chore: prepare bytes v1.4.0 (#593)

When we freeze a BytesMut, we turn it into a Vec, and then convert that
to a Bytes.  Currently, this happen using Vec::into_boxed_slice, which
reallocates to a slice of the same length as the Vev if the length and
the capacity are not equal.  This can pose a performance problem if the
Vec is large or if this happens many times in a loop.

Instead, let's compare the length and capacity, and if they're the same,
continue to handle this using into_boxed_slice.  Otherwise, since we
have a type of vtable which can handle a separate capacity, the shared
vtable, let's turn our Vec into that kind of Bytes.  While this does not
avoid allocation altogether, it performs a fixed size allocation and
avoids any need to memcpy.

.github/workflows/ci.yml

@@ -11,7 +11,7 @@ on:
 env:
   RUSTFLAGS: -Dwarnings
   RUST_BACKTRACE: 1
-  nightly: nightly-2020-12-17
+  nightly: nightly-2022-11-12
 
 defaults:
   run:
@@ -23,7 +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
@@ -35,7 +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
 
@@ -48,7 +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
@@ -65,7 +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
@@ -77,7 +77,7 @@ jobs:
     name: nightly
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
         run: rustup update $nightly && rustup default $nightly
       - name: Test
@@ -94,9 +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 }}
@@ -116,7 +116,7 @@ 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
       - name: Install rust-src
@@ -127,7 +127,7 @@ jobs:
     name: miri
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Miri
         run: ci/miri.sh
 
@@ -136,7 +136,7 @@ jobs:
     name: loom
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
         run: rustup update $nightly && rustup default $nightly
       - name: Loom tests
@@ -155,11 +155,13 @@ jobs:
       - loom
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Install Rust
-        run: rustup update stable && rustup default stable
+        run: rustup update $nightly && rustup default $nightly
       - 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 +1,87 @@
+# 1.4.0 (January 31, 2023)
+
+### Added
+
+- Make `IntoIter` constructor public (#581)
+
+### Fixed
+
+- Avoid large reallocations when freezing `BytesMut` (#592)
+
+### Documented
+
+- Document which functions require `std` (#591)
+- Fix duplicate "the the" typos (#585)
+
+# 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
@@ -10,7 +94,7 @@
 # 1.0.0 (December 22, 2020)
 
 ### Changed
-- Rename Buf/BufMut, methods to chunk/chunk_mut (#450)
+- Rename `Buf`/`BufMut` methods `bytes()` and `bytes_mut()` to `chunk()` and `chunk_mut()` (#450)
 
 ### Removed
 - remove unused Buf implementation. (#449)

Cargo.toml

@@ -2,18 +2,15 @@
 
 name = "bytes"
 # When releasing to crates.io:
-# - Update html_root_url.
 # - Update CHANGELOG.md.
-# - Update doc URL.
-# - Create "v1.0.x" git tag.
-version = "1.0.1"
+# - Create "v1.x.y" git tag.
+version = "1.4.0"
 license = "MIT"
 authors = [
     "Carl Lerche <[email protected]>",
     "Sean McArthur <[email protected]>",
 ]
 description = "Types and traits for working with bytes"
-documentation = "https://docs.rs/bytes/1.0.1/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 = "0.4"
+loom = "0.5"
+
+[package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "docsrs"]

