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bytes/src/buf/buf_mut.rs
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Carl LercheandGitHub 8135c1f606 implicitly grow BytesMut; add BufMutExt::chain_mut (#316) 
This brings `BytesMut` in line with `Vec<u8>` behavior.

This also fixes an existing bug in BytesMut::bytes_mut that exposes
invalid slices. The bug was recently introduced and was only on master
and never released to `crates.io`.

In order to fix a test, `BufMutExt::chain_mut` is provided. Withou this,
it is not possible to chain two `&mut [u8]`.

Closes #170
2019-11-20 12:11:40 -08:00

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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());
}
}
impl<T: BufMut + ?Sized> BufMut for &mut T {
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)
}
}
impl<T: BufMut + ?Sized> BufMut for Box<T> {
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)
}
}
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..]
}
}
}
// 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)
}))
}
}
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