[..]);
+
+    let b = a.slice(a.len()..a.len());
+    assert_eq!(b, b""[..]);
+
+    let b = a.slice(..5);
+    assert_eq!(b, b"hello"[..]);
+
+    let b = a.slice(3..);
+    assert_eq!(b, b"lo world"[..]);
+}
+
+#[test]
+#[should_panic]
+fn slice_oob_1() {
+    let a = Bytes::from(&b"hello world"[..]);
+    a.slice(5..44);
+}
+
+#[test]
+#[should_panic]
+fn slice_oob_2() {
+    let a = Bytes::from(&b"hello world"[..]);
+    a.slice(44..49);
+}
+
+#[test]
+fn split_off() {
+    let mut hello = Bytes::from(&b"helloworld"[..]);
+    let world = hello.split_off(5);
+
+    assert_eq!(hello, &b"hello"[..]);
+    assert_eq!(world, &b"world"[..]);
+
+    let mut hello = BytesMut::from(&b"helloworld"[..]);
+    let world = hello.split_off(5);
+
+    assert_eq!(hello, &b"hello"[..]);
+    assert_eq!(world, &b"world"[..]);
+}
+
+#[test]
+#[should_panic]
+fn split_off_oob() {
+    let mut hello = Bytes::from(&b"helloworld"[..]);
+    let _ = hello.split_off(44);
+}
+
+#[test]
+fn split_off_uninitialized() {
+    let mut bytes = BytesMut::with_capacity(1024);
+    let other = bytes.split_off(128);
+
+    assert_eq!(bytes.len(), 0);
+    assert_eq!(bytes.capacity(), 128);
+
+    assert_eq!(other.len(), 0);
+    assert_eq!(other.capacity(), 896);
+}
+
+#[test]
+fn split_off_to_loop() {
+    let s = b"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    for i in 0..(s.len() + 1) {
+        {
+            let mut bytes = Bytes::from(&s[..]);
+            let off = bytes.split_off(i);
+            assert_eq!(i, bytes.len());
+            let mut sum = Vec::new();
+            sum.extend(bytes.iter());
+            sum.extend(off.iter());
+            assert_eq!(&s[..], &sum[..]);
+        }
+        {
+            let mut bytes = BytesMut::from(&s[..]);
+            let off = bytes.split_off(i);
+            assert_eq!(i, bytes.len());
+            let mut sum = Vec::new();
+            sum.extend(&bytes);
+            sum.extend(&off);
+            assert_eq!(&s[..], &sum[..]);
+        }
+        {
+            let mut bytes = Bytes::from(&s[..]);
+            let off = bytes.split_to(i);
+            assert_eq!(i, off.len());
+            let mut sum = Vec::new();
+            sum.extend(off.iter());
+            sum.extend(bytes.iter());
+            assert_eq!(&s[..], &sum[..]);
+        }
+        {
+            let mut bytes = BytesMut::from(&s[..]);
+            let off = bytes.split_to(i);
+            assert_eq!(i, off.len());
+            let mut sum = Vec::new();
+            sum.extend(&off);
+            sum.extend(&bytes);
+            assert_eq!(&s[..], &sum[..]);
+        }
+    }
+}
+
+#[test]
+fn split_to_1() {
+    // Static
+    let mut a = Bytes::from_static(SHORT);
+    let b = a.split_to(4);
+
+    assert_eq!(SHORT[4..], a);
+    assert_eq!(SHORT[..4], b);
+
+    // Allocated
+    let mut a = Bytes::copy_from_slice(LONG);
+    let b = a.split_to(4);
+
+    assert_eq!(LONG[4..], a);
+    assert_eq!(LONG[..4], b);
+
+    let mut a = Bytes::copy_from_slice(LONG);
+    let b = a.split_to(30);
+
+    assert_eq!(LONG[30..], a);
+    assert_eq!(LONG[..30], b);
+}
+
+#[test]
+fn split_to_2() {
+    let mut a = Bytes::from(LONG);
+    assert_eq!(LONG, a);
+
+    let b = a.split_to(1);
+
+    assert_eq!(LONG[1..], a);
+    drop(b);
+}
+
+#[test]
+#[should_panic]
+fn split_to_oob() {
+    let mut hello = Bytes::from(&b"helloworld"[..]);
+    let _ = hello.split_to(33);
+}
+
+#[test]
+#[should_panic]
+fn split_to_oob_mut() {
+    let mut hello = BytesMut::from(&b"helloworld"[..]);
+    let _ = hello.split_to(33);
+}
+
+#[test]
+#[should_panic]
+fn split_to_uninitialized() {
+    let mut bytes = BytesMut::with_capacity(1024);
+    let _other = bytes.split_to(128);
+}
+
+#[test]
+fn split_off_to_at_gt_len() {
+    fn make_bytes() -> Bytes {
+        let mut bytes = BytesMut::with_capacity(100);
+        bytes.put_slice(&[10, 20, 30, 40]);
+        bytes.freeze()
+    }
+
+    use std::panic;
+
+    let _ = make_bytes().split_to(4);
+    let _ = make_bytes().split_off(4);
+
+    assert!(panic::catch_unwind(move || {
+        let _ = make_bytes().split_to(5);
