chore: prepare bytes v1.3.0 (#579)

Fixes #549

.github/workflows/ci.yml

@@ -11,6 +11,7 @@ on:
 env:
   RUSTFLAGS: -Dwarnings
   RUST_BACKTRACE: 1
+  nightly: nightly-2022-11-12
 
 defaults:
   run:
@@ -22,7 +23,7 @@ jobs:
     name: rustfmt
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
     - name: Install Rust
       run: rustup update stable && rustup default stable
     - name: Check formatting
@@ -34,7 +35,7 @@ jobs:
   #   name: clippy
   #   runs-on: ubuntu-latest
   #   steps:
-  #   - uses: actions/checkout@v2
+  #   - uses: actions/checkout@v3
   #   - name: Apply clippy lints
   #     run: cargo clippy --all-features
 
@@ -47,7 +48,7 @@ jobs:
     name: minrust
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
         run: rustup update 1.39.0 && rustup default 1.39.0
       - name: Check
@@ -64,7 +65,7 @@ jobs:
           - windows-latest
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
         # --no-self-update is necessary because the windows environment cannot self-update rustup.exe.
         run: rustup update stable --no-self-update && rustup default stable
@@ -74,14 +75,11 @@ jobs:
   # Nightly
   nightly:
     name: nightly
-    env:
-      # Pin nightly to avoid being impacted by breakage
-      RUST_VERSION: nightly-2019-09-25
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
-        run: rustup update $RUST_VERSION && rustup default $RUST_VERSION
+        run: rustup update $nightly && rustup default $nightly
       - name: Test
         run: . ci/test-stable.sh test
 
@@ -96,9 +94,9 @@ jobs:
           - powerpc-unknown-linux-gnu
           - powerpc64-unknown-linux-gnu
           - wasm32-unknown-unknown
-    runs-on: ubuntu-16.04
+    runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
         run: rustup update stable && rustup default stable
       - name: cross build --target ${{ matrix.target }}
@@ -118,25 +116,29 @@ jobs:
     name: tsan
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
-        run: rustup update nightly && rustup default nightly
+        run: rustup update $nightly && rustup default $nightly
       - name: Install rust-src
         run: rustup component add rust-src
       - name: ASAN / TSAN
         run: . ci/tsan.sh
+  miri:
+    name: miri
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Miri
+        run: ci/miri.sh
 
   # Loom
   loom:
     name: loom
-    env:
-      # Pin nightly to avoid being impacted by breakage
-      RUST_VERSION: nightly-2020-05-19
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
-        run: rustup update $RUST_VERSION && rustup default $RUST_VERSION
+        run: rustup update $nightly && rustup default $nightly
       - name: Loom tests
         run: RUSTFLAGS="--cfg loom -Dwarnings" cargo test --lib
 
@@ -149,13 +151,17 @@ jobs:
       - nightly
       - minrust
       - cross
+      - tsan
+      - loom
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
         run: rustup update stable && rustup default stable
       - name: Build documentation
         run: cargo doc --no-deps --all-features
+        env:
+          RUSTDOCFLAGS: --cfg docsrs
       - name: Publish documentation
         run: |
           cd target/doc

CHANGELOG.md

@@ -1,3 +1,105 @@
+# 1.3.0 (November 20, 2022)
+
+### Added
+
+- Rename and expose `BytesMut::spare_capacity_mut` (#572)
+- Implement native-endian get and put functions for `Buf` and `BufMut` (#576)
+
+### Fixed
+
+- Don't have important data in unused capacity when calling reserve (#563)
+
+### Documented
+
+- `Bytes::new` etc should return `Self` not `Bytes` (#568)
+
+# 1.2.1 (July 30, 2022)
+
+### Fixed
+
+- Fix unbounded memory growth when using `reserve` (#560)
+
+# 1.2.0 (July 19, 2022)
+
+### Added
+
+- Add `BytesMut::zeroed` (#517)
+- Implement `Extend<Bytes>` for `BytesMut` (#527)
+- Add conversion from `BytesMut` to `Vec<u8>` (#543, #554)
+- Add conversion from `Bytes` to `Vec<u8>` (#547)
+- Add `UninitSlice::as_uninit_slice_mut()` (#548)
+- Add const to `Bytes::{len,is_empty}` (#514)
+
+### Changed
+
+- Reuse vector in `BytesMut::reserve` (#539, #544)
+
+### Fixed
+
+- Make miri happy (#515, #523, #542, #545, #553)
+- Make tsan happy (#541)
+- Fix `remaining_mut()` on chain (#488)
+- Fix amortized asymptotics of `BytesMut` (#555)
+
+### Documented
+
+- Redraw layout diagram with box drawing characters (#539)
+- Clarify `BytesMut::unsplit` docs (#535)
+
+# 1.1.0 (August 25, 2021)
+
+### Added
+
+- `BufMut::put_bytes(self, val, cnt)` (#487)
+- Implement `From<Box<[u8]>>` for `Bytes` (#504)
+
+### Changed
+
+- Override `put_slice` for `&mut [u8]` (#483)
+- Panic on integer overflow in `Chain::remaining` (#482)
+- Add inline tags to `UninitSlice` methods (#443)
+- Override `copy_to_bytes` for Chain and Take (#481)
+- Keep capacity when unsplit on empty other buf (#502)
+
+### Documented
+
+- Clarify `BufMut` allocation guarantees (#501)
+- Clarify `BufMut::put_int` behavior (#486)
+- Clarify actions of `clear` and `truncate`. (#508)
+
+# 1.0.1 (January 11, 2021)
+
+### Changed
+- mark `Vec::put_slice` with `#[inline]` (#459)
+
+### Fixed
+- Fix deprecation warning (#457)
+- use `Box::into_raw` instead of `mem::forget`-in-disguise (#458)
+
+# 1.0.0 (December 22, 2020)
+
+### Changed
+- Rename `Buf`/`BufMut` methods `bytes()` and `bytes_mut()` to `chunk()` and `chunk_mut()` (#450)
+
+### Removed
+- remove unused Buf implementation. (#449)
+
+# 0.6.0 (October 21, 2020)
+
+API polish in preparation for a 1.0 release.
+
+### Changed
+- `BufMut` is now an `unsafe` trait (#432).
+- `BufMut::bytes_mut()` returns `&mut UninitSlice`, a type owned by `bytes` to
+  avoid undefined behavior (#433).
+- `Buf::copy_to_bytes(len)` replaces `Buf::into_bytes()` (#439).
+- `Buf`/`BufMut` utility methods are moved onto the trait and `*Ext` traits are
+  removed (#431).
+
+### Removed
+- `BufMut::bytes_vectored_mut()` (#430).
+- `new` methods on combinator types (#434).
+
 # 0.5.6 (July 13, 2020)
 
 - Improve `BytesMut` to reuse buffer when fully `advance`d.

Cargo.toml

@@ -2,18 +2,15 @@
 
 name = "bytes"
 # When releasing to crates.io:
-# - Update html_root_url.
 # - Update CHANGELOG.md.
-# - Update doc URL.
-# - Create "v0.5.x" git tag.
-version = "0.5.6"
+# - Create "v1.x.y" git tag.
+version = "1.3.0"
 license = "MIT"
 authors = [
     "Carl Lerche <[email protected]>",
     "Sean McArthur <[email protected]>",
 ]
 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"]
@@ -31,4 +28,7 @@ serde = { version = "1.0.60", optional = true, default-features = false, feature
 serde_test = "1.0"
 
 [target.'cfg(loom)'.dev-dependencies]
-loom = "0.3"
+loom = "0.5"
+
+[package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "docsrs"]

README.md

@@ -18,7 +18,7 @@ To use `bytes`, first add this to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-bytes = "0.5"
+bytes = "1"
 ```
 
 Next, add this to your crate:
@@ -33,7 +33,7 @@ Serde support is optional and disabled by default. To enable use the feature `se
 
