Import bytes-0.5.4

* Add OWNERS and Android.bp

Bug: 143953733
Test: make
Change-Id: Ica69d7252abb1c2967f2c0e11a62d0bd83192fb3

1 files changed, 1088 insertions, 0 deletions

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)
+        }))
+    }
+}