+    }).is_err());
+
+    assert!(panic::catch_unwind(move || {
+        let _ = make_bytes().split_off(5);
+    }).is_err());
+}
+
+#[test]
+fn truncate() {
+    let s = &b"helloworld"[..];
+    let mut hello = Bytes::from(s);
+    hello.truncate(15);
+    assert_eq!(hello, s);
+    hello.truncate(10);
+    assert_eq!(hello, s);
+    hello.truncate(5);
+    assert_eq!(hello, "hello");
+}
+
+#[test]
+fn freeze_clone_shared() {
+    let s = &b"abcdefgh"[..];
+    let b = BytesMut::from(s).split().freeze();
+    assert_eq!(b, s);
+    let c = b.clone();
+    assert_eq!(c, s);
+}
+
+#[test]
+fn freeze_clone_unique() {
+    let s = &b"abcdefgh"[..];
+    let b = BytesMut::from(s).freeze();
+    assert_eq!(b, s);
+    let c = b.clone();
+    assert_eq!(c, s);
+}
+
+#[test]
+fn fns_defined_for_bytes_mut() {
+    let mut bytes = BytesMut::from(&b"hello world"[..]);
+
+    bytes.as_ptr();
+    bytes.as_mut_ptr();
+
+    // Iterator
+    let v: Vec<u8> = bytes.as_ref().iter().cloned().collect();
+    assert_eq!(&v[..], bytes);
+}
+
+#[test]
+fn reserve_convert() {
+    // Vec -> Vec
+    let mut bytes = BytesMut::from(LONG);
+    bytes.reserve(64);
+    assert_eq!(bytes.capacity(), LONG.len() + 64);
+
+    // Arc -> Vec
+    let mut bytes = BytesMut::from(LONG);
+    let a = bytes.split_to(30);
+
+    bytes.reserve(128);
+    assert!(bytes.capacity() >= bytes.len() + 128);
+
+    drop(a);
+}
+
+#[test]
+fn reserve_growth() {
+    let mut bytes = BytesMut::with_capacity(64);
+    bytes.put("hello world".as_bytes());
+    let _ = bytes.split();
+
+    bytes.reserve(65);
+    assert_eq!(bytes.capacity(), 128);
+}
+
+#[test]
+fn reserve_allocates_at_least_original_capacity() {
+    let mut bytes = BytesMut::with_capacity(1024);
+
+    for i in 0..1020 {
+        bytes.put_u8(i as u8);
+    }
+
+    let _other = bytes.split();
+
+    bytes.reserve(16);
+    assert_eq!(bytes.capacity(), 1024);
+}
+
+#[test]
+fn reserve_max_original_capacity_value() {
+    const SIZE: usize = 128 * 1024;
+
+    let mut bytes = BytesMut::with_capacity(SIZE);
+
+    for _ in 0..SIZE {
+        bytes.put_u8(0u8);
+    }
+
+    let _other = bytes.split();
+
+    bytes.reserve(16);
+    assert_eq!(bytes.capacity(), 64 * 1024);
+}
+
+#[test]
+fn reserve_vec_recycling() {
+    let mut bytes = BytesMut::with_capacity(16);
+    assert_eq!(bytes.capacity(), 16);
+    let addr = bytes.as_ptr() as usize;
+    bytes.put("0123456789012345".as_bytes());
+    assert_eq!(bytes.as_ptr() as usize, addr);
+    bytes.advance(10);
+    assert_eq!(bytes.capacity(), 6);
+    bytes.reserve(8);
+    assert_eq!(bytes.capacity(), 16);
+    assert_eq!(bytes.as_ptr() as usize, addr);
+}
+
+#[test]
+fn reserve_in_arc_unique_does_not_overallocate() {
+    let mut bytes = BytesMut::with_capacity(1000);
+    let _ = bytes.split();
+
+    // now bytes is Arc and refcount == 1
+
+    assert_eq!(1000, bytes.capacity());
+    bytes.reserve(2001);
+    assert_eq!(2001, bytes.capacity());
+}
+
+#[test]
+fn reserve_in_arc_unique_doubles() {
+    let mut bytes = BytesMut::with_capacity(1000);
+    let _ = bytes.split();
+
+    // now bytes is Arc and refcount == 1
+
+    assert_eq!(1000, bytes.capacity());
+    bytes.reserve(1001);
+    assert_eq!(2000, bytes.capacity());
+}
+
+#[test]
+fn reserve_in_arc_nonunique_does_not_overallocate() {
+    let mut bytes = BytesMut::with_capacity(1000);
+    let _copy = bytes.split();
+
+    // now bytes is Arc and refcount == 2
+
+    assert_eq!(1000, bytes.capacity());
+    bytes.reserve(2001);
+    assert_eq!(2001, bytes.capacity());
+}
+
+#[test]
+fn extend_mut() {
+    let mut bytes = BytesMut::with_capacity(0);
+    bytes.extend(LONG);
+    assert_eq!(*bytes, LONG[..]);
+}
+
+#[test]
+fn extend_from_slice_mut() {
+    for &i in &[3, 34] {
+        let mut bytes = BytesMut::new();
+        bytes.extend_from_slice(&LONG[..i]);
+        bytes.extend_from_slice(&LONG[i..]);
+        assert_eq!(LONG[..], *bytes);
+    }
+}
+
+#[test]
+fn extend_mut_without_size_hint() {
+    let mut bytes = BytesMut::with_capacity(0);
+    let mut long_iter = LONG.iter();
+
