chore: prepare bytes v1.1.0 (#509)

Co-authored-by: Taiki Endo <[email protected]>

.github/workflows/ci.yml

@@ -0,0 +1,172 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - master
+  push:
+    branches:
+      - master
+
+env:
+  RUSTFLAGS: -Dwarnings
+  RUST_BACKTRACE: 1
+  nightly: nightly-2021-04-13
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  # Check formatting
+  rustfmt:
+    name: rustfmt
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Install Rust
+      run: rustup update stable && rustup default stable
+    - name: Check formatting
+      run: cargo fmt --all -- --check
+
+  # TODO
+  # # Apply clippy lints
+  # clippy:
+  #   name: clippy
+  #   runs-on: ubuntu-latest
+  #   steps:
+  #   - uses: actions/checkout@v2
+  #   - name: Apply clippy lints
+  #     run: cargo clippy --all-features
+
+  # This represents the minimum Rust version supported by
+  # Bytes. Updating this should be done in a dedicated PR.
+  #
+  # Tests are not run as tests may require newer versions of
+  # rust.
+  minrust:
+    name: minrust
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update 1.39.0 && rustup default 1.39.0
+      - name: Check
+        run: . ci/test-stable.sh check
+
+  # Stable
+  stable:
+    name: stable
+    strategy:
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-latest
+          - windows-latest
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2
+      - 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
+      - name: Test
+        run: . ci/test-stable.sh test
+
+  # Nightly
+  nightly:
+    name: nightly
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update $nightly && rustup default $nightly
+      - name: Test
+        run: . ci/test-stable.sh test
+
+  # Run tests on some extra platforms
+  cross:
+    name: cross
+    strategy:
+      matrix:
+        target:
+          - i686-unknown-linux-gnu
+          - armv7-unknown-linux-gnueabihf
+          - powerpc-unknown-linux-gnu
+          - powerpc64-unknown-linux-gnu
+          - wasm32-unknown-unknown
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update stable && rustup default stable
+      - name: cross build --target ${{ matrix.target }}
+        run: |
+          cargo install cross
+          cross build --target ${{ matrix.target }}
+        if: matrix.target != 'wasm32-unknown-unknown'
+      # WASM support
+      - name: cargo build --target ${{ matrix.target }}
+        run: |
+          rustup target add ${{ matrix.target }}
+          cargo build --target ${{ matrix.target }}
+        if: matrix.target == 'wasm32-unknown-unknown'
+
+  # Sanitizers
+  tsan:
+    name: tsan
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update $nightly && rustup default $nightly
+      - name: Install rust-src
+        run: rustup component add rust-src
+      - name: ASAN / TSAN
+        run: . ci/tsan.sh
+  miri:
+    name: miri
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Miri
+        run: ci/miri.sh
+
+  # Loom
+  loom:
+    name: loom
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update $nightly && rustup default $nightly
+      - name: Loom tests
+        run: RUSTFLAGS="--cfg loom -Dwarnings" cargo test --lib
+
+  publish_docs:
+    name: Publish Documentation
+    needs:
+      - rustfmt
+      # - clippy
+      - stable
+      - nightly
+      - minrust
+      - cross
+      - tsan
+      - loom
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update stable && rustup default stable
+      - name: Build documentation
+        run: cargo doc --no-deps --all-features
+        env:
+          RUSTDOCFLAGS: --cfg docsrs
+      - name: Publish documentation
+        run: |
+          cd target/doc
+          git init
+          git add .
+          git -c user.name='ci' -c user.email='ci' commit -m 'Deploy Bytes API documentation'
+          git push -f -q https://git:${{ secrets.github_token }}@github.com/${{ github.repository }} HEAD:gh-pages
+        if: github.event_name == 'push' && github.event.ref == 'refs/heads/master' && github.repository == 'tokio-rs/bytes'

CHANGELOG.md

@@ -1,3 +1,94 @@
+# 1.1.0 (August 25, 2021)
+
+### Added
+
+- `BufMut::put_bytes(self, val, cnt)` (#487)
+- Implement `From<Box<[u8]>>` for `Bytes` (#504)
+
+### Changed
+
+- Override `put_slice` for `&mut [u8]` (#483)
+- Panic on integer overflow in `Chain::remaining` (#482)
+- Add inline tags to `UninitSlice` methods (#443)
+- Override `copy_to_bytes` for Chain and Take (#481)
+- Keep capacity when unsplit on empty other buf (#502)
+
+### Documented
+
+- Clarify `BufMut` allocation guarantees (#501)
+- Clarify `BufMut::put_int` behavior (#486)
+- Clarify actions of `clear` and `truncate`. (#508)
+
+# 1.0.1 (January 11, 2021)
+
+### Changed
+- mark `Vec::put_slice` with `#[inline]` (#459)
+
+### Fixed
+- Fix deprecation warning (#457)
+- use `Box::into_raw` instead of `mem::forget`-in-disguise (#458)
+
+# 1.0.0 (December 22, 2020)
+
+### Changed
+- Rename `Buf`/`BufMut` methods `bytes()` and `bytes_mut()` to `chunk()` and `chunk_mut()` (#450)
+
+### Removed
+- remove unused Buf implementation. (#449)
+
+# 0.6.0 (October 21, 2020)
+
+API polish in preparation for a 1.0 release.
+
+### Changed
+- `BufMut` is now an `unsafe` trait (#432).
+- `BufMut::bytes_mut()` returns `&mut UninitSlice`, a type owned by `bytes` to
+  avoid undefined behavior (#433).
+- `Buf::copy_to_bytes(len)` replaces `Buf::into_bytes()` (#439).
+- `Buf`/`BufMut` utility methods are moved onto the trait and `*Ext` traits are
+  removed (#431).
+
+### Removed
+- `BufMut::bytes_vectored_mut()` (#430).
+- `new` methods on combinator types (#434).
+
+# 0.5.6 (July 13, 2020)
+
+- Improve `BytesMut` to reuse buffer when fully `advance`d.
+- Mark `BytesMut::{as_mut, set_len}` with `#[inline]`.
+- Relax synchronization when cloning in shared vtable of `Bytes`.
+- Move `loom` to `dev-dependencies`.
+
+# 0.5.5 (June 18, 2020)
+
+### Added
+- Allow using the `serde` feature in `no_std` environments (#385).
+
+### Fix
+- Fix `BufMut::advance_mut` to panic if advanced passed the capacity (#354)..
+- Fix `BytesMut::freeze` ignoring amount previously `advance`d (#352).
+
+# 0.5.4 (January 23, 2020)
+
+### Added
+- Make `Bytes::new` a `const fn`.
+- Add `From<BytesMut>` for `Bytes`.
+
+### Fix
+- Fix reversed arguments in `PartialOrd` for `Bytes`.
+- Fix `Bytes::truncate` losing original capacity when repr is an unshared `Vec`.
+- Fix `Bytes::from(Vec)` when allocator gave `Vec` a pointer with LSB set.
+- Fix panic in `Bytes::slice_ref` if argument is an empty slice.
+
+# 0.5.3 (December 12, 2019)
+
+### Added
+- `must_use` attributes to `split`, `split_off`, and `split_to` methods (#337).
+
+### Fix
+- Potential freeing of a null pointer in `Bytes` when constructed with an empty `Vec<u8>` (#341, #342).
+- Calling `Bytes::truncate` with a size large than the length will no longer clear the `Bytes` (#333).
+
 # 0.5.2 (November 27, 2019)
 
 ### Added

Cargo.toml

@@ -2,15 +2,15 @@
 
 name = "bytes"
 # When releasing to crates.io:
-# - Update html_root_url.
 # - Update CHANGELOG.md.
-# - Update doc URL.
-# - Create "v0.5.x" git tag.
-version = "0.5.2"
+# - Create "v1.x.y" git tag.
+version = "1.1.0"
 license = "MIT"
-authors = ["Carl Lerche <[email protected]>"]
+authors = [
+    "Carl Lerche <[email protected]>",
+    "Sean McArthur <[email protected]>",
+]
 description = "Types and traits for working with bytes"
-documentation = "https://docs.rs/bytes"
 repository = "https://github.com/tokio-rs/bytes"
 readme = "README.md"
 keywords = ["buffers", "zero-copy", "io"]
@@ -22,8 +22,13 @@ default = ["std"]
 std = []
 
 [dependencies]
-serde = { version = "1.0", optional = true }
+serde = { version = "1.0.60", optional = true, default-features = false, features = ["alloc"] }
 
 [dev-dependencies]
-loom = "0.2.10"
 serde_test = "1.0"
+
+[target.'cfg(loom)'.dev-dependencies]
+loom = "0.5"
+
+[package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "docsrs"]

README.md

@@ -3,12 +3,12 @@
 A utility library for working with bytes.
 
 [![Crates.io][crates-badge]][crates-url]
-[![Build Status][azure-badge]][azure-url]
+[![Build Status][ci-badge]][ci-url]
 
 [crates-badge]: https://img.shields.io/crates/v/bytes.svg
 [crates-url]: https://crates.io/crates/bytes
-[azure-badge]: https://dev.azure.com/tokio-rs/bytes/_apis/build/status/tokio-rs.bytes?branchName=master
-[azure-url]: https://dev.azure.com/tokio-rs/bytes/_build/latest?definitionId=3&branchName=master
+[ci-badge]: https://github.com/tokio-rs/bytes/workflows/CI/badge.svg
+[ci-url]: https://github.com/tokio-rs/bytes/actions
 
 [Documentation](https://docs.rs/bytes)
 
@@ -18,7 +18,7 @@ To use `bytes`, first add this to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-bytes = "0.5"
+bytes = "1"
 ```
 
 Next, add this to your crate:
@@ -33,7 +33,7 @@ Serde support is optional and disabled by default. To enable use the feature `se
 