README.md

@@ -36,6 +36,15 @@ Serde support is optional and disabled by default. To enable use the feature `se
 bytes = { version = "1", features = ["serde"] }
 ```
 
+## Building documentation
+
+When building the `bytes` documentation the `docsrs` option should be used, otherwise
+feature gates will not be shown. This requires a nightly toolchain:
+
+```
+RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc
+```
+
 ## License
 
 This project is licensed under the [MIT license](LICENSE).

benches/buf.rs

@@ -46,7 +46,7 @@ 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;

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

@@ -1,11 +1,11 @@
 #!/bin/bash
 set -e
 
-MIRI_NIGHTLY=nightly-$(curl -s https://rust-lang.github.io/rustup-components-history/x86_64-unknown-linux-gnu/miri)
-echo "Installing latest nightly with Miri: $MIRI_NIGHTLY"
-rustup set profile minimal
-rustup default "$MIRI_NIGHTLY"
-rustup component add miri
+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

@@ -127,6 +127,9 @@ pub trait Buf {
     /// This function should never panic. Once the end of the buffer is reached,
     /// i.e., `Buf::remaining` returns 0, calls to `chunk()` should return an
     /// empty slice.
+    // 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
@@ -157,6 +160,7 @@ pub trait Buf {
     ///
     /// [`writev`]: http://man7.org/linux/man-pages/man2/readv.2.html
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     fn chunks_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
         if dst.is_empty() {
             return 0;
@@ -351,6 +355,29 @@ 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.
@@ -391,6 +418,29 @@ 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.
@@ -431,6 +481,29 @@ 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.
@@ -471,6 +544,29 @@ 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.
@@ -511,6 +607,29 @@ 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.
@@ -551,6 +670,29 @@ 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.
@@ -591,6 +733,29 @@ 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.
@@ -631,6 +796,29 @@ 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`.
@@ -671,6 +859,33 @@ 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`.
@@ -711,6 +926,33 @@ 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.
     ///
@@ -753,6 +995,30 @@ 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.
     ///
@@ -795,6 +1061,30 @@ pub trait Buf {
         f64::from_bits(Self::get_u64_le(self))
     }
 
+    /// 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 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());
+    /// ```
+    ///
+    /// # 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.
     ///
@@ -894,6 +1184,7 @@ pub trait Buf {
     /// assert_eq!(&dst[..11], &b"hello world"[..]);
     /// ```
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     fn reader(self) -> Reader<Self>
     where
         Self: Sized,
@@ -945,6 +1236,10 @@ 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()
         }
@@ -953,6 +1248,10 @@ 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()
         }
@@ -961,6 +1260,10 @@ 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()
         }
@@ -969,6 +1272,10 @@ 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()
         }
@@ -977,6 +1284,10 @@ 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()
         }
@@ -985,6 +1296,10 @@ 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)
         }
@@ -993,6 +1308,10 @@ 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)
         }
@@ -1001,6 +1320,10 @@ macro_rules! deref_forward_buf {
             (**self).get_int_le(nbytes)
         }
 
+        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)
         }

src/buf/buf_mut.rs

@@ -33,6 +33,10 @@ pub unsafe trait BufMut {
     /// This value is greater than or equal to the length of the slice returned
     /// by `chunk_mut()`.
     ///
+    /// Writing to a `BufMut` may involve allocating more memory on the fly.
+    /// Implementations may fail before reaching the number of bytes indicated
+    /// by this method if they encounter an allocation failure.
+    ///
     /// # Examples
     ///