+    // Use iter::from_fn since it doesn't know a size_hint
+    bytes.extend(std::iter::from_fn(|| long_iter.next()));
+    assert_eq!(*bytes, LONG[..]);
+}
+
+#[test]
+fn from_static() {
+    let mut a = Bytes::from_static(b"ab");
+    let b = a.split_off(1);
+
+    assert_eq!(a, b"a"[..]);
+    assert_eq!(b, b"b"[..]);
+}
+
+#[test]
+fn advance_static() {
+    let mut a = Bytes::from_static(b"hello world");
+    a.advance(6);
+    assert_eq!(a, &b"world"[..]);
+}
+
+#[test]
+fn advance_vec() {
+    let mut a = Bytes::from(b"hello world boooo yah world zomg wat wat".to_vec());
+    a.advance(16);
+    assert_eq!(a, b"o yah world zomg wat wat"[..]);
+
+    a.advance(4);
+    assert_eq!(a, b"h world zomg wat wat"[..]);
+
+    a.advance(6);
+    assert_eq!(a, b"d zomg wat wat"[..]);
+}
+
+#[test]
+fn advance_bytes_mut() {
+    let mut a = BytesMut::from("hello world boooo yah world zomg wat wat");
+    a.advance(16);
+    assert_eq!(a, b"o yah world zomg wat wat"[..]);
+
+    a.advance(4);
+    assert_eq!(a, b"h world zomg wat wat"[..]);
+
+    // Reserve some space.
+    a.reserve(1024);
+    assert_eq!(a, b"h world zomg wat wat"[..]);
+
+    a.advance(6);
+    assert_eq!(a, b"d zomg wat wat"[..]);
+}
+
+#[test]
+#[should_panic]
+fn advance_past_len() {
+    let mut a = BytesMut::from("hello world");
+    a.advance(20);
+}
+
+#[test]
+// Only run these tests on little endian systems. CI uses qemu for testing
+// little endian... and qemu doesn't really support threading all that well.
+#[cfg(target_endian = "little")]
+fn stress() {
+    // Tests promoting a buffer from a vec -> shared in a concurrent situation
+    use std::sync::{Arc, Barrier};
+    use std::thread;
+
+    const THREADS: usize = 8;
+    const ITERS: usize = 1_000;
+
+    for i in 0..ITERS {
+        let data = [i as u8; 256];
+        let buf = Arc::new(Bytes::copy_from_slice(&data[..]));
+
+        let barrier = Arc::new(Barrier::new(THREADS));
+        let mut joins = Vec::with_capacity(THREADS);
+
+        for _ in 0..THREADS {
+            let c = barrier.clone();
+            let buf = buf.clone();
+
+            joins.push(thread::spawn(move || {
+                c.wait();
+                let buf: Bytes = (*buf).clone();
+                drop(buf);
+            }));
+        }
+
+        for th in joins {
+            th.join().unwrap();
+        }
+
+        assert_eq!(*buf, data[..]);
+    }
+}
+
+#[test]
+fn partial_eq_bytesmut() {
+    let bytes = Bytes::from(&b"The quick red fox"[..]);
+    let bytesmut = BytesMut::from(&b"The quick red fox"[..]);
+    assert!(bytes == bytesmut);
+    assert!(bytesmut == bytes);
+    let bytes2 = Bytes::from(&b"Jumped over the lazy brown dog"[..]);
+    assert!(bytes2 != bytesmut);
+    assert!(bytesmut != bytes2);
+}
+
+/*
+#[test]
+fn bytes_unsplit_basic() {
+    let buf = Bytes::from(&b"aaabbbcccddd"[..]);
+
+    let splitted = buf.split_off(6);
+    assert_eq!(b"aaabbb", &buf[..]);
+    assert_eq!(b"cccddd", &splitted[..]);
+
+    buf.unsplit(splitted);
+    assert_eq!(b"aaabbbcccddd", &buf[..]);
+}
+
+#[test]
+fn bytes_unsplit_empty_other() {
+    let buf = Bytes::from(&b"aaabbbcccddd"[..]);
+
+    // empty other
+    let other = Bytes::new();
+
+    buf.unsplit(other);
+    assert_eq!(b"aaabbbcccddd", &buf[..]);
+}
+
+#[test]
+fn bytes_unsplit_empty_self() {
+    // empty self
+    let mut buf = Bytes::new();
+
+    let mut other = Bytes::with_capacity(64);
+    other.extend_from_slice(b"aaabbbcccddd");
+
+    buf.unsplit(other);
+    assert_eq!(b"aaabbbcccddd", &buf[..]);
+}
+
+#[test]
+fn bytes_unsplit_arc_different() {
+    let mut buf = Bytes::with_capacity(64);
+    buf.extend_from_slice(b"aaaabbbbeeee");
+
+    buf.split_off(8); //arc
+
+    let mut buf2 = Bytes::with_capacity(64);
+    buf2.extend_from_slice(b"ccccddddeeee");
+
+    buf2.split_off(8); //arc
+
+    buf.unsplit(buf2);
+    assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
+}
+
+#[test]
+fn bytes_unsplit_arc_non_contiguous() {
+    let mut buf = Bytes::with_capacity(64);
+    buf.extend_from_slice(b"aaaabbbbeeeeccccdddd");
+
+    let mut buf2 = buf.split_off(8); //arc
+