 ```toml
 [dependencies]
-bytes = { version = "0.5", features = ["serde"] }
+bytes = { version = "1", features = ["serde"] }
 ```
 
 ## License
@@ -45,4 +45,3 @@ This project is licensed under the [MIT license](LICENSE).
 Unless you explicitly state otherwise, any contribution intentionally submitted
 for inclusion in `bytes` by you, shall be licensed as MIT, without any additional
 terms or conditions.
-

azure-pipelines.yml

@@ -1,68 +0,0 @@
-trigger: ["master"]
-pr: ["master"]
-
-jobs:
-# Check formatting
-# - template: ci/azure-rustfmt.yml
-#   parameters:
-#     name: rustfmt
-
-# Apply clippy lints
-# - template: ci/azure-clippy.yml
-#   parameters:
-#     name: clippy
-
-# This represents the minimum Rust version supported by
-# Bytes. Updating this should be done in a dedicated PR.
-#
-# Tests are not run as tests may require newer versions of
-# rust.
-- template: ci/azure-test-stable.yml
-  parameters:
-    name: minrust
-    rust_version: 1.39.0
-    cmd: check
-
-# Stable
-- template: ci/azure-test-stable.yml
-  parameters:
-    name: stable
-    cross: true
-    features:
-      - serde
-
-# Nightly
-- template: ci/azure-test-stable.yml
-  parameters:
-    name: nightly
-    # Pin nightly to avoid being impacted by breakage
-    rust_version: nightly-2019-09-25
-    benches: true
-
-# Run tests on some extra platforms
-- template: ci/azure-cross-compile.yml
-  parameters:
-    name: cross
-
-# Sanitizers
-- template: ci/azure-tsan.yml
-  parameters:
-    name: tsan
-    rust_version: nightly
-
-# Loom
-- template: ci/azure-loom.yml
-  parameters:
-    name: loom
-    rust_version: stable
-
-
-- template: ci/azure-deploy-docs.yml
-  parameters:
-    dependsOn:
-      # - rustfmt
-      # - clippy
-      - stable
-      - nightly
-      - minrust
-      - cross

benches/buf.rs

@@ -1,10 +1,10 @@
 #![feature(test)]
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 extern crate test;
 
-use test::Bencher;
 use bytes::Buf;
+use test::Bencher;
 
 /// Dummy Buf implementation
 struct TestBuf {
@@ -53,7 +53,7 @@ impl Buf for TestBuf {
         assert!(self.pos <= self.buf.len());
         self.next_readlen();
     }
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         if self.readlen == 0 {
             Default::default()
         } else {
@@ -87,8 +87,8 @@ impl Buf for TestBufC {
         self.inner.advance(cnt)
     }
     #[inline(never)]
-    fn bytes(&self) -> &[u8] {
-        self.inner.bytes()
+    fn chunk(&self) -> &[u8] {
+        self.inner.chunk()
     }
 }
 
@@ -159,7 +159,6 @@ macro_rules! bench_group {
 mod get_u8 {
     use super::*;
     bench_group!(get_u8);
-    bench!(option, option);
 }
 mod get_u16 {
     use super::*;

benches/bytes.rs

@@ -1,10 +1,10 @@
 #![feature(test)]
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 extern crate test;
 
-use test::Bencher;
 use bytes::Bytes;
+use test::Bencher;
 
 #[bench]
 fn deref_unique(b: &mut Bencher) {
@@ -42,7 +42,8 @@ fn deref_static(b: &mut Bencher) {
 
 #[bench]
 fn clone_static(b: &mut Bencher) {
-    let bytes = Bytes::from_static("hello world 1234567890 and have a good byte 0987654321".as_bytes());
+    let bytes =
+        Bytes::from_static("hello world 1234567890 and have a good byte 0987654321".as_bytes());
 
     b.iter(|| {
         for _ in 0..1024 {

benches/bytes_mut.rs

@@ -1,10 +1,10 @@
 #![feature(test)]
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 extern crate test;
 
-use test::Bencher;
 use bytes::{BufMut, BytesMut};
+use test::Bencher;
 
 #[bench]
 fn alloc_small(b: &mut Bencher) {
@@ -29,7 +29,6 @@ fn alloc_big(b: &mut Bencher) {
     })
 }
 
-
 #[bench]
 fn deref_unique(b: &mut Bencher) {
     let mut buf = BytesMut::with_capacity(4096);
@@ -92,7 +91,9 @@ fn deref_two(b: &mut Bencher) {
 
 #[bench]
 fn clone_frozen(b: &mut Bencher) {
-    let bytes = BytesMut::from(&b"hello world 1234567890 and have a good byte 0987654321"[..]).split().freeze();
+    let bytes = BytesMut::from(&b"hello world 1234567890 and have a good byte 0987654321"[..])
+        .split()
+        .freeze();
 
     b.iter(|| {
         for _ in 0..1024 {
@@ -137,7 +138,9 @@ fn fmt_write(b: &mut Bencher) {
     b.iter(|| {
         let _ = write!(buf, "{}", s);
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     })
 }
 
@@ -152,7 +155,9 @@ fn bytes_mut_extend(b: &mut Bencher) {
             buf.extend(&data);
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }
 
@@ -169,7 +174,9 @@ fn put_slice_bytes_mut(b: &mut Bencher) {
             buf.put_slice(&data);
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }
 
@@ -184,7 +191,9 @@ fn put_u8_bytes_mut(b: &mut Bencher) {
             buf.put_u8(b'x');
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }
 
@@ -199,7 +208,9 @@ fn put_slice_vec(b: &mut Bencher) {
             buf.put_slice(&data);
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }
 
@@ -214,7 +225,9 @@ fn put_u8_vec(b: &mut Bencher) {
             buf.put_u8(b'x');
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }
 
@@ -229,7 +242,9 @@ fn put_slice_vec_extend(b: &mut Bencher) {
             buf.extend_from_slice(&data);
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }
 
@@ -244,6 +259,8 @@ fn put_u8_vec_push(b: &mut Bencher) {
             buf.push(b'x');
         }
         test::black_box(&buf);
-        unsafe { buf.set_len(0); }
+        unsafe {
+            buf.set_len(0);
+        }
     });
 }

ci/azure-cross-compile.yml

@@ -1,46 +0,0 @@
-parameters:
-  cmd: build
-  rust_version: stable
-
-jobs:
-- job: ${{ parameters.name }}
-  displayName: Cross
-  strategy:
-    matrix:
-      i686:
-        vmImage: ubuntu-16.04
-        target: i686-unknown-linux-gnu
-      armv7:
-        vmImage: ubuntu-16.04
-        target: armv7-unknown-linux-gnueabihf
-      powerpc:
-        vmImage: ubuntu-16.04
-        target: powerpc-unknown-linux-gnu
-      powerpc64:
-        vmImage: ubuntu-16.04
-        target: powerpc64-unknown-linux-gnu
-      wasm:
-        vmImage: ubuntu-16.04
-        target: wasm32-unknown-unknown
-  pool:
-    vmImage: $(vmImage)
-
-  steps:
-    - template: azure-install-rust.yml
-      parameters:
-        rust_version: ${{parameters.rust_version}}
-
-    - script: cargo install cross
-      displayName: Install cross
-      condition: not(eq(variables['target'], 'wasm32-unknown-unknown'))
-
-    - script: cross ${{ parameters.cmd }} --target $(target)
-      displayName: cross ${{ parameters.cmd }} --target $(target)
-      condition: not(eq(variables['target'], 'wasm32-unknown-unknown'))
-
-    # WASM support
-    - script: |
-        rustup target add $(target)
-        cargo build --target $(target)
-      displayName: cargo build --target $(target)
-      condition: eq(variables['target'], 'wasm32-unknown-unknown')

ci/azure-deploy-docs.yml

@@ -1,39 +0,0 @@
-parameters:
-  dependsOn: []
-
-jobs:
-- job: documentation
-  displayName: 'Deploy API Documentation'
-  condition: and(succeeded(), eq(variables['Build.SourceBranch'], 'refs/heads/master'))
-  pool:
-    vmImage: 'Ubuntu 16.04'
-  dependsOn:
-    - ${{ parameters.dependsOn }}
-  steps:
-  - template: azure-install-rust.yml
-    parameters:
-      rust_version: stable
-  - script: |
-      cargo doc --no-deps
-      cp -R target/doc '$(Build.BinariesDirectory)'
-    displayName: 'Generate Documentation'
-  - script: |
-      set -e
-
-      git --version
-      ls -la
-      git init
-      git config user.name 'Deployment Bot (from Azure Pipelines)'
-      git config user.email '[email protected]'
-      git config --global credential.helper 'store --file ~/.my-credentials'
-      printf "protocol=https\nhost=github.com\nusername=carllerche\npassword=%s\n\n" "$GITHUB_TOKEN" | git credential-store --file ~/.my-credentials store
-      git remote add origin https://github.com/tokio-rs/bytes
-      git checkout -b gh-pages
-      git add .
-      git commit -m 'Deploy Bytes API documentation'
-      git push -f origin gh-pages
-    env:
-      GITHUB_TOKEN: $(githubPersonalToken)
-    workingDirectory: '$(Build.BinariesDirectory)'
-    displayName: 'Deploy Documentation'
-

ci/azure-install-rust.yml

@@ -1,33 +0,0 @@
-steps:
-  # Linux and macOS.
-  - script: |
-      set -e
-      curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain none
-      export PATH=$PATH:$HOME/.cargo/bin
-      rustup toolchain install $RUSTUP_TOOLCHAIN
-      rustup default $RUSTUP_TOOLCHAIN
-      echo "##vso[task.setvariable variable=PATH;]$PATH:$HOME/.cargo/bin"
-    env:
-      RUSTUP_TOOLCHAIN: ${{parameters.rust_version}}
-    displayName: "Install rust (*nix)"
-    condition: not(eq(variables['Agent.OS'], 'Windows_NT'))
-
-  # Windows.
-  - script: |
-      curl -sSf -o rustup-init.exe https://win.rustup.rs
-      rustup-init.exe -y --default-toolchain none
-      set PATH=%PATH%;%USERPROFILE%\.cargo\bin
-      rustup toolchain install %RUSTUP_TOOLCHAIN%
-      rustup default %RUSTUP_TOOLCHAIN%
-      echo "##vso[task.setvariable variable=PATH;]%PATH%;%USERPROFILE%\.cargo\bin"
-    env:
-      RUSTUP_TOOLCHAIN: ${{parameters.rust_version}}
-    displayName: "Install rust (windows)"
-    condition: eq(variables['Agent.OS'], 'Windows_NT')
-
-  # All platforms.
-  - script: |
-        rustup toolchain list
-        rustc -Vv
-        cargo -V
-    displayName: Query rust and cargo versions

ci/azure-loom.yml

@@ -1,15 +0,0 @@
-jobs:
-- job: ${{parameters.name}}
-  displayName: Loom tests
-  pool:
-    vmImage: ubuntu-16.04
-
-  steps:
-  - template: azure-install-rust.yml
-    parameters:
-      rust_version: ${{parameters.rust_version}}
-
-  - script: RUSTFLAGS="--cfg loom" cargo test --lib
-    displayName: RUSTFLAGS="--cfg loom" cargo test --lib
-
-

ci/azure-test-stable.yml

@@ -1,50 +0,0 @@
-parameters:
-  cmd: test
-  rust_version: stable
-  features: []
-
-jobs:
-- job: ${{ parameters.name }}
-  displayName: ${{ parameters.displayName }}
-  strategy:
-    matrix:
-      Linux:
-        vmImage: ubuntu-16.04
-
-      ${{ if parameters.cross }}:
-        MacOS:
-          vmImage: macOS-10.13
-        Windows:
-          vmImage: vs2017-win2016
-  pool:
-    vmImage: $(vmImage)
-
-  steps:
-  - template: azure-install-rust.yml
-    parameters:
-      rust_version: ${{parameters.rust_version}}
-
-  # Run with default crate features
-  - script: cargo ${{ parameters.cmd }}
-    displayName: cargo ${{ parameters.cmd }}
-
-  # Run with each specified feature
-  - ${{ each feature in parameters.features }}:
-    - script: cargo ${{ parameters.cmd }} --features ${{ feature }}
-      displayName: cargo ${{ parameters.cmd }} --features ${{ feature }}
-
-  - ${{ if eq(parameters.cmd, 'test') }}:
-    - script: cargo doc --no-deps
-      displayName: cargo doc --no-deps
-
-  - ${{ if parameters.benches }}:
-    - script: cargo check --benches
-      displayName: Check benchmarks
-
-  # Run with all features
-  - script: cargo ${{ parameters.cmd }} --all-features
-    displayName: cargo ${{ parameters.cmd }} --all-features
-
-  # Run with no default features
-  - script: cargo check --no-default-features
-    displayName: cargo check --no-default-features

ci/azure-tsan.yml

@@ -1,26 +0,0 @@
-jobs:
-- job: ${{ parameters.name }}
-  displayName: TSAN
-  pool:
-    vmImage: ubuntu-16.04
-
-  steps:
-  - template: azure-install-rust.yml
-    parameters:
-      rust_version: ${{ parameters.rust_version }}
-
-  - script: |
-      set -e
-
-      export RUST_TEST_THREADS=1
-      export ASAN_OPTIONS="detect_odr_violation=0 detect_leaks=0"
-      export TSAN_OPTIONS="suppressions=`pwd`/ci/tsan"
-
-      # Run address sanitizer
-      RUSTFLAGS="-Z sanitizer=address" \
-      cargo test --target x86_64-unknown-linux-gnu --test test_bytes --test test_buf --test test_buf_mut
-
-      # Run thread sanitizer
-      RUSTFLAGS="-Z sanitizer=thread" \
-      cargo test --target x86_64-unknown-linux-gnu --test test_bytes --test test_buf --test test_buf_mut
-    displayName: TSAN / MSAN

ci/miri.sh

@@ -0,0 +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
+
+cargo miri test
+cargo miri test --target mips64-unknown-linux-gnuabi64

ci/test-stable.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+
+set -ex
+
+cmd="${1:-test}"
+
+# Install cargo-hack for feature flag test
+host=$(rustc -Vv | grep host | sed 's/host: //')
+curl -LsSf https://github.com/taiki-e/cargo-hack/releases/latest/download/cargo-hack-$host.tar.gz | tar xzf - -C ~/.cargo/bin
+
+# Run with each feature
+# * --each-feature includes both default/no-default features
+# * --optional-deps is needed for serde feature
+cargo hack "${cmd}" --each-feature --optional-deps
+# Run with all features
+cargo "${cmd}" --all-features
+
+cargo doc --no-deps --all-features
+
+if [[ "${RUST_VERSION}" == "nightly"* ]]; then
+    # Check benchmarks
+    cargo check --benches
+
+    # Check minimal versions
+    cargo clean
+    cargo update -Zminimal-versions
+    cargo check --all-features
+fi

ci/tsan

@@ -1,24 +0,0 @@
-# TSAN suppressions file for `bytes`
-
-# TSAN does not understand fences and `Arc::drop` is implemented using a fence.
-# This causes many false positives.
-race:Arc*drop
-race:arc*Weak*drop
-
-# `std` mpsc is not used in any Bytes code base. This race is triggered by some
-# rust runtime logic.
-race:std*mpsc_queue
-
-# Some test runtime races. Allocation should be race free
-race:alloc::alloc
-
-# Not sure why this is warning, but it is in the test harness and not the library.
-race:TestEvent*clone
-race:test::run_tests_console::*closure
-
-# Probably more fences in std.
-race:__call_tls_dtors
-
-# This ignores a false positive caused by `thread::park()`/`thread::unpark()`.
-# See: https://github.com/rust-lang/rust/pull/54806#issuecomment-436193353
-race:pthread_cond_destroy

ci/tsan.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -ex
+
+export ASAN_OPTIONS="detect_odr_violation=0 detect_leaks=0"
+
+# Run address sanitizer
+RUSTFLAGS="-Z sanitizer=address" \
+cargo test --target x86_64-unknown-linux-gnu --test test_bytes --test test_buf --test test_buf_mut
+
+# Run thread sanitizer
+RUSTFLAGS="-Z sanitizer=thread" \
+cargo -Zbuild-std test --target x86_64-unknown-linux-gnu --test test_bytes --test test_buf --test test_buf_mut

src/buf/buf_impl.rs

@@ -1,22 +1,27 @@
-use core::{cmp, ptr, mem};
+#[cfg(feature = "std")]
+use crate::buf::{reader, Reader};
+use crate::buf::{take, Chain, Take};
+
+use core::{cmp, mem, ptr};
 
 #[cfg(feature = "std")]
 use std::io::IoSlice;
 
-use alloc::{boxed::Box};
+use alloc::boxed::Box;
 
 macro_rules! buf_get_impl {
-    ($this:ident, $typ:tt::$conv:tt) => ({
+    ($this:ident, $typ:tt::$conv:tt) => {{
         const SIZE: usize = mem::size_of::<$typ>();
-         // try to convert directly from the bytes
-         // this Option<ret> trick is to avoid keeping a borrow on self
-         // when advance() is called (mut borrow) and to call bytes() only once
-        let ret =  $this.bytes().get(..SIZE).map(|src| unsafe {
-            $typ::$conv(*(src as *const _ as *const [_; SIZE]))
-        });
+        // try to convert directly from the bytes
+        // this Option<ret> trick is to avoid keeping a borrow on self
+        // when advance() is called (mut borrow) and to call bytes() only once
+        let ret = $this
+            .chunk()
+            .get(..SIZE)
+            .map(|src| unsafe { $typ::$conv(*(src as *const _ as *const [_; SIZE])) });
 
         if let Some(ret) = ret {
-             // if the direct conversion was possible, advance and return
+            // if the direct conversion was possible, advance and return
             $this.advance(SIZE);
             return ret;
         } else {
@@ -25,8 +30,8 @@ macro_rules! buf_get_impl {
             $this.copy_to_slice(&mut buf); // (do the advance)
             return $typ::$conv(buf);
         }
-    });
-    (le => $this:ident, $typ:tt, $len_to_read:expr) => ({
+    }};
+    (le => $this:ident, $typ:tt, $len_to_read:expr) => {{
         debug_assert!(mem::size_of::<$typ>() >= $len_to_read);
 
         // The same trick as above does not improve the best case speed.
@@ -34,12 +39,12 @@ macro_rules! buf_get_impl {
         let mut buf = [0; (mem::size_of::<$typ>())];
         $this.copy_to_slice(&mut buf[..($len_to_read)]);
         return $typ::from_le_bytes(buf);
-    });
+    }};
     (be => $this:ident, $typ:tt, $len_to_read:expr) => {{
         debug_assert!(mem::size_of::<$typ>() >= $len_to_read);
 
         let mut buf = [0; (mem::size_of::<$typ>())];
-        $this.copy_to_slice(&mut buf[mem::size_of::<$typ>()-($len_to_read)..]);
+        $this.copy_to_slice(&mut buf[mem::size_of::<$typ>() - ($len_to_read)..]);
         return $typ::from_be_bytes(buf);
     }};
 }
@@ -73,7 +78,7 @@ pub trait Buf {
     /// the buffer.
     ///
     /// This value is greater than or equal to the length of the slice returned
-    /// by `bytes`.
+    /// by `chunk()`.
     ///
     /// # Examples
     ///
@@ -110,31 +115,34 @@ pub trait Buf {
     ///
     /// let mut buf = &b"hello world"[..];
     ///
-    /// assert_eq!(buf.bytes(), &b"hello world"[..]);
+    /// assert_eq!(buf.chunk(), &b"hello world"[..]);
     ///
     /// buf.advance(6);
     ///
-    /// assert_eq!(buf.bytes(), &b"world"[..]);
+    /// assert_eq!(buf.chunk(), &b"world"[..]);
     /// ```
     ///
     /// # Implementer notes
     ///
     /// This function should never panic. Once the end of the buffer is reached,
-    /// i.e., `Buf::remaining` returns 0, calls to `bytes` should return an
+    /// i.e., `Buf::remaining` returns 0, calls to `chunk()` should return an
     /// empty slice.
-    fn bytes(&self) -> &[u8];
+    // The `chunk` method was previously called `bytes`. This alias makes the rename
+    // more easily discoverable.
+    #[cfg_attr(docsrs, doc(alias = "bytes"))]
+    fn chunk(&self) -> &[u8];
 
     /// Fills `dst` with potentially multiple slices starting at `self`'s
     /// current position.
     ///
-    /// If the `Buf` is backed by disjoint slices of bytes, `bytes_vectored` enables
+    /// If the `Buf` is backed by disjoint slices of bytes, `chunk_vectored` enables
     /// fetching more than one slice at once. `dst` is a slice of `IoSlice`
     /// references, enabling the slice to be directly used with [`writev`]
     /// without any further conversion. The sum of the lengths of all the
     /// buffers in `dst` will be less than or equal to `Buf::remaining()`.
     ///
     /// The entries in `dst` will be overwritten, but the data **contained** by
-    /// the slices **will not** be modified. If `bytes_vectored` does not fill every
+    /// the slices **will not** be modified. If `chunk_vectored` does not fill every
     /// entry in `dst`, then `dst` is guaranteed to contain all remaining slices
     /// in `self.
     ///
@@ -144,7 +152,7 @@ pub trait Buf {
     /// # Implementer notes
     ///
     /// This function should never panic. Once the end of the buffer is reached,
-    /// i.e., `Buf::remaining` returns 0, calls to `bytes_vectored` must return 0
+    /// i.e., `Buf::remaining` returns 0, calls to `chunk_vectored` must return 0
     /// without mutating `dst`.
     ///
     /// Implementations should also take care to properly handle being called
@@ -152,13 +160,13 @@ pub trait Buf {
     ///
     /// [`writev`]: http://man7.org/linux/man-pages/man2/readv.2.html
     #[cfg(feature = "std")]
-    fn bytes_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
+    fn chunks_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
         if dst.is_empty() {
             return 0;
         }
 
         if self.has_remaining() {
-            dst[0] = IoSlice::new(self.bytes());
+            dst[0] = IoSlice::new(self.chunk());
             1
         } else {
             0
@@ -167,7 +175,7 @@ pub trait Buf {
 
     /// Advance the internal cursor of the Buf
     ///
-    /// The next call to `bytes` will return a slice starting `cnt` bytes
+    /// The next call to `chunk()` will return a slice starting `cnt` bytes
     /// further into the underlying buffer.
     ///
     /// # Examples
@@ -177,11 +185,11 @@ pub trait Buf {
     ///
     /// let mut buf = &b"hello world"[..];
     ///
-    /// assert_eq!(buf.bytes(), &b"hello world"[..]);
+    /// assert_eq!(buf.chunk(), &b"hello world"[..]);
     ///
     /// buf.advance(6);
     ///
-    /// assert_eq!(buf.bytes(), &b"world"[..]);
+    /// assert_eq!(buf.chunk(), &b"world"[..]);
     /// ```
     ///