 ```toml
 [dependencies]
-bytes = { version = "0.5", features = ["serde"] }
+bytes = { version = "1", features = ["serde"] }
 ```
 
 ## License

benches/buf.rs

@@ -46,14 +46,14 @@ impl TestBuf {
 }
 impl Buf for TestBuf {
     fn remaining(&self) -> usize {
-        return self.buf.len() - self.pos;
+        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] {
+    fn chunk(&self) -> &[u8] {
         if self.readlen == 0 {
             Default::default()
         } else {
@@ -87,8 +87,8 @@ impl Buf for TestBufC {
         self.inner.advance(cnt)
     }
     #[inline(never)]
-    fn bytes(&self) -> &[u8] {
-        self.inner.bytes()
+    fn chunk(&self) -> &[u8] {
+        self.inner.chunk()
     }
 }
 
@@ -159,7 +159,6 @@ macro_rules! bench_group {
 mod get_u8 {
     use super::*;
     bench_group!(get_u8);
-    bench!(option, option);
 }
 mod get_u16 {
     use super::*;

benches/bytes.rs

@@ -88,6 +88,7 @@ fn from_long_slice(b: &mut Bencher) {
 #[bench]
 fn slice_empty(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(i % 100..i % 100));

ci/miri.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+set -e
+
+rustup toolchain install nightly --component miri
+rustup override set nightly
+cargo miri setup
+
+export MIRIFLAGS="-Zmiri-strict-provenance"
+
+cargo miri test
+cargo miri test --target mips64-unknown-linux-gnuabi64

ci/test-stable.sh

@@ -5,7 +5,8 @@ set -ex
 cmd="${1:-test}"
 
 # Install cargo-hack for feature flag test
-cargo install cargo-hack
+host=$(rustc -Vv | grep host | sed 's/host: //')
+curl -LsSf https://github.com/taiki-e/cargo-hack/releases/latest/download/cargo-hack-$host.tar.gz | tar xzf - -C ~/.cargo/bin
 
 # Run with each feature
 # * --each-feature includes both default/no-default features

clippy.toml

@@ -0,0 +1 @@
+msrv = "1.39"

src/buf/buf_impl.rs

@@ -1,3 +1,7 @@
+#[cfg(feature = "std")]
+use crate::buf::{reader, Reader};
+use crate::buf::{take, Chain, Take};
+
 use core::{cmp, mem, ptr};
 
 #[cfg(feature = "std")]
@@ -12,7 +16,7 @@ macro_rules! buf_get_impl {
         // 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()
+            .chunk()
             .get(..SIZE)
             .map(|src| unsafe { $typ::$conv(*(src as *const _ as *const [_; SIZE])) });
 
@@ -74,7 +78,7 @@ pub trait Buf {
     /// the buffer.
     ///
     /// This value is greater than or equal to the length of the slice returned
-    /// by `bytes`.
+    /// by `chunk()`.
     ///
     /// # Examples
     ///
@@ -111,31 +115,34 @@ pub trait Buf {
     ///
     /// let mut buf = &b"hello world"[..];
     ///
-    /// assert_eq!(buf.bytes(), &b"hello world"[..]);
+    /// assert_eq!(buf.chunk(), &b"hello world"[..]);
     ///
     /// buf.advance(6);
     ///
-    /// assert_eq!(buf.bytes(), &b"world"[..]);
+    /// assert_eq!(buf.chunk(), &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
+    /// i.e., `Buf::remaining` returns 0, calls to `chunk()` should return an
     /// empty slice.
-    fn bytes(&self) -> &[u8];
+    // The `chunk` method was previously called `bytes`. This alias makes the rename
+    // more easily discoverable.
+    #[cfg_attr(docsrs, doc(alias = "bytes"))]
+    fn chunk(&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
+    /// If the `Buf` is backed by disjoint slices of bytes, `chunk_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
+    /// the slices **will not** be modified. If `chunk_vectored` does not fill every
     /// entry in `dst`, then `dst` is guaranteed to contain all remaining slices
     /// in `self.
     ///
@@ -145,7 +152,7 @@ pub trait Buf {
     /// # 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
+    /// i.e., `Buf::remaining` returns 0, calls to `chunk_vectored` must return 0
     /// without mutating `dst`.
     ///
     /// Implementations should also take care to properly handle being called
@@ -153,13 +160,13 @@ pub trait Buf {
     ///
     /// [`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 {
+    fn chunks_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());
+            dst[0] = IoSlice::new(self.chunk());
             1
         } else {
             0
@@ -168,7 +175,7 @@ pub trait Buf {
 
     /// Advance the internal cursor of the Buf
     ///
-    /// The next call to `bytes` will return a slice starting `cnt` bytes
+    /// The next call to `chunk()` will return a slice starting `cnt` bytes
     /// further into the underlying buffer.
     ///
     /// # Examples
@@ -178,11 +185,11 @@ pub trait Buf {
     ///
     /// let mut buf = &b"hello world"[..];
     ///
-    /// assert_eq!(buf.bytes(), &b"hello world"[..]);
+    /// assert_eq!(buf.chunk(), &b"hello world"[..]);
     ///
     /// buf.advance(6);
     ///
-    /// assert_eq!(buf.bytes(), &b"world"[..]);
+    /// assert_eq!(buf.chunk(), &b"world"[..]);
     /// ```
     ///
     /// # Panics
@@ -249,7 +256,7 @@ pub trait Buf {
             let cnt;
 
             unsafe {
-                let src = self.bytes();
+                let src = self.chunk();
                 cnt = cmp::min(src.len(), dst.len() - off);
 
                 ptr::copy_nonoverlapping(src.as_ptr(), dst[off..].as_mut_ptr(), cnt);
@@ -279,7 +286,7 @@ pub trait Buf {
     /// 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];
+        let ret = self.chunk()[0];
         self.advance(1);
         ret
     }
@@ -302,7 +309,7 @@ pub trait Buf {
     /// 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;
+        let ret = self.chunk()[0] as i8;
         self.advance(1);
         ret
     }
@@ -347,6 +354,29 @@ pub trait Buf {
         buf_get_impl!(self, u16::from_le_bytes);
     }
 
+    /// Gets an unsigned 16 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x08\x09 hello",
+    ///     false => b"\x09\x08 hello",
+    /// };
+    /// assert_eq!(0x0809, buf.get_u16_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u16_ne(&mut self) -> u16 {
+        buf_get_impl!(self, u16::from_ne_bytes);
+    }
+
     /// Gets a signed 16 bit integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by 2.
@@ -387,6 +417,29 @@ pub trait Buf {
         buf_get_impl!(self, i16::from_le_bytes);
     }
 
+    /// Gets a signed 16 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x08\x09 hello",
+    ///     false => b"\x09\x08 hello",
+    /// };
+    /// assert_eq!(0x0809, buf.get_i16_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i16_ne(&mut self) -> i16 {
+        buf_get_impl!(self, i16::from_ne_bytes);
+    }
+
     /// Gets an unsigned 32 bit integer from `self` in the big-endian byte order.
     ///
     /// The current position is advanced by 4.
@@ -427,6 +480,29 @@ pub trait Buf {
         buf_get_impl!(self, u32::from_le_bytes);
     }
 
+    /// Gets an unsigned 32 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x08\x09\xA0\xA1 hello",
+    ///     false => b"\xA1\xA0\x09\x08 hello",
+    /// };
+    /// assert_eq!(0x0809A0A1, buf.get_u32_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u32_ne(&mut self) -> u32 {
+        buf_get_impl!(self, u32::from_ne_bytes);
+    }
+
     /// Gets a signed 32 bit integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by 4.
@@ -467,6 +543,29 @@ pub trait Buf {
         buf_get_impl!(self, i32::from_le_bytes);
     }
 
+    /// Gets a signed 32 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x08\x09\xA0\xA1 hello",
+    ///     false => b"\xA1\xA0\x09\x08 hello",
+    /// };
+    /// assert_eq!(0x0809A0A1, buf.get_i32_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i32_ne(&mut self) -> i32 {
+        buf_get_impl!(self, i32::from_ne_bytes);
+    }
+
     /// Gets an unsigned 64 bit integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by 8.
@@ -507,6 +606,29 @@ pub trait Buf {
         buf_get_impl!(self, u64::from_le_bytes);
     }
 
+    /// Gets an unsigned 64 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x01\x02\x03\x04\x05\x06\x07\x08 hello",
+    ///     false => b"\x08\x07\x06\x05\x04\x03\x02\x01 hello",
+    /// };
+    /// assert_eq!(0x0102030405060708, buf.get_u64_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u64_ne(&mut self) -> u64 {
+        buf_get_impl!(self, u64::from_ne_bytes);
+    }
+
     /// Gets a signed 64 bit integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by 8.
@@ -547,6 +669,29 @@ pub trait Buf {
         buf_get_impl!(self, i64::from_le_bytes);
     }
 
+    /// Gets a signed 64 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x01\x02\x03\x04\x05\x06\x07\x08 hello",
+    ///     false => b"\x08\x07\x06\x05\x04\x03\x02\x01 hello",
+    /// };
+    /// assert_eq!(0x0102030405060708, buf.get_i64_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i64_ne(&mut self) -> i64 {
+        buf_get_impl!(self, i64::from_ne_bytes);
+    }
+
     /// Gets an unsigned 128 bit integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by 16.
@@ -587,6 +732,29 @@ pub trait Buf {
         buf_get_impl!(self, u128::from_le_bytes);
     }
 
+    /// Gets an unsigned 128 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16 hello",
+    ///     false => b"\x16\x15\x14\x13\x12\x11\x10\x09\x08\x07\x06\x05\x04\x03\x02\x01 hello",
+    /// };
+    /// assert_eq!(0x01020304050607080910111213141516, buf.get_u128_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_u128_ne(&mut self) -> u128 {
+        buf_get_impl!(self, u128::from_ne_bytes);
+    }
+
     /// Gets a signed 128 bit integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by 16.
@@ -627,6 +795,29 @@ pub trait Buf {
         buf_get_impl!(self, i128::from_le_bytes);
     }
 
+    /// Gets a signed 128 bit integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16 hello",
+    ///     false => b"\x16\x15\x14\x13\x12\x11\x10\x09\x08\x07\x06\x05\x04\x03\x02\x01 hello",
+    /// };
+    /// assert_eq!(0x01020304050607080910111213141516, buf.get_i128_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_i128_ne(&mut self) -> i128 {
+        buf_get_impl!(self, i128::from_ne_bytes);
+    }
+
     /// Gets an unsigned n-byte integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
@@ -667,6 +858,33 @@ pub trait Buf {
         buf_get_impl!(le => self, u64, nbytes);
     }
 
+    /// Gets an unsigned n-byte integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x01\x02\x03 hello",
+    ///     false => b"\x03\x02\x01 hello",
+    /// };
+    /// assert_eq!(0x010203, buf.get_uint_ne(3));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_uint_ne(&mut self, nbytes: usize) -> u64 {
+        if cfg!(target_endian = "big") {
+            self.get_uint(nbytes)
+        } else {
+            self.get_uint_le(nbytes)
+        }
+    }
+
     /// Gets a signed n-byte integer from `self` in big-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
@@ -707,6 +925,33 @@ pub trait Buf {
         buf_get_impl!(le => self, i64, nbytes);
     }
 
+    /// Gets a signed n-byte integer from `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x01\x02\x03 hello",
+    ///     false => b"\x03\x02\x01 hello",
+    /// };
+    /// assert_eq!(0x010203, buf.get_int_ne(3));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_int_ne(&mut self, nbytes: usize) -> i64 {
+        if cfg!(target_endian = "big") {
+            self.get_int(nbytes)
+        } else {
+            self.get_int_le(nbytes)
+        }
+    }
+
     /// Gets an IEEE754 single-precision (4 bytes) floating point number from
     /// `self` in big-endian byte order.
     ///
@@ -749,6 +994,30 @@ pub trait Buf {
         f32::from_bits(Self::get_u32_le(self))
     }
 
+    /// Gets an IEEE754 single-precision (4 bytes) floating point number from
+    /// `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x3F\x99\x99\x9A hello",
+    ///     false => b"\x9A\x99\x99\x3F hello",
+    /// };
+    /// assert_eq!(1.2f32, buf.get_f32_ne());
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_f32_ne(&mut self) -> f32 {
+        f32::from_bits(Self::get_u32_ne(self))
+    }
+
     /// Gets an IEEE754 double-precision (8 bytes) floating point number from
     /// `self` in big-endian byte order.
     ///
@@ -791,22 +1060,135 @@ pub trait Buf {
         f64::from_bits(Self::get_u64_le(self))
     }
 
-    /// Consumes remaining bytes inside self and returns new instance of `Bytes`
+    /// Gets an IEEE754 double-precision (8 bytes) floating point number from
+    /// `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 8.
     ///
     /// # Examples
     ///
     /// ```
     /// use bytes::Buf;
     ///
-    /// let bytes = (&b"hello world"[..]).to_bytes();
-    /// assert_eq!(&bytes[..], &b"hello world"[..]);
+    /// let mut buf: &[u8] = match cfg!(target_endian = "big") {
+    ///     true => b"\x3F\xF3\x33\x33\x33\x33\x33\x33 hello",
+    ///     false => b"\x33\x33\x33\x33\x33\x33\xF3\x3F hello",
+    /// };
+    /// assert_eq!(1.2f64, buf.get_f64_ne());
     /// ```
-    fn to_bytes(&mut self) -> crate::Bytes {
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining data in `self`.
+    fn get_f64_ne(&mut self) -> f64 {
+        f64::from_bits(Self::get_u64_ne(self))
+    }
+
+    /// Consumes `len` bytes inside self and returns new instance of `Bytes`
+    /// with this data.
+    ///
+    /// This function may be optimized by the underlying type to avoid actual
+    /// copies. For example, `Bytes` implementation will do a shallow copy
+    /// (ref-count increment).
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let bytes = (&b"hello world"[..]).copy_to_bytes(5);
+    /// assert_eq!(&bytes[..], &b"hello"[..]);
+    /// ```
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
         use super::BufMut;
-        let mut ret = crate::BytesMut::with_capacity(self.remaining());
-        ret.put(self);
+
+        assert!(len <= self.remaining(), "`len` greater than remaining");
+
+        let mut ret = crate::BytesMut::with_capacity(len);
+        ret.put(self.take(len));
         ret.freeze()
     }
+
+    /// 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};
+    ///
+    /// 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;
+    ///
+    /// let mut chain = b"hello "[..].chain(&b"world"[..]);
+    ///
+    /// let full = chain.copy_to_bytes(11);
+    /// assert_eq!(full.chunk(), 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::{Bytes, Buf};
+    /// 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)
+    }
 }
 
 macro_rules! deref_forward_buf {
@@ -815,13 +1197,13 @@ macro_rules! deref_forward_buf {
             (**self).remaining()
         }
 
-        fn bytes(&self) -> &[u8] {
-            (**self).bytes()
+        fn chunk(&self) -> &[u8] {
+            (**self).chunk()
         }
 
         #[cfg(feature = "std")]
-        fn bytes_vectored<'b>(&'b self, dst: &mut [IoSlice<'b>]) -> usize {
-            (**self).bytes_vectored(dst)
+        fn chunks_vectored<'b>(&'b self, dst: &mut [IoSlice<'b>]) -> usize {
+            (**self).chunks_vectored(dst)
         }
 
         fn advance(&mut self, cnt: usize) {
@@ -852,6 +1234,10 @@ macro_rules! deref_forward_buf {
             (**self).get_u16_le()
         }
 
+        fn get_u16_ne(&mut self) -> u16 {
+            (**self).get_u16_ne()
+        }
+
         fn get_i16(&mut self) -> i16 {
             (**self).get_i16()
         }
@@ -860,6 +1246,10 @@ macro_rules! deref_forward_buf {
             (**self).get_i16_le()
         }
 
+        fn get_i16_ne(&mut self) -> i16 {
+            (**self).get_i16_ne()
+        }
+
         fn get_u32(&mut self) -> u32 {
             (**self).get_u32()
         }
@@ -868,6 +1258,10 @@ macro_rules! deref_forward_buf {
             (**self).get_u32_le()
         }
 
+        fn get_u32_ne(&mut self) -> u32 {
+            (**self).get_u32_ne()
+        }
+
         fn get_i32(&mut self) -> i32 {
             (**self).get_i32()
         }
@@ -876,6 +1270,10 @@ macro_rules! deref_forward_buf {
             (**self).get_i32_le()
         }
 
+        fn get_i32_ne(&mut self) -> i32 {
+            (**self).get_i32_ne()
+        }
+
         fn get_u64(&mut self) -> u64 {
             (**self).get_u64()
         }
@@ -884,6 +1282,10 @@ macro_rules! deref_forward_buf {
             (**self).get_u64_le()
         }
 
+        fn get_u64_ne(&mut self) -> u64 {
+            (**self).get_u64_ne()
+        }
+
         fn get_i64(&mut self) -> i64 {
             (**self).get_i64()
         }
@@ -892,6 +1294,10 @@ macro_rules! deref_forward_buf {
             (**self).get_i64_le()
         }
 
+        fn get_i64_ne(&mut self) -> i64 {
+            (**self).get_i64_ne()
+        }
+
         fn get_uint(&mut self, nbytes: usize) -> u64 {
