chore: prepare bytes v1.10.0 (#766)

Co-authored-by: Alice Ryhl <[email protected]>
Co-authored-by: Michal 'vorner' Vaner <[email protected]>

.github/workflows/ci.yml

@@ -63,6 +63,7 @@ jobs:
       matrix:
         os:
           - ubuntu-latest
+          - ubuntu-22.04-arm # TODO: update to 24.04 when https://github.com/rust-lang/rust/issues/135867 solved
           - macos-latest
           - windows-latest
     runs-on: ${{ matrix.os }}
@@ -89,34 +90,61 @@ jobs:
       - name: Test
         run: ci/test-stable.sh test
 
+  panic-abort:
+    name: panic=abort tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust
+        run: rustup update $nightly && rustup default $nightly
+      - name: Run tests with -Cpanic=abort
+        run: ci/panic-abort.sh
+
   # 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
+        include:
+          - target: i686-unknown-linux-gnu
+            os: ubuntu-latest
+          - target: armv7-unknown-linux-gnueabihf
+            os: ubuntu-22.04-arm # TODO: update to 24.04 when https://github.com/rust-lang/rust/issues/135867 solved
+          - target: powerpc-unknown-linux-gnu
+            os: ubuntu-latest
+          - target: powerpc64-unknown-linux-gnu
+            os: ubuntu-latest
+          - target: wasm32-wasip1
+            os: ubuntu-latest
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust
+        run: rustup update stable
+      - uses: taiki-e/setup-cross-toolchain-action@v1
+        with:
+          target: ${{ matrix.target }}
+      - name: Test
+        run: cargo test --target ${{ matrix.target }}
+
+  # Build for no_std environment.
+  no-std:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - name: Install Rust
         run: rustup update stable
-      - name: Install cross
-        uses: taiki-e/install-action@cross
-        if: matrix.target != 'wasm32-unknown-unknown'
-      - name: cross build --target ${{ matrix.target }}
-        run: 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'
+      - name: Install cargo-hack
+        uses: taiki-e/install-action@cargo-hack
+      # thumbv6m-none-eabi supports atomic, but not atomic CAS.
+      # thumbv7m-none-eabi supports atomic CAS.
+      - run: rustup target add thumbv6m-none-eabi thumbv7m-none-eabi
+      # * --optional-deps is needed for serde feature
+      # * --no-dev-deps is needed to avoid https://github.com/rust-lang/cargo/issues/4866
+      - run: cargo hack build --target thumbv7m-none-eabi --feature-powerset --skip std,default --optional-deps --no-dev-deps
+      # A sound way to provide atomic CAS on platforms without native atomic CAS is system-dependent.
+      # portable-atomic provides major ways via cfgs and accepts user-defined implementations via critical-section feature.
+      - run: cargo hack build --target thumbv6m-none-eabi --feature-powerset --skip std,default --optional-deps --no-dev-deps --features extra-platforms,extra-platforms/critical-section
 
   # Sanitizers
   tsan:

CHANGELOG.md

@@ -1,3 +1,36 @@
+# 1.10.0 (February 3rd, 2025)
+
+### Added
+
+- Add feature to support platforms without atomic CAS (#467)
+- `try_get_*` methods for `Buf` trait (#753)
+- Implement `Buf::chunks_vectored` for `Take` (#617)
+- Implement `Buf::chunks_vectored` for `VecDeque<u8>` (#708)
+
+### Fixed
+
+- Remove incorrect guarantee for `chunks_vectored` (#754)
+- Ensure that tests pass under `panic=abort` (#749)
+
+# 1.9.0 (November 27, 2024)
+
+### Added
+
+- Add `Bytes::from_owner` to enable externally-allocated memory (#742)
+
+### Documented
+
+- Fix typo in Buf::chunk() comment (#744)
+
+### Internal changes
+
+- Replace BufMut::put with BufMut::put_slice in Writer impl (#745)
+- Rename hex_impl! to fmt_impl! and reuse it for fmt::Debug (#743)
+
+# 1.8.0 (October 21, 2024)
+
+- Guarantee address in `split_off`/`split_to` for empty slices (#740)
+
 # 1.7.2 (September 17, 2024)
 
 ### Fixed
@@ -10,7 +43,7 @@
 
 ### Internal changes
 
-- Ensure BytesMut::advance reduces capacity (#728) 
+- Ensure BytesMut::advance reduces capacity (#728)
 
 # 1.7.1 (August 1, 2024)
 

Cargo.toml

@@ -4,7 +4,7 @@ name = "bytes"
 # When releasing to crates.io:
 # - Update CHANGELOG.md.
 # - Create "v1.x.y" git tag.
-version = "1.7.2"
+version = "1.10.0"
 edition = "2018"
 rust-version = "1.39"
 license = "MIT"
@@ -24,6 +24,11 @@ std = []
 
 [dependencies]
 serde = { version = "1.0.60", optional = true, default-features = false, features = ["alloc"] }
+# Use portable-atomic crate to support platforms without atomic CAS.
+# See "no_std support" section in readme for more information.
+#
+# Enable require-cas feature to provide a better error message if the end user forgets to use the cfg or feature.
+extra-platforms = { package = "portable-atomic", version = "1.3", optional = true, default-features = false, features = ["require-cas"] }
 
 [dev-dependencies]
 serde_test = "1.0"
@@ -33,3 +38,8 @@ loom = "0.7"
 
 [package.metadata.docs.rs]
 rustdoc-args = ["--cfg", "docsrs"]
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = [
+  'cfg(loom)',
+] }

README.md

@@ -27,6 +27,21 @@ Next, add this to your crate:
 use bytes::{Bytes, BytesMut, Buf, BufMut};
 ```
 
+## no_std support
+
+To use `bytes` with no_std environment, disable the (enabled by default) `std` feature.
+
+```toml
+[dependencies]
+bytes = { version = "1", default-features = false }
+```
+
+To use `bytes` with no_std environment without atomic CAS, such as thumbv6m, you also need to enable
+the `extra-platforms` feature. See the [documentation for the `portable-atomic`
+crate](https://docs.rs/portable-atomic) for more information.
+
+The MSRV when `extra-platforms` feature is enabled depends on the MSRV of `portable-atomic`.
+
 ## Serde support
 
 Serde support is optional and disabled by default. To enable use the feature `serde`.
@@ -36,6 +51,8 @@ Serde support is optional and disabled by default. To enable use the feature `se
 bytes = { version = "1", features = ["serde"] }
 ```
 
+The MSRV when `serde` feature is enabled depends on the MSRV of `serde`.
+
 ## Building documentation
 
 When building the `bytes` documentation the `docsrs` option should be used, otherwise

ci/panic-abort.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+set -ex
+RUSTFLAGS="$RUSTFLAGS -Cpanic=abort -Zpanic-abort-tests" cargo test --all-features --test '*'

ci/test-stable.sh

@@ -16,7 +16,10 @@ if [[ "${RUST_VERSION}" == "nightly"* ]]; then
     cargo check --benches
 
     # Check minimal versions
-    cargo clean
-    cargo update -Zminimal-versions
+    # Remove dev-dependencies from Cargo.toml to prevent the next `cargo update`
+    # from determining minimal versions based on dev-dependencies.
+    cargo hack --remove-dev-deps --workspace
+    # Update Cargo.lock to minimal version dependencies.
+    cargo update -Z minimal-versions
     cargo check --all-features
 fi

src/buf/buf_mut.rs

@@ -1,7 +1,7 @@
 use crate::buf::{limit, Chain, Limit, UninitSlice};
 #[cfg(feature = "std")]
 use crate::buf::{writer, Writer};
-use crate::{panic_advance, panic_does_not_fit};
+use crate::{panic_advance, panic_does_not_fit, TryGetError};
 
 use core::{mem, ptr, usize};
 