     /// # Panics
@@ -248,11 +256,10 @@ pub trait Buf {
             let cnt;
 
             unsafe {
-                let src = self.bytes();
+                let src = self.chunk();
                 cnt = cmp::min(src.len(), dst.len() - off);
 
-                ptr::copy_nonoverlapping(
-                    src.as_ptr(), dst[off..].as_mut_ptr(), cnt);
+                ptr::copy_nonoverlapping(src.as_ptr(), dst[off..].as_mut_ptr(), cnt);
 
                 off += cnt;
             }
@@ -279,7 +286,7 @@ pub trait Buf {
     /// This function panics if there is no more remaining data in `self`.
     fn get_u8(&mut self) -> u8 {
         assert!(self.remaining() >= 1);
-        let ret = self.bytes()[0];
+        let ret = self.chunk()[0];
         self.advance(1);
         ret
     }
@@ -302,7 +309,7 @@ pub trait Buf {
     /// This function panics if there is no more remaining data in `self`.
     fn get_i8(&mut self) -> i8 {
         assert!(self.remaining() >= 1);
-        let ret = self.bytes()[0] as i8;
+        let ret = self.chunk()[0] as i8;
         self.advance(1);
         ret
     }
@@ -791,60 +798,224 @@ pub trait Buf {
         f64::from_bits(Self::get_u64_le(self))
     }
 
-    /// Consumes remaining bytes inside self and returns new instance of `Bytes`
+    /// Consumes `len` bytes inside self and returns new instance of `Bytes`
+    /// with this data.
+    ///
+    /// This function may be optimized by the underlying type to avoid actual
+    /// copies. For example, `Bytes` implementation will do a shallow copy
+    /// (ref-count increment).
     ///
     /// # Examples
     ///
     /// ```
     /// use bytes::Buf;
     ///
-    /// let bytes = (&b"hello world"[..]).to_bytes();
-    /// assert_eq!(&bytes[..], &b"hello world"[..]);
+    /// let bytes = (&b"hello world"[..]).copy_to_bytes(5);
+    /// assert_eq!(&bytes[..], &b"hello"[..]);
     /// ```
-    fn to_bytes(&mut self) -> crate::Bytes {
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
         use super::BufMut;
-        let mut ret = crate::BytesMut::with_capacity(self.remaining());
-        ret.put(self);
+
+        assert!(len <= self.remaining(), "`len` greater than remaining");
+
+        let mut ret = crate::BytesMut::with_capacity(len);
+        ret.put(self.take(len));
         ret.freeze()
     }
+
+    /// Creates an adaptor which will read at most `limit` bytes from `self`.
+    ///
+    /// This function returns a new instance of `Buf` which will read at most
+    /// `limit` bytes.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Buf, BufMut};
+    ///
+    /// let mut buf = b"hello world"[..].take(5);
+    /// let mut dst = vec![];
+    ///
+    /// dst.put(&mut buf);
+    /// assert_eq!(dst, b"hello");
+    ///
+    /// let mut buf = buf.into_inner();
+    /// dst.clear();
+    /// dst.put(&mut buf);
+    /// assert_eq!(dst, b" world");
+    /// ```
+    fn take(self, limit: usize) -> Take<Self>
+    where
+        Self: Sized,
+    {
+        take::new(self, limit)
+    }
+
+    /// Creates an adaptor which will chain this buffer with another.
+    ///
+    /// The returned `Buf` instance will first consume all bytes from `self`.
+    /// Afterwards the output is equivalent to the output of next.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::Buf;
+    ///
+    /// let mut chain = b"hello "[..].chain(&b"world"[..]);
+    ///
+    /// let full = chain.copy_to_bytes(11);
+    /// assert_eq!(full.chunk(), b"hello world");
+    /// ```
+    fn chain<U: Buf>(self, next: U) -> Chain<Self, U>
+    where
+        Self: Sized,
+    {
+        Chain::new(self, next)
+    }
+
+    /// Creates an adaptor which implements the `Read` trait for `self`.
+    ///
+    /// This function returns a new value which implements `Read` by adapting
+    /// the `Read` trait functions to the `Buf` trait functions. Given that
+    /// `Buf` operations are infallible, none of the `Read` functions will
+    /// return with `Err`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::{Bytes, Buf};
+    /// use std::io::Read;
+    ///
+    /// let buf = Bytes::from("hello world");
+    ///
+    /// let mut reader = buf.reader();
+    /// let mut dst = [0; 1024];
+    ///
+    /// let num = reader.read(&mut dst).unwrap();
+    ///
+    /// assert_eq!(11, num);
+    /// assert_eq!(&dst[..11], &b"hello world"[..]);
+    /// ```
+    #[cfg(feature = "std")]
+    fn reader(self) -> Reader<Self>
+    where
+        Self: Sized,
+    {
+        reader::new(self)
+    }
+}
+
+macro_rules! deref_forward_buf {
+    () => {
+        fn remaining(&self) -> usize {
+            (**self).remaining()
+        }
+
+        fn chunk(&self) -> &[u8] {
+            (**self).chunk()
+        }
+
+        #[cfg(feature = "std")]
+        fn chunks_vectored<'b>(&'b self, dst: &mut [IoSlice<'b>]) -> usize {
+            (**self).chunks_vectored(dst)
+        }
+
+        fn advance(&mut self, cnt: usize) {
+            (**self).advance(cnt)
+        }
+
+        fn has_remaining(&self) -> bool {
+            (**self).has_remaining()
+        }
+
+        fn copy_to_slice(&mut self, dst: &mut [u8]) {
+            (**self).copy_to_slice(dst)
+        }
+
+        fn get_u8(&mut self) -> u8 {
+            (**self).get_u8()
+        }
+
+        fn get_i8(&mut self) -> i8 {
+            (**self).get_i8()
+        }
+
+        fn get_u16(&mut self) -> u16 {
+            (**self).get_u16()
+        }
+
+        fn get_u16_le(&mut self) -> u16 {
+            (**self).get_u16_le()
+        }
+
+        fn get_i16(&mut self) -> i16 {
+            (**self).get_i16()
+        }
+
+        fn get_i16_le(&mut self) -> i16 {
+            (**self).get_i16_le()
+        }
+
+        fn get_u32(&mut self) -> u32 {
+            (**self).get_u32()
+        }
+
+        fn get_u32_le(&mut self) -> u32 {
+            (**self).get_u32_le()
+        }
+
+        fn get_i32(&mut self) -> i32 {
+            (**self).get_i32()
+        }
+
+        fn get_i32_le(&mut self) -> i32 {
+            (**self).get_i32_le()
+        }
+
+        fn get_u64(&mut self) -> u64 {
+            (**self).get_u64()
+        }
+
+        fn get_u64_le(&mut self) -> u64 {
+            (**self).get_u64_le()
+        }
+
+        fn get_i64(&mut self) -> i64 {
+            (**self).get_i64()
+        }
+
+        fn get_i64_le(&mut self) -> i64 {
+            (**self).get_i64_le()
+        }
+
+        fn get_uint(&mut self, nbytes: usize) -> u64 {
+            (**self).get_uint(nbytes)
+        }
+
+        fn get_uint_le(&mut self, nbytes: usize) -> u64 {
+            (**self).get_uint_le(nbytes)
+        }
+
+        fn get_int(&mut self, nbytes: usize) -> i64 {
+            (**self).get_int(nbytes)
+        }
+
+        fn get_int_le(&mut self, nbytes: usize) -> i64 {
+            (**self).get_int_le(nbytes)
+        }
+
+        fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
+            (**self).copy_to_bytes(len)
+        }
+    };
 }
 
 impl<T: Buf + ?Sized> Buf for &mut T {
-    fn remaining(&self) -> usize {
-        (**self).remaining()
-    }
-
-    fn bytes(&self) -> &[u8] {
-        (**self).bytes()
-    }
-
-    #[cfg(feature = "std")]
-    fn bytes_vectored<'b>(&'b self, dst: &mut [IoSlice<'b>]) -> usize {
-        (**self).bytes_vectored(dst)
-    }
-
-    fn advance(&mut self, cnt: usize) {
-        (**self).advance(cnt)
-    }
+    deref_forward_buf!();
 }
 
 impl<T: Buf + ?Sized> Buf for Box<T> {
-    fn remaining(&self) -> usize {
-        (**self).remaining()
-    }
-
-    fn bytes(&self) -> &[u8] {
-        (**self).bytes()
-    }
-
-    #[cfg(feature = "std")]
-    fn bytes_vectored<'b>(&'b self, dst: &mut [IoSlice<'b>]) -> usize {
-        (**self).bytes_vectored(dst)
-    }
-
-    fn advance(&mut self, cnt: usize) {
-        (**self).advance(cnt)
-    }
+    deref_forward_buf!();
 }
 
 impl Buf for &[u8] {
@@ -854,7 +1025,7 @@ impl Buf for &[u8] {
     }
 
     #[inline]
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         self
     }
 
@@ -864,34 +1035,6 @@ impl Buf for &[u8] {
     }
 }
 
-impl Buf for Option<[u8; 1]> {
-    fn remaining(&self) -> usize {
-        if self.is_some() {
-            1
-        } else {
-            0
-        }
-    }
-
-    fn bytes(&self) -> &[u8] {
-        self.as_ref().map(AsRef::as_ref)
-            .unwrap_or(Default::default())
-    }
-
-    fn advance(&mut self, cnt: usize) {
-        if cnt == 0 {
-            return;
-        }
-
-        if self.is_none() {
-            panic!("overflow");
-        } else {
-            assert_eq!(1, cnt);
-            *self = None;
-        }
-    }
-}
-
 #[cfg(feature = "std")]
 impl<T: AsRef<[u8]>> Buf for std::io::Cursor<T> {
     fn remaining(&self) -> usize {
@@ -905,7 +1048,7 @@ impl<T: AsRef<[u8]>> Buf for std::io::Cursor<T> {
         len - pos as usize
     }
 
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         let len = self.get_ref().as_ref().len();
         let pos = self.position();
 
@@ -918,7 +1061,8 @@ impl<T: AsRef<[u8]>> Buf for std::io::Cursor<T> {
 
     fn advance(&mut self, cnt: usize) {
         let pos = (self.position() as usize)
-            .checked_add(cnt).expect("overflow");
+            .checked_add(cnt)
+            .expect("overflow");
 
         assert!(pos <= self.get_ref().as_ref().len());
         self.set_position(pos as u64);

src/buf/buf_mut.rs

@@ -1,9 +1,10 @@
-use core::{cmp, mem::{self, MaybeUninit}, ptr, usize};
-
+use crate::buf::{limit, Chain, Limit, UninitSlice};
 #[cfg(feature = "std")]
-use std::fmt;
+use crate::buf::{writer, Writer};
 
-use alloc::{vec::Vec, boxed::Box};
+use core::{cmp, mem, ptr, usize};
+
+use alloc::{boxed::Box, vec::Vec};
 
 /// A trait for values that provide sequential write access to bytes.
 ///
@@ -25,12 +26,16 @@ use alloc::{vec::Vec, boxed::Box};
 ///
 /// assert_eq!(buf, b"hello world");
 /// ```
-pub trait BufMut {
+pub unsafe trait BufMut {
     /// Returns the number of bytes that can be written from the current
     /// position until the end of the buffer is reached.
     ///
     /// This value is greater than or equal to the length of the slice returned
-    /// by `bytes_mut`.
+    /// by `chunk_mut()`.
+    ///
+    /// Writing to a `BufMut` may involve allocating more memory on the fly.
+    /// Implementations may fail before reaching the number of bytes indicated
+    /// by this method if they encounter an allocation failure.
     ///
     /// # Examples
     ///
@@ -55,7 +60,7 @@ pub trait BufMut {
 
     /// Advance the internal cursor of the BufMut
     ///
-    /// The next call to `bytes_mut` will return a slice starting `cnt` bytes
+    /// The next call to `chunk_mut` will return a slice starting `cnt` bytes
     /// further into the underlying buffer.
     ///
     /// This function is unsafe because there is no guarantee that the bytes
@@ -68,19 +73,14 @@ pub trait BufMut {
     ///
     /// let mut buf = Vec::with_capacity(16);
     ///
-    /// unsafe {
-    ///     // MaybeUninit::as_mut_ptr
-    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'h');
-    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'e');
+    /// // Write some data
+    /// buf.chunk_mut()[0..2].copy_from_slice(b"he");
+    /// unsafe { buf.advance_mut(2) };
     ///
-    ///     buf.advance_mut(2);
+    /// // write more bytes
+    /// buf.chunk_mut()[0..3].copy_from_slice(b"llo");
     ///
-    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'l');
-    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'l');
-    ///     buf.bytes_mut()[2].as_mut_ptr().write(b'o');
-    ///
-    ///     buf.advance_mut(3);
-    /// }
+    /// unsafe { buf.advance_mut(3); }
     ///
     /// assert_eq!(5, buf.len());
     /// assert_eq!(buf, b"hello");
@@ -139,14 +139,14 @@ pub trait BufMut {
     ///
     /// unsafe {
     ///     // MaybeUninit::as_mut_ptr
-    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'h');
-    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'e');
+    ///     buf.chunk_mut()[0..].as_mut_ptr().write(b'h');
+    ///     buf.chunk_mut()[1..].as_mut_ptr().write(b'e');
     ///
     ///     buf.advance_mut(2);
     ///
-    ///     buf.bytes_mut()[0].as_mut_ptr().write(b'l');
-    ///     buf.bytes_mut()[1].as_mut_ptr().write(b'l');
-    ///     buf.bytes_mut()[2].as_mut_ptr().write(b'o');
+    ///     buf.chunk_mut()[0..].as_mut_ptr().write(b'l');
+    ///     buf.chunk_mut()[1..].as_mut_ptr().write(b'l');
+    ///     buf.chunk_mut()[2..].as_mut_ptr().write(b'o');
     ///
     ///     buf.advance_mut(3);
     /// }
@@ -157,54 +157,18 @@ pub trait BufMut {
     ///
     /// # Implementer notes
     ///
-    /// This function should never panic. `bytes_mut` should return an empty
-    /// slice **if and only if** `remaining_mut` returns 0. In other words,
-    /// `bytes_mut` returning an empty slice implies that `remaining_mut` will
-    /// return 0 and `remaining_mut` returning 0 implies that `bytes_mut` will
+    /// This function should never panic. `chunk_mut` should return an empty
+    /// slice **if and only if** `remaining_mut()` returns 0. In other words,
+    /// `chunk_mut()` returning an empty slice implies that `remaining_mut()` will
+    /// return 0 and `remaining_mut()` returning 0 implies that `chunk_mut()` will
     /// return an empty slice.
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>];
-
-    /// Fills `dst` with potentially multiple mutable slices starting at `self`'s
-    /// current position.
     ///
-    /// If the `BufMut` is backed by disjoint slices of bytes, `bytes_vectored_mut`
-    /// enables fetching more than one slice at once. `dst` is a slice of
-    /// mutable `IoSliceMut` references, enabling the slice to be directly used with
-    /// [`readv`] without any further conversion. The sum of the lengths of all
-    /// the buffers in `dst` will be less than or equal to
-    /// `Buf::remaining_mut()`.
-    ///
-    /// The entries in `dst` will be overwritten, but the data **contained** by
-    /// the slices **will not** be modified. If `bytes_vectored_mut` does not fill every
-    /// entry in `dst`, then `dst` is guaranteed to contain all remaining slices
-    /// in `self.
-    ///
-    /// This is a lower level function. Most operations are done with other
-    /// functions.
-    ///
-    /// # Implementer notes
-    ///
-    /// This function should never panic. Once the end of the buffer is reached,
-    /// i.e., `BufMut::remaining_mut` returns 0, calls to `bytes_vectored_mut` must
-    /// return 0 without mutating `dst`.
-    ///
-    /// Implementations should also take care to properly handle being called
-    /// with `dst` being a zero length slice.
-    ///
-    /// [`readv`]: http://man7.org/linux/man-pages/man2/readv.2.html
-    #[cfg(feature = "std")]
-    fn bytes_vectored_mut<'a>(&'a mut self, dst: &mut [IoSliceMut<'a>]) -> usize {
-        if dst.is_empty() {
-            return 0;
-        }
-
-        if self.has_remaining_mut() {
-            dst[0] = IoSliceMut::from(self.bytes_mut());
-            1
-        } else {
-            0
-        }
-    }
+    /// This function may trigger an out-of-memory abort if it tries to allocate
+    /// memory and fails to do so.
+    // The `chunk_mut` method was previously called `bytes_mut`. This alias makes the
+    // rename more easily discoverable.
+    #[cfg_attr(docsrs, doc(alias = "bytes_mut"))]
+    fn chunk_mut(&mut self) -> &mut UninitSlice;
 
     /// Transfer bytes into `self` from `src` and advance the cursor by the
     /// number of bytes written.
@@ -226,25 +190,27 @@ pub trait BufMut {
     /// # Panics
     ///
     /// Panics if `self` does not have enough capacity to contain `src`.
-    fn put<T: super::Buf>(&mut self, mut src: T) where Self: Sized {
+    fn put<T: super::Buf>(&mut self, mut src: T)
+    where
+        Self: Sized,
+    {
         assert!(self.remaining_mut() >= src.remaining());
 
         while src.has_remaining() {
             let l;
 
             unsafe {
-                let s = src.bytes();
-                let d = self.bytes_mut();
+                let s = src.chunk();
+                let d = self.chunk_mut();
                 l = cmp::min(s.len(), d.len());
 
-                ptr::copy_nonoverlapping(
-                    s.as_ptr(),
-                    d.as_mut_ptr() as *mut u8,
-                    l);
+                ptr::copy_nonoverlapping(s.as_ptr(), d.as_mut_ptr() as *mut u8, l);
             }
 
             src.advance(l);
-            unsafe { self.advance_mut(l); }
+            unsafe {
+                self.advance_mut(l);
+            }
         }
     }
 
@@ -270,25 +236,59 @@ pub trait BufMut {
     fn put_slice(&mut self, src: &[u8]) {
         let mut off = 0;
 
-        assert!(self.remaining_mut() >= src.len(), "buffer overflow; remaining = {}; src = {}", self.remaining_mut(), src.len());
+        assert!(
+            self.remaining_mut() >= src.len(),
+            "buffer overflow; remaining = {}; src = {}",
+            self.remaining_mut(),
+            src.len()
+        );
 
         while off < src.len() {
             let cnt;
 
             unsafe {
-                let dst = self.bytes_mut();
+                let dst = self.chunk_mut();
                 cnt = cmp::min(dst.len(), src.len() - off);
 
-                ptr::copy_nonoverlapping(
-                    src[off..].as_ptr(),
-                    dst.as_mut_ptr() as *mut u8,
-                    cnt);
+                ptr::copy_nonoverlapping(src[off..].as_ptr(), dst.as_mut_ptr() as *mut u8, cnt);
 
                 off += cnt;
-
             }
 
-            unsafe { self.advance_mut(cnt); }
+            unsafe {
+                self.advance_mut(cnt);
+            }
+        }
+    }
+
+    /// 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);
         }
     }
 
@@ -734,7 +734,7 @@ pub trait BufMut {
         self.put_slice(&n.to_le_bytes()[0..nbytes]);
     }
 
-    /// Writes a signed n-byte integer to `self` in big-endian byte order.
+    /// Writes low `nbytes` of a signed integer to `self` in big-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
     ///
@@ -744,19 +744,19 @@ pub trait BufMut {
     /// use bytes::BufMut;
     ///
     /// let mut buf = vec![];
-    /// buf.put_int(0x010203, 3);
+    /// buf.put_int(0x0504010203, 3);
     /// assert_eq!(buf, b"\x01\x02\x03");
     /// ```
     ///
     /// # Panics
     ///
     /// This function panics if there is not enough remaining capacity in
-    /// `self`.
+    /// `self` or if `nbytes` is greater than 8.
     fn put_int(&mut self, n: i64, nbytes: usize) {
         self.put_slice(&n.to_be_bytes()[mem::size_of_val(&n) - nbytes..]);
     }
 
-    /// Writes a signed n-byte integer to `self` in little-endian byte order.
+    /// Writes low `nbytes` of a signed integer to `self` in little-endian byte order.
     ///
     /// The current position is advanced by `nbytes`.
     ///
@@ -766,14 +766,14 @@ pub trait BufMut {
     /// use bytes::BufMut;
     ///
     /// let mut buf = vec![];
-    /// buf.put_int_le(0x010203, 3);
+    /// buf.put_int_le(0x0504010203, 3);
     /// assert_eq!(buf, b"\x03\x02\x01");
     /// ```
     ///
     /// # Panics
     ///
     /// This function panics if there is not enough remaining capacity in
-    /// `self`.
+    /// `self` or if `nbytes` is greater than 8.
     fn put_int_le(&mut self, n: i64, nbytes: usize) {
         self.put_slice(&n.to_le_bytes()[0..nbytes]);
     }
@@ -869,56 +869,179 @@ pub trait BufMut {
     fn put_f64_le(&mut self, n: f64) {
         self.put_u64_le(n.to_bits());
     }
-}
 
-impl<T: BufMut + ?Sized> BufMut for &mut T {
-    fn remaining_mut(&self) -> usize {
-        (**self).remaining_mut()
-    }
-
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
-        (**self).bytes_mut()
+    /// Creates an adaptor which can write at most `limit` bytes to `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let arr = &mut [0u8; 128][..];
+    /// assert_eq!(arr.remaining_mut(), 128);
+    ///
+    /// let dst = arr.limit(10);
+    /// assert_eq!(dst.remaining_mut(), 10);
+    /// ```
+    fn limit(self, limit: usize) -> Limit<Self>
+    where
+        Self: Sized,
+    {
+        limit::new(self, limit)
     }
 
+    /// Creates an adaptor which implements the `Write` trait for `self`.
+    ///
+    /// This function returns a new value which implements `Write` by adapting