             (**self).get_uint(nbytes)
         }
@@ -900,6 +1306,10 @@ macro_rules! deref_forward_buf {
             (**self).get_uint_le(nbytes)
         }
 
+        fn get_uint_ne(&mut self, nbytes: usize) -> u64 {
+            (**self).get_uint_ne(nbytes)
+        }
+
         fn get_int(&mut self, nbytes: usize) -> i64 {
             (**self).get_int(nbytes)
         }
@@ -908,8 +1318,12 @@ macro_rules! deref_forward_buf {
             (**self).get_int_le(nbytes)
         }
 
-        fn to_bytes(&mut self) -> crate::Bytes {
-            (**self).to_bytes()
+        fn get_int_ne(&mut self, nbytes: usize) -> i64 {
+            (**self).get_int_ne(nbytes)
+        }
+
+        fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
+            (**self).copy_to_bytes(len)
         }
     };
 }
@@ -929,7 +1343,7 @@ impl Buf for &[u8] {
     }
 
     #[inline]
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         self
     }
 
@@ -939,35 +1353,6 @@ impl Buf for &[u8] {
     }
 }
 
-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 {
@@ -981,7 +1366,7 @@ impl<T: AsRef<[u8]>> Buf for std::io::Cursor<T> {
         len - pos as usize
     }
 
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         let len = self.get_ref().as_ref().len();
         let pos = self.position();
 

src/buf/buf_mut.rs

@@ -1,11 +1,8 @@
-use core::{
-    cmp,
-    mem::{self, MaybeUninit},
-    ptr, usize,
-};
-
+use crate::buf::{limit, Chain, Limit, UninitSlice};
 #[cfg(feature = "std")]
-use std::fmt;
+use crate::buf::{writer, Writer};
+
+use core::{cmp, mem, ptr, usize};
 
 use alloc::{boxed::Box, vec::Vec};
 
@@ -29,12 +26,16 @@ use alloc::{boxed::Box, vec::Vec};
 ///
 /// assert_eq!(buf, b"hello world");
 /// ```
-pub trait BufMut {
+pub unsafe 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`.
+    /// 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
     ///
@@ -55,11 +56,15 @@ pub trait BufMut {
     /// 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.
+    ///
+    /// # Note
+    ///
+    /// `remaining_mut` may return value smaller than actual available space.
     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
+    /// The next call to `chunk_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
@@ -72,19 +77,14 @@ pub trait 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');
+    /// // Write some data
+    /// buf.chunk_mut()[0..2].copy_from_slice(b"he");
+    /// unsafe { buf.advance_mut(2) };
     ///
-    ///     buf.advance_mut(2);
+    /// // write more bytes
+    /// buf.chunk_mut()[0..3].copy_from_slice(b"llo");
     ///
-    ///     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);
-    /// }
+    /// unsafe { buf.advance_mut(3); }
     ///
     /// assert_eq!(5, buf.len());
     /// assert_eq!(buf, b"hello");
@@ -143,14 +143,14 @@ pub trait BufMut {
     ///
     /// 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.chunk_mut()[0..].as_mut_ptr().write(b'h');
+    ///     buf.chunk_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.chunk_mut()[0..].as_mut_ptr().write(b'l');
+    ///     buf.chunk_mut()[1..].as_mut_ptr().write(b'l');
+    ///     buf.chunk_mut()[2..].as_mut_ptr().write(b'o');
     ///
     ///     buf.advance_mut(3);
     /// }
@@ -161,54 +161,18 @@ pub trait BufMut {
     ///
     /// # 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
+    /// This function should never panic. `chunk_mut` should return an empty
+    /// slice **if and only if** `remaining_mut()` returns 0. In other words,
+    /// `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.
-    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
-        }
-    }
+    /// 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
     /// number of bytes written.
@@ -240,8 +204,8 @@ pub trait BufMut {
             let l;
 
             unsafe {
-                let s = src.bytes();
-                let d = self.bytes_mut();
+                let s = src.chunk();
+                let d = self.chunk_mut();
                 l = cmp::min(s.len(), d.len());
 
                 ptr::copy_nonoverlapping(s.as_ptr(), d.as_mut_ptr() as *mut u8, l);
@@ -287,7 +251,7 @@ pub trait BufMut {
             let cnt;
 
             unsafe {
-                let dst = self.bytes_mut();
+                let dst = self.chunk_mut();
                 cnt = cmp::min(dst.len(), src.len() - off);
 
                 ptr::copy_nonoverlapping(src[off..].as_ptr(), dst.as_mut_ptr() as *mut u8, cnt);
@@ -301,6 +265,37 @@ pub 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.
@@ -391,6 +386,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes an unsigned 16 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u16_ne(0x0809);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x08\x09");
+    /// } else {
+    ///     assert_eq!(buf, b"\x09\x08");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u16_ne(&mut self, n: u16) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes a signed 16 bit integer to `self` in big-endian byte order.
     ///
     /// The current position is advanced by 2.
@@ -435,6 +456,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes a signed 16 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 2.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i16_ne(0x0809);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x08\x09");
+    /// } else {
+    ///     assert_eq!(buf, b"\x09\x08");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i16_ne(&mut self, n: i16) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes an unsigned 32 bit integer to `self` in big-endian byte order.
     ///
     /// The current position is advanced by 4.
@@ -479,6 +526,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes an unsigned 32 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u32_ne(0x0809A0A1);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x08\x09\xA0\xA1");
+    /// } else {
+    ///     assert_eq!(buf, b"\xA1\xA0\x09\x08");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_u32_ne(&mut self, n: u32) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes a signed 32 bit integer to `self` in big-endian byte order.
     ///
     /// The current position is advanced by 4.
@@ -523,6 +596,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes a signed 32 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i32_ne(0x0809A0A1);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x08\x09\xA0\xA1");
+    /// } else {
+    ///     assert_eq!(buf, b"\xA1\xA0\x09\x08");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_i32_ne(&mut self, n: i32) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes an unsigned 64 bit integer to `self` in the big-endian byte order.
     ///
     /// The current position is advanced by 8.
@@ -567,6 +666,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes an unsigned 64 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u64_ne(0x0102030405060708);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08");
+    /// } else {
+    ///     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_ne(&mut self, n: u64) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes a signed 64 bit integer to `self` in the big-endian byte order.
     ///
     /// The current position is advanced by 8.
@@ -611,6 +736,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes a signed 64 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i64_ne(0x0102030405060708);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08");
+    /// } else {
+    ///     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_ne(&mut self, n: i64) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes an unsigned 128 bit integer to `self` in the big-endian byte order.
     ///
     /// The current position is advanced by 16.
@@ -655,6 +806,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes an unsigned 128 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_u128_ne(0x01020304050607080910111213141516);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16");
+    /// } else {
+    ///     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_ne(&mut self, n: u128) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes a signed 128 bit integer to `self` in the big-endian byte order.
     ///
     /// The current position is advanced by 16.
@@ -699,6 +876,32 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes())
     }
 
+    /// Writes a signed 128 bit integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 16.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_i128_ne(0x01020304050607080910111213141516);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x10\x11\x12\x13\x14\x15\x16");
+    /// } else {
+    ///     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_ne(&mut self, n: i128) {
+        self.put_slice(&n.to_ne_bytes())
+    }
+
     /// Writes an unsigned n-byte integer to `self` in big-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
@@ -743,7 +946,7 @@ pub 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 an unsigned n-byte integer to `self` in the native-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
     ///
@@ -753,19 +956,49 @@ pub trait BufMut {
     /// use bytes::BufMut;
     ///
     /// let mut buf = vec![];
-    /// buf.put_int(0x010203, 3);
+    /// buf.put_uint_ne(0x010203, 3);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x01\x02\x03");
+    /// } else {
+    ///     assert_eq!(buf, b"\x03\x02\x01");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_uint_ne(&mut self, n: u64, nbytes: usize) {
+        if cfg!(target_endian = "big") {
+            self.put_uint(n, nbytes)
+        } else {
+            self.put_uint_le(n, nbytes)
+        }
+    }
+
+    /// Writes low `nbytes` of a signed 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(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`.
     ///
@@ -775,18 +1008,48 @@ pub 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]);
     }
 
+    /// Writes low `nbytes` of a signed integer to `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by `nbytes`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_int_ne(0x010203, 3);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x01\x02\x03");
+    /// } else {
+    ///     assert_eq!(buf, b"\x03\x02\x01");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self` or if `nbytes` is greater than 8.
+    fn put_int_ne(&mut self, n: i64, nbytes: usize) {
+        if cfg!(target_endian = "big") {
+            self.put_int(n, nbytes)
+        } else {
+            self.put_int_le(n, nbytes)
+        }
+    }
+
     /// Writes  an IEEE754 single-precision (4 bytes) floating point number to
     /// `self` in big-endian byte order.
     ///
@@ -833,6 +1096,33 @@ pub trait BufMut {
         self.put_u32_le(n.to_bits());
     }
 
+    /// Writes an IEEE754 single-precision (4 bytes) floating point number to
+    /// `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 4.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_f32_ne(1.2f32);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x3F\x99\x99\x9A");
+    /// } else {
+    ///     assert_eq!(buf, b"\x9A\x99\x99\x3F");
+    /// }
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_f32_ne(&mut self, n: f32) {
+        self.put_u32_ne(n.to_bits());
+    }
+
     /// Writes  an IEEE754 double-precision (8 bytes) floating point number to
     /// `self` in big-endian byte order.
     ///
@@ -878,6 +1168,110 @@ pub trait BufMut {
     fn put_f64_le(&mut self, n: f64) {
         self.put_u64_le(n.to_bits());
     }
+
+    /// Writes  an IEEE754 double-precision (8 bytes) floating point number to
+    /// `self` in native-endian byte order.
+    ///
+    /// The current position is advanced by 8.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut buf = vec![];
+    /// buf.put_f64_ne(1.2f64);
+    /// if cfg!(target_endian = "big") {
+    ///     assert_eq!(buf, b"\x3F\xF3\x33\x33\x33\x33\x33\x33");
+    /// } else {
+    ///     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_ne(&mut self, n: f64) {
+        self.put_u64_ne(n.to_bits());
+    }
+
+    /// Creates an adaptor which can write at most `limit` bytes to `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// 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;
+    /// 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;
+    ///
+    /// 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)
+    }
 }
 
 macro_rules! deref_forward_bufmut {
@@ -886,13 +1280,8 @@ macro_rules! deref_forward_bufmut {
             (**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)
+        fn chunk_mut(&mut self) -> &mut UninitSlice {
+            (**self).chunk_mut()
         }
 
         unsafe fn advance_mut(&mut self, cnt: usize) {
@@ -919,6 +1308,10 @@ macro_rules! deref_forward_bufmut {
             (**self).put_u16_le(n)
         }
 
+        fn put_u16_ne(&mut self, n: u16) {
+            (**self).put_u16_ne(n)
+        }
+
         fn put_i16(&mut self, n: i16) {
             (**self).put_i16(n)
         }
@@ -927,6 +1320,10 @@ macro_rules! deref_forward_bufmut {
             (**self).put_i16_le(n)
         }
 
+        fn put_i16_ne(&mut self, n: i16) {
+            (**self).put_i16_ne(n)
+        }
+
         fn put_u32(&mut self, n: u32) {
             (**self).put_u32(n)
         }
@@ -935,6 +1332,10 @@ macro_rules! deref_forward_bufmut {
             (**self).put_u32_le(n)
         }
 
+        fn put_u32_ne(&mut self, n: u32) {
+            (**self).put_u32_ne(n)
+        }
+
         fn put_i32(&mut self, n: i32) {
             (**self).put_i32(n)
         }
@@ -943,6 +1344,10 @@ macro_rules! deref_forward_bufmut {
             (**self).put_i32_le(n)
         }
 
+        fn put_i32_ne(&mut self, n: i32) {
+            (**self).put_i32_ne(n)
+        }
+
         fn put_u64(&mut self, n: u64) {
             (**self).put_u64(n)
         }
@@ -951,6 +1356,10 @@ macro_rules! deref_forward_bufmut {
             (**self).put_u64_le(n)
         }
 
+        fn put_u64_ne(&mut self, n: u64) {
+            (**self).put_u64_ne(n)
+        }
+
         fn put_i64(&mut self, n: i64) {
             (**self).put_i64(n)
         }
@@ -958,27 +1367,31 @@ macro_rules! deref_forward_bufmut {
         fn put_i64_le(&mut self, n: i64) {
             (**self).put_i64_le(n)
         }
+
+        fn put_i64_ne(&mut self, n: i64) {
+            (**self).put_i64_ne(n)
+        }
     };
 }
 
-impl<T: BufMut + ?Sized> BufMut for &mut T {
+unsafe impl<T: BufMut + ?Sized> BufMut for &mut T {
     deref_forward_bufmut!();
 }
 
-impl<T: BufMut + ?Sized> BufMut for Box<T> {
+unsafe impl<T: BufMut + ?Sized> BufMut for Box<T> {
     deref_forward_bufmut!();
 }
 
-impl BufMut for &mut [u8] {
+unsafe 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) }
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
+        // UninitSlice is repr(transparent), so safe to transmute
+        unsafe { &mut *(*self as *mut [u8] as *mut _) }
     }
 
     #[inline]
@@ -987,12 +1400,29 @@ 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);
+        }
+    }
 }
 
-impl BufMut for Vec<u8> {
+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]
@@ -1011,9 +1441,7 @@ impl BufMut for Vec<u8> {
     }
 
     #[inline]
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
-        use core::slice;
-
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
         if self.capacity() == self.len() {
             self.reserve(64); // Grow the vec
         }
@@ -1021,13 +1449,12 @@ impl BufMut for Vec<u8> {
         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..] }
+        let ptr = self.as_mut_ptr();
+        unsafe { &mut UninitSlice::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,
@@ -1040,7 +1467,7 @@ impl BufMut for Vec<u8> {
 
             // a block to contain the src.bytes() borrow
             {
-                let s = src.bytes();
+                let s = src.chunk();
                 l = s.len();
                 self.extend_from_slice(s);
             }
@@ -1049,52 +1476,17 @@ impl BufMut for Vec<u8> {
         }
     }
 
+    #[inline]
     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
 // 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)
-        }))
-    }
-}

src/buf/chain.rs

@@ -1,10 +1,6 @@
-use crate::buf::IntoIter;
-use crate::{Buf, BufMut};
+use crate::buf::{IntoIter, UninitSlice};
+use crate::{Buf, BufMut, Bytes};
 
-use core::mem::MaybeUninit;
-
-#[cfg(feature = "std")]
-use crate::buf::IoSliceMut;
 #[cfg(feature = "std")]
 use std::io::IoSlice;
 
@@ -20,12 +16,12 @@ use std::io::IoSlice;
 /// # Examples
 ///