@@ -204,7 +204,10 @@ pub unsafe trait BufMut {
         Self: Sized,
     {
         if self.remaining_mut() < src.remaining() {
-            panic_advance(src.remaining(), self.remaining_mut());
+            panic_advance(&TryGetError {
+                requested: src.remaining(),
+                available: self.remaining_mut(),
+            });
         }
 
         while src.has_remaining() {
@@ -242,7 +245,10 @@ pub unsafe trait BufMut {
     #[inline]
     fn put_slice(&mut self, mut src: &[u8]) {
         if self.remaining_mut() < src.len() {
-            panic_advance(src.len(), self.remaining_mut());
+            panic_advance(&TryGetError {
+                requested: src.len(),
+                available: self.remaining_mut(),
+            });
         }
 
         while !src.is_empty() {
@@ -285,7 +291,10 @@ pub unsafe trait BufMut {
     #[inline]
     fn put_bytes(&mut self, val: u8, mut cnt: usize) {
         if self.remaining_mut() < cnt {
-            panic_advance(cnt, self.remaining_mut());
+            panic_advance(&TryGetError {
+                requested: cnt,
+                available: self.remaining_mut(),
+            })
         }
 
         while cnt > 0 {
@@ -1487,7 +1496,10 @@ unsafe impl BufMut for &mut [u8] {
     #[inline]
     unsafe fn advance_mut(&mut self, cnt: usize) {
         if self.len() < cnt {
-            panic_advance(cnt, self.len());
+            panic_advance(&TryGetError {
+                requested: cnt,
+                available: self.len(),
+            });
         }
 
         // Lifetime dance taken from `impl Write for &mut [u8]`.
@@ -1498,7 +1510,10 @@ unsafe impl BufMut for &mut [u8] {
     #[inline]
     fn put_slice(&mut self, src: &[u8]) {
         if self.len() < src.len() {
-            panic_advance(src.len(), self.len());
+            panic_advance(&TryGetError {
+                requested: src.len(),
+                available: self.len(),
+            });
         }
 
         self[..src.len()].copy_from_slice(src);
@@ -1509,7 +1524,10 @@ unsafe impl BufMut for &mut [u8] {
     #[inline]
     fn put_bytes(&mut self, val: u8, cnt: usize) {
         if self.len() < cnt {
-            panic_advance(cnt, self.len());
+            panic_advance(&TryGetError {
+                requested: cnt,
+                available: self.len(),
+            });
         }
 
         // SAFETY: We just checked that the pointer is valid for `cnt` bytes.
@@ -1534,7 +1552,10 @@ unsafe impl BufMut for &mut [core::mem::MaybeUninit<u8>] {
     #[inline]
     unsafe fn advance_mut(&mut self, cnt: usize) {
         if self.len() < cnt {
-            panic_advance(cnt, self.len());
+            panic_advance(&TryGetError {
+                requested: cnt,
+                available: self.len(),
+            });
         }
 
         // Lifetime dance taken from `impl Write for &mut [u8]`.
@@ -1545,7 +1566,10 @@ unsafe impl BufMut for &mut [core::mem::MaybeUninit<u8>] {
     #[inline]
     fn put_slice(&mut self, src: &[u8]) {
         if self.len() < src.len() {
-            panic_advance(src.len(), self.len());
+            panic_advance(&TryGetError {
+                requested: src.len(),
+                available: self.len(),
+            });
         }
 
         // SAFETY: We just checked that the pointer is valid for `src.len()` bytes.
@@ -1558,7 +1582,10 @@ unsafe impl BufMut for &mut [core::mem::MaybeUninit<u8>] {
     #[inline]
     fn put_bytes(&mut self, val: u8, cnt: usize) {
         if self.len() < cnt {
-            panic_advance(cnt, self.len());
+            panic_advance(&TryGetError {
+                requested: cnt,
+                available: self.len(),
+            });
         }
 
         // SAFETY: We just checked that the pointer is valid for `cnt` bytes.
@@ -1582,7 +1609,10 @@ unsafe impl BufMut for Vec<u8> {
         let remaining = self.capacity() - len;
 
         if remaining < cnt {
-            panic_advance(cnt, remaining);
+            panic_advance(&TryGetError {
+                requested: cnt,
+                available: remaining,
+            });
         }
 
         // Addition will not overflow since the sum is at most the capacity.

src/buf/chain.rs

@@ -1,5 +1,5 @@
 use crate::buf::{IntoIter, UninitSlice};
-use crate::{Buf, BufMut, Bytes};
+use crate::{Buf, BufMut};
 
 #[cfg(feature = "std")]
 use std::io::IoSlice;
@@ -169,7 +169,7 @@ where
         n
     }
 
-    fn copy_to_bytes(&mut self, len: usize) -> Bytes {
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
         let a_rem = self.a.remaining();
         if a_rem >= len {
             self.a.copy_to_bytes(len)

src/buf/take.rs

@@ -1,7 +1,10 @@
-use crate::{Buf, Bytes};
+use crate::Buf;
 
 use core::cmp;
 
+#[cfg(feature = "std")]
+use std::io::IoSlice;
+
 /// A `Buf` adapter which limits the bytes read from an underlying buffer.
 ///
 /// This struct is generally created by calling `take()` on `Buf`. See
@@ -145,11 +148,57 @@ impl<T: Buf> Buf for Take<T> {
         self.limit -= cnt;
     }
 
-    fn copy_to_bytes(&mut self, len: usize) -> Bytes {
+    fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
         assert!(len <= self.remaining(), "`len` greater than remaining");
 
         let r = self.inner.copy_to_bytes(len);
         self.limit -= len;
         r
     }
+
+    #[cfg(feature = "std")]
+    fn chunks_vectored<'a>(&'a self, dst: &mut [IoSlice<'a>]) -> usize {
+        if self.limit == 0 {
+            return 0;
+        }
+
+        const LEN: usize = 16;
+        let mut slices: [IoSlice<'a>; LEN] = [
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+            IoSlice::new(&[]),
+        ];
+
+        let cnt = self
+            .inner
+            .chunks_vectored(&mut slices[..dst.len().min(LEN)]);
+        let mut limit = self.limit;
+        for (i, (dst, slice)) in dst[..cnt].iter_mut().zip(slices.iter()).enumerate() {
+            if let Some(buf) = slice.get(..limit) {
+                // SAFETY: We could do this safely with `IoSlice::advance` if we had a larger MSRV.
+                let buf = unsafe { std::mem::transmute::<&[u8], &'a [u8]>(buf) };
+                *dst = IoSlice::new(buf);
+                return i + 1;
+            } else {
+                // SAFETY: We could do this safely with `IoSlice::advance` if we had a larger MSRV.
+                let buf = unsafe { std::mem::transmute::<&[u8], &'a [u8]>(slice) };
+                *dst = IoSlice::new(buf);
+                limit -= slice.len();
+            }
+        }
+        cnt
+    }
 }

src/buf/vec_deque.rs

@@ -1,4 +1,6 @@
 use alloc::collections::VecDeque;
+#[cfg(feature = "std")]
+use std::io;
 
 use super::Buf;
 