+    /// the `Write` trait functions to the `BufMut` trait functions. Given that
+    /// `BufMut` operations are infallible, none of the `Write` functions will
+    /// return with `Err`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    /// use std::io::Write;
+    ///
+    /// let mut buf = vec![].writer();
+    ///
+    /// let num = buf.write(&b"hello world"[..]).unwrap();
+    /// assert_eq!(11, num);
+    ///
+    /// let buf = buf.into_inner();
+    ///
+    /// assert_eq!(*buf, b"hello world"[..]);
+    /// ```
     #[cfg(feature = "std")]
-    fn bytes_vectored_mut<'b>(&'b mut self, dst: &mut [IoSliceMut<'b>]) -> usize {
-        (**self).bytes_vectored_mut(dst)
+    fn writer(self) -> Writer<Self>
+    where
+        Self: Sized,
+    {
+        writer::new(self)
     }
 
-    unsafe fn advance_mut(&mut self, cnt: usize) {
-        (**self).advance_mut(cnt)
+    /// Creates an adapter which will chain this buffer with another.
+    ///
+    /// The returned `BufMut` instance will first write to all bytes from
+    /// `self`. Afterwards, it will write to `next`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut a = [0u8; 5];
+    /// let mut b = [0u8; 6];
+    ///
+    /// let mut chain = (&mut a[..]).chain_mut(&mut b[..]);
+    ///
+    /// chain.put_slice(b"hello world");
+    ///
+    /// assert_eq!(&a[..], b"hello");
+    /// assert_eq!(&b[..], b" world");
+    /// ```
+    fn chain_mut<U: BufMut>(self, next: U) -> Chain<Self, U>
+    where
+        Self: Sized,
+    {
+        Chain::new(self, next)
     }
 }
 
-impl<T: BufMut + ?Sized> BufMut for Box<T> {
-    fn remaining_mut(&self) -> usize {
-        (**self).remaining_mut()
-    }
+macro_rules! deref_forward_bufmut {
+    () => {
+        fn remaining_mut(&self) -> usize {
+            (**self).remaining_mut()
+        }
 
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
-        (**self).bytes_mut()
-    }
+        fn chunk_mut(&mut self) -> &mut UninitSlice {
+            (**self).chunk_mut()
+        }
 
-    #[cfg(feature = "std")]
-    fn bytes_vectored_mut<'b>(&'b mut self, dst: &mut [IoSliceMut<'b>]) -> usize {
-        (**self).bytes_vectored_mut(dst)
-    }
+        unsafe fn advance_mut(&mut self, cnt: usize) {
+            (**self).advance_mut(cnt)
+        }
 
-    unsafe fn advance_mut(&mut self, cnt: usize) {
-        (**self).advance_mut(cnt)
-    }
+        fn put_slice(&mut self, src: &[u8]) {
+            (**self).put_slice(src)
+        }
+
+        fn put_u8(&mut self, n: u8) {
+            (**self).put_u8(n)
+        }
+
+        fn put_i8(&mut self, n: i8) {
+            (**self).put_i8(n)
+        }
+
+        fn put_u16(&mut self, n: u16) {
+            (**self).put_u16(n)
+        }
+
+        fn put_u16_le(&mut self, n: u16) {
+            (**self).put_u16_le(n)
+        }
+
+        fn put_i16(&mut self, n: i16) {
+            (**self).put_i16(n)
+        }
+
+        fn put_i16_le(&mut self, n: i16) {
+            (**self).put_i16_le(n)
+        }
+
+        fn put_u32(&mut self, n: u32) {
+            (**self).put_u32(n)
+        }
+
+        fn put_u32_le(&mut self, n: u32) {
+            (**self).put_u32_le(n)
+        }
+
+        fn put_i32(&mut self, n: i32) {
+            (**self).put_i32(n)
+        }
+
+        fn put_i32_le(&mut self, n: i32) {
+            (**self).put_i32_le(n)
+        }
+
+        fn put_u64(&mut self, n: u64) {
+            (**self).put_u64(n)
+        }
+
+        fn put_u64_le(&mut self, n: u64) {
+            (**self).put_u64_le(n)
+        }
+
+        fn put_i64(&mut self, n: i64) {
+            (**self).put_i64(n)
+        }
+
+        fn put_i64_le(&mut self, n: i64) {
+            (**self).put_i64_le(n)
+        }
+    };
 }
 
-impl BufMut for &mut [u8] {
+unsafe impl<T: BufMut + ?Sized> BufMut for &mut T {
+    deref_forward_bufmut!();
+}
+
+unsafe impl<T: BufMut + ?Sized> BufMut for Box<T> {
+    deref_forward_bufmut!();
+}
+
+unsafe impl BufMut for &mut [u8] {
     #[inline]
     fn remaining_mut(&self) -> usize {
         self.len()
     }
 
     #[inline]
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
-        // MaybeUninit is repr(transparent), so safe to transmute
-        unsafe { mem::transmute(&mut **self) }
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
+        // UninitSlice is repr(transparent), so safe to transmute
+        unsafe { &mut *(*self as *mut [u8] as *mut _) }
     }
 
     #[inline]
@@ -927,31 +1050,48 @@ impl BufMut for &mut [u8] {
         let (_, b) = core::mem::replace(self, &mut []).split_at_mut(cnt);
         *self = b;
     }
+
+    #[inline]
+    fn put_slice(&mut self, src: &[u8]) {
+        self[..src.len()].copy_from_slice(src);
+        unsafe {
+            self.advance_mut(src.len());
+        }
+    }
+
+    fn put_bytes(&mut self, val: u8, cnt: usize) {
+        assert!(self.remaining_mut() >= cnt);
+        unsafe {
+            ptr::write_bytes(self.as_mut_ptr(), val, cnt);
+            self.advance_mut(cnt);
+        }
+    }
 }
 
-impl BufMut for Vec<u8> {
+unsafe impl BufMut for Vec<u8> {
     #[inline]
     fn remaining_mut(&self) -> usize {
-        usize::MAX - self.len()
+        // A vector can never have more than isize::MAX bytes
+        core::isize::MAX as usize - self.len()
     }
 
     #[inline]
     unsafe fn advance_mut(&mut self, cnt: usize) {
         let len = self.len();
         let remaining = self.capacity() - len;
-        if cnt > remaining {
-            // Reserve additional capacity, and ensure that the total length
-            // will not overflow usize.
-            self.reserve(cnt);
-        }
+
+        assert!(
+            cnt <= remaining,
+            "cannot advance past `remaining_mut`: {:?} <= {:?}",
+            cnt,
+            remaining
+        );
 
         self.set_len(len + cnt);
     }
 
     #[inline]
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
-        use core::slice;
-
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
         if self.capacity() == self.len() {
             self.reserve(64); // Grow the vec
         }
@@ -959,54 +1099,44 @@ impl BufMut for Vec<u8> {
         let cap = self.capacity();
         let len = self.len();
 
-        let ptr = self.as_mut_ptr() as *mut MaybeUninit<u8>;
-        unsafe {
-            &mut slice::from_raw_parts_mut(ptr, cap)[len..]
+        let ptr = self.as_mut_ptr();
+        unsafe { &mut UninitSlice::from_raw_parts_mut(ptr, cap)[len..] }
+    }
+
+    // Specialize these methods so they can skip checking `remaining_mut`
+    // and `advance_mut`.
+    fn put<T: super::Buf>(&mut self, mut src: T)
+    where
+        Self: Sized,
+    {
+        // In case the src isn't contiguous, reserve upfront
+        self.reserve(src.remaining());
+
+        while src.has_remaining() {
+            let l;
+
+            // a block to contain the src.bytes() borrow
+            {
+                let s = src.chunk();
+                l = s.len();
+                self.extend_from_slice(s);
+            }
+
+            src.advance(l);
         }
     }
+
+    #[inline]
+    fn put_slice(&mut self, src: &[u8]) {
+        self.extend_from_slice(src);
+    }
+
+    fn put_bytes(&mut self, val: u8, cnt: usize) {
+        let new_len = self.len().checked_add(cnt).unwrap();
+        self.resize(new_len, val);
+    }
 }
 
 // The existence of this function makes the compiler catch if the BufMut
 // trait is "object-safe" or not.
 fn _assert_trait_object(_b: &dyn BufMut) {}
-
-// ===== impl IoSliceMut =====
-
-/// A buffer type used for `readv`.
-///
-/// This is a wrapper around an `std::io::IoSliceMut`, but does not expose
-/// the inner bytes in a safe API, as they may point at uninitialized memory.
-///
-/// This is `repr(transparent)` of the `std::io::IoSliceMut`, so it is valid to
-/// transmute them. However, as the memory might be uninitialized, care must be
-/// taken to not *read* the internal bytes, only *write* to them.
-#[repr(transparent)]
-#[cfg(feature = "std")]
-pub struct IoSliceMut<'a>(std::io::IoSliceMut<'a>);
-
-#[cfg(feature = "std")]
-impl fmt::Debug for IoSliceMut<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("IoSliceMut")
-            .field("len", &self.0.len())
-            .finish()
-    }
-}
-
-#[cfg(feature = "std")]
-impl<'a> From<&'a mut [u8]> for IoSliceMut<'a> {
-    fn from(buf: &'a mut [u8]) -> IoSliceMut<'a> {
-        IoSliceMut(std::io::IoSliceMut::new(buf))
-    }
-}
-
-#[cfg(feature = "std")]
-impl<'a> From<&'a mut [MaybeUninit<u8>]> for IoSliceMut<'a> {
-    fn from(buf: &'a mut [MaybeUninit<u8>]) -> IoSliceMut<'a> {
-        IoSliceMut(std::io::IoSliceMut::new(unsafe {
-            // We don't look at the contents, and `std::io::IoSliceMut`
-            // doesn't either.
-            mem::transmute::<&'a mut [MaybeUninit<u8>], &'a mut [u8]>(buf)
-        }))
-    }
-}

src/buf/chain.rs

@@ -1,12 +1,8 @@
-use crate::{Buf, BufMut};
-use crate::buf::IntoIter;
-
-use core::mem::MaybeUninit;
+use crate::buf::{IntoIter, UninitSlice};
+use crate::{Buf, BufMut, Bytes};
 
 #[cfg(feature = "std")]
-use std::io::{IoSlice};
-#[cfg(feature = "std")]
-use crate::buf::IoSliceMut;
+use std::io::IoSlice;
 
 /// A `Chain` sequences two buffers.
 ///
@@ -20,12 +16,12 @@ use crate::buf::IoSliceMut;
 /// # Examples
 ///
 /// ```
-/// use bytes::{Bytes, Buf, buf::BufExt};
+/// use bytes::{Bytes, Buf};
 ///
 /// let mut buf = (&b"hello "[..])
 ///     .chain(&b"world"[..]);
 ///
-/// let full: Bytes = buf.to_bytes();
+/// let full: Bytes = buf.copy_to_bytes(11);
 /// assert_eq!(full[..], b"hello world"[..]);
 /// ```
 ///
@@ -40,11 +36,8 @@ pub struct Chain<T, U> {
 
 impl<T, U> Chain<T, U> {
     /// Creates a new `Chain` sequencing the provided values.
-    pub fn new(a: T, b: U) -> Chain<T, U> {
-        Chain {
-            a,
-            b,
-        }
+    pub(crate) fn new(a: T, b: U) -> Chain<T, U> {
+        Chain { a, b }
     }
 
     /// Gets a reference to the first underlying `Buf`.
@@ -52,7 +45,7 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let buf = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
@@ -68,14 +61,14 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let mut buf = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
     ///
     /// buf.first_mut().advance(1);
     ///
-    /// let full = buf.to_bytes();
+    /// let full = buf.copy_to_bytes(9);
     /// assert_eq!(full, b"elloworld"[..]);
     /// ```
     pub fn first_mut(&mut self) -> &mut T {
@@ -87,7 +80,7 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let buf = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
@@ -103,14 +96,14 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let mut buf = (&b"hello "[..])
     ///     .chain(&b"world"[..]);
     ///
     /// buf.last_mut().advance(1);
     ///
-    /// let full = buf.to_bytes();
+    /// let full = buf.copy_to_bytes(10);
     /// assert_eq!(full, b"hello orld"[..]);
     /// ```
     pub fn last_mut(&mut self) -> &mut U {
@@ -122,7 +115,7 @@ impl<T, U> Chain<T, U> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
     /// let chain = (&b"hello"[..])
     ///     .chain(&b"world"[..]);
@@ -137,18 +130,19 @@ impl<T, U> Chain<T, U> {
 }
 
 impl<T, U> Buf for Chain<T, U>
-    where T: Buf,
-          U: Buf,
+where
+    T: Buf,
+    U: Buf,
 {
     fn remaining(&self) -> usize {
-        self.a.remaining() + self.b.remaining()
+        self.a.remaining().checked_add(self.b.remaining()).unwrap()
     }
 
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         if self.a.has_remaining() {
-            self.a.bytes()
+            self.a.chunk()
         } else {
-            self.b.bytes()
+            self.b.chunk()
         }
     }
 
@@ -171,26 +165,48 @@ impl<T, U> Buf for Chain<T, U>
     }
 
     #[cfg(feature = "std")]
-    fn bytes_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
-        let mut n = self.a.bytes_vectored(dst);
-        n += self.b.bytes_vectored(&mut dst[n..]);
+    fn chunks_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
+        let mut n = self.a.chunks_vectored(dst);
+        n += self.b.chunks_vectored(&mut dst[n..]);
         n
     }
+
+    fn copy_to_bytes(&mut self, len: usize) -> Bytes {
+        let a_rem = self.a.remaining();
+        if a_rem >= len {
+            self.a.copy_to_bytes(len)
+        } else if a_rem == 0 {
+            self.b.copy_to_bytes(len)
+        } else {
+            assert!(
+                len - a_rem <= self.b.remaining(),
+                "`len` greater than remaining"
+            );
+            let mut ret = crate::BytesMut::with_capacity(len);
+            ret.put(&mut self.a);
+            ret.put((&mut self.b).take(len - a_rem));
+            ret.freeze()
+        }
+    }
 }
 
-impl<T, U> BufMut for Chain<T, U>
-    where T: BufMut,
-          U: BufMut,
+unsafe impl<T, U> BufMut for Chain<T, U>
+where
+    T: BufMut,
+    U: BufMut,
 {
     fn remaining_mut(&self) -> usize {
-        self.a.remaining_mut() + self.b.remaining_mut()
+        self.a
+            .remaining_mut()
+            .checked_add(self.b.remaining_mut())
+            .unwrap()
     }
 
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
         if self.a.has_remaining_mut() {
-            self.a.bytes_mut()
+            self.a.chunk_mut()
         } else {
-            self.b.bytes_mut()
+            self.b.chunk_mut()
         }
     }
 
@@ -211,13 +227,6 @@ impl<T, U> BufMut for Chain<T, U>
 
         self.b.advance_mut(cnt);
     }
-
-    #[cfg(feature = "std")]
-    fn bytes_vectored_mut<'a>(&'a mut self, dst: &mut [IoSliceMut<'a>]) -> usize {
-        let mut n = self.a.bytes_vectored_mut(dst);
-        n += self.b.bytes_vectored_mut(&mut dst[n..]);
-        n
-    }
 }
 
 impl<T, U> IntoIterator for Chain<T, U>

src/buf/ext/mod.rs

@@ -1,176 +0,0 @@
-//! Extra utilities for `Buf` and `BufMut` types.
-
-use super::{Buf, BufMut};
-
-mod chain;
-mod limit;
-#[cfg(feature = "std")]
-mod reader;
-mod take;
-#[cfg(feature = "std")]
-mod writer;
-
-pub use self::limit::Limit;
-pub use self::take::Take;
-pub use self::chain::Chain;
-
-#[cfg(feature = "std")]
-pub use self::{reader::Reader, writer::Writer};
-
-/// Extra methods for implementations of `Buf`.
-pub trait BufExt: Buf {
-    /// Creates an adaptor which will read at most `limit` bytes from `self`.
-    ///
-    /// This function returns a new instance of `Buf` which will read at most
-    /// `limit` bytes.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use bytes::{Buf, BufMut, buf::BufExt};
-    ///
-    /// let mut buf = b"hello world"[..].take(5);
-    /// let mut dst = vec![];
-    ///
-    /// dst.put(&mut buf);
-    /// assert_eq!(dst, b"hello");
-    ///
-    /// let mut buf = buf.into_inner();
-    /// dst.clear();
-    /// dst.put(&mut buf);
-    /// assert_eq!(dst, b" world");
-    /// ```
-    fn take(self, limit: usize) -> Take<Self>
-        where Self: Sized
-    {
-        take::new(self, limit)
-    }
-
-    /// Creates an adaptor which will chain this buffer with another.
-    ///
-    /// The returned `Buf` instance will first consume all bytes from `self`.
-    /// Afterwards the output is equivalent to the output of next.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use bytes::{Buf, buf::BufExt};
-    ///
-    /// let mut chain = b"hello "[..].chain(&b"world"[..]);
-    ///
-    /// let full = chain.to_bytes();
-    /// assert_eq!(full.bytes(), b"hello world");
-    /// ```
-    fn chain<U: Buf>(self, next: U) -> Chain<Self, U>
-        where Self: Sized
-    {
-        Chain::new(self, next)
-    }
-
-    /// Creates an adaptor which implements the `Read` trait for `self`.
-    ///
-    /// This function returns a new value which implements `Read` by adapting
-    /// the `Read` trait functions to the `Buf` trait functions. Given that
-    /// `Buf` operations are infallible, none of the `Read` functions will
-    /// return with `Err`.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use bytes::{Buf, Bytes, buf::BufExt};
-    /// use std::io::Read;
-    ///
-    /// let buf = Bytes::from("hello world");
-    ///
-    /// let mut reader = buf.reader();
-    /// let mut dst = [0; 1024];
-    ///
-    /// let num = reader.read(&mut dst).unwrap();
-    ///
-    /// assert_eq!(11, num);
-    /// assert_eq!(&dst[..11], &b"hello world"[..]);
-    /// ```
-    #[cfg(feature = "std")]
-    fn reader(self) -> Reader<Self> where Self: Sized {
-        reader::new(self)
-    }
-}
-
-impl<B: Buf + ?Sized> BufExt for B {}
-
-/// Extra methods for implementations of `BufMut`.
-pub trait BufMutExt: BufMut {
-    /// Creates an adaptor which can write at most `limit` bytes to `self`.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use bytes::{BufMut, buf::BufMutExt};
-    ///
-    /// let arr = &mut [0u8; 128][..];
-    /// assert_eq!(arr.remaining_mut(), 128);
-    ///
-    /// let dst = arr.limit(10);
-    /// assert_eq!(dst.remaining_mut(), 10);
-    /// ```
-    fn limit(self, limit: usize) -> Limit<Self>
-        where Self: Sized
-    {
-        limit::new(self, limit)
-    }
-
-    /// Creates an adaptor which implements the `Write` trait for `self`.
-    ///
-    /// This function returns a new value which implements `Write` by adapting
-    /// the `Write` trait functions to the `BufMut` trait functions. Given that
-    /// `BufMut` operations are infallible, none of the `Write` functions will
-    /// return with `Err`.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use bytes::{BufMut, buf::BufMutExt};
-    /// use std::io::Write;
-    ///
-    /// let mut buf = vec![].writer();
-    ///
-    /// let num = buf.write(&b"hello world"[..]).unwrap();
-    /// assert_eq!(11, num);
-    ///
-    /// let buf = buf.into_inner();
-    ///
-    /// assert_eq!(*buf, b"hello world"[..]);
-    /// ```
-    #[cfg(feature = "std")]
-    fn writer(self) -> Writer<Self> where Self: Sized {
-        writer::new(self)
-    }
-
-    /// Creates an adapter which will chain this buffer with another.
-    ///
-    /// The returned `BufMut` instance will first write to all bytes from
-    /// `self`. Afterwards, it will write to `next`.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// use bytes::{BufMut, buf::BufMutExt};
-    ///
-    /// let mut a = [0u8; 5];
-    /// let mut b = [0u8; 6];
-    ///
-    /// let mut chain = (&mut a[..]).chain_mut(&mut b[..]);
-    ///
-    /// chain.put_slice(b"hello world");
-    ///
-    /// assert_eq!(&a[..], b"hello");
-    /// assert_eq!(&b[..], b" world");
-    /// ```
-    fn chain_mut<U: BufMut>(self, next: U) -> Chain<Self, U>
-        where Self: Sized
-    {
-        Chain::new(self, next)
-    }
-}
-
-impl<B: BufMut + ?Sized> BufMutExt for B {}

src/buf/iter.rs

@@ -9,7 +9,7 @@ use crate::Buf;
 /// Basic usage:
 ///
 /// ```
-/// use bytes::{Buf, Bytes};
+/// use bytes::Bytes;
 ///
 /// let buf = Bytes::from(&b"abc"[..]);
 /// let mut iter = buf.into_iter();
@@ -33,20 +33,20 @@ impl<T> IntoIter<T> {
     /// # Examples
     ///
     /// ```
-    /// use bytes::{Buf, Bytes};
-    /// use bytes::buf::IntoIter;
+    /// use bytes::Bytes;
     ///
     /// let buf = Bytes::from_static(b"abc");
-    /// let mut iter = IntoIter::new(buf);
+    /// let mut iter = buf.into_iter();
     ///
     /// assert_eq!(iter.next(), Some(b'a'));
     /// assert_eq!(iter.next(), Some(b'b'));
     /// assert_eq!(iter.next(), Some(b'c'));
     /// assert_eq!(iter.next(), None);
     /// ```
-    pub fn new(inner: T) -> IntoIter<T> {
+    pub(crate) fn new(inner: T) -> IntoIter<T> {
         IntoIter { inner }
     }
+
     /// Consumes this `IntoIter`, returning the underlying value.
     ///
     /// # Examples
@@ -109,7 +109,6 @@ impl<T> IntoIter<T> {
     }
 }
 
-
 impl<T: Buf> Iterator for IntoIter<T> {
     type Item = u8;
 
@@ -118,7 +117,7 @@ impl<T: Buf> Iterator for IntoIter<T> {
             return None;
         }
 
-        let b = self.inner.bytes()[0];
+        let b = self.inner.chunk()[0];
         self.inner.advance(1);
 
         Some(b)
@@ -130,4 +129,4 @@ impl<T: Buf> Iterator for IntoIter<T> {
     }
 }
 
-impl<T: Buf> ExactSizeIterator for IntoIter<T> { }
+impl<T: Buf> ExactSizeIterator for IntoIter<T> {}

src/buf/limit.rs

@@ -1,6 +1,7 @@
+use crate::buf::UninitSlice;
 use crate::BufMut;
 
-use core::{cmp, mem::MaybeUninit};
+use core::cmp;
 
 /// A `BufMut` adapter which limits the amount of bytes that can be written
 /// to an underlying buffer.
@@ -11,10 +12,7 @@ pub struct Limit<T> {