+    let buf3 = buf2.split_off(4); //arc
+
+    buf.unsplit(buf3);
+    assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
+}
+
+#[test]
+fn bytes_unsplit_two_split_offs() {
+    let mut buf = Bytes::with_capacity(64);
+    buf.extend_from_slice(b"aaaabbbbccccdddd");
+
+    let mut buf2 = buf.split_off(8); //arc
+    let buf3 = buf2.split_off(4); //arc
+
+    buf2.unsplit(buf3);
+    buf.unsplit(buf2);
+    assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
+}
+
+#[test]
+fn bytes_unsplit_overlapping_references() {
+    let mut buf = Bytes::with_capacity(64);
+    buf.extend_from_slice(b"abcdefghijklmnopqrstuvwxyz");
+    let mut buf0010 = buf.slice(0..10);
+    let buf1020 = buf.slice(10..20);
+    let buf0515 = buf.slice(5..15);
+    buf0010.unsplit(buf1020);
+    assert_eq!(b"abcdefghijklmnopqrst", &buf0010[..]);
+    assert_eq!(b"fghijklmno", &buf0515[..]);
+}
+*/
+
+#[test]
+fn bytes_mut_unsplit_basic() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aaabbbcccddd");
+
+    let splitted = buf.split_off(6);
+    assert_eq!(b"aaabbb", &buf[..]);
+    assert_eq!(b"cccddd", &splitted[..]);
+
+    buf.unsplit(splitted);
+    assert_eq!(b"aaabbbcccddd", &buf[..]);
+}
+
+#[test]
+fn bytes_mut_unsplit_empty_other() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aaabbbcccddd");
+
+    // empty other
+    let other = BytesMut::new();
+
+    buf.unsplit(other);
+    assert_eq!(b"aaabbbcccddd", &buf[..]);
+}
+
+#[test]
+fn bytes_mut_unsplit_empty_self() {
+    // empty self
+    let mut buf = BytesMut::new();
+
+    let mut other = BytesMut::with_capacity(64);
+    other.extend_from_slice(b"aaabbbcccddd");
+
+    buf.unsplit(other);
+    assert_eq!(b"aaabbbcccddd", &buf[..]);
+}
+
+#[test]
+fn bytes_mut_unsplit_arc_different() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aaaabbbbeeee");
+
+    let _ = buf.split_off(8); //arc
+
+    let mut buf2 = BytesMut::with_capacity(64);
+    buf2.extend_from_slice(b"ccccddddeeee");
+
+    let _ = buf2.split_off(8); //arc
+
+    buf.unsplit(buf2);
+    assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
+}
+
+#[test]
+fn bytes_mut_unsplit_arc_non_contiguous() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aaaabbbbeeeeccccdddd");
+
+    let mut buf2 = buf.split_off(8); //arc
+
+    let buf3 = buf2.split_off(4); //arc
+
+    buf.unsplit(buf3);
+    assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
+}
+
+#[test]
+fn bytes_mut_unsplit_two_split_offs() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aaaabbbbccccdddd");
+
+    let mut buf2 = buf.split_off(8); //arc
+    let buf3 = buf2.split_off(4); //arc
+
+    buf2.unsplit(buf3);
+    buf.unsplit(buf2);
+    assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
+}
+
+#[test]
+fn from_iter_no_size_hint() {
+    use std::iter;
+
+    let mut expect = vec![];
+
+    let actual: Bytes = iter::repeat(b'x')
+        .scan(100, |cnt, item| {
+            if *cnt >= 1 {
+                *cnt -= 1;
+                expect.push(item);
+                Some(item)
+            } else {
+                None
+            }
+        })
+        .collect();
+
+    assert_eq!(&actual[..], &expect[..]);
+}
+
+fn test_slice_ref(bytes: &Bytes, start: usize, end: usize, expected: &[u8]) {
+    let slice = &(bytes.as_ref()[start..end]);
+    let sub = bytes.slice_ref(&slice);
+    assert_eq!(&sub[..], expected);
+}
+
+#[test]
+fn slice_ref_works() {
+    let bytes = Bytes::from(&b"012345678"[..]);
+
+    test_slice_ref(&bytes, 0, 0, b"");
+    test_slice_ref(&bytes, 0, 3, b"012");
+    test_slice_ref(&bytes, 2, 6, b"2345");
+    test_slice_ref(&bytes, 7, 9, b"78");
+    test_slice_ref(&bytes, 9, 9, b"");
+}
+
+
+#[test]
+fn slice_ref_empty() {
+    let bytes = Bytes::from(&b""[..]);
+    let slice = &(bytes.as_ref()[0..0]);
+
+    let sub = bytes.slice_ref(&slice);
+    assert_eq!(&sub[..], b"");
+}
+
+#[test]
+fn slice_ref_empty_subslice() {
+    let bytes = Bytes::from(&b"abcde"[..]);
+    let subbytes = bytes.slice(0..0);
+    let slice = &subbytes[..];
+    // The `slice` object is derived from the original `bytes` object
+    // so `slice_ref` should work.