@@ -16,6 +18,22 @@ impl Buf for VecDeque<u8> {
         }
     }
 
+    #[cfg(feature = "std")]
+    fn chunks_vectored<'a>(&'a self, dst: &mut [io::IoSlice<'a>]) -> usize {
+        if self.is_empty() || dst.is_empty() {
+            return 0;
+        }
+
+        let (s1, s2) = self.as_slices();
+        dst[0] = io::IoSlice::new(s1);
+        if s2.is_empty() || dst.len() == 1 {
+            return 1;
+        }
+
+        dst[1] = io::IoSlice::new(s2);
+        2
+    }
+
     fn advance(&mut self, cnt: usize) {
         self.drain(..cnt);
     }

src/buf/writer.rs

@@ -78,7 +78,7 @@ impl<B: BufMut + Sized> io::Write for Writer<B> {
     fn write(&mut self, src: &[u8]) -> io::Result<usize> {
         let n = cmp::min(self.buf.remaining_mut(), src.len());
 
-        self.buf.put(&src[0..n]);
+        self.buf.put_slice(&src[..n]);
         Ok(n)
     }
 

src/bytes.rs

@@ -1,6 +1,7 @@
 use core::iter::FromIterator;
 use core::mem::{self, ManuallyDrop};
 use core::ops::{Deref, RangeBounds};
+use core::ptr::NonNull;
 use core::{cmp, fmt, hash, ptr, slice, usize};
 
 use alloc::{
@@ -184,6 +185,110 @@ impl Bytes {
         }
     }
 
+    /// Creates a new `Bytes` with length zero and the given pointer as the address.
+    fn new_empty_with_ptr(ptr: *const u8) -> Self {
+        debug_assert!(!ptr.is_null());
+
+        // Detach this pointer's provenance from whichever allocation it came from, and reattach it
+        // to the provenance of the fake ZST [u8;0] at the same address.
+        let ptr = without_provenance(ptr as usize);
+
+        Bytes {
+            ptr,
+            len: 0,
+            data: AtomicPtr::new(ptr::null_mut()),
+            vtable: &STATIC_VTABLE,
+        }
+    }
+
+    /// Create [Bytes] with a buffer whose lifetime is controlled
+    /// via an explicit owner.
+    ///
+    /// A common use case is to zero-copy construct from mapped memory.
+    ///
+    /// ```
+    /// # struct File;
+    /// #
+    /// # impl File {
+    /// #     pub fn open(_: &str) -> Result<Self, ()> {
+    /// #         Ok(Self)
+    /// #     }
+    /// # }
+    /// #
+    /// # mod memmap2 {
+    /// #     pub struct Mmap;
+    /// #
+    /// #     impl Mmap {
+    /// #         pub unsafe fn map(_file: &super::File) -> Result<Self, ()> {
+    /// #             Ok(Self)
+    /// #         }
+    /// #     }
+    /// #
+    /// #     impl AsRef<[u8]> for Mmap {
+    /// #         fn as_ref(&self) -> &[u8] {
+    /// #             b"buf"
+    /// #         }
+    /// #     }
+    /// # }
+    /// use bytes::Bytes;
+    /// use memmap2::Mmap;
+    ///
+    /// # fn main() -> Result<(), ()> {
+    /// let file = File::open("upload_bundle.tar.gz")?;
+    /// let mmap = unsafe { Mmap::map(&file) }?;
+    /// let b = Bytes::from_owner(mmap);
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// The `owner` will be transferred to the constructed [Bytes] object, which
+    /// will ensure it is dropped once all remaining clones of the constructed
+    /// object are dropped. The owner will then be responsible for dropping the
+    /// specified region of memory as part of its [Drop] implementation.
+    ///
+    /// Note that converting [Bytes] constructed from an owner into a [BytesMut]
+    /// will always create a deep copy of the buffer into newly allocated memory.
+    pub fn from_owner<T>(owner: T) -> Self
+    where
+        T: AsRef<[u8]> + Send + 'static,
+    {
+        // Safety & Miri:
+        // The ownership of `owner` is first transferred to the `Owned` wrapper and `Bytes` object.
+        // This ensures that the owner is pinned in memory, allowing us to call `.as_ref()` safely
+        // since the lifetime of the owner is controlled by the lifetime of the new `Bytes` object,
+        // and the lifetime of the resulting borrowed `&[u8]` matches that of the owner.
+        // Note that this remains safe so long as we only call `.as_ref()` once.
+        //
+        // There are some additional special considerations here:
+        //   * We rely on Bytes's Drop impl to clean up memory should `.as_ref()` panic.
+        //   * Setting the `ptr` and `len` on the bytes object last (after moving the owner to
+        //     Bytes) allows Miri checks to pass since it avoids obtaining the `&[u8]` slice
+        //     from a stack-owned Box.
+        // More details on this: https://github.com/tokio-rs/bytes/pull/742/#discussion_r1813375863
+        //                  and: https://github.com/tokio-rs/bytes/pull/742/#discussion_r1813316032
+
+        let owned = Box::into_raw(Box::new(Owned {
+            lifetime: OwnedLifetime {
+                ref_cnt: AtomicUsize::new(1),
+                drop: owned_box_and_drop::<T>,
+            },
+            owner,
+        }));
+
+        let mut ret = Bytes {
+            ptr: NonNull::dangling().as_ptr(),
+            len: 0,
+            data: AtomicPtr::new(owned.cast()),
+            vtable: &OWNED_VTABLE,
+        };
+
+        let buf = unsafe { &*owned }.owner.as_ref();
+        ret.ptr = buf.as_ptr();
+        ret.len = buf.len();
+
+        ret
+    }
+
     /// Returns the number of bytes contained in this `Bytes`.
     ///
     /// # Examples
@@ -214,14 +319,16 @@ impl Bytes {
         self.len == 0
     }
 
-    /// Returns true if this is the only reference to the data.
+    /// Returns true if this is the only reference to the data and
+    /// `Into<BytesMut>` would avoid cloning the underlying buffer.
     ///
-    /// Always returns false if the data is backed by a static slice.
+    /// Always returns false if the data is backed by a [static slice](Bytes::from_static),
+    /// or an [owner](Bytes::from_owner).
     ///
     /// The result of this method may be invalidated immediately if another
     /// thread clones this value while this is being called. Ensure you have
     /// unique access to this value (`&mut Bytes`) first if you need to be
-    /// certain the result is valid (i.e. for safety reasons)
+    /// certain the result is valid (i.e. for safety reasons).
     /// # Examples
     ///
     /// ```
@@ -366,7 +473,9 @@ impl Bytes {
     /// Splits the bytes into two at the given index.
     ///
     /// Afterwards `self` contains elements `[0, at)`, and the returned `Bytes`
-    /// contains elements `[at, len)`.
+    /// contains elements `[at, len)`. It's guaranteed that the memory does not
+    /// move, that is, the address of `self` does not change, and the address of
+    /// the returned slice is `at` bytes after that.
     ///
     /// This is an `O(1)` operation that just increases the reference count and
     /// sets a few indices.
@@ -389,11 +498,11 @@ impl Bytes {
     #[must_use = "consider Bytes::truncate if you don't need the other half"]
     pub fn split_off(&mut self, at: usize) -> Self {
         if at == self.len() {
-            return Bytes::new();
+            return Bytes::new_empty_with_ptr(self.ptr.wrapping_add(at));
         }
 
         if at == 0 {
-            return mem::replace(self, Bytes::new());
+            return mem::replace(self, Bytes::new_empty_with_ptr(self.ptr));
         }
 
         assert!(
@@ -438,11 +547,12 @@ impl Bytes {
     #[must_use = "consider Bytes::advance if you don't need the other half"]
     pub fn split_to(&mut self, at: usize) -> Self {
         if at == self.len() {
-            return mem::replace(self, Bytes::new());
+            let end_ptr = self.ptr.wrapping_add(at);
+            return mem::replace(self, Bytes::new_empty_with_ptr(end_ptr));
         }
 
         if at == 0 {
-            return Bytes::new();
+            return Bytes::new_empty_with_ptr(self.ptr);
         }
 
         assert!(
@@ -517,6 +627,9 @@ impl Bytes {
     /// If `self` is not unique for the entire original buffer, this will fail
     /// and return self.
     ///
+    /// This will also always fail if the buffer was constructed via either
+    /// [from_owner](Bytes::from_owner) or [from_static](Bytes::from_static).
+    ///
     /// # Examples
     ///
     /// ```
@@ -993,6 +1106,83 @@ unsafe fn static_drop(_: &mut AtomicPtr<()>, _: *const u8, _: usize) {
     // nothing to drop for &'static [u8]
 }
 