     /// ```
@@ -52,6 +56,10 @@ pub unsafe 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
@@ -158,6 +166,12 @@ pub unsafe trait BufMut {
     /// `chunk_mut()` returning an empty slice implies that `remaining_mut()` will
     /// return 0 and `remaining_mut()` returning 0 implies that `chunk_mut()` will
     /// return an empty slice.
+    ///
+    /// This function may trigger an out-of-memory abort if it tries to allocate
+    /// memory and fails to do so.
+    // The `chunk_mut` method was previously called `bytes_mut`. This alias makes the
+    // rename more easily discoverable.
+    #[cfg_attr(docsrs, doc(alias = "bytes_mut"))]
     fn chunk_mut(&mut self) -> &mut UninitSlice;
 
     /// Transfer bytes into `self` from `src` and advance the cursor by the
@@ -251,6 +265,37 @@ pub unsafe trait BufMut {
         }
     }
 
+    /// Put `cnt` bytes `val` into `self`.
+    ///
+    /// Logically equivalent to calling `self.put_u8(val)` `cnt` times, but may work faster.
+    ///
+    /// `self` must have at least `cnt` remaining capacity.
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut dst = [0; 6];
+    ///
+    /// {
+    ///     let mut buf = &mut dst[..];
+    ///     buf.put_bytes(b'a', 4);
+    ///
+    ///     assert_eq!(2, buf.remaining_mut());
+    /// }
+    ///
+    /// assert_eq!(b"aaaa\0\0", &dst);
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if there is not enough remaining capacity in
+    /// `self`.
+    fn put_bytes(&mut self, val: u8, cnt: usize) {
+        for _ in 0..cnt {
+            self.put_u8(val);
+        }
+    }
+
     /// Writes an unsigned 8 bit integer to `self`.
     ///
     /// The current position is advanced by 1.
@@ -341,6 +386,32 @@ pub unsafe 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.
@@ -385,6 +456,32 @@ pub unsafe 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.
@@ -429,6 +526,32 @@ pub unsafe 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.
@@ -473,6 +596,32 @@ pub unsafe 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.
@@ -517,6 +666,32 @@ pub unsafe 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.
@@ -561,6 +736,32 @@ pub unsafe 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.
@@ -605,6 +806,32 @@ pub unsafe 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.
@@ -649,6 +876,32 @@ pub unsafe 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`.
@@ -693,7 +946,7 @@ pub unsafe trait BufMut {
         self.put_slice(&n.to_le_bytes()[0..nbytes]);
     }
 
-    /// Writes a signed n-byte integer to `self` in big-endian byte order.
+    /// Writes an unsigned n-byte integer to `self` in the native-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
     ///
@@ -703,19 +956,49 @@ pub unsafe 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`.
     ///
@@ -725,18 +1008,48 @@ pub unsafe trait BufMut {
     /// use bytes::BufMut;
     ///
     /// let mut buf = vec![];
-    /// buf.put_int_le(0x010203, 3);
+    /// buf.put_int_le(0x0504010203, 3);
     /// assert_eq!(buf, b"\x03\x02\x01");
     /// ```
     ///
     /// # Panics
     ///
     /// This function panics if there is not enough remaining capacity in
-    /// `self`.
+    /// `self` or if `nbytes` is greater than 8.
     fn put_int_le(&mut self, n: i64, nbytes: usize) {
         self.put_slice(&n.to_le_bytes()[0..nbytes]);
     }
 
+    /// 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.
     ///
@@ -783,6 +1096,33 @@ pub unsafe 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.
     ///
@@ -829,6 +1169,33 @@ pub unsafe trait BufMut {
         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
@@ -872,6 +1239,7 @@ pub unsafe trait BufMut {
     /// assert_eq!(*buf, b"hello world"[..]);
     /// ```
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     fn writer(self) -> Writer<Self>
     where
         Self: Sized,
@@ -941,6 +1309,10 @@ 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)
         }
@@ -949,6 +1321,10 @@ 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)
         }
@@ -957,6 +1333,10 @@ 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)
         }
@@ -965,6 +1345,10 @@ 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)
         }