+    assert_eq!(Bytes::new(), bytes.slice_ref(slice));
+}
+
+#[test]
+#[should_panic]
+fn slice_ref_catches_not_a_subset() {
+    let bytes = Bytes::from(&b"012345678"[..]);
+    let slice = &b"012345"[0..4];
+
+    bytes.slice_ref(slice);
+}
+
+#[test]
+fn slice_ref_not_an_empty_subset() {
+    let bytes = Bytes::from(&b"012345678"[..]);
+    let slice = &b""[0..0];
+
+    assert_eq!(Bytes::new(), bytes.slice_ref(slice));
+}
+
+#[test]
+fn empty_slice_ref_not_an_empty_subset() {
+    let bytes = Bytes::new();
+    let slice = &b"some other slice"[0..0];
+
+    assert_eq!(Bytes::new(), bytes.slice_ref(slice));
+}
+
+#[test]
+fn bytes_buf_mut_advance() {
+    let mut bytes = BytesMut::with_capacity(1024);
+
+    unsafe {
+        let ptr = bytes.bytes_mut().as_ptr();
+        assert_eq!(1024, bytes.bytes_mut().len());
+
+        bytes.advance_mut(10);
+
+        let next = bytes.bytes_mut().as_ptr();
+        assert_eq!(1024 - 10, bytes.bytes_mut().len());
+        assert_eq!(ptr.offset(10), next);
+
+        // advance to the end
+        bytes.advance_mut(1024 - 10);
+
+        // The buffer size is doubled
+        assert_eq!(1024, bytes.bytes_mut().len());
+    }
+}
+
+#[test]
+#[should_panic]
+fn bytes_reserve_overflow() {
+    let mut bytes = BytesMut::with_capacity(1024);
+    bytes.put_slice(b"hello world");
+
+    bytes.reserve(usize::MAX);
+}
+
+#[test]
+fn bytes_with_capacity_but_empty() {
+    // See https://github.com/tokio-rs/bytes/issues/340
+    let vec = Vec::with_capacity(1);
+    let _ = Bytes::from(vec);
+}
diff --git a/tests/test_bytes_odd_alloc.rs b/tests/test_bytes_odd_alloc.rs
new file mode 100644
index 0000000..4ce424b
--- /dev/null
+++ b/tests/test_bytes_odd_alloc.rs
@@ -0,0 +1,67 @@
+//! Test using `Bytes` with an allocator that hands out "odd" pointers for
+//! vectors (pointers where the LSB is set).