+// ===== impl OwnedVtable =====
+
+#[repr(C)]
+struct OwnedLifetime {
+    ref_cnt: AtomicUsize,
+    drop: unsafe fn(*mut ()),
+}
+
+#[repr(C)]
+struct Owned<T> {
+    lifetime: OwnedLifetime,
+    owner: T,
+}
+
+unsafe fn owned_box_and_drop<T>(ptr: *mut ()) {
+    let b: Box<Owned<T>> = Box::from_raw(ptr as _);
+    drop(b);
+}
+
+unsafe fn owned_clone(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Bytes {
+    let owned = data.load(Ordering::Relaxed);
+    let ref_cnt = &(*owned.cast::<OwnedLifetime>()).ref_cnt;
+    let old_cnt = ref_cnt.fetch_add(1, Ordering::Relaxed);
+    if old_cnt > usize::MAX >> 1 {
+        crate::abort()
+    }
+
+    Bytes {
+        ptr,
+        len,
+        data: AtomicPtr::new(owned as _),
+        vtable: &OWNED_VTABLE,
+    }
+}
+
+unsafe fn owned_to_vec(_data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> Vec<u8> {
+    let slice = slice::from_raw_parts(ptr, len);
+    slice.to_vec()
+}
+
+unsafe fn owned_to_mut(data: &AtomicPtr<()>, ptr: *const u8, len: usize) -> BytesMut {
+    let bytes_mut = BytesMut::from_vec(owned_to_vec(data, ptr, len));
+    owned_drop_impl(data.load(Ordering::Relaxed));
+    bytes_mut
+}
+
+unsafe fn owned_is_unique(_data: &AtomicPtr<()>) -> bool {
+    false
+}
+
+unsafe fn owned_drop_impl(owned: *mut ()) {
+    let lifetime = owned.cast::<OwnedLifetime>();
+    let ref_cnt = &(*lifetime).ref_cnt;
+
+    let old_cnt = ref_cnt.fetch_sub(1, Ordering::Release);
+    if old_cnt != 1 {
+        return;
+    }
+    ref_cnt.load(Ordering::Acquire);
+
+    let drop_fn = &(*lifetime).drop;
+    drop_fn(owned)
+}
+
+unsafe fn owned_drop(data: &mut AtomicPtr<()>, _ptr: *const u8, _len: usize) {
+    let owned = data.load(Ordering::Relaxed);
+    owned_drop_impl(owned);
+}
+
+static OWNED_VTABLE: Vtable = Vtable {
+    clone: owned_clone,
+    to_vec: owned_to_vec,
+    to_mut: owned_to_mut,
+    is_unique: owned_is_unique,
+    drop: owned_drop,
+};
+
 // ===== impl PromotableVtable =====
 
 static PROMOTABLE_EVEN_VTABLE: Vtable = Vtable {
@@ -1426,6 +1616,10 @@ where
     new_addr as *mut u8
 }
 
+fn without_provenance(ptr: usize) -> *const u8 {
+    core::ptr::null::<u8>().wrapping_add(ptr)
+}
+
 // compile-fails
 
 /// ```compile_fail

src/bytes_mut.rs

@@ -17,7 +17,7 @@ use crate::bytes::Vtable;
 #[allow(unused)]
 use crate::loom::sync::atomic::AtomicMut;
 use crate::loom::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
-use crate::{offset_from, Buf, BufMut, Bytes};
+use crate::{offset_from, Buf, BufMut, Bytes, TryGetError};
 
 /// A unique reference to a contiguous slice of memory.
 ///
@@ -291,7 +291,9 @@ impl BytesMut {
     /// Splits the bytes into two at the given index.
     ///
     /// Afterwards `self` contains elements `[0, at)`, and the returned
-    /// `BytesMut` contains elements `[at, capacity)`.
+    /// `BytesMut` contains elements `[at, capacity)`. It's guaranteed that the
+    /// memory does not move, that is, the address of `self` does not change,
+    /// and the address of the returned slice is `at` bytes after that.
     ///
     /// This is an `O(1)` operation that just increases the reference count
     /// and sets a few indices.
@@ -1176,7 +1178,10 @@ unsafe impl BufMut for BytesMut {
     unsafe fn advance_mut(&mut self, cnt: usize) {
         let remaining = self.cap - self.len();
         if cnt > remaining {
-            super::panic_advance(cnt, remaining);
+            super::panic_advance(&TryGetError {
+                requested: cnt,
+                available: remaining,
+            });
         }
         // Addition won't overflow since it is at most `self.cap`.
         self.len = self.len() + cnt;

src/fmt/debug.rs

@@ -36,14 +36,5 @@ impl Debug for BytesRef<'_> {
     }
 }
 
-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)
-    }
-}
+fmt_impl!(Debug, Bytes);
+fmt_impl!(Debug, BytesMut);

src/fmt/hex.rs

@@ -21,17 +21,7 @@ impl UpperHex for BytesRef<'_> {
     }
 }
 
-macro_rules! hex_impl {
-    ($tr:ident, $ty:ty) => {
-        impl $tr for $ty {
-            fn fmt(&self, f: &mut Formatter<'_>) -> Result {
-                $tr::fmt(&BytesRef(self.as_ref()), f)
-            }
-        }
-    };
-}
-
-hex_impl!(LowerHex, Bytes);
-hex_impl!(LowerHex, BytesMut);
-hex_impl!(UpperHex, Bytes);
-hex_impl!(UpperHex, BytesMut);
+fmt_impl!(LowerHex, Bytes);
+fmt_impl!(LowerHex, BytesMut);
+fmt_impl!(UpperHex, Bytes);
+fmt_impl!(UpperHex, BytesMut);

src/fmt/mod.rs

@@ -1,3 +1,13 @@
+macro_rules! fmt_impl {
+    ($tr:ident, $ty:ty) => {
+        impl $tr for $ty {
+            fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+                $tr::fmt(&BytesRef(self.as_ref()), f)
+            }
+        }
+    };
+}
+
 mod debug;
 mod hex;
 

src/lib.rs

@@ -1,4 +1,3 @@
-#![allow(unknown_lints, unexpected_cfgs)]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
 #![doc(test(
     no_crate_inject,
@@ -132,12 +131,47 @@ fn min_u64_usize(a: u64, b: usize) -> usize {
     }
 }
 