@@ -973,6 +1357,10 @@ 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)
         }
@@ -980,6 +1368,10 @@ 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)
+        }
     };
 }
 
@@ -1009,12 +1401,29 @@ unsafe impl BufMut for &mut [u8] {
         let (_, b) = core::mem::replace(self, &mut []).split_at_mut(cnt);
         *self = b;
     }
+
+    #[inline]
+    fn put_slice(&mut self, src: &[u8]) {
+        self[..src.len()].copy_from_slice(src);
+        unsafe {
+            self.advance_mut(src.len());
+        }
+    }
+
+    fn put_bytes(&mut self, val: u8, cnt: usize) {
+        assert!(self.remaining_mut() >= cnt);
+        unsafe {
+            ptr::write_bytes(self.as_mut_ptr(), val, cnt);
+            self.advance_mut(cnt);
+        }
+    }
 }
 
 unsafe impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {
-        usize::MAX - self.len()
+        // A vector can never have more than isize::MAX bytes
+        core::isize::MAX as usize - self.len()
     }
 
     #[inline]
@@ -1072,6 +1481,11 @@ unsafe impl BufMut for Vec<u8> {
     fn put_slice(&mut self, src: &[u8]) {
         self.extend_from_slice(src);
     }
+
+    fn put_bytes(&mut self, val: u8, cnt: usize) {
+        let new_len = self.len().checked_add(cnt).unwrap();
+        self.resize(new_len, val);
+    }
 }
 
 // The existence of this function makes the compiler catch if the BufMut

src/buf/chain.rs

@@ -1,5 +1,5 @@
 use crate::buf::{IntoIter, UninitSlice};
-use crate::{Buf, BufMut};
+use crate::{Buf, BufMut, Bytes};
 
 #[cfg(feature = "std")]
 use std::io::IoSlice;
@@ -135,7 +135,7 @@ where
     U: Buf,
 {
     fn remaining(&self) -> usize {
-        self.a.remaining() + self.b.remaining()
+        self.a.remaining().checked_add(self.b.remaining()).unwrap()
     }
 
     fn chunk(&self) -> &[u8] {
@@ -170,6 +170,24 @@ where
         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()
+        }
+    }
 }
 
 unsafe impl<T, U> BufMut for Chain<T, U>
@@ -178,7 +196,9 @@ where
     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 chunk_mut(&mut self) -> &mut UninitSlice {

src/buf/iter.rs

@@ -2,8 +2,6 @@ use crate::Buf;
 
 /// Iterator over the bytes contained by the buffer.
 ///
-/// This struct is created by the [`iter`] method on [`Buf`].
-///
 /// # Examples
 ///
 /// Basic usage:
@@ -43,7 +41,7 @@ impl<T> IntoIter<T> {
     /// assert_eq!(iter.next(), Some(b'c'));
     /// assert_eq!(iter.next(), None);
     /// ```
-    pub(crate) fn new(inner: T) -> IntoIter<T> {
+    pub fn new(inner: T) -> IntoIter<T> {
         IntoIter { inner }
     }
 

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,
@@ -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

@@ -22,6 +22,10 @@ use core::ops::{
 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
@@ -40,10 +44,11 @@ impl UninitSlice {
     ///
     /// 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);
-        &mut *(maybe_init as *mut [MaybeUninit<u8>] as *mut UninitSlice)
+        Self::from_slice(maybe_init)
     }
 
     /// Write a single byte at the specified offset.
@@ -64,6 +69,7 @@ impl UninitSlice {
     ///
     /// assert_eq!(b"boo", &data[..]);
     /// ```
+    #[inline]
     pub fn write_byte(&mut self, index: usize, byte: u8) {
         assert!(index < self.len());
 
@@ -90,6 +96,7 @@ impl UninitSlice {
     ///
     /// assert_eq!(b"bar", &data[..]);
     /// ```
+    #[inline]
     pub fn copy_from_slice(&mut self, src: &[u8]) {
         use core::ptr;
 
@@ -116,10 +123,37 @@ impl UninitSlice {
     /// 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
@@ -133,6 +167,7 @@ impl UninitSlice {
     ///
     /// assert_eq!(len, 3);
     /// ```
+    #[inline]
     pub fn len(&self) -> usize {
         self.0.len()
     }
@@ -150,6 +185,7 @@ macro_rules! impl_index {
             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) }
@@ -157,6 +193,7 @@ macro_rules! impl_index {
             }
 
             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) }

src/bytes.rs

@@ -2,12 +2,18 @@ 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 cheaply cloneable and sliceable chunk of contiguous memory.
@@ -26,7 +32,7 @@ use crate::Buf;
 /// 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.