 }
 
 pub(super) fn new<T>(inner: T, limit: usize) -> Limit<T> {
-    Limit {
-        inner,
-        limit,
-    }
+    Limit { inner, limit }
 }
 
 impl<T> Limit<T> {
@@ -58,13 +56,13 @@ impl<T> Limit<T> {
     }
 }
 
-impl<T: BufMut> BufMut for Limit<T> {
+unsafe impl<T: BufMut> BufMut for Limit<T> {
     fn remaining_mut(&self) -> usize {
         cmp::min(self.inner.remaining_mut(), self.limit)
     }
 
-    fn bytes_mut(&mut self) -> &mut [MaybeUninit<u8>] {
-        let bytes = self.inner.bytes_mut();
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
+        let bytes = self.inner.chunk_mut();
         let end = cmp::min(bytes.len(), self.limit);
         &mut bytes[..end]
     }

src/buf/mod.rs

@@ -18,14 +18,24 @@
 
 mod buf_impl;
 mod buf_mut;
-pub mod ext;
+mod chain;
 mod iter;
+mod limit;
+#[cfg(feature = "std")]
+mod reader;
+mod take;
+mod uninit_slice;
 mod vec_deque;
+#[cfg(feature = "std")]
+mod writer;
 
 pub use self::buf_impl::Buf;
 pub use self::buf_mut::BufMut;
-pub use self::ext::{BufExt, BufMutExt};
-#[cfg(feature = "std")]
-pub use self::buf_mut::IoSliceMut;
+pub use self::chain::Chain;
 pub use self::iter::IntoIter;
+pub use self::limit::Limit;
+pub use self::take::Take;
+pub use self::uninit_slice::UninitSlice;
 
+#[cfg(feature = "std")]
+pub use self::{reader::Reader, writer::Writer};

src/buf/reader.rs

@@ -1,4 +1,4 @@
-use crate::{Buf};
+use crate::Buf;
 
 use std::{cmp, io};
 
@@ -24,9 +24,9 @@ impl<B: Buf> Reader<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufExt;
+    /// use bytes::Buf;
     ///
-    /// let mut buf = b"hello world".reader();
+    /// let buf = b"hello world".reader();
     ///
     /// assert_eq!(b"hello world", buf.get_ref());
     /// ```
@@ -46,7 +46,7 @@ impl<B: Buf> Reader<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     /// use std::io;
     ///
     /// let mut buf = b"hello world".reader();
@@ -73,7 +73,7 @@ impl<B: Buf + Sized> io::Read for Reader<B> {
 
 impl<B: Buf + Sized> io::BufRead for Reader<B> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
-        Ok(self.buf.bytes())
+        Ok(self.buf.chunk())
     }
     fn consume(&mut self, amt: usize) {
         self.buf.advance(amt)

src/buf/take.rs

@@ -1,4 +1,4 @@
-use crate::Buf;
+use crate::{Buf, Bytes};
 
 use core::cmp;
 
@@ -13,10 +13,7 @@ pub struct Take<T> {
 }
 
 pub fn new<T>(inner: T, limit: usize) -> Take<T> {
-    Take {
-        inner,
-        limit,
-    }
+    Take { inner, limit }
 }
 
 impl<T> Take<T> {
@@ -25,7 +22,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::{Buf, BufMut, BufExt};
+    /// use bytes::{Buf, BufMut};
     ///
     /// let mut buf = b"hello world".take(2);
     /// let mut dst = vec![];
@@ -50,9 +47,9 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
-    /// let mut buf = b"hello world".take(2);
+    /// let buf = b"hello world".take(2);
     ///
     /// assert_eq!(11, buf.get_ref().remaining());
     /// ```
@@ -67,7 +64,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, BufMut, buf::BufExt};
+    /// use bytes::{Buf, BufMut};
     ///
     /// let mut buf = b"hello world".take(2);
     /// let mut dst = vec![];
@@ -91,7 +88,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, buf::BufExt};
+    /// use bytes::Buf;
     ///
     /// let mut buf = b"hello world".take(2);
     ///
@@ -113,7 +110,7 @@ impl<T> Take<T> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::{Buf, BufMut, buf::BufExt};
+    /// use bytes::{Buf, BufMut};
     ///
     /// let mut buf = b"hello world".take(2);
     /// let mut dst = vec![];
@@ -137,8 +134,8 @@ impl<T: Buf> Buf for Take<T> {
         cmp::min(self.inner.remaining(), self.limit)
     }
 
-    fn bytes(&self) -> &[u8] {
-        let bytes = self.inner.bytes();
+    fn chunk(&self) -> &[u8] {
+        let bytes = self.inner.chunk();
         &bytes[..cmp::min(bytes.len(), self.limit)]
     }
 
@@ -147,4 +144,12 @@ impl<T: Buf> Buf for Take<T> {
         self.inner.advance(cnt);
         self.limit -= cnt;
     }
+
+    fn copy_to_bytes(&mut self, len: usize) -> Bytes {
+        assert!(len <= self.remaining(), "`len` greater than remaining");
+
+        let r = self.inner.copy_to_bytes(len);
+        self.limit -= len;
+        r
+    }
 }

src/buf/uninit_slice.rs

@@ -0,0 +1,183 @@
+use core::fmt;
+use core::mem::MaybeUninit;
+use core::ops::{
+    Index, IndexMut, Range, RangeFrom, RangeFull, RangeInclusive, RangeTo, RangeToInclusive,
+};
+
+/// Uninitialized byte slice.
+///
+/// Returned by `BufMut::chunk_mut()`, the referenced byte slice may be
+/// uninitialized. The wrapper provides safe access without introducing
+/// undefined behavior.
+///
+/// The safety invariants of this wrapper are:
+///
+///  1. Reading from an `UninitSlice` is undefined behavior.
+///  2. Writing uninitialized bytes to an `UninitSlice` is undefined behavior.
+///
+/// The difference between `&mut UninitSlice` and `&mut [MaybeUninit<u8>]` is
+/// that it is possible in safe code to write uninitialized bytes to an
+/// `&mut [MaybeUninit<u8>]`, which this type prohibits.
+#[repr(transparent)]
+pub struct UninitSlice([MaybeUninit<u8>]);
+
+impl UninitSlice {
+    /// Create a `&mut UninitSlice` from a pointer and a length.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that `ptr` references a valid memory region owned
+    /// by the caller representing a byte slice for the duration of `'a`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::UninitSlice;
+    ///
+    /// let bytes = b"hello world".to_vec();
+    /// let ptr = bytes.as_ptr() as *mut _;
+    /// let len = bytes.len();
+    ///
+    /// let slice = unsafe { UninitSlice::from_raw_parts_mut(ptr, len) };
+    /// ```
+    #[inline]
+    pub unsafe fn from_raw_parts_mut<'a>(ptr: *mut u8, len: usize) -> &'a mut UninitSlice {
+        let maybe_init: &mut [MaybeUninit<u8>] =
+            core::slice::from_raw_parts_mut(ptr as *mut _, len);
+        &mut *(maybe_init as *mut [MaybeUninit<u8>] as *mut UninitSlice)
+    }
+
+    /// Write a single byte at the specified offset.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if `index` is out of bounds.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::UninitSlice;
+    ///
+    /// let mut data = [b'f', b'o', b'o'];
+    /// let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    ///
+    /// slice.write_byte(0, b'b');
+    ///
+    /// assert_eq!(b"boo", &data[..]);
+    /// ```
+    #[inline]
+    pub fn write_byte(&mut self, index: usize, byte: u8) {
+        assert!(index < self.len());
+
+        unsafe { self[index..].as_mut_ptr().write(byte) }
+    }
+
+    /// Copies bytes  from `src` into `self`.
+    ///
+    /// The length of `src` must be the same as `self`.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if `src` has a different length than `self`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::buf::UninitSlice;
+    ///
+    /// let mut data = [b'f', b'o', b'o'];
+    /// let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    ///
+    /// slice.copy_from_slice(b"bar");
+    ///
+    /// assert_eq!(b"bar", &data[..]);
+    /// ```
+    #[inline]
+    pub fn copy_from_slice(&mut self, src: &[u8]) {
+        use core::ptr;
+
+        assert_eq!(self.len(), src.len());
+
+        unsafe {
+            ptr::copy_nonoverlapping(src.as_ptr(), self.as_mut_ptr(), self.len());
+        }
+    }
+
+    /// Return a raw pointer to the slice's buffer.
+    ///
+    /// # Safety
+    ///
+    /// The caller **must not** read from the referenced memory and **must not**
+    /// write **uninitialized** bytes to the slice either.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut data = [0, 1, 2];
+    /// let mut slice = &mut data[..];
+    /// let ptr = BufMut::chunk_mut(&mut slice).as_mut_ptr();
+    /// ```
+    #[inline]
+    pub fn as_mut_ptr(&mut self) -> *mut u8 {
+        self.0.as_mut_ptr() as *mut _
+    }
+
+    /// Returns the number of bytes in the slice.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use bytes::BufMut;
+    ///
+    /// let mut data = [0, 1, 2];
+    /// let mut slice = &mut data[..];
+    /// let len = BufMut::chunk_mut(&mut slice).len();
+    ///
+    /// assert_eq!(len, 3);
+    /// ```
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+}
+
+impl fmt::Debug for UninitSlice {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("UninitSlice[...]").finish()
+    }
+}
+
+macro_rules! impl_index {
+    ($($t:ty),*) => {
+        $(
+            impl Index<$t> for UninitSlice {
+                type Output = UninitSlice;
+
+                #[inline]
+                fn index(&self, index: $t) -> &UninitSlice {
+                    let maybe_uninit: &[MaybeUninit<u8>] = &self.0[index];
+                    unsafe { &*(maybe_uninit as *const [MaybeUninit<u8>] as *const UninitSlice) }
+                }
+            }
+
+            impl IndexMut<$t> for UninitSlice {
+                #[inline]
+                fn index_mut(&mut self, index: $t) -> &mut UninitSlice {
+                    let maybe_uninit: &mut [MaybeUninit<u8>] = &mut self.0[index];
+                    unsafe { &mut *(maybe_uninit as *mut [MaybeUninit<u8>] as *mut UninitSlice) }
+                }
+            }
+        )*
+    };
+}
+
+impl_index!(
+    Range<usize>,
+    RangeFrom<usize>,
+    RangeFull,
+    RangeInclusive<usize>,
+    RangeTo<usize>,
+    RangeToInclusive<usize>
+);

src/buf/vec_deque.rs

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

src/buf/writer.rs

@@ -24,9 +24,9 @@ impl<B: BufMut> Writer<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufMutExt;
+    /// use bytes::BufMut;
     ///
-    /// let mut buf = Vec::with_capacity(1024).writer();
+    /// let buf = Vec::with_capacity(1024).writer();
     ///
     /// assert_eq!(1024, buf.get_ref().capacity());
     /// ```
@@ -41,7 +41,7 @@ impl<B: BufMut> Writer<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufMutExt;
+    /// use bytes::BufMut;
     ///
     /// let mut buf = vec![].writer();
     ///
@@ -58,7 +58,7 @@ impl<B: BufMut> Writer<B> {
     /// # Examples
     ///
     /// ```rust
-    /// use bytes::buf::BufMutExt;
+    /// use bytes::BufMut;
     /// use std::io;
     ///
     /// let mut buf = vec![].writer();

src/bytes.rs

@@ -1,24 +1,32 @@
-use core::{cmp, fmt, hash, mem, ptr, slice, usize};
-use core::iter::{FromIterator};
+use core::iter::FromIterator;
 use core::ops::{Deref, RangeBounds};
+use core::{cmp, fmt, hash, mem, ptr, slice, usize};
 
-use alloc::{vec::Vec, string::String, boxed::Box, borrow::Borrow};
+use alloc::{borrow::Borrow, boxed::Box, string::String, vec::Vec};
 
-use crate::Buf;
 use crate::buf::IntoIter;
-use crate::debug;
+#[allow(unused)]
+use crate::loom::sync::atomic::AtomicMut;
 use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+use crate::Buf;
 
-/// A reference counted contiguous slice of memory.
+/// A cheaply cloneable and sliceable chunk of contiguous memory.
 ///
 /// `Bytes` is an efficient container for storing and operating on contiguous
 /// slices of memory. It is intended for use primarily in networking code, but
 /// could have applications elsewhere as well.
 ///
 /// `Bytes` values facilitate zero-copy network programming by allowing multiple
-/// `Bytes` objects to point to the same underlying memory. This is managed by
-/// using a reference count to track when the memory is no longer needed and can
-/// be freed.
+/// `Bytes` objects to point to the same underlying memory.
+///
+/// `Bytes` does not have a single implementation. It is an interface, whose
+/// exact behavior is implemented through dynamic dispatch in several underlying
+/// implementations of `Bytes`.
+///
+/// All `Bytes` implementations must fulfill the following requirements:
+/// - They are cheaply cloneable and thereby shareable between an unlimited amount
+///   of components, for example by modifying a reference count.
+/// - Instances can be sliced to refer to a subset of the the original buffer.
 ///
 /// ```
 /// use bytes::Bytes;
@@ -40,17 +48,33 @@ use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
 /// to track information about which segment of the underlying memory the
 /// `Bytes` handle has access to.
 ///
-/// `Bytes` keeps both a pointer to the shared `Arc` containing the full memory
+/// `Bytes` keeps both a pointer to the shared state containing the full memory
 /// slice and a pointer to the start of the region visible by the handle.
 /// `Bytes` also tracks the length of its view into the memory.
 ///
 /// # Sharing
 ///
-/// The memory itself is reference counted, and multiple `Bytes` objects may
-/// point to the same region. Each `Bytes` handle point to different sections within
-/// the memory region, and `Bytes` handle may or may not have overlapping views
+/// `Bytes` contains a vtable, which allows implementations of `Bytes` to define
+/// how sharing/cloneing is implemented in detail.
+/// When `Bytes::clone()` is called, `Bytes` will call the vtable function for
+/// cloning the backing storage in order to share it behind between multiple
+/// `Bytes` instances.
+///
+/// For `Bytes` implementations which refer to constant memory (e.g. created
+/// via `Bytes::from_static()`) the cloning implementation will be a no-op.
+///
+/// For `Bytes` implementations which point to a reference counted shared storage
+/// (e.g. an `Arc<[u8]>`), sharing will be implemented by increasing the
+/// the reference count.
+///
+/// Due to this mechanism, multiple `Bytes` instances may point to the same
+/// shared memory region.
+/// Each `Bytes` instance can point to different sections within that
+/// memory region, and `Bytes` instances may or may not have overlapping views
 /// into the memory.
 ///
+/// The following diagram visualizes a scenario where 2 `Bytes` instances make
+/// use of an `Arc`-based backing storage, and provide access to different views:
 ///
 /// ```text
 ///
@@ -96,8 +120,18 @@ impl Bytes {
     /// assert_eq!(&b[..], b"");
     /// ```
     #[inline]
+    #[cfg(not(all(loom, test)))]
+    pub const fn new() -> Bytes {
+        // Make it a named const to work around
+        // "unsizing casts are not allowed in const fn"
+        const EMPTY: &[u8] = &[];
+        Bytes::from_static(EMPTY)
+    }
+
+    #[cfg(all(loom, test))]
     pub fn new() -> Bytes {
-        Bytes::from_static(b"")
+        const EMPTY: &[u8] = &[];
+        Bytes::from_static(EMPTY)
     }
 
     /// Creates a new `Bytes` from a static slice.
@@ -164,8 +198,7 @@ impl Bytes {
         self.len == 0
     }
 
-
-    ///Creates `Bytes` instance from slice, by copying it.
+    /// Creates `Bytes` instance from slice, by copying it.
     pub fn copy_from_slice(data: &[u8]) -> Self {
         data.to_vec().into()
     }
@@ -204,19 +237,28 @@ impl Bytes {
         };
 
         let end = match range.end_bound() {
-            Bound::Included(&n) => n + 1,
+            Bound::Included(&n) => n.checked_add(1).expect("out of range"),
             Bound::Excluded(&n) => n,
             Bound::Unbounded => len,
         };
 
-        assert!(begin <= end);
-        assert!(end <= len);
+        assert!(
+            begin <= end,
+            "range start must not be greater than end: {:?} <= {:?}",
+            begin,
+            end,
+        );
+        assert!(
+            end <= len,
+            "range end out of bounds: {:?} <= {:?}",
+            end,
+            len,
+        );
 
         if end == begin {
             return Bytes::new();
         }
 
-
         let mut ret = self.clone();
 
         ret.len = end - begin;
@@ -251,14 +293,32 @@ 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 {
+        // 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() {
+            return Bytes::new();
+        }
+
         let bytes_p = self.as_ptr() as usize;
         let bytes_len = self.len();
 
         let sub_p = subset.as_ptr() as usize;
         let sub_len = subset.len();
 
-        assert!(sub_p >= bytes_p);
-        assert!(sub_p + sub_len <= bytes_p + bytes_len);
+        assert!(
+            sub_p >= bytes_p,
+            "subset pointer ({:p}) is smaller than self pointer ({:p})",
+            sub_p as *const u8,
+            bytes_p as *const u8,
+        );
+        assert!(
+            sub_p + sub_len <= bytes_p + bytes_len,
+            "subset is out of bounds: self = ({:p}, {}), subset = ({:p}, {})",
+            bytes_p as *const u8,
+            bytes_len,
+            sub_p as *const u8,
+            sub_len,
+        );
 
         let sub_offset = sub_p - bytes_p;
 
@@ -288,8 +348,14 @@ impl Bytes {
     /// # Panics
     ///
     /// 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 {
-        assert!(at <= self.len());
+        assert!(
+            at <= self.len(),
+            "split_off out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
 
         if at == self.len() {
             return Bytes::new();
@@ -331,8 +397,14 @@ impl Bytes {
     /// # Panics
     ///
     /// 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 {
-        assert!(at <= self.len());
+        assert!(
+            at <= self.len(),
+            "split_to out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
 
         if at == self.len() {
             return mem::replace(self, Bytes::new());
@@ -342,7 +414,6 @@ impl Bytes {
             return Bytes::new();
         }
 
-
         let mut ret = self.clone();
 
         unsafe { self.inc_start(at) };
@@ -373,10 +444,17 @@ impl Bytes {
     /// [`split_off`]: #method.split_off
     #[inline]
     pub fn truncate(&mut self, len: usize) {
-        if len >= self.len {
-            self.len = 0;
-        } else {
-            self.len = len;
+        if len < self.len {
+            // The Vec "promotable" vtables do not store the capacity,
+            // so we cannot truncate while using this repr. We *have* to
+            // promote using `split_off` so the capacity can be stored.
+            if self.vtable as *const Vtable == &PROMOTABLE_EVEN_VTABLE
+                || self.vtable as *const Vtable == &PROMOTABLE_ODD_VTABLE
+            {
+                drop(self.split_off(len));
+            } else {
+                self.len = len;
+            }
         }
     }
 
@@ -397,7 +475,12 @@ impl Bytes {
     }
 
     #[inline]
-    pub(crate) unsafe fn with_vtable(ptr: *const u8, len: usize, data: AtomicPtr<()>, vtable: &'static Vtable) -> Bytes {
+    pub(crate) unsafe fn with_vtable(
+        ptr: *const u8,
+        len: usize,
+        data: AtomicPtr<()>,
+        vtable: &'static Vtable,
+    ) -> Bytes {
         Bytes {
             ptr,
             len,
@@ -410,15 +493,13 @@ impl Bytes {
 
     #[inline]
     fn as_slice(&self) -> &[u8] {
-        unsafe {
-            slice::from_raw_parts(self.ptr, self.len)
-        }
+        unsafe { slice::from_raw_parts(self.ptr, self.len) }
     }
 
     #[inline]
     unsafe fn inc_start(&mut self, by: usize) {
         // should already be asserted, but debug assert for tests
-        debug_assert!(self.len >= by);
+        debug_assert!(self.len >= by, "internal: inc_start out of bounds");
         self.len -= by;
         self.ptr = self.ptr.offset(by as isize);
     }
@@ -431,24 +512,14 @@ unsafe impl Sync for Bytes {}
 impl Drop for Bytes {
     #[inline]
     fn drop(&mut self) {
-        unsafe {
-            (self.vtable.drop)(&mut self.data, self.ptr, self.len)
-        }
+        unsafe { (self.vtable.drop)(&mut self.data, self.ptr, self.len) }
     }
 }
 
 impl Clone for Bytes {
     #[inline]
     fn clone(&self) -> Bytes {
-        unsafe {
-            (self.vtable.clone)(&self.data, self.ptr, self.len)
-        }
-    }
-}
-
-impl fmt::Debug for Bytes {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(&debug::BsDebug(&self.as_slice()), f)
+        unsafe { (self.vtable.clone)(&self.data, self.ptr, self.len) }
     }
 }
 
@@ -459,20 +530,32 @@ impl Buf for Bytes {
     }
 
     #[inline]
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         self.as_slice()
     }
 
     #[inline]
     fn advance(&mut self, cnt: usize) {
-        assert!(cnt <= self.len(), "cannot advance past `remaining`");
+        assert!(
+            cnt <= self.len(),
+            "cannot advance past `remaining`: {:?} <= {:?}",
+            cnt,
+            self.len(),
+        );
+
         unsafe {
             self.inc_start(cnt);
         }
     }
 
-    fn to_bytes(&mut self) -> crate::Bytes {