+/// Error type for the `try_get_` methods of [`Buf`].
+/// Indicates that there were not enough remaining
+/// bytes in the buffer while attempting
+/// to get a value from a [`Buf`] with one
+/// of the `try_get_` methods.
+#[derive(Debug, PartialEq, Eq)]
+pub struct TryGetError {
+    /// The number of bytes necessary to get the value
+    pub requested: usize,
+
+    /// The number of bytes available in the buffer
+    pub available: usize,
+}
+
+impl core::fmt::Display for TryGetError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> Result<(), core::fmt::Error> {
+        write!(
+            f,
+            "Not enough bytes remaining in buffer to read value (requested {} but only {} available)",
+            self.requested,
+            self.available
+        )
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for TryGetError {}
+
+#[cfg(feature = "std")]
+impl From<TryGetError> for std::io::Error {
+    fn from(error: TryGetError) -> Self {
+        std::io::Error::new(std::io::ErrorKind::Other, error)
+    }
+}
+
 /// Panic with a nice error message.
 #[cold]
-fn panic_advance(idx: usize, len: usize) -> ! {
+fn panic_advance(error_info: &TryGetError) -> ! {
     panic!(
         "advance out of bounds: the len is {} but advancing by {}",
-        len, idx
+        error_info.available, error_info.requested
     );
 }
 

src/loom.rs

@@ -1,7 +1,10 @@
 #[cfg(not(all(test, loom)))]
 pub(crate) mod sync {
     pub(crate) mod atomic {
+        #[cfg(not(feature = "extra-platforms"))]
         pub(crate) use core::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+        #[cfg(feature = "extra-platforms")]
+        pub(crate) use extra_platforms::{AtomicPtr, AtomicUsize, Ordering};
 
         pub(crate) trait AtomicMut<T> {
             fn with_mut<F, R>(&mut self, f: F) -> R

tests/test_buf.rs

@@ -1,88 +1,410 @@
 #![warn(rust_2018_idioms)]
 
-use bytes::Buf;
+use ::bytes::{Buf, Bytes, BytesMut};
+use core::{cmp, mem};
+use std::collections::VecDeque;
 #[cfg(feature = "std")]
 use std::io::IoSlice;
 
-#[test]
-fn test_fresh_cursor_vec() {
-    let mut buf = &b"hello"[..];
+// A random 64-byte ascii string, with the first 8 bytes altered to
+// give valid representations of f32 and f64 (making them easier to compare)
+// and negative signed numbers when interpreting as big endian
+// (testing Sign Extension for `Buf::get_int' and `Buf::get_int_ne`).
+const INPUT: &[u8] = b"\xffFqrjrDqPhvTc45vvq33f6bJrUtyHESuTeklWKgYd64xgzxJwvAkpYYnpNJyZSRn";
 
-    assert_eq!(buf.remaining(), 5);
-    assert_eq!(buf.chunk(), b"hello");
-
-    buf.advance(2);
-
-    assert_eq!(buf.remaining(), 3);
-    assert_eq!(buf.chunk(), b"llo");
-
-    buf.advance(3);
-
-    assert_eq!(buf.remaining(), 0);
-    assert_eq!(buf.chunk(), b"");
+macro_rules! e {
+    ($big_endian_val:expr, $little_endian_val:expr) => {
+        if cfg!(target_endian = "big") {
+            $big_endian_val
+        } else {
+            $little_endian_val
+        }
+    };
 }
 