+
+use std::alloc::{GlobalAlloc, Layout, System};
+use std::ptr;
+
+use bytes::Bytes;
+
+#[global_allocator]
+static ODD: Odd = Odd;
+
+struct Odd;
+
+unsafe impl GlobalAlloc for Odd {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if layout.align() == 1 && layout.size() > 0 {
+            // Allocate slightly bigger so that we can offset the pointer by 1
+            let size = layout.size() + 1;
+            let new_layout = match Layout::from_size_align(size, 1) {
+                Ok(layout) => layout,
+                Err(_err) => return ptr::null_mut(),
+            };
+            let ptr = System.alloc(new_layout);
+            if !ptr.is_null() {
+                let ptr = ptr.offset(1);
+                ptr
+            } else {
+                ptr
+            }
+        } else {
+            System.alloc(layout)
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        if layout.align() == 1 && layout.size() > 0 {
+            let size = layout.size() + 1;
+            let new_layout = match Layout::from_size_align(size, 1) {
+                Ok(layout) => layout,
+                Err(_err) => std::process::abort(),
+            };
+            System.dealloc(ptr.offset(-1), new_layout);
+        } else {
+            System.dealloc(ptr, layout);
+        }
+    }
+}
+
+#[test]
+fn sanity_check_odd_allocator() {
+    let vec = vec![33u8; 1024];
+    let p = vec.as_ptr() as usize;
+    assert!(p & 0x1 == 0x1, "{:#b}", p);
+}
+
+#[test]
+fn test_bytes_from_vec_drop() {
+    let vec = vec![33u8; 1024];
+    let _b = Bytes::from(vec);
+}
+
+#[test]
+fn test_bytes_clone_drop() {
+    let vec = vec![33u8; 1024];
+    let b1 = Bytes::from(vec);
+    let _b2 = b1.clone();
+}
diff --git a/tests/test_bytes_vec_alloc.rs b/tests/test_bytes_vec_alloc.rs
new file mode 100644
index 0000000..dc007cf
--- /dev/null
+++ b/tests/test_bytes_vec_alloc.rs
@@ -0,0 +1,75 @@
+use std::alloc::{GlobalAlloc, Layout, System};
+use std::{mem, ptr};
+
+use bytes::{Buf, Bytes};
+
+#[global_allocator]
+static LEDGER: Ledger = Ledger;
+
+struct Ledger;
+
+const USIZE_SIZE: usize = mem::size_of::<usize>();
+
+unsafe impl GlobalAlloc for Ledger {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if layout.align() == 1 && layout.size() > 0 {
+            // Allocate extra space to stash a record of
+            // how much space there was.
+            let orig_size = layout.size();
+            let size = orig_size + USIZE_SIZE;
+            let new_layout = match Layout::from_size_align(size, 1) {
+                Ok(layout) => layout,
+                Err(_err) => return ptr::null_mut(),
+            };
+            let ptr = System.alloc(new_layout);
+            if !ptr.is_null() {
+                (ptr as *mut usize).write(orig_size);
+                let ptr = ptr.offset(USIZE_SIZE as isize);
+                ptr
+            } else {
+                ptr
+            }
+        } else {
+            System.alloc(layout)
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        if layout.align() == 1 && layout.size() > 0 {
+            let off_ptr = (ptr as *mut usize).offset(-1);
+            let orig_size = off_ptr.read();
+            if orig_size != layout.size() {
+                panic!("bad dealloc: alloc size was {}, dealloc size is {}", orig_size, layout.size());
+            }
+
+            let new_layout = match Layout::from_size_align(layout.size() + USIZE_SIZE, 1) {
+                Ok(layout) => layout,
+                Err(_err) => std::process::abort(),
+            };
+            System.dealloc(off_ptr as *mut u8, new_layout);
+        } else {
+            System.dealloc(ptr, layout);
+        }
+    }
+}
+#[test]
+fn test_bytes_advance() {
+    let mut bytes = Bytes::from(vec![10, 20, 30]);
+    bytes.advance(1);
+    drop(bytes);
+}
+
+#[test]
+fn test_bytes_truncate() {
+    let mut bytes = Bytes::from(vec![10, 20, 30]);
+    bytes.truncate(2);
+    drop(bytes);
+}
+
+#[test]
+fn test_bytes_truncate_and_advance() {
+    let mut bytes = Bytes::from(vec![10, 20, 30]);
+    bytes.truncate(2);
+    bytes.advance(1);
+    drop(bytes);