+/// - Instances can be sliced to refer to a subset of the original buffer.
 ///
 /// ```
 /// use bytes::Bytes;
@@ -55,7 +61,7 @@ use crate::Buf;
 /// # Sharing
 ///
 /// `Bytes` contains a vtable, which allows implementations of `Bytes` to define
-/// how sharing/cloneing is implemented in detail.
+/// 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.
@@ -65,7 +71,7 @@ use crate::Buf;
 ///
 /// 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.
+/// reference count.
 ///
 /// Due to this mechanism, multiple `Bytes` instances may point to the same
 /// shared memory region.
@@ -78,18 +84,18 @@ use crate::Buf;
 ///
 /// ```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,
@@ -103,6 +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),
 }
 
@@ -121,7 +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] = &[];
@@ -129,7 +139,7 @@ impl Bytes {
     }
 
     #[cfg(all(loom, test))]
-    pub fn new() -> Bytes {
+    pub fn new() -> Self {
         const EMPTY: &[u8] = &[];
         Bytes::from_static(EMPTY)
     }
@@ -149,7 +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(),
@@ -159,7 +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(),
@@ -179,7 +189,7 @@ impl Bytes {
     /// assert_eq!(b.len(), 5);
     /// ```
     #[inline]
-    pub fn len(&self) -> usize {
+    pub const fn len(&self) -> usize {
         self.len
     }
 
@@ -194,7 +204,7 @@ impl Bytes {
     /// assert!(b.is_empty());
     /// ```
     #[inline]
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.len == 0
     }
 
@@ -225,7 +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();
@@ -262,7 +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
     }
@@ -292,7 +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() {
@@ -308,15 +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,
         );
 
@@ -349,7 +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: {:?} <= {:?}",
@@ -398,7 +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: {:?} <= {:?}",
@@ -501,7 +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);
     }
 }
 
@@ -604,7 +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()
     }
 }
 
@@ -686,7 +696,7 @@ impl PartialOrd<Bytes> for str {
 
 impl PartialEq<Vec<u8>> for Bytes {
     fn eq(&self, other: &Vec<u8>) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
@@ -710,7 +720,7 @@ impl PartialOrd<Bytes> for Vec<u8> {
 
 impl PartialEq<String> for Bytes {
     fn eq(&self, other: &String) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
@@ -797,30 +807,64 @@ 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 mut vec = vec;
+        let ptr = vec.as_mut_ptr();
+        let len = vec.len();
+        let cap = vec.capacity();
+
+        // Avoid an extra allocation if possible.
+        if len == cap {
+            return Bytes::from(vec.into_boxed_slice());
+        }
+
+        let shared = Box::new(Shared {
+            buf: ptr,
+            cap,
+            ref_cnt: AtomicUsize::new(1),
+        });
+        mem::forget(vec);
+
+        let shared = Box::into_raw(shared);
+        // The pointer should be aligned, so this assert should
+        // always succeed.
+        debug_assert!(
+            0 == (shared as usize & KIND_MASK),
+            "internal: Box<Shared> should have an aligned pointer",
+        );
+        Bytes {
+            ptr,
+            len,
+            data: AtomicPtr::new(shared as _),
+            vtable: &SHARED_VTABLE,
+        }
+    }
+}
+
+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 = 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,
             }
         }
@@ -833,6 +877,13 @@ 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 {
@@ -848,6 +899,7 @@ impl fmt::Debug for Vtable {
 
 const STATIC_VTABLE: Vtable = Vtable {
     clone: static_clone,
+    to_vec: static_to_vec,
     drop: static_drop,
 };
 
@@ -856,6 +908,11 @@ 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]
 }
@@ -864,11 +921,13 @@ 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,
 };
 
@@ -877,25 +936,57 @@ 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);
         }
     });
 }
@@ -908,38 +999,49 @@ 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.