-        core::mem::replace(self, Bytes::new())
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
+        if len == self.remaining() {
+            core::mem::replace(self, Bytes::new())
+        } else {
+            let ret = self.slice(..len);
+            self.advance(len);
+            ret
+        }
     }
 }
 
@@ -493,7 +576,10 @@ impl AsRef<[u8]> for Bytes {
 }
 
 impl hash::Hash for Bytes {
-    fn hash<H>(&self, state: &mut H) where H: hash::Hasher {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: hash::Hasher,
+    {
         self.as_slice().hash(state);
     }
 }
@@ -570,7 +656,7 @@ impl PartialEq<Bytes> for [u8] {
 
 impl PartialOrd<Bytes> for [u8] {
     fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
     }
 }
 
@@ -594,7 +680,7 @@ impl PartialEq<Bytes> for str {
 
 impl PartialOrd<Bytes> for str {
     fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
     }
 }
 
@@ -618,7 +704,7 @@ impl PartialEq<Bytes> for Vec<u8> {
 
 impl PartialOrd<Bytes> for Vec<u8> {
     fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
     }
 }
 
@@ -642,7 +728,7 @@ impl PartialEq<Bytes> for String {
 
 impl PartialOrd<Bytes> for String {
     fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
     }
 }
 
@@ -654,7 +740,7 @@ impl PartialEq<Bytes> for &[u8] {
 
 impl PartialOrd<Bytes> for &[u8] {
     fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
     }
 }
 
@@ -666,12 +752,13 @@ impl PartialEq<Bytes> for &str {
 
 impl PartialOrd<Bytes> for &str {
     fn partial_cmp(&self, other: &Bytes) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
     }
 }
 
 impl<'a, T: ?Sized> PartialEq<&'a T> for Bytes
-    where Bytes: PartialEq<T>
+where
+    Bytes: PartialEq<T>,
 {
     fn eq(&self, other: &&'a T) -> bool {
         *self == **other
@@ -679,7 +766,8 @@ impl<'a, T: ?Sized> PartialEq<&'a T> for Bytes
 }
 
 impl<'a, T: ?Sized> PartialOrd<&'a T> for Bytes
-    where Bytes: PartialOrd<T>
+where
+    Bytes: PartialOrd<T>,
 {
     fn partial_cmp(&self, other: &&'a T) -> Option<cmp::Ordering> {
         self.partial_cmp(&**other)
@@ -710,16 +798,37 @@ impl From<&'static str> for Bytes {
 impl From<Vec<u8>> for Bytes {
     fn from(vec: Vec<u8>) -> Bytes {
         let slice = vec.into_boxed_slice();
-        let len = slice.len();
-        let ptr = slice.as_ptr();
-        drop(Box::into_raw(slice));
+        slice.into()
+    }
+}
 
-        let data = ptr as usize | KIND_VEC;
-        Bytes {
-            ptr,
-            len,
-            data: AtomicPtr::new(data as *mut _),
-            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 slice.is_empty() {
+            return Bytes::new();
+        }
+
+        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;
+            Bytes {
+                ptr,
+                len,
+                data: AtomicPtr::new(data as *mut _),
+                vtable: &PROMOTABLE_EVEN_VTABLE,
+            }
+        } else {
+            Bytes {
+                ptr,
+                len,
+                data: AtomicPtr::new(ptr as *mut _),
+                vtable: &PROMOTABLE_ODD_VTABLE,
+            }
         }
     }
 }
@@ -757,6 +866,78 @@ unsafe fn static_drop(_: &mut AtomicPtr<()>, _: *const u8, _: usize) {
     // nothing to drop for &'static [u8]
 }
 
+// ===== impl PromotableVtable =====
+
+static PROMOTABLE_EVEN_VTABLE: Vtable = Vtable {
+    clone: promotable_even_clone,
+    drop: promotable_even_drop,
+};
+
+static PROMOTABLE_ODD_VTABLE: Vtable = Vtable {
+    clone: promotable_odd_clone,
+    drop: promotable_odd_drop,
+};
+
+unsafe fn promotable_even_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let shared = data.load(Ordering::Acquire);
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        shallow_clone_arc(shared as _, ptr, len)
+    } else {
+        debug_assert_eq!(kind, KIND_VEC);
+        let buf = (shared as usize & !KIND_MASK) as *mut u8;
+        shallow_clone_vec(data, shared, buf, ptr, len)
+    }
+}
+
+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);
+        } else {
+            debug_assert_eq!(kind, KIND_VEC);
+            let buf = (shared as usize & !KIND_MASK) as *mut u8;
+            drop(rebuild_boxed_slice(buf, ptr, len));
+        }
+    });
+}
+
+unsafe fn promotable_odd_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let shared = data.load(Ordering::Acquire);
+    let kind = shared as usize & KIND_MASK;
+
+    if kind == KIND_ARC {
+        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)
+    }
+}
+
+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);
+        } else {
+            debug_assert_eq!(kind, KIND_VEC);
+
+            drop(rebuild_boxed_slice(shared as *mut u8, ptr, len));
+        }
+    });
+}
+
+unsafe fn rebuild_boxed_slice(buf: *mut u8, offset: *const u8, len: usize) -> Box<[u8]> {
+    let cap = (offset as usize - buf as usize) + len;
+    Box::from_raw(slice::from_raw_parts_mut(buf, cap))
+}
+
 // ===== impl SharedVtable =====
 
 struct Shared {
@@ -765,6 +946,12 @@ struct Shared {
     ref_cnt: AtomicUsize,
 }
 
+// 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.
+// This flag is set when the LSB is 0.
+const _: [(); 0 - mem::align_of::<Shared>() % 2] = []; // Assert that the alignment of `Shared` is divisible by 2.
+
 static SHARED_VTABLE: Vtable = Vtable {
     clone: shared_clone,
     drop: shared_drop,
@@ -775,37 +962,14 @@ const KIND_VEC: usize = 0b1;
 const KIND_MASK: usize = 0b1;
 
 unsafe fn shared_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
-    let shared = data.load(Ordering::Acquire);
-    let kind = shared as usize & KIND_MASK;
-
-    if kind == KIND_ARC {
-        shallow_clone_arc(shared as _, ptr, len)
-    } else {
-        debug_assert_eq!(kind, KIND_VEC);
-        shallow_clone_vec(data, shared, ptr, len)
-    }
+    let shared = data.load(Ordering::Relaxed);
+    shallow_clone_arc(shared as _, ptr, len)
 }
 
-unsafe fn shared_drop(data: &mut AtomicPtr<()>, ptr: *const u8, len: usize) {
-    let shared = *data.get_mut();
-    let kind = shared as usize & KIND_MASK;
-
-
-    if kind == KIND_ARC {
-        release_shared(shared as *mut Shared);
-    } else {
-        debug_assert_eq!(kind, KIND_VEC);
-
-        drop(rebuild_vec(shared, ptr, len));
-    }
-}
-
-unsafe fn rebuild_vec(shared: *const (), offset: *const u8, len: usize) -> Vec<u8> {
-    debug_assert_eq!(shared as usize & KIND_MASK, KIND_VEC);
-
-    let buf = (shared as usize & !KIND_MASK) as *mut u8;
-    let cap = (offset as usize - buf as usize) + len;
-    Vec::from_raw_parts(buf, cap, cap)
+unsafe fn shared_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
+    data.with_mut(|shared| {
+        release_shared(*shared as *mut Shared);
+    });
 }
 
 unsafe fn shallow_clone_arc(shared: *mut Shared, ptr: *const u8, len: usize) -> Bytes {
@@ -824,13 +988,17 @@ unsafe fn shallow_clone_arc(shared: *mut Shared, ptr: *const u8, len: usize) ->
 }
 
 #[cold]
-unsafe fn shallow_clone_vec(atom: &AtomicPtr<()>, ptr: *const (), offset: *const u8, len: usize) -> Bytes {
+unsafe fn shallow_clone_vec(
+    atom: &AtomicPtr<()>,
+    ptr: *const (),
+    buf: *mut u8,
+    offset: *const u8,
+    len: usize,
+) -> Bytes {
     // If  the buffer is still tracked in a `Vec<u8>`. It is time to
     // promote the vec to an `Arc`. This could potentially be called
     // concurrently, so some care must be taken.
 
-    debug_assert_eq!(ptr as usize & KIND_MASK, KIND_VEC);
-
     // First, allocate a new `Shared` instance containing the
     // `Vec` fields. It's important to note that `ptr`, `len`,
     // and `cap` cannot be mutated without having `&mut self`.
@@ -838,7 +1006,7 @@ unsafe fn shallow_clone_vec(atom: &AtomicPtr<()>, ptr: *const (), offset: *const
     // 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_vec(ptr as *const (), offset, len);
+    let vec = rebuild_boxed_slice(buf, offset, len).into_vec();
     let shared = Box::new(Shared {
         _vec: vec,
         // Initialize refcount to 2. One for this reference, and one
@@ -851,39 +1019,44 @@ unsafe fn shallow_clone_vec(atom: &AtomicPtr<()>, ptr: *const (), offset: *const
 
     // The pointer should be aligned, so this assert should
     // always succeed.
-    debug_assert!(0 == (shared as usize & KIND_MASK));
+    debug_assert!(
+        0 == (shared as usize & KIND_MASK),
+        "internal: Box<Shared> should have an aligned pointer",
+    );
 
     // Try compare & swapping the pointer into the `arc` field.
     // `Release` is used synchronize with other threads that
     // will load the `arc` field.
     //
-    // If the `compare_and_swap` fails, then the thread lost the
+    // If the `compare_exchange` fails, then the thread lost the
     // race to promote the buffer to shared. The `Acquire`
-    // ordering will synchronize with the `compare_and_swap`
+    // ordering will synchronize with the `compare_exchange`
     // that happened in the other thread and the `Shared`
     // pointed to by `actual` will be visible.
-    let actual = atom.compare_and_swap(ptr as _, shared as _, Ordering::AcqRel);
+    match atom.compare_exchange(ptr as _, shared as _, Ordering::AcqRel, Ordering::Acquire) {
+        Ok(actual) => {
+            debug_assert!(actual as usize == ptr as usize);
+            // The upgrade was successful, the new handle can be
+            // returned.
+            Bytes {
+                ptr: offset,
+                len,
+                data: AtomicPtr::new(shared as _),
+                vtable: &SHARED_VTABLE,
+            }
+        }
+        Err(actual) => {
+            // The upgrade failed, a concurrent clone happened. Release
+            // the allocation that was made in this thread, it will not
+            // be needed.
+            let shared = Box::from_raw(shared);
+            mem::forget(*shared);
 
-    if actual as usize == ptr as usize {
-        // The upgrade was successful, the new handle can be
-        // returned.
-        return Bytes {
-            ptr: offset,
-            len,
-            data: AtomicPtr::new(shared as _),
-            vtable: &SHARED_VTABLE,
-        };
+            // Buffer already promoted to shared storage, so increment ref
+            // count.
+            shallow_clone_arc(actual as _, offset, len)
+        }
     }
-
-    // The upgrade failed, a concurrent clone happened. Release
-    // the allocation that was made in this thread, it will not
-    // be needed.
-    let shared = Box::from_raw(shared);
-    mem::forget(*shared);
-
-    // Buffer already promoted to shared storage, so increment ref
-    // count.
-    shallow_clone_arc(actual as _, offset, len)
 }
 
 unsafe fn release_shared(ptr: *mut Shared) {
@@ -915,10 +1088,32 @@ unsafe fn release_shared(ptr: *mut Shared) {
     Box::from_raw(ptr);
 }
 
+// compile-fails
+
+/// ```compile_fail
+/// use bytes::Bytes;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = Bytes::from("hello world");
+///     b1.split_to(6);
+/// }
+/// ```
+fn _split_to_must_use() {}
+
+/// ```compile_fail
+/// use bytes::Bytes;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = Bytes::from("hello world");
+///     b1.split_off(6);
+/// }
+/// ```
+fn _split_off_must_use() {}
+
 // fuzz tests
 #[cfg(all(test, loom))]
 mod fuzz {
-    use std::sync::Arc;
+    use loom::sync::Arc;
     use loom::thread;
 
     use super::Bytes;

src/bytes_mut.rs

@@ -1,23 +1,33 @@
-use core::{cmp, fmt, hash, isize, slice, usize};
+use core::iter::{FromIterator, Iterator};
 use core::mem::{self, ManuallyDrop};
 use core::ops::{Deref, DerefMut};
 use core::ptr::{self, NonNull};
-use core::iter::{FromIterator, Iterator};
+use core::{cmp, fmt, hash, isize, slice, usize};
 
-use alloc::{vec::Vec, string::String, boxed::Box, borrow::{Borrow, BorrowMut}};
+use alloc::{
+    borrow::{Borrow, BorrowMut},
+    boxed::Box,
+    string::String,
+    vec::Vec,
+};
 
-use crate::{Bytes, Buf, BufMut};
+use crate::buf::{IntoIter, UninitSlice};
 use crate::bytes::Vtable;
-use crate::buf::IntoIter;
-use crate::debug;
+#[allow(unused)]
+use crate::loom::sync::atomic::AtomicMut;
 use crate::loom::sync::atomic::{self, AtomicPtr, AtomicUsize, Ordering};
+use crate::{Buf, BufMut, Bytes};
 
 /// A unique reference to a contiguous slice of memory.
 ///
 /// `BytesMut` represents a unique view into a potentially shared memory region.
 /// Given the uniqueness guarantee, owners of `BytesMut` handles are able to
-/// mutate the memory. It is similar to a `Vec<u8>` but with less copies and
-/// allocations.
+/// mutate the memory.
+///
+/// `BytesMut` can be thought of as containing a `buf: Arc<Vec<u8>>`, an offset
+/// into `buf`, a slice length, and a guarantee that no other `BytesMut` for the
+/// same `buf` overlaps with its slice. That guarantee means that a write lock
+/// is not required.
 ///
 /// # Growth
 ///
@@ -108,8 +118,7 @@ impl BytesMut {
     /// Creates a new `BytesMut` with the specified capacity.
     ///
     /// The returned `BytesMut` will be able to hold at least `capacity` bytes
-    /// without reallocating. If `capacity` is under `4 * size_of::<usize>() - 1`,
-    /// then `BytesMut` will not allocate.
+    /// without reallocating.
     ///
     /// It is important to note that this function does not specify the length
     /// of the returned `BytesMut`, but only the capacity.
@@ -234,7 +243,9 @@ impl BytesMut {
                 let (off, _) = self.get_vec_pos();
                 let vec = rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off);
                 mem::forget(self);
-                vec.into()
+                let mut b: Bytes = vec.into();
+                b.advance(off);
+                b
             }
         } else {
             debug_assert_eq!(self.kind(), KIND_ARC);
@@ -243,9 +254,7 @@ impl BytesMut {
             let len = self.len;
             let data = AtomicPtr::new(self.data as _);
             mem::forget(self);
-            unsafe {
-                Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE)
-            }
+            unsafe { Bytes::with_vtable(ptr, len, data, &SHARED_VTABLE) }
         }
     }
 
@@ -275,8 +284,14 @@ impl BytesMut {
     /// # Panics
     ///
     /// Panics if `at > capacity`.
+    #[must_use = "consider BytesMut::truncate if you don't need the other half"]
     pub fn split_off(&mut self, at: usize) -> BytesMut {
-        assert!(at <= self.capacity());
+        assert!(
+            at <= self.capacity(),
+            "split_off out of bounds: {:?} <= {:?}",
+            at,
+            self.capacity(),
+        );
         unsafe {
             let mut other = self.shallow_clone();
             other.set_start(at);
@@ -310,6 +325,7 @@ impl BytesMut {
     ///
     /// assert_eq!(other, b"hello world"[..]);
     /// ```
+    #[must_use = "consider BytesMut::advance(len()) if you don't need the other half"]
     pub fn split(&mut self) -> BytesMut {
         let len = self.len();
         self.split_to(len)
@@ -341,8 +357,14 @@ impl BytesMut {
     /// # Panics
     ///
     /// Panics if `at > len`.
+    #[must_use = "consider BytesMut::advance if you don't need the other half"]
     pub fn split_to(&mut self, at: usize) -> BytesMut {
-        assert!(at <= self.len());
+        assert!(
+            at <= self.len(),
+            "split_to out of bounds: {:?} <= {:?}",
+            at,
+            self.len(),
+        );
 
         unsafe {
             let mut other = self.shallow_clone();
@@ -358,6 +380,8 @@ 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.
     ///
@@ -374,11 +398,13 @@ impl BytesMut {
     /// [`split_off`]: #method.split_off
     pub fn truncate(&mut self, len: usize) {
         if len <= self.len() {
-            unsafe { self.set_len(len); }
+            unsafe {
+                self.set_len(len);
+            }
         }
     }
 
-    /// Clears the buffer, removing all data.
+    /// Clears the buffer, removing all data. Existing capacity is preserved.
     ///
     /// # Examples
     ///
@@ -421,7 +447,7 @@ impl BytesMut {
             let additional = new_len - len;
             self.reserve(additional);
             unsafe {
-                let dst = self.bytes_mut().as_mut_ptr();
+                let dst = self.chunk_mut().as_mut_ptr();
                 ptr::write_bytes(dst, value, additional);
                 self.set_len(new_len);
             }
@@ -455,8 +481,9 @@ impl BytesMut {
     ///
     /// assert_eq!(&b[..], b"hello world");
     /// ```
+    #[inline]
     pub unsafe fn set_len(&mut self, len: usize) {
-        debug_assert!(len <= self.cap);
+        debug_assert!(len <= self.cap, "set_len out of bounds");
         self.len = len;
     }
 
@@ -538,9 +565,8 @@ impl BytesMut {
             unsafe {
                 let (off, prev) = self.get_vec_pos();
 
-                // Only reuse space if we stand to gain at least capacity/2
-                // bytes of space back
-                if off >= additional && off >= (self.cap / 2) {
+                // Only reuse space if we can satisfy the requested additional space.
+                if self.capacity() - self.len() + off >= additional {
                     // There's space - reuse it
                     //
                     // Just move the pointer back to the start after copying
@@ -555,7 +581,8 @@ impl BytesMut {
                     self.cap += off;
                 } else {
                     // No space - allocate more
-                    let mut v = ManuallyDrop::new(rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off));
+                    let mut v =
+                        ManuallyDrop::new(rebuild_vec(self.ptr.as_ptr(), self.len, self.cap, off));
                     v.reserve(additional);
 
                     // Update the info
@@ -571,7 +598,6 @@ impl BytesMut {
         debug_assert_eq!(kind, KIND_ARC);
         let shared: *mut Shared = self.data as _;
 
-
         // Reserving involves abandoning the currently shared buffer and
         // allocating a new vector with the requested capacity.
         //
@@ -615,9 +641,7 @@ impl BytesMut {
                 // check.
                 let double = v.capacity().checked_shl(1).unwrap_or(new_cap);
 
-                new_cap = cmp::max(
-                    cmp::max(double, new_cap),
-                    original_capacity);
+                new_cap = cmp::max(cmp::max(double, new_cap), original_capacity);
             } else {
                 new_cap = cmp::max(new_cap, original_capacity);
             }
@@ -640,10 +664,11 @@ impl BytesMut {
         self.len = v.len();
         self.cap = v.capacity();
     }
-    /// Appends given bytes to this object.
+
+    /// Appends given bytes to this `BytesMut`.
     ///
-    /// If this `BytesMut` object has not enough capacity, it is resized first.
-    /// So unlike `put_slice` operation, `extend_from_slice` does not panic.
+    /// If this `BytesMut` object does not have enough capacity, it is resized
+    /// first.
     ///
     /// # Examples
     ///
@@ -657,13 +682,29 @@ impl BytesMut {
     /// assert_eq!(b"aaabbbcccddd", &buf[..]);
     /// ```
     pub fn extend_from_slice(&mut self, extend: &[u8]) {
-        self.reserve(extend.len());
-        self.put_slice(extend);
+        let cnt = extend.len();
+        self.reserve(cnt);
+
+        unsafe {
+            let dst = self.uninit_slice();
+            // Reserved above
+            debug_assert!(dst.len() >= cnt);
+
+            ptr::copy_nonoverlapping(extend.as_ptr(), dst.as_mut_ptr() as *mut u8, cnt);
+        }
+
+        unsafe {
+            self.advance_mut(cnt);
+        }
     }
 
-    /// Combine splitted BytesMut objects back as contiguous.
+    /// Absorbs a `BytesMut` that was previously split off.
     ///
-    /// If `BytesMut` objects were not contiguous originally, they will be extended.
+    /// 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
+    /// `self.extend_from_slice(other.as_ref())`.
     ///
     /// # Examples
     ///
@@ -673,11 +714,11 @@ impl BytesMut {
     /// let mut buf = BytesMut::with_capacity(64);
     /// buf.extend_from_slice(b"aaabbbcccddd");
     ///
-    /// let splitted = buf.split_off(6);
+    /// let split = buf.split_off(6);
     /// assert_eq!(b"aaabbb", &buf[..]);
-    /// assert_eq!(b"cccddd", &splitted[..]);
+    /// assert_eq!(b"cccddd", &split[..]);
     ///
-    /// buf.unsplit(splitted);
+    /// buf.unsplit(split);
     /// assert_eq!(b"aaabbbcccddd", &buf[..]);