 /// ```
-/// use bytes::{Bytes, Buf, buf::BufExt};
+/// use bytes::{Bytes, Buf};
 ///
 /// let mut buf = (&b"hello "[..])
 ///     .chain(&b"world"[..]);
 ///
-/// let full: Bytes = buf.to_bytes();
+/// let full: Bytes = buf.copy_to_bytes(11);
 /// assert_eq!(full[..], b"hello world"[..]);
 /// ```
 ///
@@ -40,7 +36,7 @@ pub struct Chain<T, 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> {
+    pub(crate) fn new(a: T, b: U) -> Chain<T, U> {
         Chain { a, b }
     }
 
@@ -49,7 +45,7 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let buf = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
@@ -65,14 +61,14 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let mut buf = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
     ///
     /// buf.first_mut().advance(1);
     ///
-    /// let full = buf.to_bytes();
+    /// let full = buf.copy_to_bytes(9);
     /// assert_eq!(full, b"elloworld"[..]);
     /// ```
     pub fn first_mut(&mut self) -> &mut T {
@@ -84,7 +80,7 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let buf = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
@@ -100,14 +96,14 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let mut buf = (&b"hello "[..])
     ///     .chain(&b"world"[..]);
     ///
     /// buf.last_mut().advance(1);
     ///
-    /// let full = buf.to_bytes();
+    /// let full = buf.copy_to_bytes(10);
     /// assert_eq!(full, b"hello orld"[..]);
     /// ```
     pub fn last_mut(&mut self) -> &mut U {
@@ -119,7 +115,7 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let chain = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
@@ -139,14 +135,14 @@ where
     U: Buf,
 {
     fn remaining(&self) -> usize {
-        self.a.remaining() + self.b.remaining()
+        self.a.remaining().checked_add(self.b.remaining()).unwrap()
     }
 
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         if self.a.has_remaining() {
-            self.a.bytes()
+            self.a.chunk()
         } else {
-            self.b.bytes()
+            self.b.chunk()
         }
     }
 
@@ -169,27 +165,47 @@ where
     }
 
     #[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..]);
+    fn chunks_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
+        let mut n = self.a.chunks_vectored(dst);
+        n += self.b.chunks_vectored(&mut dst[n..]);
         n
     }
+
+    fn copy_to_bytes(&mut self, len: usize) -> Bytes {
+        let a_rem = self.a.remaining();
+        if a_rem >= len {
+            self.a.copy_to_bytes(len)
+        } else if a_rem == 0 {
+            self.b.copy_to_bytes(len)
+        } else {
+            assert!(
+                len - a_rem <= self.b.remaining(),
+                "`len` greater than remaining"
+            );
+            let mut ret = crate::BytesMut::with_capacity(len);
+            ret.put(&mut self.a);
+            ret.put((&mut self.b).take(len - a_rem));
+            ret.freeze()
+        }
+    }
 }
 
-impl<T, U> BufMut for Chain<T, U>
+unsafe 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()
+        self.a
+            .remaining_mut()
+            .saturating_add(self.b.remaining_mut())
     }
 
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
         if self.a.has_remaining_mut() {
-            self.a.bytes_mut()
+            self.a.chunk_mut()
         } else {
-            self.b.bytes_mut()
+            self.b.chunk_mut()
         }
     }
 
@@ -210,13 +226,6 @@ where
 
         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>

src/buf/ext/mod.rs

@@ -1,186 +0,0 @@
-//! 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::chain::Chain;
-pub use self::limit::Limit;
-pub use self::take::Take;
-
-#[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::{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::{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::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 {}

src/buf/iter.rs

@@ -34,17 +34,16 @@ impl<T> IntoIter<T> {
     ///
     /// ```
     /// use bytes::Bytes;
-    /// use bytes::buf::IntoIter;
     ///
     /// let buf = Bytes::from_static(b"abc");
-    /// let mut iter = IntoIter::new(buf);
+    /// 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);
     /// ```
-    pub fn new(inner: T) -> IntoIter<T> {
+    pub(crate) fn new(inner: T) -> IntoIter<T> {
         IntoIter { inner }
     }
 
@@ -118,7 +117,7 @@ impl<T: Buf> Iterator for IntoIter<T> {
             return None;
         }
 
-        let b = self.inner.bytes()[0];
+        let b = self.inner.chunk()[0];
         self.inner.advance(1);
 
         Some(b)

src/buf/limit.rs

@@ -1,6 +1,7 @@
+use crate::buf::UninitSlice;
 use crate::BufMut;
 
-use core::{cmp, mem::MaybeUninit};
+use core::cmp;
 
 /// A `BufMut` adapter which limits the amount of bytes that can be written
 /// to an underlying buffer.
@@ -55,13 +56,13 @@ impl<T> Limit<T> {
     }
 }
 
-impl<T: BufMut> BufMut for Limit<T> {
+unsafe 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();
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
+        let bytes = self.inner.chunk_mut();
         let end = cmp::min(bytes.len(), self.limit);
         &mut bytes[..end]
     }

src/buf/mod.rs

@@ -18,13 +18,24 @@
 
 mod buf_impl;
 mod buf_mut;
-pub mod ext;
+mod chain;
 mod iter;
+mod limit;
+#[cfg(feature = "std")]
+mod reader;
+mod take;
+mod uninit_slice;
 mod vec_deque;
+#[cfg(feature = "std")]
+mod writer;
 
 pub use self::buf_impl::Buf;
 pub use self::buf_mut::BufMut;
-#[cfg(feature = "std")]
-pub use self::buf_mut::IoSliceMut;
-pub use self::ext::{BufExt, BufMutExt};
+pub use self::chain::Chain;
 pub use self::iter::IntoIter;
+pub use self::limit::Limit;
+pub use self::take::Take;
+pub use self::uninit_slice::UninitSlice;
+
+#[cfg(feature = "std")]
+pub use self::{reader::Reader, writer::Writer};

src/buf/reader.rs

@@ -24,7 +24,7 @@ impl<B: Buf> Reader<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let buf = b"hello world".reader();
     ///
@@ -46,7 +46,7 @@ impl<B: Buf> Reader<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     /// use std::io;
     ///
     /// let mut buf = b"hello world".reader();
@@ -73,7 +73,7 @@ impl<B: Buf + Sized> io::Read for Reader<B> {
 
 impl<B: Buf + Sized> io::BufRead for Reader<B> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
-        Ok(self.buf.bytes())
+        Ok(self.buf.chunk())
     }
     fn consume(&mut self, amt: usize) {
         self.buf.advance(amt)

src/buf/take.rs

@@ -1,11 +1,11 @@
-use crate::Buf;
+use crate::{Buf, Bytes};
 
 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.BufExt.html#method.take) for more details.
+/// documentation of [`take()`](trait.Buf.html#method.take) for more details.
 #[derive(Debug)]
 pub struct Take<T> {
     inner: T,
@@ -22,7 +22,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::{BufMut, BufExt};
+    /// use bytes::{Buf, BufMut};
     ///
     /// let mut buf = b"hello world".take(2);
     /// let mut dst = vec![];
@@ -47,7 +47,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let buf = b"hello world".take(2);
     ///
@@ -64,7 +64,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, BufMut, buf::BufExt};
+    /// use bytes::{Buf, BufMut};
     ///
     /// let mut buf = b"hello world".take(2);
     /// let mut dst = vec![];
@@ -88,7 +88,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let mut buf = b"hello world".take(2);
     ///
@@ -110,7 +110,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{BufMut, buf::BufExt};
+    /// use bytes::{Buf, BufMut};
     ///
     /// let mut buf = b"hello world".take(2);
     /// let mut dst = vec![];
@@ -134,8 +134,8 @@ impl<T: Buf> Buf for Take<T> {
         cmp::min(self.inner.remaining(), self.limit)
     }
 
-    fn bytes(&self) -> &[u8] {
-        let bytes = self.inner.bytes();
+    fn chunk(&self) -> &[u8] {
+        let bytes = self.inner.chunk();
         &bytes[..cmp::min(bytes.len(), self.limit)]
     }
 
@@ -144,4 +144,12 @@ impl<T: Buf> Buf for Take<T> {
         self.inner.advance(cnt);
         self.limit -= cnt;
     }
+
+    fn copy_to_bytes(&mut self, len: usize) -> Bytes {
+        assert!(len <= self.remaining(), "`len` greater than remaining");
+
+        let r = self.inner.copy_to_bytes(len);
+        self.limit -= len;
+        r
+    }
 }

src/buf/uninit_slice.rs

@@ -0,0 +1,213 @@
+use core::fmt;
+use core::mem::MaybeUninit;
+use core::ops::{
+    Index, IndexMut, Range, RangeFrom, RangeFull, RangeInclusive, RangeTo, RangeToInclusive,
+};
+
+/// Uninitialized byte slice.
+///
+/// Returned by `BufMut::chunk_mut()`, the referenced byte slice may be
+/// uninitialized. The wrapper provides safe access without introducing
+/// undefined behavior.
+///
+/// The safety invariants of this wrapper are:
+///
+///  1. Reading from an `UninitSlice` is undefined behavior.
+///  2. Writing uninitialized bytes to an `UninitSlice` is undefined behavior.
+///
+/// The difference between `&mut UninitSlice` and `&mut [MaybeUninit<u8>]` is
+/// that it is possible in safe code to write uninitialized bytes to an
+/// `&mut [MaybeUninit<u8>]`, which this type prohibits.
+#[repr(transparent)]
+pub struct UninitSlice([MaybeUninit<u8>]);
+
+impl UninitSlice {
+    pub(crate) fn from_slice(slice: &mut [MaybeUninit<u8>]) -> &mut UninitSlice {
+        unsafe { &mut *(slice as *mut [MaybeUninit<u8>] as *mut UninitSlice) }
+    }
+
+    /// Create a `&mut UninitSlice` from a pointer and a length.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` references a valid memory region owned
+    /// by the caller representing a byte slice for the duration of `'a`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::UninitSlice;
+    ///
+    /// let bytes = b"hello world".to_vec();
+    /// let ptr = bytes.as_ptr() as *mut _;
+    /// let len = bytes.len();
+    ///
+    /// let slice = unsafe { UninitSlice::from_raw_parts_mut(ptr, len) };
+    /// ```
+    #[inline]
+    pub unsafe fn from_raw_parts_mut<'a>(ptr: *mut u8, len: usize) -> &'a mut UninitSlice {
+        let maybe_init: &mut [MaybeUninit<u8>] =
+            core::slice::from_raw_parts_mut(ptr as *mut _, len);
+        Self::from_slice(maybe_init)
+    }
+
+    /// Write a single byte at the specified offset.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if `index` is out of bounds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::UninitSlice;
+    ///
+    /// let mut data = [b'f', b'o', b'o'];
+    /// let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    ///
+    /// slice.write_byte(0, b'b');
+    ///
+    /// assert_eq!(b"boo", &data[..]);
+    /// ```
+    #[inline]
+    pub fn write_byte(&mut self, index: usize, byte: u8) {
+        assert!(index < self.len());
+
+        unsafe { self[index..].as_mut_ptr().write(byte) }
+    }
+
+    /// Copies bytes  from `src` into `self`.
+    ///
+    /// The length of `src` must be the same as `self`.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if `src` has a different length than `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::UninitSlice;
+    ///
+    /// let mut data = [b'f', b'o', b'o'];
+    /// let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    ///
+    /// slice.copy_from_slice(b"bar");
+    ///
+    /// assert_eq!(b"bar", &data[..]);
+    /// ```
+    #[inline]
+    pub fn copy_from_slice(&mut self, src: &[u8]) {
+        use core::ptr;
+
+        assert_eq!(self.len(), src.len());
+
+        unsafe {
+            ptr::copy_nonoverlapping(src.as_ptr(), self.as_mut_ptr(), self.len());
+        }
+    }
+
+    /// Return a raw pointer to the slice's buffer.
+    ///
+    /// # Safety
+    ///
+    /// The caller **must not** read from the referenced memory and **must not**
+    /// write **uninitialized** bytes to the slice either.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut data = [0, 1, 2];
+    /// let mut slice = &mut data[..];
+    /// let ptr = BufMut::chunk_mut(&mut slice).as_mut_ptr();
+    /// ```
+    #[inline]
+    pub fn as_mut_ptr(&mut self) -> *mut u8 {
+        self.0.as_mut_ptr() as *mut _
+    }
+
+    /// Return a `&mut [MaybeUninit<u8>]` to this slice's buffer.
+    ///
+    /// # Safety
+    ///
+    /// The caller **must not** read from the referenced memory and **must not** write
+    /// **uninitialized** bytes to the slice either. This is because `BufMut` implementation
+    /// that created the `UninitSlice` knows which parts are initialized. Writing uninitalized
+    /// bytes to the slice may cause the `BufMut` to read those bytes and trigger undefined
+    /// behavior.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut data = [0, 1, 2];
+    /// let mut slice = &mut data[..];
+    /// unsafe {
+    ///     let uninit_slice = BufMut::chunk_mut(&mut slice).as_uninit_slice_mut();
+    /// };
+    /// ```
+    #[inline]
+    pub unsafe fn as_uninit_slice_mut<'a>(&'a mut self) -> &'a mut [MaybeUninit<u8>] {
+        &mut *(self as *mut _ as *mut [MaybeUninit<u8>])
+    }
+
+    /// Returns the number of bytes in the slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut data = [0, 1, 2];
+    /// let mut slice = &mut data[..];
+    /// let len = BufMut::chunk_mut(&mut slice).len();
+    ///
+    /// assert_eq!(len, 3);
+    /// ```
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+}
+
+impl fmt::Debug for UninitSlice {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("UninitSlice[...]").finish()
+    }
+}
+
+macro_rules! impl_index {
+    ($($t:ty),*) => {
+        $(
+            impl Index<$t> for UninitSlice {
+                type Output = UninitSlice;
+
+                #[inline]
+                fn index(&self, index: $t) -> &UninitSlice {
+                    let maybe_uninit: &[MaybeUninit<u8>] = &self.0[index];
+                    unsafe { &*(maybe_uninit as *const [MaybeUninit<u8>] as *const UninitSlice) }
+                }
+            }
+
+            impl IndexMut<$t> for UninitSlice {
+                #[inline]
+                fn index_mut(&mut self, index: $t) -> &mut UninitSlice {
+                    let maybe_uninit: &mut [MaybeUninit<u8>] = &mut self.0[index];
+                    unsafe { &mut *(maybe_uninit as *mut [MaybeUninit<u8>] as *mut UninitSlice) }
+                }
+            }
+        )*
+    };
+}
+
+impl_index!(
+    Range<usize>,
+    RangeFrom<usize>,
+    RangeFull,
+    RangeInclusive<usize>,
+    RangeTo<usize>,
+    RangeToInclusive<usize>
+);

src/buf/vec_deque.rs

@@ -7,7 +7,7 @@ impl Buf for VecDeque<u8> {
         self.len()
     }
 
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         let (s1, s2) = self.as_slices();
         if s1.is_empty() {
             s2

src/buf/writer.rs

@@ -24,7 +24,7 @@ impl<B: BufMut> Writer<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufMutExt;
+    /// use bytes::BufMut;
     ///
     /// let buf = Vec::with_capacity(1024).writer();
     ///
@@ -41,7 +41,7 @@ impl<B: BufMut> Writer<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufMutExt;
+    /// use bytes::BufMut;
     ///
     /// let mut buf = vec![].writer();
     ///
@@ -58,7 +58,7 @@ impl<B: BufMut> Writer<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufMutExt;
+    /// use bytes::BufMut;
     /// use std::io;
     ///
     /// let mut buf = vec![].writer();

src/bytes.rs

@@ -2,24 +2,37 @@ use core::iter::FromIterator;
 use core::ops::{Deref, RangeBounds};
 use core::{cmp, fmt, hash, mem, ptr, slice, usize};
 
-use alloc::{borrow::Borrow, boxed::Box, string::String, vec::Vec};
+use alloc::{
+    alloc::{dealloc, Layout},
+    borrow::Borrow,
+    boxed::Box,
+    string::String,
+    vec::Vec,
+};
 
 use crate::buf::IntoIter;
 #[allow(unused)]
 use crate::loom::sync::atomic::AtomicMut;
-use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+use crate::loom::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
 use crate::Buf;
 
-/// A reference counted contiguous slice of memory.
+/// A cheaply cloneable and sliceable chunk of contiguous 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.
+/// `Bytes` objects to point to the same underlying memory.
+///
+/// `Bytes` does not have a single implementation. It is an interface, whose
+/// exact behavior is implemented through dynamic dispatch in several underlying
+/// implementations of `Bytes`.
+///
+/// All `Bytes` implementations must fulfill the following requirements:
+/// - They are cheaply cloneable and thereby shareable between an unlimited amount
+///   of components, for example by modifying a reference count.
+/// - Instances can be sliced to refer to a subset of the the original buffer.
 ///
 /// ```