+}
diff --git a/tests/test_chain.rs b/tests/test_chain.rs
new file mode 100644
index 0000000..332571d
--- /dev/null
+++ b/tests/test_chain.rs
@@ -0,0 +1,133 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::{Buf, BufMut, Bytes};
+use bytes::buf::{BufExt, BufMutExt};
+use std::io::IoSlice;
+
+#[test]
+fn collect_two_bufs() {
+    let a = Bytes::from(&b"hello"[..]);
+    let b = Bytes::from(&b"world"[..]);
+
+    let res = a.chain(b).to_bytes();
+    assert_eq!(res, &b"helloworld"[..]);
+}
+
+#[test]
+fn writing_chained() {
+    let mut a = [0u8; 64];
+    let mut b = [0u8; 64];
+
+    {
+        let mut buf = (&mut a[..]).chain_mut(&mut b[..]);
+
+        for i in 0u8..128 {
+            buf.put_u8(i);
+        }
+    }
+
+    for i in 0..64 {
+        let expect = i as u8;
+        assert_eq!(expect, a[i]);
+        assert_eq!(expect + 64, b[i]);
+    }
+}
+
+#[test]
+fn iterating_two_bufs() {
+    let a = Bytes::from(&b"hello"[..]);
+    let b = Bytes::from(&b"world"[..]);
+
+    let res: Vec<u8> = a.chain(b).into_iter().collect();
+    assert_eq!(res, &b"helloworld"[..]);
+}
+
+#[test]
+fn vectored_read() {
+    let a = Bytes::from(&b"hello"[..]);
+    let b = Bytes::from(&b"world"[..]);
+
+    let mut buf = a.chain(b);
+
+    {
+        let b1: &[u8] = &mut [];
+        let b2: &[u8] = &mut [];
+        let b3: &[u8] = &mut [];
+        let b4: &[u8] = &mut [];
+        let mut iovecs = [
+            IoSlice::new(b1),
+            IoSlice::new(b2),
+            IoSlice::new(b3),
+            IoSlice::new(b4),
+        ];
+
+        assert_eq!(2, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(iovecs[0][..], b"hello"[..]);
+        assert_eq!(iovecs[1][..], b"world"[..]);
+        assert_eq!(iovecs[2][..], b""[..]);
+        assert_eq!(iovecs[3][..], b""[..]);
+    }
+
+    buf.advance(2);
+
+    {
+        let b1: &[u8] = &mut [];
+        let b2: &[u8] = &mut [];
+        let b3: &[u8] = &mut [];
+        let b4: &[u8] = &mut [];
+        let mut iovecs = [
+            IoSlice::new(b1),
+            IoSlice::new(b2),
+            IoSlice::new(b3),
+            IoSlice::new(b4),
+        ];
+
+        assert_eq!(2, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(iovecs[0][..], b"llo"[..]);
+        assert_eq!(iovecs[1][..], b"world"[..]);
+        assert_eq!(iovecs[2][..], b""[..]);
+        assert_eq!(iovecs[3][..], b""[..]);
+    }
+
+    buf.advance(3);
+
+    {
+        let b1: &[u8] = &mut [];
+        let b2: &[u8] = &mut [];
+        let b3: &[u8] = &mut [];
+        let b4: &[u8] = &mut [];
+        let mut iovecs = [
+            IoSlice::new(b1),
+            IoSlice::new(b2),
+            IoSlice::new(b3),
+            IoSlice::new(b4),
+        ];
+
+        assert_eq!(1, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(iovecs[0][..], b"world"[..]);
+        assert_eq!(iovecs[1][..], b""[..]);
+        assert_eq!(iovecs[2][..], b""[..]);
+        assert_eq!(iovecs[3][..], b""[..]);
+    }
+
+    buf.advance(3);
+
+    {
+        let b1: &[u8] = &mut [];
+        let b2: &[u8] = &mut [];
+        let b3: &[u8] = &mut [];
+        let b4: &[u8] = &mut [];
+        let mut iovecs = [
+            IoSlice::new(b1),
+            IoSlice::new(b2),
+            IoSlice::new(b3),
+            IoSlice::new(b4),
+        ];
+
+        assert_eq!(1, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(iovecs[0][..], b"ld"[..]);
+        assert_eq!(iovecs[1][..], b""[..]);
+        assert_eq!(iovecs[2][..], b""[..]);
+        assert_eq!(iovecs[3][..], b""[..]);
+    }
+}
diff --git a/tests/test_debug.rs b/tests/test_debug.rs
new file mode 100644
index 0000000..7528bac
--- /dev/null
+++ b/tests/test_debug.rs
@@ -0,0 +1,35 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::Bytes;
+
+#[test]
+fn fmt() {
+    let vec: Vec<_> = (0..0x100).map(|b| b as u8).collect();
+
+    let expected = "b\"\
+        \\0\\x01\\x02\\x03\\x04\\x05\\x06\\x07\
+        \\x08\\t\\n\\x0b\\x0c\\r\\x0e\\x0f\
+        \\x10\\x11\\x12\\x13\\x14\\x15\\x16\\x17\
+        \\x18\\x19\\x1a\\x1b\\x1c\\x1d\\x1e\\x1f\
+        \x20!\\\"#$%&'()*+,-./0123456789:;<=>?\