     /// ```
     pub fn unsplit(&mut self, other: BytesMut) {
@@ -719,16 +760,12 @@ impl BytesMut {
 
     #[inline]
     fn as_slice(&self) -> &[u8] {
-        unsafe {
-            slice::from_raw_parts(self.ptr.as_ptr(), self.len)
-        }
+        unsafe { slice::from_raw_parts(self.ptr.as_ptr(), self.len) }
     }
 
     #[inline]
     fn as_slice_mut(&mut self) -> &mut [u8] {
-        unsafe {
-            slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len)
-        }
+        unsafe { slice::from_raw_parts_mut(self.ptr.as_ptr(), self.len) }
     }
 
     unsafe fn set_start(&mut self, start: usize) {
@@ -738,7 +775,7 @@ impl BytesMut {
             return;
         }
 
-        debug_assert!(start <= self.cap);
+        debug_assert!(start <= self.cap, "internal: set_start out of bounds");
 
         let kind = self.kind();
 
@@ -757,7 +794,7 @@ impl BytesMut {
                 // on 64 bit systems and will only happen on 32 bit systems
                 // when shifting past 134,217,727 bytes. As such, we don't
                 // worry too much about performance here.
-                self.promote_to_shared(/*ref_count = */1);
+                self.promote_to_shared(/*ref_count = */ 1);
             }
         }
 
@@ -777,22 +814,22 @@ impl BytesMut {
 
     unsafe fn set_end(&mut self, end: usize) {
         debug_assert_eq!(self.kind(), KIND_ARC);
-        assert!(end <= self.cap);
+        assert!(end <= self.cap, "set_end out of bounds");
 
         self.cap = end;
         self.len = cmp::min(self.len, end);
     }
 
     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) };
-        if ptr == other.ptr.as_ptr() &&
-           self.kind() == KIND_ARC &&
-           other.kind() == KIND_ARC &&
-           self.data == other.data
+        if ptr == other.ptr.as_ptr()
+            && self.kind() == KIND_ARC
+            && other.kind() == KIND_ARC
+            && self.data == other.data
         {
             // Contiguous blocks, just combine directly
             self.len += other.len;
@@ -853,7 +890,7 @@ impl BytesMut {
             increment_shared(self.data);
             ptr::read(self)
         } else {
-            self.promote_to_shared(/*ref_count = */2);
+            self.promote_to_shared(/*ref_count = */ 2);
             ptr::read(self)
         }
     }
@@ -873,6 +910,16 @@ impl BytesMut {
 
         self.data = ((pos << VEC_POS_OFFSET) | (prev & NOT_VEC_POS_MASK)) as *mut _;
     }
+
+    #[inline]
+    fn uninit_slice(&mut self) -> &mut UninitSlice {
+        unsafe {
+            let ptr = self.ptr.as_ptr().offset(self.len as isize);
+            let len = self.cap - self.len;
+
+            UninitSlice::from_raw_parts_mut(ptr, len)
+        }
+    }
 }
 
 impl Drop for BytesMut {
@@ -899,22 +946,29 @@ impl Buf for BytesMut {
     }
 
     #[inline]
-    fn bytes(&self) -> &[u8] {
+    fn chunk(&self) -> &[u8] {
         self.as_slice()
     }
 
     #[inline]
     fn advance(&mut self, cnt: usize) {
-        assert!(cnt <= self.remaining(), "cannot advance past `remaining`");
-        unsafe { self.set_start(cnt); }
+        assert!(
+            cnt <= self.remaining(),
+            "cannot advance past `remaining`: {:?} <= {:?}",
+            cnt,
+            self.remaining(),
+        );
+        unsafe {
+            self.set_start(cnt);
+        }
     }
 
-    fn to_bytes(&mut self) -> crate::Bytes {
-        self.split().freeze()
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
+        self.split_to(len).freeze()
     }
 }
 
-impl BufMut for BytesMut {
+unsafe impl BufMut for BytesMut {
     #[inline]
     fn remaining_mut(&self) -> usize {
         usize::MAX - self.len()
@@ -923,21 +977,52 @@ impl BufMut for BytesMut {
     #[inline]
     unsafe fn advance_mut(&mut self, cnt: usize) {
         let new_len = self.len() + cnt;
-        assert!(new_len <= self.cap, "new_len = {}; capacity = {}", new_len, self.cap);
+        assert!(
+            new_len <= self.cap,
+            "new_len = {}; capacity = {}",
+            new_len,
+            self.cap
+        );
         self.len = new_len;
     }
 
     #[inline]
-    fn bytes_mut(&mut self) -> &mut [mem::MaybeUninit<u8>] {
+    fn chunk_mut(&mut self) -> &mut UninitSlice {
         if self.capacity() == self.len() {
             self.reserve(64);
         }
+        self.uninit_slice()
+    }
 
+    // Specialize these methods so they can skip checking `remaining_mut`
+    // and `advance_mut`.
+
+    fn put<T: crate::Buf>(&mut self, mut src: T)
+    where
+        Self: Sized,
+    {
+        while src.has_remaining() {
+            let s = src.chunk();
+            let l = s.len();
+            self.extend_from_slice(s);
+            src.advance(l);
+        }
+    }
+
+    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 ptr = self.ptr.as_ptr().offset(self.len as isize);
-            let len = self.cap - self.len;
+            let dst = self.uninit_slice();
+            // Reserved above
+            debug_assert!(dst.len() >= cnt);
 
-            slice::from_raw_parts_mut(ptr as *mut mem::MaybeUninit<u8>, len)
+            ptr::write_bytes(dst.as_mut_ptr(), val, cnt);
+
+            self.advance_mut(cnt);
         }
     }
 }
@@ -959,6 +1044,7 @@ impl Deref for BytesMut {
 }
 
 impl AsMut<[u8]> for BytesMut {
+    #[inline]
     fn as_mut(&mut self) -> &mut [u8] {
         self.as_slice_mut()
     }
@@ -983,6 +1069,12 @@ impl<'a> From<&'a str> for BytesMut {
     }
 }
 
+impl From<BytesMut> for Bytes {
+    fn from(src: BytesMut) -> Bytes {
+        src.freeze()
+    }
+}
+
 impl PartialEq for BytesMut {
     fn eq(&self, other: &BytesMut) -> bool {
         self.as_slice() == other.as_slice()
@@ -1001,8 +1093,7 @@ impl Ord for BytesMut {
     }
 }
 
-impl Eq for BytesMut {
-}
+impl Eq for BytesMut {}
 
 impl Default for BytesMut {
     #[inline]
@@ -1011,14 +1102,11 @@ impl Default for BytesMut {
     }
 }
 
-impl fmt::Debug for BytesMut {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Debug::fmt(&debug::BsDebug(&self.as_slice()), fmt)
-    }
-}
-
 impl hash::Hash for BytesMut {
-    fn hash<H>(&self, state: &mut H) where H: hash::Hasher {
+    fn hash<H>(&self, state: &mut H)
+    where
+        H: hash::Hasher,
+    {
         let s: &[u8] = self.as_ref();
         s.hash(state);
     }
@@ -1078,7 +1166,10 @@ impl<'a> IntoIterator for &'a BytesMut {
 }
 
 impl Extend<u8> for BytesMut {
-    fn extend<T>(&mut self, iter: T) where T: IntoIterator<Item = u8> {
+    fn extend<T>(&mut self, iter: T)
+    where
+        T: IntoIterator<Item = u8>,
+    {
         let iter = iter.into_iter();
 
         let (lower, _) = iter.size_hint();
@@ -1095,7 +1186,10 @@ impl Extend<u8> for BytesMut {
 }
 
 impl<'a> Extend<&'a u8> for BytesMut {
-    fn extend<T>(&mut self, iter: T) where T: IntoIterator<Item = &'a u8> {
+    fn extend<T>(&mut self, iter: T)
+    where
+        T: IntoIterator<Item = &'a u8>,
+    {
         self.extend(iter.into_iter().map(|b| *b))
     }
 }
@@ -1171,9 +1265,13 @@ 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(width, MAX_ORIGINAL_CAPACITY_WIDTH - MIN_ORIGINAL_CAPACITY_WIDTH)
+    cmp::min(
+        width,
+        MAX_ORIGINAL_CAPACITY_WIDTH - MIN_ORIGINAL_CAPACITY_WIDTH,
+    )
 }
 
 fn original_capacity_from_repr(repr: usize) -> usize {
@@ -1264,7 +1362,7 @@ impl PartialEq<BytesMut> for [u8] {
 
 impl PartialOrd<BytesMut> for [u8] {
     fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
     }
 }
 
@@ -1288,7 +1386,7 @@ impl PartialEq<BytesMut> for str {
 
 impl PartialOrd<BytesMut> for str {
     fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
     }
 }
 
@@ -1336,12 +1434,13 @@ impl PartialEq<BytesMut> for String {
 
 impl PartialOrd<BytesMut> for String {
     fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self.as_bytes(), other)
     }
 }
 
 impl<'a, T: ?Sized> PartialEq<&'a T> for BytesMut
-    where BytesMut: PartialEq<T>
+where
+    BytesMut: PartialEq<T>,
 {
     fn eq(&self, other: &&'a T) -> bool {
         *self == **other
@@ -1349,7 +1448,8 @@ impl<'a, T: ?Sized> PartialEq<&'a T> for BytesMut
 }
 
 impl<'a, T: ?Sized> PartialOrd<&'a T> for BytesMut
-    where BytesMut: PartialOrd<T>
+where
+    BytesMut: PartialOrd<T>,
 {
     fn partial_cmp(&self, other: &&'a T) -> Option<cmp::Ordering> {
         self.partial_cmp(*other)
@@ -1364,7 +1464,7 @@ impl PartialEq<BytesMut> for &[u8] {
 
 impl PartialOrd<BytesMut> for &[u8] {
     fn partial_cmp(&self, other: &BytesMut) -> Option<cmp::Ordering> {
-        other.partial_cmp(self)
+        <[u8] as PartialOrd<[u8]>>::partial_cmp(self, other)
     }
 }
 
@@ -1392,6 +1492,7 @@ impl PartialEq<Bytes> for BytesMut {
     }
 }
 
+#[inline]
 fn vptr(ptr: *mut u8) -> NonNull<u8> {
     if cfg!(debug_assertions) {
         NonNull::new(ptr).expect("Vec pointer should be non-null")
@@ -1416,7 +1517,7 @@ static SHARED_VTABLE: Vtable = Vtable {
 };
 
 unsafe fn shared_v_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
-    let shared = data.load(Ordering::Acquire) as *mut Shared;
+    let shared = data.load(Ordering::Relaxed) as *mut Shared;
     increment_shared(shared);
 
     let data = AtomicPtr::new(shared as _);
@@ -1424,18 +1525,51 @@ unsafe fn shared_v_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> By
 }
 
 unsafe fn shared_v_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
-    let shared = (*data.get_mut()) as *mut Shared;
-    release_shared(shared as *mut Shared);
+    data.with_mut(|shared| {
+        release_shared(*shared as *mut Shared);
+    });
 }
 
+// compile-fails
+
+/// ```compile_fail
+/// use bytes::BytesMut;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = BytesMut::from("hello world");
+///     b1.split_to(6);
+/// }
+/// ```
+fn _split_to_must_use() {}
+
+/// ```compile_fail
+/// use bytes::BytesMut;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = BytesMut::from("hello world");
+///     b1.split_off(6);
+/// }
+/// ```
+fn _split_off_must_use() {}
+
+/// ```compile_fail
+/// use bytes::BytesMut;
+/// #[deny(unused_must_use)]
+/// {
+///     let mut b1 = BytesMut::from("hello world");
+///     b1.split();
+/// }
+/// ```
+fn _split_must_use() {}
+
 // fuzz tests
 #[cfg(all(test, loom))]
 mod fuzz {
-    use std::sync::Arc;
+    use loom::sync::Arc;
     use loom::thread;
 
-    use crate::Bytes;
     use super::BytesMut;
+    use crate::Bytes;
 
     #[test]
     fn bytes_mut_cloning_frozen() {

src/debug.rs

@@ -1,40 +0,0 @@
-use core::fmt;
-
-/// Alternative implementation of `fmt::Debug` for byte slice.
-///
-/// Standard `Debug` implementation for `[u8]` is comma separated
-/// list of numbers. Since large amount of byte strings are in fact
-/// ASCII strings or contain a lot of ASCII strings (e. g. HTTP),
-/// it is convenient to print strings as ASCII when possible.
-///
-/// This struct wraps `&[u8]` just to override `fmt::Debug`.
-///
-/// `BsDebug` is not a part of public API of bytes crate.
-pub struct BsDebug<'a>(pub &'a [u8]);
-
-impl fmt::Debug for BsDebug<'_> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        write!(fmt, "b\"")?;
-        for &c in self.0 {
-            // https://doc.rust-lang.org/reference.html#byte-escapes
-            if c == b'\n' {
-                write!(fmt, "\\n")?;
-            } else if c == b'\r' {
-                write!(fmt, "\\r")?;
-            } else if c == b'\t' {
-                write!(fmt, "\\t")?;
-            } else if c == b'\\' || c == b'"' {
-                write!(fmt, "\\{}", c as char)?;
-            } else if c == b'\0' {
-                write!(fmt, "\\0")?;
-            // ASCII printable
-            } else if c >= 0x20 && c < 0x7f {
-                write!(fmt, "{}", c as char)?;
-            } else {
-                write!(fmt, "\\x{:02x}", c)?;
-            }
-        }
-        write!(fmt, "\"")?;
-        Ok(())
-    }
-}

src/fmt/debug.rs

@@ -0,0 +1,49 @@
+use core::fmt::{Debug, Formatter, Result};
+
+use super::BytesRef;
+use crate::{Bytes, BytesMut};
+
+/// Alternative implementation of `std::fmt::Debug` for byte slice.
+///
+/// Standard `Debug` implementation for `[u8]` is comma separated
+/// list of numbers. Since large amount of byte strings are in fact
+/// ASCII strings or contain a lot of ASCII strings (e. g. HTTP),
+/// it is convenient to print strings as ASCII when possible.
+impl Debug for BytesRef<'_> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        write!(f, "b\"")?;
+        for &b in self.0 {
+            // https://doc.rust-lang.org/reference/tokens.html#byte-escapes
+            if b == b'\n' {
+                write!(f, "\\n")?;
+            } else if b == b'\r' {
+                write!(f, "\\r")?;
+            } else if b == b'\t' {
+                write!(f, "\\t")?;
+            } else if b == b'\\' || b == b'"' {
+                write!(f, "\\{}", b as char)?;
+            } else if b == b'\0' {
+                write!(f, "\\0")?;
+            // ASCII printable
+            } else if b >= 0x20 && b < 0x7f {
+                write!(f, "{}", b as char)?;
+            } else {
+                write!(f, "\\x{:02x}", b)?;
+            }
+        }
+        write!(f, "\"")?;
+        Ok(())
+    }
+}
+
+impl Debug for Bytes {
+    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        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)
+    }
+}

src/fmt/hex.rs

@@ -1,20 +1,20 @@
-use crate::{Bytes, BytesMut};
 use core::fmt::{Formatter, LowerHex, Result, UpperHex};
 
-struct BytesRef<'a>(&'a [u8]);
+use super::BytesRef;
+use crate::{Bytes, BytesMut};
 
-impl<'a> LowerHex for BytesRef<'a> {
+impl LowerHex for BytesRef<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        for b in self.0 {
+        for &b in self.0 {
             write!(f, "{:02x}", b)?;
         }
         Ok(())
     }
 }
 
-impl<'a> UpperHex for BytesRef<'a> {
+impl UpperHex for BytesRef<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-        for b in self.0 {
+        for &b in self.0 {
             write!(f, "{:02X}", b)?;
         }
         Ok(())

src/fmt/mod.rs

@@ -0,0 +1,5 @@
+mod debug;
+mod hex;
+
+/// `BytesRef` is not a part of public API of bytes crate.
+struct BytesRef<'a>(&'a [u8]);

src/lib.rs

@@ -1,5 +1,8 @@
-#![deny(warnings, missing_docs, missing_debug_implementations, rust_2018_idioms)]
-#![doc(html_root_url = "https://docs.rs/bytes/0.5.2")]
+#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+#![doc(test(
+    no_crate_inject,
+    attr(deny(warnings, rust_2018_idioms), allow(dead_code, unused_variables))
+))]
 #![no_std]
 
 //! Provides abstractions for working with bytes.
@@ -72,25 +75,20 @@
 //! perform a syscall, which has the potential of failing. Operations on `Buf`
 //! and `BufMut` are infallible.
 
-
 extern crate alloc;
 
 #[cfg(feature = "std")]
 extern crate std;
 
 pub mod buf;
-pub use crate::buf::{
-    Buf,
-    BufMut,
-};
+pub use crate::buf::{Buf, BufMut};
 
-mod bytes_mut;
 mod bytes;
-mod debug;
-mod hex;
+mod bytes_mut;
+mod fmt;
 mod loom;
-pub use crate::bytes_mut::BytesMut;
 pub use crate::bytes::Bytes;
+pub use crate::bytes_mut::BytesMut;
 
 // Optional Serde support
 #[cfg(feature = "serde")]

src/loom.rs

@@ -2,8 +2,29 @@
 pub(crate) mod sync {
     pub(crate) mod atomic {
         pub(crate) use core::sync::atomic::{fence, AtomicPtr, AtomicUsize, Ordering};
+
+        pub(crate) trait AtomicMut<T> {
+            fn with_mut<F, R>(&mut self, f: F) -> R
+            where
+                F: FnOnce(&mut *mut T) -> R;
+        }
+
+        impl<T> AtomicMut<T> for AtomicPtr<T> {
+            fn with_mut<F, R>(&mut self, f: F) -> R
+            where
+                F: FnOnce(&mut *mut T) -> R,
+            {
+                f(self.get_mut())
+            }
+        }
     }
 }
 
 #[cfg(all(test, loom))]
-pub(crate) use ::loom::sync;
+pub(crate) mod sync {
+    pub(crate) mod atomic {
+        pub(crate) use loom::sync::atomic::{fence, AtomicPtr, AtomicUsize, Ordering};
+
+        pub(crate) trait AtomicMut<T> {}
+    }
+}

src/serde.rs

@@ -1,15 +1,16 @@
+use super::{Bytes, BytesMut};
 use alloc::string::String;
 use alloc::vec::Vec;
 use core::{cmp, fmt};
-use serde::{Serialize, Serializer, Deserialize, Deserializer, de};
-use super::{Bytes, BytesMut};
+use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
 
 macro_rules! serde_impl {
-    ($ty:ident, $visitor_ty:ident, $from_slice:ident, $from_vec:ident) => (
+    ($ty:ident, $visitor_ty:ident, $from_slice:ident, $from_vec:ident) => {
         impl Serialize for $ty {
             #[inline]
             fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-                where S: Serializer
+            where
+                S: Serializer,
             {
                 serializer.serialize_bytes(&self)
             }
@@ -26,7 +27,8 @@ macro_rules! serde_impl {
 
             #[inline]
             fn visit_seq<V>(self, mut seq: V) -> Result<Self::Value, V::Error>
-                where V: de::SeqAccess<'de>
+            where
+                V: de::SeqAccess<'de>,
             {
                 let len = cmp::min(seq.size_hint().unwrap_or(0), 4096);
                 let mut values: Vec<u8> = Vec::with_capacity(len);
@@ -40,28 +42,32 @@ macro_rules! serde_impl {
 
             #[inline]
             fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
-                where E: de::Error
+            where
+                E: de::Error,
             {
                 Ok($ty::$from_slice(v))
             }
 
             #[inline]
             fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
-                where E: de::Error
+            where
+                E: de::Error,
             {
                 Ok($ty::$from_vec(v))
             }
 
             #[inline]
             fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
-                where E: de::Error
+            where
+                E: de::Error,
             {
                 Ok($ty::$from_slice(v.as_bytes()))
             }
 
             #[inline]
             fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
-                where E: de::Error
+            where
+                E: de::Error,
             {
                 Ok($ty::$from_vec(v.into_bytes()))
             }
@@ -70,12 +76,13 @@ macro_rules! serde_impl {
         impl<'de> Deserialize<'de> for $ty {
             #[inline]
             fn deserialize<D>(deserializer: D) -> Result<$ty, D::Error>
-                where D: Deserializer<'de>
+            where
+                D: Deserializer<'de>,
             {
                 deserializer.deserialize_byte_buf($visitor_ty)
             }
         }
-    );
+    };
 }
 
 serde_impl!(Bytes, BytesVisitor, copy_from_slice, from);

tests/test_buf.rs

@@ -1,6 +1,7 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 use bytes::Buf;
+#[cfg(feature = "std")]
 use std::io::IoSlice;
 
 #[test]
@@ -8,17 +9,17 @@ fn test_fresh_cursor_vec() {
     let mut buf = &b"hello"[..];
 
     assert_eq!(buf.remaining(), 5);
-    assert_eq!(buf.bytes(), b"hello");
+    assert_eq!(buf.chunk(), b"hello");
 
     buf.advance(2);
 
     assert_eq!(buf.remaining(), 3);
-    assert_eq!(buf.bytes(), b"llo");
+    assert_eq!(buf.chunk(), b"llo");
 
     buf.advance(3);
 
     assert_eq!(buf.remaining(), 0);
-    assert_eq!(buf.bytes(), b"");
+    assert_eq!(buf.chunk(), b"");
 }
 
 #[test]
@@ -42,6 +43,7 @@ fn test_get_u16_buffer_underflow() {
     buf.get_u16();
 }
 
+#[cfg(feature = "std")]
 #[test]
 fn test_bufs_vec() {
     let buf = &b"hello world"[..];
@@ -51,7 +53,7 @@ fn test_bufs_vec() {
 
     let mut dst = [IoSlice::new(b1), IoSlice::new(b2)];
 
-    assert_eq!(1, buf.bytes_vectored(&mut dst[..]));
+    assert_eq!(1, buf.chunks_vectored(&mut dst[..]));
 }
 
 #[test]
@@ -61,11 +63,58 @@ fn test_vec_deque() {
     let mut buffer: VecDeque<u8> = VecDeque::new();
     buffer.extend(b"hello world");
     assert_eq!(11, buffer.remaining());
-    assert_eq!(b"hello world", buffer.bytes());
+    assert_eq!(b"hello world", buffer.chunk());
     buffer.advance(6);
-    assert_eq!(b"world", buffer.bytes());
+    assert_eq!(b"world", buffer.chunk());
     buffer.extend(b" piece");
     let mut out = [0; 11];
     buffer.copy_to_slice(&mut out);
     assert_eq!(b"world piece", &out[..]);
 }
+
+#[test]
+fn test_deref_buf_forwards() {
+    struct Special;
+
+    impl Buf for Special {
+        fn remaining(&self) -> usize {
+            unreachable!("remaining");