 /// use bytes::Bytes;
@@ -41,32 +54,48 @@ use crate::Buf;
 /// 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
+/// `Bytes` keeps both a pointer to the shared state 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
+/// `Bytes` contains a vtable, which allows implementations of `Bytes` to define
+/// how sharing/cloning is implemented in detail.
+/// When `Bytes::clone()` is called, `Bytes` will call the vtable function for
+/// cloning the backing storage in order to share it behind between multiple
+/// `Bytes` instances.
+///
+/// For `Bytes` implementations which refer to constant memory (e.g. created
+/// via `Bytes::from_static()`) the cloning implementation will be a no-op.
+///
+/// For `Bytes` implementations which point to a reference counted shared storage
+/// (e.g. an `Arc<[u8]>`), sharing will be implemented by increasing the
+/// the reference count.
+///
+/// Due to this mechanism, multiple `Bytes` instances may point to the same
+/// shared memory region.
+/// Each `Bytes` instance can point to different sections within that
+/// memory region, and `Bytes` instances may or may not have overlapping views
 /// into the memory.
 ///
+/// The following diagram visualizes a scenario where 2 `Bytes` instances make
+/// use of an `Arc`-based backing storage, and provide access to different views:
 ///
 /// ```text
 ///
-///    Arc ptrs                   +---------+
-///    ________________________ / | Bytes 2 |
-///   /                           +---------+
-///  /          +-----------+     |         |
-/// |_________/ |  Bytes 1  |     |         |
-/// |           +-----------+     |         |
+///    Arc ptrs                   ┌─────────┐
+///    ________________________ / │ Bytes 2 │
+///   /                           └─────────┘
+///  /          ┌───────────┐     |         |
+/// |_________/ │  Bytes 1  │     |         |
+/// |           └───────────┘     |         |
 /// |           |           | ___/ data     | tail
 /// |      data |      tail |/              |
 /// v           v           v               v
-/// +-----+---------------------------------+-----+
-/// | Arc |     |           |               |     |
-/// +-----+---------------------------------+-----+
+/// ┌─────┬─────┬───────────┬───────────────┬─────┐
+/// │ Arc │     │           │               │     │
+/// └─────┴─────┴───────────┴───────────────┴─────┘
 /// ```
 pub struct Bytes {
     ptr: *const u8,
@@ -80,6 +109,10 @@ pub(crate) struct Vtable {
     /// fn(data, ptr, len)
     pub clone: unsafe fn(&AtomicPtr<()>, *const u8, usize) -> Bytes,
     /// fn(data, ptr, len)
+    ///
+    /// takes `Bytes` to value
+    pub to_vec: unsafe fn(&AtomicPtr<()>, *const u8, usize) -> Vec<u8>,
+    /// fn(data, ptr, len)
     pub drop: unsafe fn(&mut AtomicPtr<()>, *const u8, usize),
 }
 
@@ -98,7 +131,7 @@ impl Bytes {
     /// ```
     #[inline]
     #[cfg(not(all(loom, test)))]
-    pub const fn new() -> Bytes {
+    pub const fn new() -> Self {
         // Make it a named const to work around
         // "unsizing casts are not allowed in const fn"
         const EMPTY: &[u8] = &[];
@@ -106,7 +139,7 @@ impl Bytes {
     }
 
     #[cfg(all(loom, test))]
-    pub fn new() -> Bytes {
+    pub fn new() -> Self {
         const EMPTY: &[u8] = &[];
         Bytes::from_static(EMPTY)
     }
@@ -126,7 +159,7 @@ impl Bytes {
     /// ```
     #[inline]
     #[cfg(not(all(loom, test)))]
-    pub const fn from_static(bytes: &'static [u8]) -> Bytes {
+    pub const fn from_static(bytes: &'static [u8]) -> Self {
         Bytes {
             ptr: bytes.as_ptr(),
             len: bytes.len(),
@@ -136,7 +169,7 @@ impl Bytes {
     }
 
     #[cfg(all(loom, test))]
-    pub fn from_static(bytes: &'static [u8]) -> Bytes {
+    pub fn from_static(bytes: &'static [u8]) -> Self {
         Bytes {
             ptr: bytes.as_ptr(),
             len: bytes.len(),
@@ -156,7 +189,7 @@ impl Bytes {
     /// assert_eq!(b.len(), 5);
     /// ```
     #[inline]
-    pub fn len(&self) -> usize {
+    pub const fn len(&self) -> usize {
         self.len
     }
 
@@ -171,11 +204,11 @@ impl Bytes {
     /// assert!(b.is_empty());
     /// ```
     #[inline]
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.len == 0
     }
 
-    ///Creates `Bytes` instance from slice, by copying it.
+    /// Creates `Bytes` instance from slice, by copying it.
     pub fn copy_from_slice(data: &[u8]) -> Self {
         data.to_vec().into()
     }
@@ -202,7 +235,7 @@ impl Bytes {
     ///
     /// Requires that `begin <= end` and `end <= self.len()`, otherwise slicing
     /// will panic.
-    pub fn slice(&self, range: impl RangeBounds<usize>) -> Bytes {
+    pub fn slice(&self, range: impl RangeBounds<usize>) -> Self {
         use core::ops::Bound;
 
         let len = self.len();
@@ -214,7 +247,7 @@ impl Bytes {
         };
 
         let end = match range.end_bound() {
-            Bound::Included(&n) => n + 1,
+            Bound::Included(&n) => n.checked_add(1).expect("out of range"),
             Bound::Excluded(&n) => n,
             Bound::Unbounded => len,
         };
@@ -239,7 +272,7 @@ impl Bytes {
         let mut ret = self.clone();
 
         ret.len = end - begin;
-        ret.ptr = unsafe { ret.ptr.offset(begin as isize) };
+        ret.ptr = unsafe { ret.ptr.add(begin) };
 
         ret
     }
@@ -269,7 +302,7 @@ impl Bytes {
     ///
     /// 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 {
+    pub fn slice_ref(&self, subset: &[u8]) -> Self {
         // 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() {
@@ -285,15 +318,15 @@ impl Bytes {
         assert!(
             sub_p >= bytes_p,
             "subset pointer ({:p}) is smaller than self pointer ({:p})",
-            sub_p as *const u8,
-            bytes_p as *const u8,
+            subset.as_ptr(),
+            self.as_ptr(),
         );
         assert!(
             sub_p + sub_len <= bytes_p + bytes_len,
             "subset is out of bounds: self = ({:p}, {}), subset = ({:p}, {})",
-            bytes_p as *const u8,
+            self.as_ptr(),
             bytes_len,
-            sub_p as *const u8,
+            subset.as_ptr(),
             sub_len,
         );
 
@@ -326,7 +359,7 @@ impl Bytes {
     ///
     /// 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 {
+    pub fn split_off(&mut self, at: usize) -> Self {
         assert!(
             at <= self.len(),
             "split_off out of bounds: {:?} <= {:?}",
@@ -375,7 +408,7 @@ impl Bytes {
     ///
     /// 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 {
+    pub fn split_to(&mut self, at: usize) -> Self {
         assert!(
             at <= self.len(),
             "split_to out of bounds: {:?} <= {:?}",
@@ -478,7 +511,7 @@ impl Bytes {
         // 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);
+        self.ptr = self.ptr.add(by);
     }
 }
 
@@ -507,7 +540,7 @@ impl Buf for Bytes {
     }
 
     #[inline]
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         self.as_slice()
     }
 
@@ -525,8 +558,14 @@ impl Buf for Bytes {
         }
     }
 
-    fn to_bytes(&mut self) -> crate::Bytes {
-        core::mem::replace(self, Bytes::new())
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
+        if len == self.remaining() {
+            core::mem::replace(self, Bytes::new())
+        } else {
+            let ret = self.slice(..len);
+            self.advance(len);
+            ret
+        }
     }
 }
 
@@ -575,7 +614,7 @@ impl<'a> IntoIterator for &'a Bytes {
     type IntoIter = core::slice::Iter<'a, u8>;
 
     fn into_iter(self) -> Self::IntoIter {
-        self.as_slice().into_iter()
+        self.as_slice().iter()
     }
 }
 
@@ -657,7 +696,7 @@ impl PartialOrd<Bytes> for str {
 
 impl PartialEq<Vec<u8>> for Bytes {
     fn eq(&self, other: &Vec<u8>) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
@@ -681,7 +720,7 @@ impl PartialOrd<Bytes> for Vec<u8> {
 
 impl PartialEq<String> for Bytes {
     fn eq(&self, other: &String) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
@@ -768,31 +807,36 @@ impl From<&'static str> for 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,
+        let slice = vec.into_boxed_slice();
+        slice.into()
+    }
+}
+
+impl From<Box<[u8]>> for Bytes {
+    fn from(slice: Box<[u8]>) -> Bytes {
+        // Box<[u8]> doesn't contain a heap allocation for empty slices,
         // so the pointer isn't aligned enough for the KIND_VEC stashing to
         // work.
-        if vec.is_empty() {
+        if slice.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));
+        let ptr = Box::into_raw(slice) as *mut u8;
 
         if ptr as usize & 0x1 == 0 {
-            let data = ptr as usize | KIND_VEC;
+            let data = ptr_map(ptr, |addr| addr | KIND_VEC);
             Bytes {
                 ptr,
                 len,
-                data: AtomicPtr::new(data as *mut _),
+                data: AtomicPtr::new(data.cast()),
                 vtable: &PROMOTABLE_EVEN_VTABLE,
             }
         } else {
             Bytes {
                 ptr,
                 len,
-                data: AtomicPtr::new(ptr as *mut _),
+                data: AtomicPtr::new(ptr.cast()),
                 vtable: &PROMOTABLE_ODD_VTABLE,
             }
         }
@@ -805,6 +849,13 @@ impl From<String> for Bytes {
     }
 }
 
+impl From<Bytes> for Vec<u8> {
+    fn from(bytes: Bytes) -> Vec<u8> {
+        let bytes = mem::ManuallyDrop::new(bytes);
+        unsafe { (bytes.vtable.to_vec)(&bytes.data, bytes.ptr, bytes.len) }
+    }
+}
+
 // ===== impl Vtable =====
 
 impl fmt::Debug for Vtable {
@@ -820,6 +871,7 @@ impl fmt::Debug for Vtable {
 
 const STATIC_VTABLE: Vtable = Vtable {
     clone: static_clone,
+    to_vec: static_to_vec,
     drop: static_drop,
 };
 
@@ -828,6 +880,11 @@ unsafe fn static_clone(_: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
     Bytes::from_static(slice)
 }
 
+unsafe fn static_to_vec(_: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Vec<u8> {
+    let slice = slice::from_raw_parts(ptr, len);
+    slice.to_vec()
+}
+
 unsafe fn static_drop(_: &mut AtomicPtr<()>, _: *const u8, _: usize) {
     // nothing to drop for &'static [u8]
 }
@@ -836,11 +893,13 @@ unsafe fn static_drop(_: &mut AtomicPtr<()>, _: *const u8, _: usize) {
 
 static PROMOTABLE_EVEN_VTABLE: Vtable = Vtable {
     clone: promotable_even_clone,
+    to_vec: promotable_even_to_vec,
     drop: promotable_even_drop,
 };
 
 static PROMOTABLE_ODD_VTABLE: Vtable = Vtable {
     clone: promotable_odd_clone,
+    to_vec: promotable_odd_to_vec,
     drop: promotable_odd_drop,
 };
 
@@ -849,25 +908,57 @@ unsafe fn promotable_even_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize
     let kind = shared as usize & KIND_MASK;
 
     if kind == KIND_ARC {
-        shallow_clone_arc(shared as _, ptr, len)
+        shallow_clone_arc(shared.cast(), ptr, len)
     } else {
         debug_assert_eq!(kind, KIND_VEC);
-        let buf = (shared as usize & !KIND_MASK) as *mut u8;
+        let buf = ptr_map(shared.cast(), |addr| addr & !KIND_MASK);
         shallow_clone_vec(data, shared, buf, ptr, len)
     }
 }
 
+unsafe fn promotable_to_vec(
+    data: &AtomicPtr<()>,
+    ptr: *const u8,
+    len: usize,
+    f: fn(*mut ()) -> *mut u8,
+) -> Vec<u8> {
+    let shared = data.load(Ordering::Acquire);
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        shared_to_vec_impl(shared.cast(), ptr, len)
+    } else {
+        // If Bytes holds a Vec, then the offset must be 0.
+        debug_assert_eq!(kind, KIND_VEC);
+
+        let buf = f(shared);
+
+        let cap = (ptr as usize - buf as usize) + len;
+
+        // Copy back buffer
+        ptr::copy(ptr, buf, len);
+
+        Vec::from_raw_parts(buf, len, cap)
+    }
+}
+
+unsafe fn promotable_even_to_vec(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Vec<u8> {
+    promotable_to_vec(data, ptr, len, |shared| {
+        ptr_map(shared.cast(), |addr| addr & !KIND_MASK)
+    })
+}
+
 unsafe fn promotable_even_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) {
     data.with_mut(|shared| {
         let shared = *shared;
         let kind = shared as usize & KIND_MASK;
 
         if kind == KIND_ARC {
-            release_shared(shared as *mut Shared);
+            release_shared(shared.cast());
         } else {
             debug_assert_eq!(kind, KIND_VEC);
-            let buf = (shared as usize & !KIND_MASK) as *mut u8;
-            drop(rebuild_boxed_slice(buf, ptr, len));
+            let buf = ptr_map(shared.cast(), |addr| addr & !KIND_MASK);
+            free_boxed_slice(buf, ptr, len);
         }
     });
 }
@@ -880,38 +971,49 @@ unsafe fn promotable_odd_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize)
         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)
+        shallow_clone_vec(data, shared, shared.cast(), ptr, len)
     }
 }
 
+unsafe fn promotable_odd_to_vec(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Vec<u8> {
+    promotable_to_vec(data, ptr, len, |shared| shared.cast())
+}
+
 unsafe fn promotable_odd_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) {
     data.with_mut(|shared| {
         let shared = *shared;
         let kind = shared as usize & KIND_MASK;
 
         if kind == KIND_ARC {
-            release_shared(shared as *mut Shared);
+            release_shared(shared.cast());
         } else {
             debug_assert_eq!(kind, KIND_VEC);
 
-            drop(rebuild_boxed_slice(shared as *mut u8, ptr, len));
+            free_boxed_slice(shared.cast(), ptr, len);
         }
     });
 }
 
-unsafe fn rebuild_boxed_slice(buf: *mut u8, offset: *const u8, len: usize) -> Box<[u8]> {
+unsafe fn free_boxed_slice(buf: *mut u8, offset: *const u8, len: usize) {
     let cap = (offset as usize - buf as usize) + len;
-    Box::from_raw(slice::from_raw_parts_mut(buf, cap))
+    dealloc(buf, Layout::from_size_align(cap, 1).unwrap())
 }
 
 // ===== impl SharedVtable =====
 
 struct Shared {
-    // holds vec for drop, but otherwise doesnt access it
-    _vec: Vec<u8>,
+    // Holds arguments to dealloc upon Drop, but otherwise doesn't use them
+    buf: *mut u8,
+    cap: usize,
     ref_cnt: AtomicUsize,
 }
 
+impl Drop for Shared {
+    fn drop(&mut self) {
+        unsafe { dealloc(self.buf, Layout::from_size_align(self.cap, 1).unwrap()) }
+    }
+}
+
 // 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.
@@ -920,6 +1022,7 @@ const _: [(); 0 - mem::align_of::<Shared>() % 2] = []; // Assert that the alignm
 
 static SHARED_VTABLE: Vtable = Vtable {
     clone: shared_clone,
+    to_vec: shared_to_vec,
     drop: shared_drop,
 };
 
@@ -932,9 +1035,42 @@ unsafe fn shared_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Byte
     shallow_clone_arc(shared as _, ptr, len)
 }
 
+unsafe fn shared_to_vec_impl(shared: *mut Shared, ptr: *const u8, len: usize) -> Vec<u8> {
+    // Check that the ref_cnt is 1 (unique).
+    //
+    // If it is unique, then it is set to 0 with AcqRel fence for the same
+    // reason in release_shared.
+    //
+    // Otherwise, we take the other branch and call release_shared.
+    if (*shared)
+        .ref_cnt
+        .compare_exchange(1, 0, Ordering::AcqRel, Ordering::Relaxed)
+        .is_ok()
+    {
+        let buf = (*shared).buf;
+        let cap = (*shared).cap;
+
+        // Deallocate Shared
+        drop(Box::from_raw(shared as *mut mem::ManuallyDrop<Shared>));
+
+        // Copy back buffer
+        ptr::copy(ptr, buf, len);
+
+        Vec::from_raw_parts(buf, len, cap)
+    } else {
+        let v = slice::from_raw_parts(ptr, len).to_vec();
+        release_shared(shared);
+        v
+    }
+}
+
+unsafe fn shared_to_vec(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Vec<u8> {
+    shared_to_vec_impl(data.load(Ordering::Relaxed).cast(), ptr, len)
+}
+
 unsafe fn shared_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
     data.with_mut(|shared| {
-        release_shared(*shared as *mut Shared);
+        release_shared(shared.cast());
     });
 }
 
@@ -972,9 +1108,9 @@ unsafe fn shallow_clone_vec(
     // 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,
+        buf,
+        cap: (offset as usize - buf as usize) + len,
         // Initialize refcount to 2. One for this reference, and one
         // for the new clone that will be returned from
         // `shallow_clone`.
@@ -994,33 +1130,35 @@ unsafe fn shallow_clone_vec(
     // `Release` is used synchronize with other threads that
     // will load the `arc` field.
     //
-    // If the `compare_and_swap` fails, then the thread lost the