-#[test]
-fn test_get_u8() {
-    let mut buf = &b"\x21zomg"[..];
-    assert_eq!(0x21, buf.get_u8());
+macro_rules! buf_tests {
+    ($make_input:ident) => {
+        buf_tests!($make_input, true);
+    };
+    ($make_input:ident, $checks_vectored_is_complete:expr) => {
+        use super::*;
+
+        #[test]
+        fn empty_state() {
+            let buf = $make_input(&[]);
+            assert_eq!(buf.remaining(), 0);
+            assert!(!buf.has_remaining());
+            assert!(buf.chunk().is_empty());
+        }
+
+        #[test]
+        fn fresh_state() {
+            let buf = $make_input(INPUT);
+            assert_eq!(buf.remaining(), 64);
+            assert!(buf.has_remaining());
+
+            let chunk = buf.chunk();
+            assert!(chunk.len() <= 64);
+            assert!(INPUT.starts_with(chunk));
+        }
+
+        #[test]
+        fn advance() {
+            let mut buf = $make_input(INPUT);
+            buf.advance(8);
+            assert_eq!(buf.remaining(), 64 - 8);
+            assert!(buf.has_remaining());
+
+            let chunk = buf.chunk();
+            assert!(chunk.len() <= 64 - 8);
+            assert!(INPUT[8..].starts_with(chunk));
+        }
+
+        #[test]
+        fn advance_to_end() {
+            let mut buf = $make_input(INPUT);
+            buf.advance(64);
+            assert_eq!(buf.remaining(), 0);
+            assert!(!buf.has_remaining());
+
+            let chunk = buf.chunk();
+            assert!(chunk.is_empty());
+        }
+
+        #[test]
+        #[should_panic]
+        fn advance_past_end() {
+            let  mut buf = $make_input(INPUT);
+            buf.advance(65);
+        }
+
+        #[test]
+        #[cfg(feature = "std")]
+        fn chunks_vectored_empty() {
+            let  buf = $make_input(&[]);
+            let mut bufs = [IoSlice::new(&[]); 16];
+
+            let n = buf.chunks_vectored(&mut bufs);
+            assert_eq!(n, 0);
+            assert!(bufs.iter().all(|buf| buf.is_empty()));
+        }
+
+        #[test]
+        #[cfg(feature = "std")]
+        fn chunks_vectored_is_complete() {
+            let buf = $make_input(INPUT);
+            let mut bufs = [IoSlice::new(&[]); 16];
+
+            let n = buf.chunks_vectored(&mut bufs);
+            assert!(n > 0);
+            assert!(n <= 16);
+
+            let bufs_concat = bufs[..n]
+                .iter()
+                .flat_map(|b| b.iter().copied())
+                .collect::<Vec<u8>>();
+            if $checks_vectored_is_complete {
+                assert_eq!(bufs_concat, INPUT);
+            } else {
+                // If this panics then `buf` implements `chunks_vectored`.
+                // Remove the `false` argument from `buf_tests!` for that type.
+                assert!(bufs_concat.len() < INPUT.len());
+                assert!(INPUT.starts_with(&bufs_concat));
+            }
+
+            for i in n..16 {
+                assert!(bufs[i].is_empty());
+            }
+        }
+
+        #[test]
+        fn copy_to_slice() {
+            let mut buf = $make_input(INPUT);
+
+            let mut chunk = [0u8; 8];
+            buf.copy_to_slice(&mut chunk);
+            assert_eq!(buf.remaining(), 64 - 8);
+            assert!(buf.has_remaining());
+            assert_eq!(chunk, INPUT[..8]);
+
+            let chunk = buf.chunk();
+            assert!(chunk.len() <= 64 - 8);
+            assert!(INPUT[8..].starts_with(chunk));
+        }
+
+        #[test]
+        fn copy_to_slice_big() {
+            let mut buf = $make_input(INPUT);
+
+            let mut chunk = [0u8; 56];
+            buf.copy_to_slice(&mut chunk);
+            assert_eq!(buf.remaining(), 64 - 56);
+            assert!(buf.has_remaining());
+            assert_eq!(chunk, INPUT[..56]);
+
+            let chunk = buf.chunk();
+            assert!(chunk.len() <= 64 - 56);
+            assert!(INPUT[56..].starts_with(chunk));
+        }
+
+        #[test]
+        fn copy_to_slice_to_end() {
+            let mut buf = $make_input(INPUT);
+
+            let mut chunk = [0u8; 64];
+            buf.copy_to_slice(&mut chunk);
+            assert_eq!(buf.remaining(), 0);
+            assert!(!buf.has_remaining());
+            assert_eq!(chunk, INPUT);
+
+            assert!(buf.chunk().is_empty());
+        }
+
+        #[test]
+        #[should_panic]
+        fn copy_to_slice_overflow() {
+            let mut buf = $make_input(INPUT);
+
+            let mut chunk = [0u8; 65];
+            buf.copy_to_slice(&mut chunk);
+        }
+
+        #[test]
+        fn copy_to_bytes() {
+            let mut buf = $make_input(INPUT);
+
+            let chunk = buf.copy_to_bytes(8);
+            assert_eq!(buf.remaining(), 64 - 8);
+            assert!(buf.has_remaining());
+            assert_eq!(chunk, INPUT[..8]);
+
+            let chunk = buf.chunk();
+            assert!(chunk.len() <= 64 - 8);
+            assert!(INPUT[8..].starts_with(chunk));
+        }
+
+        #[test]
+        fn copy_to_bytes_big() {
+            let mut buf = $make_input(INPUT);
+
+            let chunk = buf.copy_to_bytes(56);
+            assert_eq!(buf.remaining(), 64 - 56);
+            assert!(buf.has_remaining());
+            assert_eq!(chunk, INPUT[..56]);
+
+            let chunk = buf.chunk();
+            assert!(chunk.len() <= 64 - 56);
+            assert!(INPUT[56..].starts_with(chunk));
+        }
+
+        #[test]
+        fn copy_to_bytes_to_end() {
+            let mut buf = $make_input(INPUT);
+
+            let chunk = buf.copy_to_bytes(64);
+            assert_eq!(buf.remaining(), 0);
+            assert!(!buf.has_remaining());
+            assert_eq!(chunk, INPUT);
+
+            assert!(buf.chunk().is_empty());
+        }
+
+        #[test]
+        #[should_panic]
+        fn copy_to_bytes_overflow() {
+            let mut buf = $make_input(INPUT);
+
+            let _ = buf.copy_to_bytes(65);
+        }
+
+        buf_tests!(number $make_input, get_u8, get_u8_overflow, u8, get_u8, 0xff);
+        buf_tests!(number $make_input, get_i8, get_i8_overflow, i8, get_i8, 0xffu8 as i8);
+        buf_tests!(number $make_input, get_u16_be, get_u16_be_overflow, u16, get_u16, 0xff46);
+        buf_tests!(number $make_input, get_u16_le, get_u16_le_overflow, u16, get_u16_le, 0x46ff);
+        buf_tests!(number $make_input, get_u16_ne, get_u16_ne_overflow, u16, get_u16_ne, e!(0xff46, 0x46ff));
+        buf_tests!(number $make_input, get_i16_be, get_i16_be_overflow, i16, get_i16, 0xff46u16 as i16);
+        buf_tests!(number $make_input, get_i16_le, get_i16_le_overflow, i16, get_i16_le, 0x46ff);
+        buf_tests!(number $make_input, get_i16_ne, get_i16_ne_overflow, i16, get_i16_ne, e!(0xff46u16 as i16, 0x46ff));
+        buf_tests!(number $make_input, get_u32_be, get_u32_be_overflow, u32, get_u32, 0xff467172);
+        buf_tests!(number $make_input, get_u32_le, get_u32_le_overflow, u32, get_u32_le, 0x727146ff);
+        buf_tests!(number $make_input, get_u32_ne, get_u32_ne_overflow, u32, get_u32_ne, e!(0xff467172, 0x727146ff));
+        buf_tests!(number $make_input, get_i32_be, get_i32_be_overflow, i32, get_i32, 0xff467172u32 as i32);
+        buf_tests!(number $make_input, get_i32_le, get_i32_le_overflow, i32, get_i32_le, 0x727146ff);
+        buf_tests!(number $make_input, get_i32_ne, get_i32_ne_overflow, i32, get_i32_ne, e!(0xff467172u32 as i32, 0x727146ff));
+        buf_tests!(number $make_input, get_u64_be, get_u64_be_overflow, u64, get_u64, 0xff4671726a724471);
+        buf_tests!(number $make_input, get_u64_le, get_u64_le_overflow, u64, get_u64_le, 0x7144726a727146ff);
+        buf_tests!(number $make_input, get_u64_ne, get_u64_ne_overflow, u64, get_u64_ne, e!(0xff4671726a724471, 0x7144726a727146ff));
+        buf_tests!(number $make_input, get_i64_be, get_i64_be_overflow, i64, get_i64, 0xff4671726a724471u64 as i64);
+        buf_tests!(number $make_input, get_i64_le, get_i64_le_overflow, i64, get_i64_le, 0x7144726a727146ff);
+        buf_tests!(number $make_input, get_i64_ne, get_i64_ne_overflow, i64, get_i64_ne, e!(0xff4671726a724471u64 as i64, 0x7144726a727146ff));
+        buf_tests!(number $make_input, get_u128_be, get_u128_be_overflow, u128, get_u128, 0xff4671726a7244715068765463343576);
+        buf_tests!(number $make_input, get_u128_le, get_u128_le_overflow, u128, get_u128_le, 0x76353463547668507144726a727146ff);
+        buf_tests!(number $make_input, get_u128_ne, get_u128_ne_overflow, u128, get_u128_ne, e!(0xff4671726a7244715068765463343576, 0x76353463547668507144726a727146ff));
+        buf_tests!(number $make_input, get_i128_be, get_i128_be_overflow, i128, get_i128, 0xff4671726a7244715068765463343576u128 as i128);
+        buf_tests!(number $make_input, get_i128_le, get_i128_le_overflow, i128, get_i128_le, 0x76353463547668507144726a727146ff);
+        buf_tests!(number $make_input, get_i128_ne, get_i128_ne_overflow, i128, get_i128_ne, e!(0xff4671726a7244715068765463343576u128 as i128, 0x76353463547668507144726a727146ff));
+        buf_tests!(number $make_input, get_f32_be, get_f32_be_overflow, f32, get_f32, f32::from_bits(0xff467172));
+        buf_tests!(number $make_input, get_f32_le, get_f32_le_overflow, f32, get_f32_le, f32::from_bits(0x727146ff));
+        buf_tests!(number $make_input, get_f32_ne, get_f32_ne_overflow, f32, get_f32_ne, f32::from_bits(e!(0xff467172, 0x727146ff)));
+        buf_tests!(number $make_input, get_f64_be, get_f64_be_overflow, f64, get_f64, f64::from_bits(0xff4671726a724471));
+        buf_tests!(number $make_input, get_f64_le, get_f64_le_overflow, f64, get_f64_le, f64::from_bits(0x7144726a727146ff));
+        buf_tests!(number $make_input, get_f64_ne, get_f64_ne_overflow, f64, get_f64_ne, f64::from_bits(e!(0xff4671726a724471, 0x7144726a727146ff)));
+
+        buf_tests!(var_number $make_input, get_uint_be, get_uint_be_overflow, u64, get_uint, 3, 0xff4671);
+        buf_tests!(var_number $make_input, get_uint_le, get_uint_le_overflow, u64, get_uint_le, 3, 0x7146ff);
+        buf_tests!(var_number $make_input, get_uint_ne, get_uint_ne_overflow, u64, get_uint_ne, 3, e!(0xff4671, 0x7146ff));
+        buf_tests!(var_number $make_input, get_int_be, get_int_be_overflow, i64, get_int, 3, 0xffffffffffff4671u64 as i64);
+        buf_tests!(var_number $make_input, get_int_le, get_int_le_overflow, i64, get_int_le, 3, 0x7146ff);
+        buf_tests!(var_number $make_input, get_int_ne, get_int_ne_overflow, i64, get_int_ne, 3, e!(0xffffffffffff4671u64 as i64, 0x7146ff));
+    };
+    (number $make_input:ident, $ok_name:ident, $panic_name:ident, $number:ty, $method:ident, $value:expr) => {
+        #[test]
+        fn $ok_name() {
+            let mut buf = $make_input(INPUT);
+
+            let value = buf.$method();
+            assert_eq!(buf.remaining(), 64 - mem::size_of::<$number>());
+            assert!(buf.has_remaining());
+            assert_eq!(value, $value);
+        }
+
+        #[test]
+        #[should_panic]
+        fn $panic_name() {
+            let mut buf = $make_input(&[]);
+
+            let _ = buf.$method();
+        }
+    };
+    (var_number $make_input:ident, $ok_name:ident, $panic_name:ident, $number:ty, $method:ident, $len:expr, $value:expr) => {
+        #[test]
+        fn $ok_name() {
+            let mut buf = $make_input(INPUT);
+
+            let value = buf.$method($len);
+            assert_eq!(buf.remaining(), 64 - $len);
+            assert!(buf.has_remaining());
+            assert_eq!(value, $value);
+        }
+
+        #[test]
+        #[should_panic]
+        fn $panic_name() {
+            let mut buf = $make_input(&[]);
+
+            let _ = buf.$method($len);
+        }
+    };
 }
 