+        }
+
+        fn chunk(&self) -> &[u8] {
+            unreachable!("chunk");
+        }
+
+        fn advance(&mut self, _: usize) {
+            unreachable!("advance");
+        }
+
+        fn get_u8(&mut self) -> u8 {
+            // specialized!
+            b'x'
+        }
+    }
+
+    // these should all use the specialized method
+    assert_eq!(Special.get_u8(), b'x');
+    assert_eq!((&mut Special as &mut dyn Buf).get_u8(), b'x');
+    assert_eq!((Box::new(Special) as Box<dyn Buf>).get_u8(), b'x');
+    assert_eq!(Box::new(Special).get_u8(), b'x');
+}
+
+#[test]
+fn copy_to_bytes_less() {
+    let mut buf = &b"hello world"[..];
+
+    let bytes = buf.copy_to_bytes(5);
+    assert_eq!(bytes, &b"hello"[..]);
+    assert_eq!(buf, &b" world"[..])
+}
+
+#[test]
+#[should_panic]
+fn copy_to_bytes_overflow() {
+    let mut buf = &b"hello world"[..];
+
+    let _bytes = buf.copy_to_bytes(12);
+}

tests/test_buf_mut.rs

@@ -1,22 +1,23 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
-use bytes::{buf::IoSliceMut, BufMut, BytesMut};
-use std::usize;
-use std::fmt::Write;
+use bytes::buf::UninitSlice;
+use bytes::{BufMut, BytesMut};
+use core::fmt::Write;
+use core::usize;
 
 #[test]
 fn test_vec_as_mut_buf() {
     let mut buf = Vec::with_capacity(64);
 
-    assert_eq!(buf.remaining_mut(), usize::MAX);
+    assert_eq!(buf.remaining_mut(), isize::MAX as usize);
 
-    assert!(buf.bytes_mut().len() >= 64);
+    assert!(buf.chunk_mut().len() >= 64);
 
     buf.put(&b"zomg"[..]);
 
     assert_eq!(&buf, b"zomg");
 
-    assert_eq!(buf.remaining_mut(), usize::MAX - 4);
+    assert_eq!(buf.remaining_mut(), isize::MAX as usize - 4);
     assert_eq!(buf.capacity(), 64);
 
     for _ in 0..16 {
@@ -26,6 +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);
@@ -45,13 +54,40 @@ fn test_put_u16() {
 }
 
 #[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() {
-    // Regression test for carllerche/bytes#108.
+    // Verify fix for #354
     let mut buf = Vec::with_capacity(8);
     unsafe {
         buf.advance_mut(12);
-        assert_eq!(buf.len(), 12);
-        assert!(buf.capacity() >= 12, "capacity: {}", buf.capacity());
     }
 }
 
@@ -65,25 +101,78 @@ fn test_clone() {
     assert!(buf != buf2);
 }
 
-#[test]
-fn test_bufs_vec_mut() {
-    let b1: &mut [u8] = &mut [];
-    let b2: &mut [u8] = &mut [];
-    let mut dst = [IoSliceMut::from(b1), IoSliceMut::from(b2)];
-
-    // with no capacity
-    let mut buf = BytesMut::new();
-    assert_eq!(buf.capacity(), 0);
-    assert_eq!(1, buf.bytes_vectored_mut(&mut dst[..]));
-
-    // with capacity
-    let mut buf = BytesMut::with_capacity(64);
-    assert_eq!(1, buf.bytes_vectored_mut(&mut dst[..]));
-}
-
 #[test]
 fn test_mut_slice() {
     let mut v = vec![0, 0, 0, 0];
     let mut s = &mut v[..];
     s.put_u32(42);
+
+    assert_eq!(s.len(), 0);
+    assert_eq!(&v, &[0, 0, 0, 42]);
+}
+
+#[test]
+fn test_slice_put_bytes() {
+    let mut v = [0, 0, 0, 0];
+    let mut s = &mut v[..];
+    s.put_u8(17);
+    s.put_bytes(19, 2);
+    assert_eq!(1, s.remaining_mut());
+    assert_eq!(&[17, 19, 19, 0], &v[..]);
+}
+
+#[test]
+fn test_deref_bufmut_forwards() {
+    struct Special;
+
+    unsafe impl BufMut for Special {
+        fn remaining_mut(&self) -> usize {
+            unreachable!("remaining_mut");
+        }
+
+        fn chunk_mut(&mut self) -> &mut UninitSlice {
+            unreachable!("chunk_mut");
+        }
+
+        unsafe fn advance_mut(&mut self, _: usize) {
+            unreachable!("advance");
+        }
+
+        fn put_u8(&mut self, _: u8) {
+            // specialized!
+        }
+    }
+
+    // these should all use the specialized method
+    Special.put_u8(b'x');
+    (&mut Special as &mut dyn BufMut).put_u8(b'x');
+    (Box::new(Special) as Box<dyn BufMut>).put_u8(b'x');
+    Box::new(Special).put_u8(b'x');
+}
+
+#[test]
+#[should_panic]
+fn write_byte_panics_if_out_of_bounds() {
+    let mut data = [b'b', b'a', b'r'];
+
+    let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    slice.write_byte(4, b'f');
+}
+
+#[test]
+#[should_panic]
+fn copy_from_slice_panics_if_different_length_1() {
+    let mut data = [b'b', b'a', b'r'];
+
+    let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    slice.copy_from_slice(b"a");
+}
+
+#[test]
+#[should_panic]
+fn copy_from_slice_panics_if_different_length_2() {
+    let mut data = [b'b', b'a', b'r'];
+
+    let slice = unsafe { UninitSlice::from_raw_parts_mut(data.as_mut_ptr(), 3) };
+    slice.copy_from_slice(b"abcd");
 }

tests/test_bytes.rs

@@ -1,6 +1,6 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
-use bytes::{Bytes, BytesMut, Buf, BufMut};
+use bytes::{Buf, BufMut, Bytes, BytesMut};
 
 use std::usize;
 
@@ -44,7 +44,6 @@ fn test_layout() {
         mem::size_of::<Option<BytesMut>>(),
         "BytesMut should be same size as Option<BytesMut>",
     );
-
 }
 
 #[test]
@@ -87,13 +86,11 @@ fn fmt_write() {
     write!(a, "{}", &s[..64]).unwrap();
     assert_eq!(a, s[..64].as_bytes());
 
-
     let mut b = BytesMut::with_capacity(64);
     write!(b, "{}", &s[..32]).unwrap();
     write!(b, "{}", &s[32..64]).unwrap();
     assert_eq!(b, s[..64].as_bytes());
 
-
     let mut c = BytesMut::with_capacity(64);
     write!(c, "{}", s).unwrap();
     assert_eq!(c, s[..].as_bytes());
@@ -176,7 +173,7 @@ fn split_off() {
 #[should_panic]
 fn split_off_oob() {
     let mut hello = Bytes::from(&b"helloworld"[..]);
-    hello.split_off(44);
+    let _ = hello.split_off(44);
 }
 
 #[test]
@@ -273,14 +270,14 @@ fn split_to_2() {
 #[should_panic]
 fn split_to_oob() {
     let mut hello = Bytes::from(&b"helloworld"[..]);
-    hello.split_to(33);
+    let _ = hello.split_to(33);
 }
 
 #[test]
 #[should_panic]
 fn split_to_oob_mut() {
     let mut hello = BytesMut::from(&b"helloworld"[..]);
-    hello.split_to(33);
+    let _ = hello.split_to(33);
 }
 
 #[test]
@@ -300,16 +297,30 @@ fn split_off_to_at_gt_len() {
 
     use std::panic;
 
-    make_bytes().split_to(4);
-    make_bytes().split_off(4);
+    let _ = make_bytes().split_to(4);
+    let _ = make_bytes().split_off(4);
 
     assert!(panic::catch_unwind(move || {
-        make_bytes().split_to(5);
-    }).is_err());
+        let _ = make_bytes().split_to(5);
+    })
+    .is_err());
 
     assert!(panic::catch_unwind(move || {
-        make_bytes().split_off(5);
-    }).is_err());
+        let _ = make_bytes().split_off(5);
+    })
+    .is_err());
+}
+
+#[test]
+fn truncate() {
+    let s = &b"helloworld"[..];
+    let mut hello = Bytes::from(s);
+    hello.truncate(15);
+    assert_eq!(hello, s);
+    hello.truncate(10);
+    assert_eq!(hello, s);
+    hello.truncate(5);
+    assert_eq!(hello, "hello");
 }
 
 #[test]
@@ -330,6 +341,72 @@ fn freeze_clone_unique() {
     assert_eq!(c, s);
 }
 
+#[test]
+fn freeze_after_advance() {
+    let s = &b"abcdefgh"[..];
+    let mut b = BytesMut::from(s);
+    b.advance(1);
+    assert_eq!(b, s[1..]);
+    let b = b.freeze();
+    // Verify fix for #352. Previously, freeze would ignore the start offset
+    // for BytesMuts in Vec mode.
+    assert_eq!(b, s[1..]);
+}
+
+#[test]
+fn freeze_after_advance_arc() {
+    let s = &b"abcdefgh"[..];
+    let mut b = BytesMut::from(s);
+    // Make b Arc
+    let _ = b.split_to(0);
+    b.advance(1);
+    assert_eq!(b, s[1..]);
+    let b = b.freeze();
+    assert_eq!(b, s[1..]);
+}
+
+#[test]
+fn freeze_after_split_to() {
+    let s = &b"abcdefgh"[..];
+    let mut b = BytesMut::from(s);
+    let _ = b.split_to(1);
+    assert_eq!(b, s[1..]);
+    let b = b.freeze();
+    assert_eq!(b, s[1..]);
+}
+
+#[test]
+fn freeze_after_truncate() {
+    let s = &b"abcdefgh"[..];
+    let mut b = BytesMut::from(s);
+    b.truncate(7);
+    assert_eq!(b, s[..7]);
+    let b = b.freeze();
+    assert_eq!(b, s[..7]);
+}
+
+#[test]
+fn freeze_after_truncate_arc() {
+    let s = &b"abcdefgh"[..];
+    let mut b = BytesMut::from(s);
+    // Make b Arc
+    let _ = b.split_to(0);
+    b.truncate(7);
+    assert_eq!(b, s[..7]);
+    let b = b.freeze();
+    assert_eq!(b, s[..7]);
+}
+
+#[test]
+fn freeze_after_split_off() {
+    let s = &b"abcdefgh"[..];
+    let mut b = BytesMut::from(s);
+    let _ = b.split_off(7);
+    assert_eq!(b, s[..7]);
+    let b = b.freeze();
+    assert_eq!(b, s[..7]);
+}
+
 #[test]
 fn fns_defined_for_bytes_mut() {
     let mut bytes = BytesMut::from(&b"hello world"[..]);
@@ -384,6 +461,7 @@ fn reserve_allocates_at_least_original_capacity() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore)] // Miri is too slow
 fn reserve_max_original_capacity_value() {
     const SIZE: usize = 128 * 1024;
 
@@ -416,7 +494,7 @@ fn reserve_vec_recycling() {
 #[test]
 fn reserve_in_arc_unique_does_not_overallocate() {
     let mut bytes = BytesMut::with_capacity(1000);
-    bytes.split();
+    let _ = bytes.split();
 
     // now bytes is Arc and refcount == 1
 
@@ -428,7 +506,7 @@ fn reserve_in_arc_unique_does_not_overallocate() {
 #[test]
 fn reserve_in_arc_unique_doubles() {
     let mut bytes = BytesMut::with_capacity(1000);
-    bytes.split();
+    let _ = bytes.split();
 
     // now bytes is Arc and refcount == 1
 
@@ -531,15 +609,15 @@ fn advance_past_len() {
 
 #[test]
 // Only run these tests on little endian systems. CI uses qemu for testing
-// little endian... and qemu doesn't really support threading all that well.
-#[cfg(target_endian = "little")]
+// big endian... and qemu doesn't really support threading all that well.
+#[cfg(any(miri, target_endian = "little"))]
 fn stress() {
     // Tests promoting a buffer from a vec -> shared in a concurrent situation
     use std::sync::{Arc, Barrier};
     use std::thread;
 
     const THREADS: usize = 8;
-    const ITERS: usize = 1_000;
+    const ITERS: usize = if cfg!(miri) { 100 } else { 1_000 };
 
     for i in 0..ITERS {
         let data = [i as u8; 256];
@@ -706,17 +784,42 @@ 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);
     buf.extend_from_slice(b"aaaabbbbeeee");
 
-    buf.split_off(8); //arc
+    let _ = buf.split_off(8); //arc
 
     let mut buf2 = BytesMut::with_capacity(64);
     buf2.extend_from_slice(b"ccccddddeeee");
 
-    buf2.split_off(8); //arc
+    let _ = buf2.split_off(8); //arc
 
     buf.unsplit(buf2);
     assert_eq!(b"aaaabbbbccccdddd", &buf[..]);
@@ -786,7 +889,6 @@ fn slice_ref_works() {
     test_slice_ref(&bytes, 9, 9, b"");
 }
 
-
 #[test]
 fn slice_ref_empty() {
     let bytes = Bytes::from(&b""[..]);
@@ -796,6 +898,16 @@ fn slice_ref_empty() {
     assert_eq!(&sub[..], b"");
 }
 
+#[test]
+fn slice_ref_empty_subslice() {
+    let bytes = Bytes::from(&b"abcde"[..]);
+    let subbytes = bytes.slice(0..0);
+    let slice = &subbytes[..];
+    // The `slice` object is derived from the original `bytes` object
+    // so `slice_ref` should work.
+    assert_eq!(Bytes::new(), bytes.slice_ref(slice));
+}
+
 #[test]
 #[should_panic]
 fn slice_ref_catches_not_a_subset() {
@@ -806,21 +918,19 @@ fn slice_ref_catches_not_a_subset() {
 }
 
 #[test]
-#[should_panic]
-fn slice_ref_catches_not_an_empty_subset() {
+fn slice_ref_not_an_empty_subset() {
     let bytes = Bytes::from(&b"012345678"[..]);
     let slice = &b""[0..0];
 
-    bytes.slice_ref(slice);
+    assert_eq!(Bytes::new(), bytes.slice_ref(slice));
 }
 
 #[test]
-#[should_panic]
-fn empty_slice_ref_catches_not_an_empty_subset() {
-    let bytes = Bytes::copy_from_slice(&b""[..]);
-    let slice = &b""[0..0];
+fn empty_slice_ref_not_an_empty_subset() {
+    let bytes = Bytes::new();
+    let slice = &b"some other slice"[0..0];
 
-    bytes.slice_ref(slice);
+    assert_eq!(Bytes::new(), bytes.slice_ref(slice));
 }
 
 #[test]
@@ -828,23 +938,39 @@ fn bytes_buf_mut_advance() {
     let mut bytes = BytesMut::with_capacity(1024);
 
     unsafe {
-        let ptr = bytes.bytes_mut().as_ptr();
-        assert_eq!(1024, bytes.bytes_mut().len());
+        let ptr = bytes.chunk_mut().as_mut_ptr();
+        assert_eq!(1024, bytes.chunk_mut().len());
 
         bytes.advance_mut(10);
 
-        let next = bytes.bytes_mut().as_ptr();
-        assert_eq!(1024 - 10, bytes.bytes_mut().len());
+        let next = bytes.chunk_mut().as_mut_ptr();
+        assert_eq!(1024 - 10, bytes.chunk_mut().len());
         assert_eq!(ptr.offset(10), next);
 
         // advance to the end
         bytes.advance_mut(1024 - 10);
 
         // The buffer size is doubled
-        assert_eq!(1024, bytes.bytes_mut().len());
+        assert_eq!(1024, bytes.chunk_mut().len());
     }
 }
 
+#[test]
+fn bytes_buf_mut_reuse_when_fully_consumed() {
+    use bytes::{Buf, BytesMut};
+    let mut buf = BytesMut::new();
+    buf.reserve(8192);
+    buf.extend_from_slice(&[0u8; 100][..]);
+
+    let p = &buf[0] as *const u8;
+    buf.advance(100);
+
+    buf.reserve(8192);
+    buf.extend_from_slice(b" ");
+
+    assert_eq!(&buf[0] as *const u8, p);
+}
+
 #[test]
 #[should_panic]
 fn bytes_reserve_overflow() {
@@ -853,3 +979,26 @@ fn bytes_reserve_overflow() {
 
     bytes.reserve(usize::MAX);
 }
+
+#[test]
+fn bytes_with_capacity_but_empty() {
+    // See https://github.com/tokio-rs/bytes/issues/340
+    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());
+}

tests/test_bytes_odd_alloc.rs

@@ -0,0 +1,69 @@
+//! Test using `Bytes` with an allocator that hands out "odd" pointers for
+//! vectors (pointers where the LSB is set).
+
+#![cfg(not(miri))] // Miri does not support custom allocators (also, Miri is "odd" by default with 50% chance)
+
+use std::alloc::{GlobalAlloc, Layout, System};
+use std::ptr;
+
+use bytes::Bytes;
+
+#[global_allocator]
+static ODD: Odd = Odd;
+
+struct Odd;
+
+unsafe impl GlobalAlloc for Odd {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if layout.align() == 1 && layout.size() > 0 {
+            // Allocate slightly bigger so that we can offset the pointer by 1
+            let size = layout.size() + 1;
+            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() {
+                let ptr = ptr.offset(1);
+                ptr
+            } else {
+                ptr
+            }
+        } else {
+            System.alloc(layout)
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        if layout.align() == 1 && layout.size() > 0 {
+            let size = layout.size() + 1;
+            let new_layout = match Layout::from_size_align(size, 1) {
+                Ok(layout) => layout,
+                Err(_err) => std::process::abort(),
+            };
+            System.dealloc(ptr.offset(-1), new_layout);
+        } else {
+            System.dealloc(ptr, layout);
+        }
+    }
+}
+
+#[test]
+fn sanity_check_odd_allocator() {
+    let vec = vec![33u8; 1024];
+    let p = vec.as_ptr() as usize;
+    assert!(p & 0x1 == 0x1, "{:#b}", p);
+}
+
+#[test]
+fn test_bytes_from_vec_drop() {
+    let vec = vec![33u8; 1024];
+    let _b = Bytes::from(vec);
+}
+
+#[test]
+fn test_bytes_clone_drop() {
+    let vec = vec![33u8; 1024];
+    let b1 = Bytes::from(vec);
+    let _b2 = b1.clone();
+}

tests/test_bytes_vec_alloc.rs

@@ -0,0 +1,79 @@
+use std::alloc::{GlobalAlloc, Layout, System};
+use std::{mem, ptr};
+
+use bytes::{Buf, Bytes};
+
+#[global_allocator]
+static LEDGER: Ledger = Ledger;
+
+struct Ledger;
+
+const USIZE_SIZE: usize = mem::size_of::<usize>();
+
+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
+            }
+        } 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()
+                );
+            }
+
+            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);
+        } else {
+            System.dealloc(ptr, layout);
+        }
+    }
+}
+#[test]
+fn test_bytes_advance() {
+    let mut bytes = Bytes::from(vec![10, 20, 30]);
+    bytes.advance(1);
+    drop(bytes);
+}
+
+#[test]
+fn test_bytes_truncate() {
+    let mut bytes = Bytes::from(vec![10, 20, 30]);
+    bytes.truncate(2);
+    drop(bytes);
+}
+
+#[test]
+fn test_bytes_truncate_and_advance() {
+    let mut bytes = Bytes::from(vec![10, 20, 30]);
+    bytes.truncate(2);
+    bytes.advance(1);
+    drop(bytes);
+}

tests/test_chain.rs

@@ -1,7 +1,7 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 use bytes::{Buf, BufMut, Bytes};
-use bytes::buf::{BufExt, BufMutExt};
+#[cfg(feature = "std")]
 use std::io::IoSlice;
 
 #[test]
@@ -9,7 +9,7 @@ fn collect_two_bufs() {
     let a = Bytes::from(&b"hello"[..]);
     let b = Bytes::from(&b"world"[..]);
 
-    let res = a.chain(b).to_bytes();
+    let res = a.chain(b).copy_to_bytes(10);
     assert_eq!(res, &b"helloworld"[..]);
 }
 
@@ -42,6 +42,7 @@ fn iterating_two_bufs() {
     assert_eq!(res, &b"helloworld"[..]);
 }
 
+#[cfg(feature = "std")]
 #[test]
 fn vectored_read() {
     let a = Bytes::from(&b"hello"[..]);
@@ -61,7 +62,7 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(2, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(2, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"hello"[..]);
         assert_eq!(iovecs[1][..], b"world"[..]);
         assert_eq!(iovecs[2][..], b""[..]);
@@ -82,7 +83,7 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(2, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(2, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"llo"[..]);
         assert_eq!(iovecs[1][..], b"world"[..]);
         assert_eq!(iovecs[2][..], b""[..]);
@@ -103,7 +104,7 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(1, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(1, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"world"[..]);
         assert_eq!(iovecs[1][..], b""[..]);
         assert_eq!(iovecs[2][..], b""[..]);
@@ -124,10 +125,31 @@ fn vectored_read() {
             IoSlice::new(b4),
         ];
 
-        assert_eq!(1, buf.bytes_vectored(&mut iovecs));
+        assert_eq!(1, buf.chunks_vectored(&mut iovecs));
         assert_eq!(iovecs[0][..], b"ld"[..]);
         assert_eq!(iovecs[1][..], b""[..]);
         assert_eq!(iovecs[2][..], b""[..]);
         assert_eq!(iovecs[3][..], b""[..]);
     }
 }
+
+#[test]
+fn chain_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_debug.rs

@@ -1,4 +1,4 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 use bytes::Bytes;
 

tests/test_iter.rs

@@ -1,4 +1,4 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 use bytes::Bytes;
 
@@ -11,7 +11,6 @@ fn iter_len() {
     assert_eq!(iter.len(), 11);
 }
 
-
 #[test]
 fn empty_iter_len() {
     let buf = Bytes::from_static(b"");

tests/test_reader.rs

@@ -1,14 +1,15 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "std")]
 
 use std::io::{BufRead, Read};
 
-use bytes::buf::{BufExt};
+use bytes::Buf;
 
 #[test]
 fn read() {
     let buf1 = &b"hello "[..];
     let buf2 = &b"world"[..];
-    let buf = BufExt::chain(buf1, buf2); // Disambiguate with Read::chain
+    let buf = Buf::chain(buf1, buf2); // Disambiguate with Read::chain
     let mut buffer = Vec::new();
     buf.reader().read_to_end(&mut buffer).unwrap();
     assert_eq!(b"hello world", &buffer[..]);
@@ -18,7 +19,7 @@ fn read() {
 fn buf_read() {
     let buf1 = &b"hell"[..];
     let buf2 = &b"o\nworld"[..];
-    let mut reader = BufExt::chain(buf1, buf2).reader();
+    let mut reader = Buf::chain(buf1, buf2).reader();
     let mut line = String::new();
     reader.read_line(&mut line).unwrap();
     assert_eq!("hello\n", &line);

tests/test_serde.rs

@@ -1,7 +1,7 @@
 #![cfg(feature = "serde")]
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
-use serde_test::{Token, assert_tokens};
+use serde_test::{assert_tokens, Token};
 
 #[test]
 fn test_ser_de_empty() {

tests/test_take.rs

@@ -1,6 +1,7 @@
-#![deny(warnings, rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
-use bytes::buf::{Buf, BufExt};
+use bytes::buf::Buf;
+use bytes::Bytes;
 
 #[test]
 fn long_take() {
@@ -8,5 +9,24 @@ fn long_take() {
     // overrun the buffer. Regression test for #138.
     let buf = b"hello world".take(100);
     assert_eq!(11, buf.remaining());
-    assert_eq!(b"hello world", buf.bytes());
+    assert_eq!(b"hello world", buf.chunk());
+}
+
+#[test]
+fn take_copy_to_bytes() {
+    let mut abcd = Bytes::copy_from_slice(b"abcd");
+    let abcd_ptr = abcd.as_ptr();
+    let mut take = (&mut abcd).take(2);
+    let a = take.copy_to_bytes(1);
+    assert_eq!(Bytes::copy_from_slice(b"a"), a);
+    // assert `to_bytes` did not allocate
+    assert_eq!(abcd_ptr, a.as_ptr());
+    assert_eq!(Bytes::copy_from_slice(b"bcd"), abcd);
+}
+
+#[test]
+#[should_panic]
+fn take_copy_to_bytes_panics() {
+    let abcd = Bytes::copy_from_slice(b"abcd");
+    abcd.take(2).copy_to_bytes(3);
 }