+    // If the `compare_exchange` fails, then the thread lost the
     // race to promote the buffer to shared. The `Acquire`
-    // ordering will synchronize with the `compare_and_swap`
+    // ordering will synchronize with the `compare_exchange`
     // 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);
+    match atom.compare_exchange(ptr as _, shared as _, Ordering::AcqRel, Ordering::Acquire) {
+        Ok(actual) => {
+            debug_assert!(actual as usize == ptr as usize);
+            // The upgrade was successful, the new handle can be
+            // returned.
+            Bytes {
+                ptr: offset,
+                len,
+                data: AtomicPtr::new(shared as _),
+                vtable: &SHARED_VTABLE,
+            }
+        }
+        Err(actual) => {
+            // 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);
 
-    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,
-        };
+            // Buffer already promoted to shared storage, so increment ref
+            // count.
+            shallow_clone_arc(actual as _, offset, len)
+        }
     }
-
-    // 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) {
@@ -1046,10 +1184,40 @@ unsafe fn release_shared(ptr: *mut Shared) {
     // > "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);
+    //
+    // Thread sanitizer does not support atomic fences. Use an atomic load
+    // instead.
+    (*ptr).ref_cnt.load(Ordering::Acquire);
 
     // Drop the data
-    Box::from_raw(ptr);
+    drop(Box::from_raw(ptr));
+}
+
+// Ideally we would always use this version of `ptr_map` since it is strict
+// provenance compatible, but it results in worse codegen. We will however still
+// use it on miri because it gives better diagnostics for people who test bytes
+// code with miri.
+//
+// See https://github.com/tokio-rs/bytes/pull/545 for more info.
+#[cfg(miri)]
+fn ptr_map<F>(ptr: *mut u8, f: F) -> *mut u8
+where
+    F: FnOnce(usize) -> usize,
+{
+    let old_addr = ptr as usize;
+    let new_addr = f(old_addr);
+    let diff = new_addr.wrapping_sub(old_addr);
+    ptr.wrapping_add(diff)
+}
+
+#[cfg(not(miri))]
+fn ptr_map<F>(ptr: *mut u8, f: F) -> *mut u8
+where
+    F: FnOnce(usize) -> usize,
+{
+    let old_addr = ptr as usize;
+    let new_addr = f(old_addr);
+    new_addr as *mut u8
 }
 
 // compile-fails

src/bytes_mut.rs

@@ -1,5 +1,5 @@
 use core::iter::{FromIterator, Iterator};
-use core::mem::{self, ManuallyDrop};
+use core::mem::{self, ManuallyDrop, MaybeUninit};
 use core::ops::{Deref, DerefMut};
 use core::ptr::{self, NonNull};
 use core::{cmp, fmt, hash, isize, slice, usize};
@@ -8,14 +8,15 @@ use alloc::{
     borrow::{Borrow, BorrowMut},
     boxed::Box,
     string::String,
+    vec,
     vec::Vec,
 };
 
-use crate::buf::IntoIter;
+use crate::buf::{IntoIter, UninitSlice};
 use crate::bytes::Vtable;
 #[allow(unused)]
 use crate::loom::sync::atomic::AtomicMut;
-use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+use crate::loom::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
 use crate::{Buf, BufMut, Bytes};
 
 /// A unique reference to a contiguous slice of memory.
@@ -252,12 +253,28 @@ impl BytesMut {
 
             let ptr = self.ptr.as_ptr();
             let len = self.len;
-            let data = AtomicPtr::new(self.data as _);
+            let data = AtomicPtr::new(self.data.cast());
             mem::forget(self);
             unsafe { Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE) }
         }
     }
 
+    /// Creates a new `BytesMut`, which is initialized with zero.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// let zeros = BytesMut::zeroed(42);
+    ///
+    /// assert_eq!(zeros.len(), 42);
+    /// zeros.into_iter().for_each(|x| assert_eq!(x, 0));
+    /// ```
+    pub fn zeroed(len: usize) -> BytesMut {
+        BytesMut::from_vec(vec![0; len])
+    }
+
     /// Splits the bytes into two at the given index.
     ///
     /// Afterwards `self` contains elements `[0, at)`, and the returned
@@ -380,6 +397,8 @@ impl BytesMut {
     /// If `len` is greater than the buffer's current length, this has no
     /// effect.
     ///
+    /// Existing underlying capacity is preserved.
+    ///
     /// The [`split_off`] method can emulate `truncate`, but this causes the
     /// excess bytes to be returned instead of dropped.
     ///
@@ -402,7 +421,7 @@ impl BytesMut {
         }
     }
 
-    /// Clears the buffer, removing all data.
+    /// Clears the buffer, removing all data. Existing capacity is preserved.
     ///
     /// # Examples
     ///
@@ -445,7 +464,7 @@ impl BytesMut {
             let additional = new_len - len;
             self.reserve(additional);
             unsafe {
-                let dst = self.bytes_mut().as_mut_ptr();
+                let dst = self.chunk_mut().as_mut_ptr();
                 ptr::write_bytes(dst, value, additional);
                 self.set_len(new_len);
             }
@@ -492,11 +511,20 @@ impl BytesMut {
     /// 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.
+    /// space in the existing buffer. If the current handle references a view
+    /// into a larger original buffer, and all other handles referencing part
+    /// of the same original buffer have been dropped, then the current view
+    /// can be copied/shifted to the front of the buffer and the handle can take
+    /// ownership of the full buffer, provided that the full buffer is large
+    /// enough to fit the requested additional capacity.
+    ///
+    /// This optimization will only happen if shifting the data from the current
+    /// view to the front of the buffer is not too expensive in terms of the
+    /// (amortized) time required. The precise condition is subject to change;
+    /// as of now, the length of the data being shifted needs to be at least as
+    /// large as the distance that it's shifted by. If the current view is empty
+    /// and the original buffer is large enough to fit the requested additional
+    /// capacity, then reallocations will never happen.
     ///
     /// # Examples
     ///
@@ -560,17 +588,34 @@ impl BytesMut {
             // space.
             //
             // Otherwise, since backed by a vector, use `Vec::reserve`
+            //
+            // We need to make sure that this optimization does not kill the
+            // amortized runtimes of BytesMut's operations.
             unsafe {
                 let (off, prev) = self.get_vec_pos();
 
                 // Only reuse space if we can satisfy the requested additional space.
-                if self.capacity() - self.len() + off >= additional {
-                    // There's space - reuse it
+                //
+                // Also check if the value of `off` suggests that enough bytes
+                // have been read to account for the overhead of shifting all
+                // the data (in an amortized analysis).
+                // Hence the condition `off >= self.len()`.
+                //
+                // This condition also already implies that the buffer is going
+                // to be (at least) half-empty in the end; so we do not break
+                // the (amortized) runtime with future resizes of the underlying
+                // `Vec`.
+                //
+                // [For more details check issue #524, and PR #525.]
+                if self.capacity() - self.len() + off >= additional && off >= self.len() {
+                    // There's enough space, and it's not too much overhead:
+                    // reuse the space!
                     //
                     // 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);
+                    // Since `off >= self.len()`, the two regions don't overlap.
+                    ptr::copy_nonoverlapping(self.ptr.as_ptr(), base_ptr, self.len);
                     self.ptr = vptr(base_ptr);
                     self.set_vec_pos(0, prev);
 
@@ -578,13 +623,14 @@ impl BytesMut {
                     // can gain capacity back.
                     self.cap += off;
                 } else {
-                    // No space - allocate more
+                    // Not enough space, or reusing might be too much overhead:
+                    // allocate more space!
                     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.ptr = vptr(v.as_mut_ptr().add(off));
                     self.len = v.len() - off;
                     self.cap = v.capacity() - off;
                 }
@@ -594,7 +640,7 @@ impl BytesMut {
         }
 
         debug_assert_eq!(kind, KIND_ARC);
-        let shared: *mut Shared = self.data as _;
+        let shared: *mut Shared = self.data;
 
         // Reserving involves abandoning the currently shared buffer and
         // allocating a new vector with the requested capacity.
@@ -617,29 +663,65 @@ impl BytesMut {
                 // 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();
+                let v_capacity = v.capacity();
+                let ptr = v.as_mut_ptr();
 
-                    ptr::copy(self.ptr.as_ptr(), ptr, len);
+                let offset = offset_from(self.ptr.as_ptr(), ptr);
+
+                // Compare the condition in the `kind == KIND_VEC` case above
+                // for more details.
+                if v_capacity >= new_cap + offset {
+                    self.cap = new_cap;
+                    // no copy is necessary
+                } else if v_capacity >= new_cap && offset >= len {
+                    // The capacity is sufficient, and copying is not too much
+                    // overhead: reclaim the buffer!
+
+                    // `offset >= len` means: no overlap
+                    ptr::copy_nonoverlapping(self.ptr.as_ptr(), ptr, len);
 
                     self.ptr = vptr(ptr);
                     self.cap = v.capacity();
+                } else {
+                    // calculate offset
+                    let off = (self.ptr.as_ptr() as usize) - (v.as_ptr() as usize);
 
-                    return;
+                    // new_cap is calculated in terms of `BytesMut`, not the underlying
+                    // `Vec`, so it does not take the offset into account.
+                    //
+                    // Thus we have to manually add it here.
+                    new_cap = new_cap.checked_add(off).expect("overflow");
+
+                    // 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(double, new_cap);
+
+                    // No space - allocate more
+                    //
+                    // The length field of `Shared::vec` is not used by the `BytesMut`;
+                    // instead we use the `len` field in the `BytesMut` itself. However,
+                    // when calling `reserve`, it doesn't guarantee that data stored in
+                    // the unused capacity of the vector is copied over to the new
+                    // allocation, so we need to ensure that we don't have any data we
+                    // care about in the unused capacity before calling `reserve`.
+                    debug_assert!(off + len <= v.capacity());
+                    v.set_len(off + len);
+                    v.reserve(new_cap - v.len());
+
+                    // Update the info
+                    self.ptr = vptr(v.as_mut_ptr().add(off));
+                    self.cap = v.capacity() - off;
                 }
 
-                // 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);
+                return;
             } else {
                 new_cap = cmp::max(new_cap, original_capacity);
             }
@@ -657,7 +739,7 @@ impl BytesMut {
 
         // Update self
         let data = (original_capacity_repr << ORIGINAL_CAPACITY_OFFSET) | KIND_VEC;
-        self.data = data as _;
+        self.data = invalid_ptr(data);
         self.ptr = vptr(v.as_mut_ptr());
         self.len = v.len();
         self.cap = v.capacity();
@@ -684,11 +766,11 @@ impl BytesMut {
         self.reserve(cnt);
 
         unsafe {
-            let dst = self.maybe_uninit_bytes();
+            let dst = self.spare_capacity_mut();
             // Reserved above
             debug_assert!(dst.len() >= cnt);
 
-            ptr::copy_nonoverlapping(extend.as_ptr(), dst.as_mut_ptr() as *mut u8, cnt);
+            ptr::copy_nonoverlapping(extend.as_ptr(), dst.as_mut_ptr().cast(), cnt);
         }
 
         unsafe {
@@ -698,10 +780,11 @@ impl BytesMut {
 
     /// 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
+    /// If the two `BytesMut` objects were previously contiguous and not mutated
+    /// in a way that causes re-allocation 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
@@ -752,7 +835,7 @@ impl BytesMut {
             ptr,
             len,
             cap,
-            data: data as *mut _,
+            data: invalid_ptr(data),
         }
     }
 
@@ -799,7 +882,7 @@ impl BytesMut {
         // 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));
+        self.ptr = vptr(self.ptr.as_ptr().add(start));
 
         if self.len >= start {
             self.len -= start;
@@ -819,11 +902,11 @@ impl BytesMut {
     }
 
     fn try_unsplit(&mut self, other: BytesMut) -> Result<(), BytesMut> {
-        if other.is_empty() {
+        if other.capacity() == 0 {
             return Ok(());
         }
 
-        let ptr = unsafe { self.ptr.as_ptr().offset(self.len as isize) };
+        let ptr = unsafe { self.ptr.as_ptr().add(self.len) };
         if ptr == other.ptr.as_ptr()
             && self.kind() == KIND_ARC
             && other.kind() == KIND_ARC
@@ -873,7 +956,7 @@ impl BytesMut {
         // always succeed.
         debug_assert_eq!(shared as usize & KIND_MASK, KIND_ARC);
 
-        self.data = shared as _;
+        self.data = shared;
     }
 
     /// Makes an exact shallow clone of `self`.
@@ -906,16 +989,45 @@ impl BytesMut {
         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 _;
+        self.data = invalid_ptr((pos << VEC_POS_OFFSET) | (prev & NOT_VEC_POS_MASK));
     }
 
+    /// Returns the remaining spare capacity of the buffer as a slice of `MaybeUninit<u8>`.
+    ///
+    /// The returned slice can be used to fill the buffer with data (e.g. by
+    /// reading from a file) before marking the data as initialized using the
+    /// [`set_len`] method.
+    ///
+    /// [`set_len`]: BytesMut::set_len
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BytesMut;
+    ///
+    /// // Allocate buffer big enough for 10 bytes.
+    /// let mut buf = BytesMut::with_capacity(10);
+    ///
+    /// // Fill in the first 3 elements.
+    /// let uninit = buf.spare_capacity_mut();
+    /// uninit[0].write(0);
+    /// uninit[1].write(1);
+    /// uninit[2].write(2);
+    ///
+    /// // Mark the first 3 bytes of the buffer as being initialized.
+    /// unsafe {
+    ///     buf.set_len(3);
+    /// }
+    ///
+    /// assert_eq!(&buf[..], &[0, 1, 2]);
+    /// ```
     #[inline]
-    fn maybe_uninit_bytes(&mut self) -> &mut [mem::MaybeUninit<u8>] {
+    pub fn spare_capacity_mut(&mut self) -> &mut [MaybeUninit<u8>] {
         unsafe {
-            let ptr = self.ptr.as_ptr().offset(self.len as isize);
+            let ptr = self.ptr.as_ptr().add(self.len);
             let len = self.cap - self.len;
 
-            slice::from_raw_parts_mut(ptr as *mut mem::MaybeUninit<u8>, len)
+            slice::from_raw_parts_mut(ptr.cast(), len)
         }
     }
 }
@@ -932,7 +1044,7 @@ impl Drop for BytesMut {
                 let _ = rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off);
             }
         } else if kind == KIND_ARC {
-            unsafe { release_shared(self.data as _) };
+            unsafe { release_shared(self.data) };
         }
     }
 }
@@ -944,7 +1056,7 @@ impl Buf for BytesMut {
     }
 
     #[inline]
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         self.as_slice()
     }
 
@@ -961,12 +1073,12 @@ impl Buf for BytesMut {
         }
     }
 
-    fn to_bytes(&mut self) -> crate::Bytes {
-        self.split().freeze()
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
+        self.split_to(len).freeze()
     }
 }
 
-impl BufMut for BytesMut {
+unsafe impl BufMut for BytesMut {
     #[inline]
     fn remaining_mut(&self) -> usize {
         usize::MAX - self.len()
@@ -985,11 +1097,11 @@ impl BufMut for BytesMut {
     }
 
     #[inline]
-    fn bytes_mut(&mut self) -> &mut [mem::MaybeUninit<u8>] {
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
         if self.capacity() == self.len() {
             self.reserve(64);
         }
-        self.maybe_uninit_bytes()
+        UninitSlice::from_slice(self.spare_capacity_mut())