-#[test]
-fn test_get_u16() {
-    let mut buf = &b"\x21\x54zomg"[..];
-    assert_eq!(0x2154, buf.get_u16());
-    let mut buf = &b"\x21\x54zomg"[..];
-    assert_eq!(0x5421, buf.get_u16_le());
+mod u8_slice {
+    fn make_input(buf: &'static [u8]) -> &'static [u8] {
+        buf
+    }
+
+    buf_tests!(make_input);
 }
 
-#[test]
-fn test_get_int() {
-    let mut buf = &b"\xd6zomg"[..];
-    assert_eq!(-42, buf.get_int(1));
-    let mut buf = &b"\xd6zomg"[..];
-    assert_eq!(-42, buf.get_int_le(1));
+mod bytes {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        Bytes::from_static(buf)
+    }
 
-    let mut buf = &b"\xfe\x1d\xc0zomg"[..];
-    assert_eq!(0xffffffffffc01dfeu64 as i64, buf.get_int_le(3));
-    let mut buf = &b"\xfe\x1d\xc0zomg"[..];
-    assert_eq!(0xfffffffffffe1dc0u64 as i64, buf.get_int(3));
+    buf_tests!(make_input);
 }
 
-#[test]
-#[should_panic]
-fn test_get_u16_buffer_underflow() {
-    let mut buf = &b"\x21"[..];
-    buf.get_u16();
+mod bytes_mut {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        BytesMut::from(buf)
+    }
+
+    buf_tests!(make_input);
+}
+
+mod vec_deque {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        let mut deque = VecDeque::new();
+
+        if !buf.is_empty() {
+            // Construct |b|some bytes|a| `VecDeque`
+            let mid = buf.len() / 2;
+            let (a, b) = buf.split_at(mid);
+
+            deque.reserve_exact(buf.len() + 1);
+
+            let extra_space = deque.capacity() - b.len() - 1;
+            deque.resize(extra_space, 0);
+
+            deque.extend(a);
+            deque.drain(..extra_space);
+            deque.extend(b);
+
+            let (a, b) = deque.as_slices();
+            assert!(
+                !a.is_empty(),
+                "could not setup test - attempt to create discontiguous VecDeque failed"
+            );
+            assert!(
+                !b.is_empty(),
+                "could not setup test - attempt to create discontiguous VecDeque failed"
+            );
+        }
+
+        deque
+    }
+
+    buf_tests!(make_input, true);
 }
 
 #[cfg(feature = "std")]
-#[test]
-fn test_bufs_vec() {
-    let buf = &b"hello world"[..];
+mod cursor {
+    use std::io::Cursor;
 
-    let b1: &[u8] = &mut [];
-    let b2: &[u8] = &mut [];
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        Cursor::new(buf)
+    }
 
-    let mut dst = [IoSlice::new(b1), IoSlice::new(b2)];
-
-    assert_eq!(1, buf.chunks_vectored(&mut dst[..]));
+    buf_tests!(make_input);
 }
 
-#[test]
-fn test_vec_deque() {
-    use std::collections::VecDeque;
+mod box_bytes {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        Box::new(Bytes::from_static(buf))
+    }
 
-    let mut buffer: VecDeque<u8> = VecDeque::new();
-    buffer.extend(b"hello world");
-    assert_eq!(11, buffer.remaining());
-    assert_eq!(b"hello world", buffer.chunk());
-    buffer.advance(6);
-    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[..]);
+    buf_tests!(make_input);
+}
+
+mod chain_u8_slice {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        let (a, b) = buf.split_at(buf.len() / 2);
+        Buf::chain(a, b)
+    }
+
+    buf_tests!(make_input);
+}
+
+mod chain_small_big_u8_slice {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        let mid = cmp::min(1, buf.len());
+        let (a, b) = buf.split_at(mid);
+        Buf::chain(a, b)
+    }
+
+    buf_tests!(make_input);
+}
+
+mod chain_limited_slices {
+    fn make_input(buf: &'static [u8]) -> impl Buf {
+        let buf3 = &buf[cmp::min(buf.len(), 3)..];
+        let a = Buf::take(buf3, 0);
+        let b = Buf::take(buf, 3);
+        let c = Buf::take(buf3, usize::MAX);
+        let d = buf;
+        Buf::take(Buf::chain(Buf::chain(a, b), Buf::chain(c, d)), buf.len())
+    }
+
+    buf_tests!(make_input, true);
 }
 
 #[allow(unused_allocation)] // This is intentional.
@@ -115,20 +437,3 @@ fn test_deref_buf_forwards() {
     assert_eq!((Box::new(Special) as Box<dyn Buf>).get_u8(), b'x');
     assert_eq!(Box::new(Special).get_u8(), b'x');
 }
-
-#[test]
-fn copy_to_bytes_less() {
-    let mut buf = &b"hello world"[..];
-
-    let bytes = buf.copy_to_bytes(5);
-    assert_eq!(bytes, &b"hello"[..]);
-    assert_eq!(buf, &b" world"[..])
-}
-
-#[test]
-#[should_panic]
-fn copy_to_bytes_overflow() {
-    let mut buf = &b"hello world"[..];
-
-    let _bytes = buf.copy_to_bytes(12);
-}

tests/test_bytes.rs

@@ -1,7 +1,10 @@
 #![warn(rust_2018_idioms)]
 
 use bytes::{Buf, BufMut, Bytes, BytesMut};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
 
+use std::panic::{self, AssertUnwindSafe};
 use std::usize;
 
 const LONG: &[u8] = b"mary had a little lamb, little lamb, little lamb";
@@ -288,6 +291,7 @@ fn split_to_uninitialized() {
 }
 
