diff options
Diffstat (limited to 'src/buf/buf_mut.rs')
-rw-r--r-- | src/buf/buf_mut.rs | 77 |
1 files changed, 70 insertions, 7 deletions
diff --git a/src/buf/buf_mut.rs b/src/buf/buf_mut.rs index f736727..4c2bd2c 100644 --- a/src/buf/buf_mut.rs +++ b/src/buf/buf_mut.rs @@ -33,6 +33,10 @@ pub unsafe trait BufMut { /// This value is greater than or equal to the length of the slice returned /// by `chunk_mut()`. /// + /// Writing to a `BufMut` may involve allocating more memory on the fly. + /// Implementations may fail before reaching the number of bytes indicated + /// by this method if they encounter an allocation failure. + /// /// # Examples /// /// ``` @@ -158,6 +162,12 @@ pub unsafe trait BufMut { /// `chunk_mut()` returning an empty slice implies that `remaining_mut()` will /// return 0 and `remaining_mut()` returning 0 implies that `chunk_mut()` will /// return an empty slice. + /// + /// This function may trigger an out-of-memory abort if it tries to allocate + /// memory and fails to do so. + // The `chunk_mut` method was previously called `bytes_mut`. This alias makes the + // rename more easily discoverable. + #[cfg_attr(docsrs, doc(alias = "bytes_mut"))] fn chunk_mut(&mut self) -> &mut UninitSlice; /// Transfer bytes into `self` from `src` and advance the cursor by the @@ -251,6 +261,37 @@ pub unsafe trait BufMut { } } + /// Put `cnt` bytes `val` into `self`. + /// + /// Logically equivalent to calling `self.put_u8(val)` `cnt` times, but may work faster. + /// + /// `self` must have at least `cnt` remaining capacity. + /// + /// ``` + /// use bytes::BufMut; + /// + /// let mut dst = [0; 6]; + /// + /// { + /// let mut buf = &mut dst[..]; + /// buf.put_bytes(b'a', 4); + /// + /// assert_eq!(2, buf.remaining_mut()); + /// } + /// + /// assert_eq!(b"aaaa\0\0", &dst); + /// ``` + /// + /// # Panics + /// + /// This function panics if there is not enough remaining capacity in + /// `self`. + fn put_bytes(&mut self, val: u8, cnt: usize) { + for _ in 0..cnt { + self.put_u8(val); + } + } + /// Writes an unsigned 8 bit integer to `self`. /// /// The current position is advanced by 1. @@ -693,7 +734,7 @@ pub unsafe trait BufMut { self.put_slice(&n.to_le_bytes()[0..nbytes]); } - /// Writes a signed n-byte integer to `self` in big-endian byte order. + /// Writes low `nbytes` of a signed integer to `self` in big-endian byte order. /// /// The current position is advanced by `nbytes`. /// @@ -703,19 +744,19 @@ pub unsafe trait BufMut { /// use bytes::BufMut; /// /// let mut buf = vec![]; - /// buf.put_int(0x010203, 3); + /// buf.put_int(0x0504010203, 3); /// assert_eq!(buf, b"\x01\x02\x03"); /// ``` /// /// # Panics /// /// This function panics if there is not enough remaining capacity in - /// `self`. + /// `self` or if `nbytes` is greater than 8. 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. + /// Writes low `nbytes` of a signed integer to `self` in little-endian byte order. /// /// The current position is advanced by `nbytes`. /// @@ -725,14 +766,14 @@ pub unsafe trait BufMut { /// use bytes::BufMut; /// /// let mut buf = vec![]; - /// buf.put_int_le(0x010203, 3); + /// buf.put_int_le(0x0504010203, 3); /// assert_eq!(buf, b"\x03\x02\x01"); /// ``` /// /// # Panics /// /// This function panics if there is not enough remaining capacity in - /// `self`. + /// `self` or if `nbytes` is greater than 8. fn put_int_le(&mut self, n: i64, nbytes: usize) { self.put_slice(&n.to_le_bytes()[0..nbytes]); } @@ -1009,12 +1050,29 @@ unsafe impl BufMut for &mut [u8] { let (_, b) = core::mem::replace(self, &mut []).split_at_mut(cnt); *self = b; } + + #[inline] + fn put_slice(&mut self, src: &[u8]) { + self[..src.len()].copy_from_slice(src); + unsafe { + self.advance_mut(src.len()); + } + } + + fn put_bytes(&mut self, val: u8, cnt: usize) { + assert!(self.remaining_mut() >= cnt); + unsafe { + ptr::write_bytes(self.as_mut_ptr(), val, cnt); + self.advance_mut(cnt); + } + } } unsafe impl BufMut for Vec<u8> { #[inline] fn remaining_mut(&self) -> usize { - usize::MAX - self.len() + // A vector can never have more than isize::MAX bytes + core::isize::MAX as usize - self.len() } #[inline] @@ -1072,6 +1130,11 @@ unsafe impl BufMut for Vec<u8> { fn put_slice(&mut self, src: &[u8]) { self.extend_from_slice(src); } + + fn put_bytes(&mut self, val: u8, cnt: usize) { + let new_len = self.len().checked_add(cnt).unwrap(); + self.resize(new_len, val); + } } // The existence of this function makes the compiler catch if the BufMut |