     }
 
     // Specialize these methods so they can skip checking `remaining_mut`
@@ -1000,7 +1112,7 @@ impl BufMut for BytesMut {
         Self: Sized,
     {
         while src.has_remaining() {
-            let s = src.bytes();
+            let s = src.chunk();
             let l = s.len();
             self.extend_from_slice(s);
             src.advance(l);
@@ -1010,6 +1122,19 @@ impl BufMut for BytesMut {
     fn put_slice(&mut self, src: &[u8]) {
         self.extend_from_slice(src);
     }
+
+    fn put_bytes(&mut self, val: u8, cnt: usize) {
+        self.reserve(cnt);
+        unsafe {
+            let dst = self.spare_capacity_mut();
+            // Reserved above
+            debug_assert!(dst.len() >= cnt);
+
+            ptr::write_bytes(dst.as_mut_ptr(), val, cnt);
+
+            self.advance_mut(cnt);
+        }
+    }
 }
 
 impl AsRef<[u8]> for BytesMut {
@@ -1146,7 +1271,7 @@ impl<'a> IntoIterator for &'a BytesMut {
     type IntoIter = core::slice::Iter<'a, u8>;
 
     fn into_iter(self) -> Self::IntoIter {
-        self.as_ref().into_iter()
+        self.as_ref().iter()
     }
 }
 
@@ -1175,7 +1300,18 @@ impl<'a> Extend<&'a u8> for BytesMut {
     where
         T: IntoIterator<Item = &'a u8>,
     {
-        self.extend(iter.into_iter().map(|b| *b))
+        self.extend(iter.into_iter().copied())
+    }
+}
+
+impl Extend<Bytes> for BytesMut {
+    fn extend<T>(&mut self, iter: T)
+    where
+        T: IntoIterator<Item = Bytes>,
+    {
+        for bytes in iter {
+            self.extend_from_slice(&bytes)
+        }
     }
 }
 
@@ -1187,7 +1323,7 @@ impl FromIterator<u8> for BytesMut {
 
 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))
+        BytesMut::from_iter(into_iter.into_iter().copied())
     }
 }
 
@@ -1228,10 +1364,13 @@ unsafe fn release_shared(ptr: *mut Shared) {
     // > "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);
+    //
+    // Thread sanitizer does not support atomic fences. Use an atomic load
+    // instead.
+    (*ptr).ref_count.load(Ordering::Acquire);
 
     // Drop the data
-    Box::from_raw(ptr);
+    drop(Box::from_raw(ptr));
 }
 
 impl Shared {
@@ -1250,6 +1389,7 @@ impl Shared {
     }
 }
 
+#[inline]
 fn original_capacity_to_repr(cap: usize) -> usize {
     let width = PTR_WIDTH - ((cap >> MIN_ORIGINAL_CAPACITY_WIDTH).leading_zeros() as usize);
     cmp::min(
@@ -1376,7 +1516,7 @@ impl PartialOrd<BytesMut> for str {
 
 impl PartialEq<Vec<u8>> for BytesMut {
     fn eq(&self, other: &Vec<u8>) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
@@ -1400,7 +1540,7 @@ impl PartialOrd<BytesMut> for Vec<u8> {
 
 impl PartialEq<String> for BytesMut {
     fn eq(&self, other: &String) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
@@ -1466,16 +1606,55 @@ impl PartialOrd<BytesMut> for &str {
 
 impl PartialEq<BytesMut> for Bytes {
     fn eq(&self, other: &BytesMut) -> bool {
-        &other[..] == &self[..]
+        other[..] == self[..]
     }
 }
 
 impl PartialEq<Bytes> for BytesMut {
     fn eq(&self, other: &Bytes) -> bool {
-        &other[..] == &self[..]
+        other[..] == self[..]
     }
 }
 
+impl From<BytesMut> for Vec<u8> {
+    fn from(mut bytes: BytesMut) -> Self {
+        let kind = bytes.kind();
+
+        let mut vec = if kind == KIND_VEC {
+            unsafe {
+                let (off, _) = bytes.get_vec_pos();
+                rebuild_vec(bytes.ptr.as_ptr(), bytes.len, bytes.cap, off)
+            }
+        } else if kind == KIND_ARC {
+            let shared = bytes.data as *mut Shared;
+
+            if unsafe { (*shared).is_unique() } {
+                let vec = mem::replace(unsafe { &mut (*shared).vec }, Vec::new());
+
+                unsafe { release_shared(shared) };
+
+                vec
+            } else {
+                return bytes.deref().to_vec();
+            }
+        } else {
+            return bytes.deref().to_vec();
+        };
+
+        let len = bytes.len;
+
+        unsafe {
+            ptr::copy(bytes.ptr.as_ptr(), vec.as_mut_ptr(), len);
+            vec.set_len(len);
+        }
+
+        mem::forget(bytes);
+
+        vec
+    }
+}
+
+#[inline]
 fn vptr(ptr: *mut u8) -> NonNull<u8> {
     if cfg!(debug_assertions) {
         NonNull::new(ptr).expect("Vec pointer should be non-null")
@@ -1484,6 +1663,35 @@ fn vptr(ptr: *mut u8) -> NonNull<u8> {
     }
 }
 
+/// Returns a dangling pointer with the given address. This is used to store
+/// integer data in pointer fields.
+///
+/// It is equivalent to `addr as *mut T`, but this fails on miri when strict
+/// provenance checking is enabled.
+#[inline]
+fn invalid_ptr<T>(addr: usize) -> *mut T {
+    let ptr = core::ptr::null_mut::<u8>().wrapping_add(addr);
+    debug_assert_eq!(ptr as usize, addr);
+    ptr.cast::<T>()
+}
+
+/// Precondition: dst >= original
+///
+/// The following line is equivalent to:
+///
+/// ```rust,ignore
+/// self.ptr.as_ptr().offset_from(ptr) as usize;
+/// ```
+///
+/// But due to min rust is 1.39 and it is only stablised
+/// in 1.47, we cannot use it.
+#[inline]
+fn offset_from(dst: *mut u8, original: *mut u8) -> usize {
+    debug_assert!(dst >= original);
+
+    dst as usize - original as usize
+}
+
 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;
@@ -1496,6 +1704,7 @@ unsafe fn rebuild_vec(ptr: *mut u8, mut len: usize, mut cap: usize, off: usize)
 
 static SHARED_VTABLE: Vtable = Vtable {
     clone: shared_v_clone,
+    to_vec: shared_v_to_vec,
     drop: shared_v_drop,
 };
 
@@ -1503,10 +1712,32 @@ unsafe fn shared_v_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> By
     let shared = data.load(Ordering::Relaxed) as *mut Shared;
     increment_shared(shared);
 
-    let data = AtomicPtr::new(shared as _);
+    let data = AtomicPtr::new(shared as *mut ());
     Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE)
 }
 
+unsafe fn shared_v_to_vec(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Vec<u8> {
+    let shared: *mut Shared = data.load(Ordering::Relaxed).cast();
+
+    if (*shared).is_unique() {
+        let shared = &mut *shared;
+
+        // Drop shared
+        let mut vec = mem::replace(&mut shared.vec, Vec::new());
+        release_shared(shared);
+
+        // Copy back buffer
+        ptr::copy(ptr, vec.as_mut_ptr(), len);
+        vec.set_len(len);
+
+        vec
+    } else {
+        let v = slice::from_raw_parts(ptr, len).to_vec();
+        release_shared(shared);
+        v
+    }
+}
+
 unsafe fn shared_v_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
     data.with_mut(|shared| {
         release_shared(*shared as *mut Shared);

src/fmt/debug.rs

@@ -25,7 +25,7 @@ impl Debug for BytesRef<'_> {
             } else if b == b'\0' {
                 write!(f, "\\0")?;
             // ASCII printable
-            } else if b >= 0x20 && b < 0x7f {
+            } else if (0x20..0x7f).contains(&b) {
                 write!(f, "{}", b as char)?;
             } else {
                 write!(f, "\\x{:02x}", b)?;
@@ -38,12 +38,12 @@ impl Debug for BytesRef<'_> {
 
 impl Debug for Bytes {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        Debug::fmt(&BytesRef(&self.as_ref()), f)
+        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)
+        Debug::fmt(&BytesRef(self.as_ref()), f)
     }
 }

src/lib.rs

@@ -3,7 +3,6 @@
     no_crate_inject,
     attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
 ))]
-#![doc(html_root_url = "https://docs.rs/bytes/0.5.6")]
 #![no_std]
 
 //! Provides abstractions for working with bytes.

src/loom.rs

@@ -1,7 +1,7 @@
 #[cfg(not(all(test, loom)))]
 pub(crate) mod sync {
     pub(crate) mod atomic {
-        pub(crate) use core::sync::atomic::{fence, AtomicPtr, AtomicUsize, Ordering};
+        pub(crate) use core::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
 
         pub(crate) trait AtomicMut<T> {
             fn with_mut<F, R>(&mut self, f: F) -> R
@@ -23,7 +23,7 @@ pub(crate) mod sync {
 #[cfg(all(test, loom))]
 pub(crate) mod sync {
     pub(crate) mod atomic {
-        pub(crate) use loom::sync::atomic::{fence, AtomicPtr, AtomicUsize, Ordering};
+        pub(crate) use loom::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
 
         pub(crate) trait AtomicMut<T> {}
     }

tests/test_buf.rs

@@ -9,17 +9,17 @@ fn test_fresh_cursor_vec() {
     let mut buf = &b"hello"[..];
 
     assert_eq!(buf.remaining(), 5);
-    assert_eq!(buf.bytes(), b"hello");
+    assert_eq!(buf.chunk(), b"hello");
 
     buf.advance(2);
 
     assert_eq!(buf.remaining(), 3);
-    assert_eq!(buf.bytes(), b"llo");
+    assert_eq!(buf.chunk(), b"llo");
 
     buf.advance(3);
 
     assert_eq!(buf.remaining(), 0);
-    assert_eq!(buf.bytes(), b"");
+    assert_eq!(buf.chunk(), b"");
 }
 
 #[test]
@@ -53,7 +53,7 @@ fn test_bufs_vec() {
 
     let mut dst = [IoSlice::new(b1), IoSlice::new(b2)];
 
-    assert_eq!(1, buf.bytes_vectored(&mut dst[..]));
+    assert_eq!(1, buf.chunks_vectored(&mut dst[..]));
 }
 
 #[test]
@@ -63,9 +63,9 @@ fn test_vec_deque() {
     let mut buffer: VecDeque<u8> = VecDeque::new();
     buffer.extend(b"hello world");
     assert_eq!(11, buffer.remaining());
-    assert_eq!(b"hello world", buffer.bytes());
+    assert_eq!(b"hello world", buffer.chunk());
     buffer.advance(6);
-    assert_eq!(b"world", buffer.bytes());
+    assert_eq!(b"world", buffer.chunk());
     buffer.extend(b" piece");
     let mut out = [0; 11];
     buffer.copy_to_slice(&mut out);
@@ -81,8 +81,8 @@ fn test_deref_buf_forwards() {
             unreachable!("remaining");
         }
 
-        fn bytes(&self) -> &[u8] {
-            unreachable!("bytes");
+        fn chunk(&self) -> &[u8] {
+            unreachable!("chunk");
         }
 
         fn advance(&mut self, _: usize) {
@@ -101,3 +101,20 @@ fn test_deref_buf_forwards() {
     assert_eq!((Box::new(Special) as Box<dyn Buf>).get_u8(), b'x');
     assert_eq!(Box::new(Special).get_u8(), b'x');
 }
+
+#[test]
+fn copy_to_bytes_less() {
+    let mut buf = &b"hello world"[..];
+
+    let bytes = buf.copy_to_bytes(5);
+    assert_eq!(bytes, &b"hello"[..]);
+    assert_eq!(buf, &b" world"[..])
+}
+
+#[test]
+#[should_panic]
+fn copy_to_bytes_overflow() {
+    let mut buf = &b"hello world"[..];
+
+    let _bytes = buf.copy_to_bytes(12);
+}

tests/test_buf_mut.rs

@@ -1,7 +1,6 @@
 #![warn(rust_2018_idioms)]
 
-#[cfg(feature = "std")]
-use bytes::buf::IoSliceMut;
+use bytes::buf::UninitSlice;
 use bytes::{BufMut, BytesMut};
 use core::fmt::Write;
 use core::usize;
@@ -10,15 +9,15 @@ use core::usize;
 fn test_vec_as_mut_buf() {
     let mut buf = Vec::with_capacity(64);
 
-    assert_eq!(buf.remaining_mut(), usize::MAX);
+    assert_eq!(buf.remaining_mut(), isize::MAX as usize);
 
-    assert!(buf.bytes_mut().len() >= 64);
+    assert!(buf.chunk_mut().len() >= 64);
 
     buf.put(&b"zomg"[..]);
 
     assert_eq!(&buf, b"zomg");
 
-    assert_eq!(buf.remaining_mut(), usize::MAX - 4);
+    assert_eq!(buf.remaining_mut(), isize::MAX as usize - 4);
     assert_eq!(buf.capacity(), 64);
 
     for _ in 0..16 {
@@ -28,6 +27,14 @@ fn test_vec_as_mut_buf() {
     assert_eq!(buf.len(), 68);
 }
 
+#[test]
+fn test_vec_put_bytes() {
+    let mut buf = Vec::new();
+    buf.push(17);
+    buf.put_bytes(19, 2);
+    assert_eq!([17, 19, 19], &buf[..]);
+}
+
 #[test]
 fn test_put_u8() {
     let mut buf = Vec::with_capacity(8);
@@ -46,6 +53,34 @@ fn test_put_u16() {
     assert_eq!(b"\x54\x21", &buf[..]);
 }
 
+#[test]
+fn test_put_int() {
+    let mut buf = Vec::with_capacity(8);
+    buf.put_int(0x1020304050607080, 3);
+    assert_eq!(b"\x60\x70\x80", &buf[..]);
+}
+
+#[test]
+#[should_panic]
+fn test_put_int_nbytes_overflow() {
+    let mut buf = Vec::with_capacity(8);
+    buf.put_int(0x1020304050607080, 9);
+}
+
+#[test]
+fn test_put_int_le() {
+    let mut buf = Vec::with_capacity(8);
+    buf.put_int_le(0x1020304050607080, 3);
+    assert_eq!(b"\x80\x70\x60", &buf[..]);
+}
+
+#[test]
+#[should_panic]
+fn test_put_int_le_nbytes_overflow() {
+    let mut buf = Vec::with_capacity(8);
+    buf.put_int_le(0x1020304050607080, 9);
+}
+
 #[test]
 #[should_panic(expected = "cannot advance")]
 fn test_vec_advance_mut() {
@@ -66,41 +101,37 @@ fn test_clone() {
     assert!(buf != buf2);
 }
 
-#[cfg(feature = "std")]
-#[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);
+
+    assert_eq!(s.len(), 0);
+    assert_eq!(&v, &[0, 0, 0, 42]);
+}
+
+#[test]
+fn test_slice_put_bytes() {
+    let mut v = [0, 0, 0, 0];
+    let mut s = &mut v[..];
+    s.put_u8(17);
+    s.put_bytes(19, 2);
+    assert_eq!(1, s.remaining_mut());
+    assert_eq!(&[17, 19, 19, 0], &v[..]);
 }
 
 #[test]
 fn test_deref_bufmut_forwards() {
     struct Special;
 
-    impl BufMut for Special {
+    unsafe 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");
+        fn chunk_mut(&mut self) -> &mut UninitSlice {
+            unreachable!("chunk_mut");
         }
 
         unsafe fn advance_mut(&mut self, _: usize) {
@@ -118,3 +149,30 @@ fn test_deref_bufmut_forwards() {
     (Box::new(Special) as Box<dyn BufMut>).put_u8(b'x');
     Box::new(Special).put_u8(b'x');
 }
+
+#[test]
+#[should_panic]
+fn write_byte_panics_if_out_of_bounds() {
+    let mut data = [b'b', b'a', b'r'];
+
+    let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    slice.write_byte(4, b'f');
+}
+
+#[test]
+#[should_panic]
+fn copy_from_slice_panics_if_different_length_1() {
+    let mut data = [b'b', b'a', b'r'];
+
+    let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    slice.copy_from_slice(b"a");
+}
+
+#[test]
+#[should_panic]
+fn copy_from_slice_panics_if_different_length_2() {
+    let mut data = [b'b', b'a', b'r'];
+
+    let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    slice.copy_from_slice(b"abcd");
+}

tests/test_bytes.rs

@@ -4,8 +4,8 @@ use bytes::{Buf, BufMut, Bytes, BytesMut};
 
 use std::usize;
 
-const LONG: &'static [u8] = b"mary had a little lamb, little lamb, little lamb";
-const SHORT: &'static [u8] = b"hello world";
+const LONG: &[u8] = b"mary had a little lamb, little lamb, little lamb";
+const SHORT: &[u8] = b"hello world";
 
 fn is_sync<T: Sync>() {}
 fn is_send<T: Send>() {}
@@ -411,8 +411,8 @@ fn freeze_after_split_off() {
 fn fns_defined_for_bytes_mut() {
     let mut bytes = BytesMut::from(&b"hello world"[..]);
 
-    bytes.as_ptr();
-    bytes.as_mut_ptr();
+    let _ = bytes.as_ptr();
+    let _ = bytes.as_mut_ptr();
 
     // Iterator
     let v: Vec<u8> = bytes.as_ref().iter().cloned().collect();
@@ -443,7 +443,7 @@ fn reserve_growth() {
     let _ = bytes.split();
 
     bytes.reserve(65);
-    assert_eq!(bytes.capacity(), 128);
+    assert_eq!(bytes.capacity(), 117);
 }
 
 #[test]
@@ -461,6 +461,7 @@ fn reserve_allocates_at_least_original_capacity() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore)] // Miri is too slow
 fn reserve_max_original_capacity_value() {
     const SIZE: usize = 128 * 1024;
 
@@ -514,6 +515,34 @@ fn reserve_in_arc_unique_doubles() {
     assert_eq!(2000, bytes.capacity());
 }
 
+#[test]
+fn reserve_in_arc_unique_does_not_overallocate_after_split() {
+    let mut bytes = BytesMut::from(LONG);
+    let orig_capacity = bytes.capacity();
+    drop(bytes.split_off(LONG.len() / 2));
+
+    // now bytes is Arc and refcount == 1
+
+    let new_capacity = bytes.capacity();
+    bytes.reserve(orig_capacity - new_capacity);
+    assert_eq!(bytes.capacity(), orig_capacity);
+}
+
+#[test]
+fn reserve_in_arc_unique_does_not_overallocate_after_multiple_splits() {
+    let mut bytes = BytesMut::from(LONG);
+    let orig_capacity = bytes.capacity();
+    for _ in 0..10 {
+        drop(bytes.split_off(LONG.len() / 2));
+
+        // now bytes is Arc and refcount == 1
+
+        let new_capacity = bytes.capacity();
+        bytes.reserve(orig_capacity - new_capacity);
+    }
+    assert_eq!(bytes.capacity(), orig_capacity);
+}
+
 #[test]
 fn reserve_in_arc_nonunique_does_not_overallocate() {
     let mut bytes = BytesMut::with_capacity(1000);
@@ -526,6 +555,25 @@ fn reserve_in_arc_nonunique_does_not_overallocate() {
     assert_eq!(2001, bytes.capacity());
 }
 
+/// This function tests `BytesMut::reserve_inner`, where `BytesMut` holds
+/// a unique reference to the shared vector and decide to reuse it
+/// by reallocating the `Vec`.
+#[test]
+fn reserve_shared_reuse() {
+    let mut bytes = BytesMut::with_capacity(1000);
+    bytes.put_slice(b"Hello, World!");
+    drop(bytes.split());
+
+    bytes.put_slice(b"!123ex123,sadchELLO,_wORLD!");
+    // Use split_off so that v.capacity() - self.cap != off
+    drop(bytes.split_off(9));
+    assert_eq!(&*bytes, b"!123ex123");