@@ -948,6 +1050,7 @@ 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,
 };
 
@@ -960,9 +1063,42 @@ 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());
     });
 }
 
@@ -1000,9 +1136,9 @@ 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`.
@@ -1076,10 +1212,40 @@ 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};
@@ -8,6 +8,7 @@ use alloc::{
     borrow::{Borrow, BorrowMut},
     boxed::Box,
     string::String,
+    vec,
     vec::Vec,
 };
 
@@ -15,7 +16,7 @@ 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
     ///
@@ -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.uninit_slice();
+            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 uninit_slice(&mut self) -> &mut UninitSlice {
+    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;
 
-            UninitSlice::from_raw_parts_mut(ptr, 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) };
         }
     }
 }
@@ -989,7 +1101,7 @@ unsafe impl BufMut for BytesMut {
         if self.capacity() == self.len() {
             self.reserve(64);
         }
-        self.uninit_slice()
+        UninitSlice::from_slice(self.spare_capacity_mut())
     }
 
     // Specialize these methods so they can skip checking `remaining_mut`
@@ -1010,6 +1122,19 @@ unsafe 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

@@ -3,8 +3,8 @@
     no_crate_inject,
     attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
 ))]
-#![doc(html_root_url = "https://docs.rs/bytes/1.0.1")]
 #![no_std]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 
 //! 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_mut.rs

@@ -9,7 +9,7 @@ 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.chunk_mut().len() >= 64);
 
@@ -17,7 +17,7 @@ fn test_vec_as_mut_buf() {
 
     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 {
@@ -27,6 +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);
@@ -45,6 +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() {
@@ -70,6 +106,19 @@ 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]

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]
@@ -515,6 +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);
@@ -527,6 +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);
@@ -544,6 +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);
@@ -784,6 +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);
@@ -849,7 +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);
 }
 
@@ -869,7 +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"");
 }
 
@@ -961,3 +1040,171 @@ 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]);
+}
+
+#[test]
+fn test_bytes_vec_conversion() {
+    let mut vec = Vec::with_capacity(10);
+    vec.extend(b"abcdefg");
+    let b = Bytes::from(vec);
+    let v = Vec::from(b);
+    assert_eq!(v.len(), 7);
+    assert_eq!(v.capacity(), 10);
+
+    let mut b = Bytes::from(v);
+    b.advance(1);
+    let v = Vec::from(b);
+    assert_eq!(v.len(), 6);
+    assert_eq!(v.capacity(), 10);
+    assert_eq!(v.as_slice(), b"bcdefg");
+}
+
+#[test]
+fn test_bytes_mut_conversion() {
+    let mut b1 = BytesMut::with_capacity(10);
+    b1.extend(b"abcdefg");
+    let b2 = Bytes::from(b1);
+    let v = Vec::from(b2);
+    assert_eq!(v.len(), 7);
+    assert_eq!(v.capacity(), 10);
+
+    let mut b = Bytes::from(v);
+    b.advance(1);
+    let v = Vec::from(b);
+    assert_eq!(v.len(), 6);
+    assert_eq!(v.capacity(), 10);
+    assert_eq!(v.as_slice(), b"bcdefg");
+}
+
+#[test]
+fn test_bytes_capacity_len() {
+    for cap in 0..100 {
+        for len in 0..=cap {
+            let mut v = Vec::with_capacity(cap);
+            v.resize(len, 0);
+            let _ = Bytes::from(v);
+        }
+    }
+}

tests/test_bytes_odd_alloc.rs

@@ -24,8 +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
             }
@@ -67,3 +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

@@ -132,3 +132,46 @@ fn vectored_read() {
         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_take.rs

@@ -1,6 +1,7 @@
 #![warn(rust_2018_idioms)]
 
 use bytes::buf::Buf;
+use bytes::Bytes;
 
 #[test]
 fn long_take() {
@@ -10,3 +11,22 @@ fn long_take() {
     assert_eq!(11, buf.remaining());
     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);
+}