+        @ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\\\]^_\
+        `abcdefghijklmnopqrstuvwxyz{|}~\\x7f\
+        \\x80\\x81\\x82\\x83\\x84\\x85\\x86\\x87\
+        \\x88\\x89\\x8a\\x8b\\x8c\\x8d\\x8e\\x8f\
+        \\x90\\x91\\x92\\x93\\x94\\x95\\x96\\x97\
+        \\x98\\x99\\x9a\\x9b\\x9c\\x9d\\x9e\\x9f\
+        \\xa0\\xa1\\xa2\\xa3\\xa4\\xa5\\xa6\\xa7\
+        \\xa8\\xa9\\xaa\\xab\\xac\\xad\\xae\\xaf\
+        \\xb0\\xb1\\xb2\\xb3\\xb4\\xb5\\xb6\\xb7\
+        \\xb8\\xb9\\xba\\xbb\\xbc\\xbd\\xbe\\xbf\
+        \\xc0\\xc1\\xc2\\xc3\\xc4\\xc5\\xc6\\xc7\
+        \\xc8\\xc9\\xca\\xcb\\xcc\\xcd\\xce\\xcf\
+        \\xd0\\xd1\\xd2\\xd3\\xd4\\xd5\\xd6\\xd7\
+        \\xd8\\xd9\\xda\\xdb\\xdc\\xdd\\xde\\xdf\
+        \\xe0\\xe1\\xe2\\xe3\\xe4\\xe5\\xe6\\xe7\
+        \\xe8\\xe9\\xea\\xeb\\xec\\xed\\xee\\xef\
+        \\xf0\\xf1\\xf2\\xf3\\xf4\\xf5\\xf6\\xf7\
+        \\xf8\\xf9\\xfa\\xfb\\xfc\\xfd\\xfe\\xff\"";
+
+    assert_eq!(expected, format!("{:?}", Bytes::from(vec)));
+}
diff --git a/tests/test_iter.rs b/tests/test_iter.rs
new file mode 100644
index 0000000..13b86cd
--- /dev/null
+++ b/tests/test_iter.rs
@@ -0,0 +1,22 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::Bytes;
+
+#[test]
+fn iter_len() {
+    let buf = Bytes::from_static(b"hello world");
+    let iter = buf.iter();
+
+    assert_eq!(iter.size_hint(), (11, Some(11)));
+    assert_eq!(iter.len(), 11);
+}
+
+
+#[test]
+fn empty_iter_len() {
+    let buf = Bytes::from_static(b"");
+    let iter = buf.iter();
+
+    assert_eq!(iter.size_hint(), (0, Some(0)));
+    assert_eq!(iter.len(), 0);
+}
diff --git a/tests/test_reader.rs b/tests/test_reader.rs
new file mode 100644
index 0000000..9c5972a
--- /dev/null
+++ b/tests/test_reader.rs
@@ -0,0 +1,28 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use std::io::{BufRead, Read};
+
+use bytes::buf::{BufExt};
+
+#[test]
+fn read() {
+    let buf1 = &b"hello "[..];
+    let buf2 = &b"world"[..];
+    let buf = BufExt::chain(buf1, buf2); // Disambiguate with Read::chain
+    let mut buffer = Vec::new();
+    buf.reader().read_to_end(&mut buffer).unwrap();
+    assert_eq!(b"hello world", &buffer[..]);
+}
+
+#[test]
+fn buf_read() {
+    let buf1 = &b"hell"[..];
+    let buf2 = &b"o\nworld"[..];
+    let mut reader = BufExt::chain(buf1, buf2).reader();
+    let mut line = String::new();
+    reader.read_line(&mut line).unwrap();
+    assert_eq!("hello\n", &line);
+    line.clear();
+    reader.read_line(&mut line).unwrap();
+    assert_eq!("world", &line);
+}
diff --git a/tests/test_serde.rs b/tests/test_serde.rs
new file mode 100644
index 0000000..18b1356
--- /dev/null
+++ b/tests/test_serde.rs
@@ -0,0 +1,20 @@
+#![cfg(feature = "serde")]
+#![deny(warnings, rust_2018_idioms)]
+
+use serde_test::{Token, assert_tokens};
+
+#[test]
+fn test_ser_de_empty() {
+    let b = bytes::Bytes::new();
+    assert_tokens(&b, &[Token::Bytes(b"")]);
+    let b = bytes::BytesMut::with_capacity(0);
+    assert_tokens(&b, &[Token::Bytes(b"")]);
+}
+
+#[test]
+fn test_ser_de() {
+    let b = bytes::Bytes::from(&b"bytes"[..]);
+    assert_tokens(&b, &[Token::Bytes(b"bytes")]);
+    let b = bytes::BytesMut::from(&b"bytes"[..]);
+    assert_tokens(&b, &[Token::Bytes(b"bytes")]);
+}
diff --git a/tests/test_take.rs b/tests/test_take.rs
new file mode 100644
index 0000000..b9b525b
--- /dev/null
+++ b/tests/test_take.rs
@@ -0,0 +1,12 @@
+#![deny(warnings, rust_2018_idioms)]
+
+use bytes::buf::{Buf, BufExt};
+
+#[test]
+fn long_take() {
+    // Tests that get a take with a size greater than the buffer length will not
+    // overrun the buffer. Regression test for #138.
+    let buf = b"hello world".take(100);
+    assert_eq!(11, buf.remaining());
+    assert_eq!(b"hello world", buf.bytes());
+}
author	Chih-Hung Hsieh <chh@google.com>	2020-06-10 20:15:59 -0700
committer	Chih-Hung Hsieh <chh@google.com>	2020-06-10 20:15:59 -0700
commit	01ae379526218e7f6ca28510b6c06098419b7380 (patch)
tree	ded7cfd36c57807924e0b2e62439a8df9f6d32c1
parent	7457df12a2eb70afcfa283968f7d1fadf123b0a1 (diff)
download	bytes-01ae379526218e7f6ca28510b6c06098419b7380.tar.gz