+
+    bytes.reserve(2000);
+    assert_eq!(&*bytes, b"!123ex123");
+    assert_eq!(bytes.capacity(), 2009);
+}
+
 #[test]
 fn extend_mut() {
     let mut bytes = BytesMut::with_capacity(0);
@@ -543,6 +591,13 @@ fn extend_from_slice_mut() {
     }
 }
 
+#[test]
+fn extend_mut_from_bytes() {
+    let mut bytes = BytesMut::with_capacity(0);
+    bytes.extend([Bytes::from(LONG)]);
+    assert_eq!(*bytes, LONG[..]);
+}
+
 #[test]
 fn extend_mut_without_size_hint() {
     let mut bytes = BytesMut::with_capacity(0);
@@ -608,15 +663,15 @@ fn advance_past_len() {
 
 #[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")]
+// big endian... and qemu doesn't really support threading all that well.
+#[cfg(any(miri, 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;
+    const ITERS: usize = if cfg!(miri) { 100 } else { 1_000 };
 
     for i in 0..ITERS {
         let data = [i as u8; 256];
@@ -783,6 +838,31 @@ fn bytes_mut_unsplit_empty_self() {
     assert_eq!(b"aaabbbcccddd", &buf[..]);
 }
 
+#[test]
+fn bytes_mut_unsplit_other_keeps_capacity() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aabb");
+
+    // non empty other created "from" buf
+    let mut other = buf.split_off(buf.len());
+    other.extend_from_slice(b"ccddee");
+    buf.unsplit(other);
+
+    assert_eq!(buf.capacity(), 64);
+}
+
+#[test]
+fn bytes_mut_unsplit_empty_other_keeps_capacity() {
+    let mut buf = BytesMut::with_capacity(64);
+    buf.extend_from_slice(b"aabbccddee");
+
+    // empty other created "from" buf
+    let other = buf.split_off(buf.len());
+    buf.unsplit(other);
+
+    assert_eq!(buf.capacity(), 64);
+}
+
 #[test]
 fn bytes_mut_unsplit_arc_different() {
     let mut buf = BytesMut::with_capacity(64);
@@ -848,7 +928,7 @@ fn from_iter_no_size_hint() {
 
 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);
+    let sub = bytes.slice_ref(slice);
     assert_eq!(&sub[..], expected);
 }
 
@@ -868,7 +948,7 @@ fn slice_ref_empty() {
     let bytes = Bytes::from(&b""[..]);
     let slice = &(bytes.as_ref()[0..0]);
 
-    let sub = bytes.slice_ref(&slice);
+    let sub = bytes.slice_ref(slice);
     assert_eq!(&sub[..], b"");
 }
 
@@ -912,20 +992,20 @@ 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());
+        let ptr = bytes.chunk_mut().as_mut_ptr();
+        assert_eq!(1024, bytes.chunk_mut().len());
 
         bytes.advance_mut(10);
 
-        let next = bytes.bytes_mut().as_ptr();
-        assert_eq!(1024 - 10, bytes.bytes_mut().len());
+        let next = bytes.chunk_mut().as_mut_ptr();
+        assert_eq!(1024 - 10, bytes.chunk_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());
+        assert_eq!(1024, bytes.chunk_mut().len());
     }
 }
 
@@ -960,3 +1040,126 @@ fn bytes_with_capacity_but_empty() {
     let vec = Vec::with_capacity(1);
     let _ = Bytes::from(vec);
 }
+
+#[test]
+fn bytes_put_bytes() {
+    let mut bytes = BytesMut::new();
+    bytes.put_u8(17);
+    bytes.put_bytes(19, 2);
+    assert_eq!([17, 19, 19], bytes.as_ref());
+}
+
+#[test]
+fn box_slice_empty() {
+    // See https://github.com/tokio-rs/bytes/issues/340
+    let empty: Box<[u8]> = Default::default();
+    let b = Bytes::from(empty);
+    assert!(b.is_empty());
+}
+
+#[test]
+fn bytes_into_vec() {
+    // Test kind == KIND_VEC
+    let content = b"helloworld";
+
+    let mut bytes = BytesMut::new();
+    bytes.put_slice(content);
+
+    let vec: Vec<u8> = bytes.into();
+    assert_eq!(&vec, content);
+
+    // Test kind == KIND_ARC, shared.is_unique() == True
+    let mut bytes = BytesMut::new();
+    bytes.put_slice(b"abcdewe23");
+    bytes.put_slice(content);
+
+    // Overwrite the bytes to make sure only one reference to the underlying
+    // Vec exists.
+    bytes = bytes.split_off(9);
+
+    let vec: Vec<u8> = bytes.into();
+    assert_eq!(&vec, content);
+
+    // Test kind == KIND_ARC, shared.is_unique() == False
+    let prefix = b"abcdewe23";
+
+    let mut bytes = BytesMut::new();
+    bytes.put_slice(prefix);
+    bytes.put_slice(content);
+
+    let vec: Vec<u8> = bytes.split_off(prefix.len()).into();
+    assert_eq!(&vec, content);
+
+    let vec: Vec<u8> = bytes.into();
+    assert_eq!(&vec, prefix);
+}
+
+#[test]
+fn test_bytes_into_vec() {
+    // Test STATIC_VTABLE.to_vec
+    let bs = b"1b23exfcz3r";
+    let vec: Vec<u8> = Bytes::from_static(bs).into();
+    assert_eq!(&*vec, bs);
+
+    // Test bytes_mut.SHARED_VTABLE.to_vec impl
+    eprintln!("1");
+    let mut bytes_mut: BytesMut = bs[..].into();
+
+    // Set kind to KIND_ARC so that after freeze, Bytes will use bytes_mut.SHARED_VTABLE
+    eprintln!("2");
+    drop(bytes_mut.split_off(bs.len()));
+
+    eprintln!("3");
+    let b1 = bytes_mut.freeze();
+    eprintln!("4");
+    let b2 = b1.clone();
+
+    eprintln!("{:#?}", (&*b1).as_ptr());
+
+    // shared.is_unique() = False
+    eprintln!("5");
+    assert_eq!(&*Vec::from(b2), bs);
+
+    // shared.is_unique() = True
+    eprintln!("6");
+    assert_eq!(&*Vec::from(b1), bs);
+
+    // Test bytes_mut.SHARED_VTABLE.to_vec impl where offset != 0
+    let mut bytes_mut1: BytesMut = bs[..].into();
+    let bytes_mut2 = bytes_mut1.split_off(9);
+
+    let b1 = bytes_mut1.freeze();
+    let b2 = bytes_mut2.freeze();
+
+    assert_eq!(Vec::from(b2), bs[9..]);
+    assert_eq!(Vec::from(b1), bs[..9]);
+}
+
+#[test]
+fn test_bytes_into_vec_promotable_even() {
+    let vec = vec![33u8; 1024];
+
+    // Test cases where kind == KIND_VEC
+    let b1 = Bytes::from(vec.clone());
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where kind == KIND_ARC, ref_cnt == 1
+    let b1 = Bytes::from(vec.clone());
+    drop(b1.clone());
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where kind == KIND_ARC, ref_cnt == 2
+    let b1 = Bytes::from(vec.clone());
+    let b2 = b1.clone();
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where vtable = SHARED_VTABLE, kind == KIND_ARC, ref_cnt == 1
+    assert_eq!(Vec::from(b2), vec);
+
+    // Test cases where offset != 0
+    let mut b1 = Bytes::from(vec.clone());
+    let b2 = b1.split_off(20);
+
+    assert_eq!(Vec::from(b2), vec[20..]);
+    assert_eq!(Vec::from(b1), vec[..20]);
+}

tests/test_bytes_odd_alloc.rs

@@ -1,6 +1,8 @@
 //! Test using `Bytes` with an allocator that hands out "odd" pointers for
 //! vectors (pointers where the LSB is set).
 
+#![cfg(not(miri))] // Miri does not support custom allocators (also, Miri is "odd" by default with 50% chance)
+
 use std::alloc::{GlobalAlloc, Layout, System};
 use std::ptr;
 
@@ -22,8 +24,7 @@ unsafe impl GlobalAlloc for Odd {
             };
             let ptr = System.alloc(new_layout);
             if !ptr.is_null() {
-                let ptr = ptr.offset(1);
-                ptr
+                ptr.offset(1)
             } else {
                 ptr
             }
@@ -65,3 +66,32 @@ fn test_bytes_clone_drop() {
     let b1 = Bytes::from(vec);
     let _b2 = b1.clone();
 }
+
+#[test]
+fn test_bytes_into_vec() {
+    let vec = vec![33u8; 1024];
+
+    // Test cases where kind == KIND_VEC
+    let b1 = Bytes::from(vec.clone());
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where kind == KIND_ARC, ref_cnt == 1
+    let b1 = Bytes::from(vec.clone());
+    drop(b1.clone());
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where kind == KIND_ARC, ref_cnt == 2
+    let b1 = Bytes::from(vec.clone());
+    let b2 = b1.clone();
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where vtable = SHARED_VTABLE, kind == KIND_ARC, ref_cnt == 1
+    assert_eq!(Vec::from(b2), vec);
+
+    // Test cases where offset != 0
+    let mut b1 = Bytes::from(vec.clone());
+    let b2 = b1.split_off(20);
+
+    assert_eq!(Vec::from(b2), vec[20..]);
+    assert_eq!(Vec::from(b1), vec[..20]);
+}

tests/test_bytes_vec_alloc.rs

@@ -1,61 +1,87 @@
 use std::alloc::{GlobalAlloc, Layout, System};
-use std::{mem, ptr};
+use std::ptr::null_mut;
+use std::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
 
 use bytes::{Buf, Bytes};
 
 #[global_allocator]
-static LEDGER: Ledger = Ledger;
+static LEDGER: Ledger = Ledger::new();
 
-struct Ledger;
+const LEDGER_LENGTH: usize = 2048;
 
-const USIZE_SIZE: usize = mem::size_of::<usize>();
+struct Ledger {
+    alloc_table: [(AtomicPtr<u8>, AtomicUsize); LEDGER_LENGTH],
+}
 
-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
+impl Ledger {
+    const fn new() -> Self {
+        const ELEM: (AtomicPtr<u8>, AtomicUsize) =
+            (AtomicPtr::new(null_mut()), AtomicUsize::new(0));
+        let alloc_table = [ELEM; LEDGER_LENGTH];
+
+        Self { alloc_table }
+    }
+
+    /// Iterate over our table until we find an open entry, then insert into said entry
+    fn insert(&self, ptr: *mut u8, size: usize) {
+        for (entry_ptr, entry_size) in self.alloc_table.iter() {
+            // SeqCst is good enough here, we don't care about perf, i just want to be correct!
+            if entry_ptr
+                .compare_exchange(null_mut(), ptr, Ordering::SeqCst, Ordering::SeqCst)
+                .is_ok()
+            {
+                entry_size.store(size, Ordering::SeqCst);
+                break;
             }
-        } 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()
-                );
+    fn remove(&self, ptr: *mut u8) -> usize {
+        for (entry_ptr, entry_size) in self.alloc_table.iter() {
+            // set the value to be something that will never try and be deallocated, so that we
+            // don't have any chance of a race condition
+            //
+            // dont worry, LEDGER_LENGTH is really long to compensate for us not reclaiming space
+            if entry_ptr
+                .compare_exchange(
+                    ptr,
+                    invalid_ptr(usize::MAX),
+                    Ordering::SeqCst,
+                    Ordering::SeqCst,
+                )
+                .is_ok()
+            {
+                return entry_size.load(Ordering::SeqCst);
             }
+        }
 
-            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);
+        panic!("Couldn't find a matching entry for {:x?}", ptr);
+    }
+}
+
+unsafe impl GlobalAlloc for Ledger {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let size = layout.size();
+        let ptr = System.alloc(layout);
+        self.insert(ptr, size);
+        ptr
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        let orig_size = self.remove(ptr);
+
+        if orig_size != layout.size() {
+            panic!(
+                "bad dealloc: alloc size was {}, dealloc size is {}",
+                orig_size,
+                layout.size()
+            );
         } else {
             System.dealloc(ptr, layout);
         }
     }
 }
+
 #[test]
 fn test_bytes_advance() {
     let mut bytes = Bytes::from(vec![10, 20, 30]);
@@ -77,3 +103,41 @@ fn test_bytes_truncate_and_advance() {
     bytes.advance(1);
     drop(bytes);
 }
+
+/// Returns a dangling pointer with the given address. This is used to store
+/// integer data in pointer fields.
+#[inline]
+fn invalid_ptr<T>(addr: usize) -> *mut T {
+    let ptr = std::ptr::null_mut::<u8>().wrapping_add(addr);
+    debug_assert_eq!(ptr as usize, addr);
+    ptr.cast::<T>()
+}
+
+#[test]
+fn test_bytes_into_vec() {
+    let vec = vec![33u8; 1024];
+
+    // Test cases where kind == KIND_VEC
+    let b1 = Bytes::from(vec.clone());
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where kind == KIND_ARC, ref_cnt == 1
+    let b1 = Bytes::from(vec.clone());
+    drop(b1.clone());
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where kind == KIND_ARC, ref_cnt == 2
+    let b1 = Bytes::from(vec.clone());
+    let b2 = b1.clone();
+    assert_eq!(Vec::from(b1), vec);
+
+    // Test cases where vtable = SHARED_VTABLE, kind == KIND_ARC, ref_cnt == 1
+    assert_eq!(Vec::from(b2), vec);
+
+    // Test cases where offset != 0
+    let mut b1 = Bytes::from(vec.clone());
+    let b2 = b1.split_off(20);
+
+    assert_eq!(Vec::from(b2), vec[20..]);
+    assert_eq!(Vec::from(b1), vec[..20]);
+}

tests/test_chain.rs

@@ -1,6 +1,5 @@
 #![warn(rust_2018_idioms)]
 
-use bytes::buf::{BufExt, BufMutExt};
 use bytes::{Buf, BufMut, Bytes};
 #[cfg(feature = "std")]
 use std::io::IoSlice;
@@ -10,7 +9,7 @@ fn collect_two_bufs() {
     let a = Bytes::from(&b"hello"[..]);
     let b = Bytes::from(&b"world"[..]);
 
-    let res = a.chain(b).to_bytes();
+    let res = a.chain(b).copy_to_bytes(10);
     assert_eq!(res, &b"helloworld"[..]);
 }
 
@@ -63,7 +62,7 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(2, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(2, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"hello"[..]);
         assert_eq!(iovecs[1][..], b"world"[..]);
         assert_eq!(iovecs[2][..], b""[..]);
@@ -84,7 +83,7 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(2, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(2, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"llo"[..]);
         assert_eq!(iovecs[1][..], b"world"[..]);
         assert_eq!(iovecs[2][..], b""[..]);
@@ -105,7 +104,7 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(1, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(1, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"world"[..]);
         assert_eq!(iovecs[1][..], b""[..]);
         assert_eq!(iovecs[2][..], b""[..]);
@@ -126,10 +125,53 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(1, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(1, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"ld"[..]);
         assert_eq!(iovecs[1][..], b""[..]);
         assert_eq!(iovecs[2][..], b""[..]);
         assert_eq!(iovecs[3][..], b""[..]);
     }
 }
+
+#[test]
+fn chain_growing_buffer() {
+    let mut buff = [' ' as u8; 10];
+    let mut vec = b"wassup".to_vec();
+
+    let mut chained = (&mut buff[..]).chain_mut(&mut vec).chain_mut(Vec::new()); // Required for potential overflow because remaining_mut for Vec is isize::MAX - vec.len(), but for chain_mut is usize::MAX
+
+    chained.put_slice(b"hey there123123");
+
+    assert_eq!(&buff, b"hey there1");
+    assert_eq!(&vec, b"wassup23123");
+}
+
+#[test]
+fn chain_overflow_remaining_mut() {
+    let mut chained = Vec::<u8>::new().chain_mut(Vec::new()).chain_mut(Vec::new());
+
+    assert_eq!(chained.remaining_mut(), usize::MAX);
+    chained.put_slice(&[0; 256]);
+    assert_eq!(chained.remaining_mut(), usize::MAX);
+}
+
+#[test]
+fn chain_get_bytes() {
+    let mut ab = Bytes::copy_from_slice(b"ab");
+    let mut cd = Bytes::copy_from_slice(b"cd");
+    let ab_ptr = ab.as_ptr();
+    let cd_ptr = cd.as_ptr();
+    let mut chain = (&mut ab).chain(&mut cd);
+    let a = chain.copy_to_bytes(1);
+    let bc = chain.copy_to_bytes(2);
+    let d = chain.copy_to_bytes(1);
+
+    assert_eq!(Bytes::copy_from_slice(b"a"), a);
+    assert_eq!(Bytes::copy_from_slice(b"bc"), bc);
+    assert_eq!(Bytes::copy_from_slice(b"d"), d);
+
+    // assert `get_bytes` did not allocate
+    assert_eq!(ab_ptr, a.as_ptr());
+    // assert `get_bytes` did not allocate
+    assert_eq!(cd_ptr.wrapping_offset(1), d.as_ptr());
+}

tests/test_reader.rs

@@ -3,13 +3,13 @@
 
 use std::io::{BufRead, Read};
 
-use bytes::buf::BufExt;
+use bytes::Buf;
 
 #[test]
 fn read() {
     let buf1 = &b"hello "[..];
     let buf2 = &b"world"[..];
-    let buf = BufExt::chain(buf1, buf2); // Disambiguate with Read::chain
+    let buf = Buf::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[..]);
@@ -19,7 +19,7 @@ fn read() {
 fn buf_read() {
     let buf1 = &b"hell"[..];
     let buf2 = &b"o\nworld"[..];
-    let mut reader = BufExt::chain(buf1, buf2).reader();
+    let mut reader = Buf::chain(buf1, buf2).reader();
     let mut line = String::new();
     reader.read_line(&mut line).unwrap();
     assert_eq!("hello\n", &line);

tests/test_take.rs

@@ -1,6 +1,7 @@
 #![warn(rust_2018_idioms)]
 
-use bytes::buf::{Buf, BufExt};
+use bytes::buf::Buf;
+use bytes::Bytes;
 
 #[test]
 fn long_take() {
@@ -8,5 +9,24 @@ fn long_take() {
     // 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());
+    assert_eq!(b"hello world", buf.chunk());
+}
+
+#[test]
+fn take_copy_to_bytes() {
+    let mut abcd = Bytes::copy_from_slice(b"abcd");
+    let abcd_ptr = abcd.as_ptr();
+    let mut take = (&mut abcd).take(2);
+    let a = take.copy_to_bytes(1);
+    assert_eq!(Bytes::copy_from_slice(b"a"), a);
+    // assert `to_bytes` did not allocate
+    assert_eq!(abcd_ptr, a.as_ptr());
+    assert_eq!(Bytes::copy_from_slice(b"bcd"), abcd);
+}
+
+#[test]
+#[should_panic]
+fn take_copy_to_bytes_panics() {
+    let abcd = Bytes::copy_from_slice(b"abcd");
+    abcd.take(2).copy_to_bytes(3);
 }