 #[test]
+#[cfg_attr(not(panic = "unwind"), ignore)]
 fn split_off_to_at_gt_len() {
     fn make_bytes() -> Bytes {
         let mut bytes = BytesMut::with_capacity(100);
@@ -724,6 +728,7 @@ fn advance_past_len() {
 // Only run these tests on little endian systems. CI uses qemu for testing
 // big endian... and qemu doesn't really support threading all that well.
 #[cfg(any(miri, target_endian = "little"))]
+#[cfg(not(target_family = "wasm"))] // wasm without experimental threads proposal doesn't support threads
 fn stress() {
     // Tests promoting a buffer from a vec -> shared in a concurrent situation
     use std::sync::{Arc, Barrier};
@@ -1399,3 +1404,233 @@ fn try_reclaim_arc() {
     buf.advance(2);
     assert_eq!(true, buf.try_reclaim(6));
 }
+
+#[test]
+fn split_off_empty_addr() {
+    let mut buf = Bytes::from(vec![0; 1024]);
+
+    let ptr_start = buf.as_ptr();
+    let ptr_end = ptr_start.wrapping_add(1024);
+
+    let empty_end = buf.split_off(1024);
+    assert_eq!(empty_end.len(), 0);
+    assert_eq!(empty_end.as_ptr(), ptr_end);
+
+    let _ = buf.split_off(0);
+    assert_eq!(buf.len(), 0);
+    assert_eq!(buf.as_ptr(), ptr_start);
+
+    // Is miri happy about the provenance?
+    let _ = &empty_end[..];
+    let _ = &buf[..];
+}
+
+#[test]
+fn split_to_empty_addr() {
+    let mut buf = Bytes::from(vec![0; 1024]);
+
+    let ptr_start = buf.as_ptr();
+    let ptr_end = ptr_start.wrapping_add(1024);
+
+    let empty_start = buf.split_to(0);
+    assert_eq!(empty_start.len(), 0);
+    assert_eq!(empty_start.as_ptr(), ptr_start);
+
+    let _ = buf.split_to(1024);
+    assert_eq!(buf.len(), 0);
+    assert_eq!(buf.as_ptr(), ptr_end);
+
+    // Is miri happy about the provenance?
+    let _ = &empty_start[..];
+    let _ = &buf[..];
+}
+
+#[test]
+fn split_off_empty_addr_mut() {
+    let mut buf = BytesMut::from([0; 1024].as_slice());
+
+    let ptr_start = buf.as_ptr();
+    let ptr_end = ptr_start.wrapping_add(1024);
+
+    let empty_end = buf.split_off(1024);
+    assert_eq!(empty_end.len(), 0);
+    assert_eq!(empty_end.as_ptr(), ptr_end);
+
+    let _ = buf.split_off(0);
+    assert_eq!(buf.len(), 0);
+    assert_eq!(buf.as_ptr(), ptr_start);
+
+    // Is miri happy about the provenance?
+    let _ = &empty_end[..];
+    let _ = &buf[..];
+}
+
+#[test]
+fn split_to_empty_addr_mut() {
+    let mut buf = BytesMut::from([0; 1024].as_slice());
+
+    let ptr_start = buf.as_ptr();
+    let ptr_end = ptr_start.wrapping_add(1024);
+
+    let empty_start = buf.split_to(0);
+    assert_eq!(empty_start.len(), 0);
+    assert_eq!(empty_start.as_ptr(), ptr_start);
+
+    let _ = buf.split_to(1024);
+    assert_eq!(buf.len(), 0);
+    assert_eq!(buf.as_ptr(), ptr_end);
+
+    // Is miri happy about the provenance?
+    let _ = &empty_start[..];
+    let _ = &buf[..];
+}
+
+#[derive(Clone)]
+struct SharedAtomicCounter(Arc<AtomicUsize>);
+
+impl SharedAtomicCounter {
+    pub fn new() -> Self {
+        SharedAtomicCounter(Arc::new(AtomicUsize::new(0)))
+    }
+
+    pub fn increment(&self) {
+        self.0.fetch_add(1, Ordering::AcqRel);
+    }
+
+    pub fn get(&self) -> usize {
+        self.0.load(Ordering::Acquire)
+    }
+}
+
+#[derive(Clone)]
+struct OwnedTester<const L: usize> {
+    buf: [u8; L],
+    drop_count: SharedAtomicCounter,
+    pub panic_as_ref: bool,
+}
+
+impl<const L: usize> OwnedTester<L> {
+    fn new(buf: [u8; L], drop_count: SharedAtomicCounter) -> Self {
+        Self {
+            buf,
+            drop_count,
+            panic_as_ref: false,
+        }
+    }
+}
+
+impl<const L: usize> AsRef<[u8]> for OwnedTester<L> {
+    fn as_ref(&self) -> &[u8] {
+        if self.panic_as_ref {
+            panic!("test-triggered panic in `AsRef<[u8]> for OwnedTester`");
+        }
+        self.buf.as_slice()
+    }
+}
+
+impl<const L: usize> Drop for OwnedTester<L> {
+    fn drop(&mut self) {
+        self.drop_count.increment();
+    }
+}
+
+#[test]
+fn owned_is_unique_always_false() {
+    let b1 = Bytes::from_owner([1, 2, 3, 4, 5, 6, 7]);
+    assert!(!b1.is_unique()); // even if ref_cnt == 1
+    let b2 = b1.clone();
+    assert!(!b1.is_unique());
+    assert!(!b2.is_unique());
+    drop(b1);
+    assert!(!b2.is_unique()); // even if ref_cnt == 1
+}
+
+#[test]
+fn owned_buf_sharing() {
+    let buf = [1, 2, 3, 4, 5, 6, 7];
+    let b1 = Bytes::from_owner(buf);
+    let b2 = b1.clone();
+    assert_eq!(&buf[..], &b1[..]);
+    assert_eq!(&buf[..], &b2[..]);
+    assert_eq!(b1.as_ptr(), b2.as_ptr());
+    assert_eq!(b1.len(), b2.len());
+    assert_eq!(b1.len(), buf.len());
+}
+
+#[test]
+fn owned_buf_slicing() {
+    let b1 = Bytes::from_owner(SHORT);
+    assert_eq!(SHORT, &b1[..]);
+    let b2 = b1.slice(1..(b1.len() - 1));
+    assert_eq!(&SHORT[1..(SHORT.len() - 1)], b2);
+    assert_eq!(unsafe { SHORT.as_ptr().add(1) }, b2.as_ptr());
+    assert_eq!(SHORT.len() - 2, b2.len());
+}
+
+#[test]
+fn owned_dropped_exactly_once() {
+    let buf: [u8; 5] = [1, 2, 3, 4, 5];
+    let drop_counter = SharedAtomicCounter::new();
+    let owner = OwnedTester::new(buf, drop_counter.clone());
+    let b1 = Bytes::from_owner(owner);
+    let b2 = b1.clone();
+    assert_eq!(drop_counter.get(), 0);
+    drop(b1);
+    assert_eq!(drop_counter.get(), 0);
+    let b3 = b2.slice(1..b2.len() - 1);
+    drop(b2);
+    assert_eq!(drop_counter.get(), 0);
+    drop(b3);
+    assert_eq!(drop_counter.get(), 1);
+}
+
+#[test]
+fn owned_to_mut() {
+    let buf: [u8; 10] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+    let drop_counter = SharedAtomicCounter::new();
+    let owner = OwnedTester::new(buf, drop_counter.clone());
+    let b1 = Bytes::from_owner(owner);
+
+    // Holding an owner will fail converting to a BytesMut,
+    // even when the bytes instance has a ref_cnt == 1.
+    let b1 = b1.try_into_mut().unwrap_err();
+
+    // That said, it's still possible, just not cheap.
+    let bm1: BytesMut = b1.into();
+    let new_buf = &bm1[..];
+    assert_eq!(new_buf, &buf[..]);
+
+    // `.into::<BytesMut>()` has correctly dropped the owner
+    assert_eq!(drop_counter.get(), 1);
+}
+
+#[test]
+fn owned_to_vec() {
+    let buf: [u8; 10] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+    let drop_counter = SharedAtomicCounter::new();
+    let owner = OwnedTester::new(buf, drop_counter.clone());
+    let b1 = Bytes::from_owner(owner);
+
+    let v1 = b1.to_vec();
+    assert_eq!(&v1[..], &buf[..]);
+    assert_eq!(&v1[..], &b1[..]);
+
+    drop(b1);
+    assert_eq!(drop_counter.get(), 1);
+}
+
+#[test]
+#[cfg_attr(not(panic = "unwind"), ignore)]
+fn owned_safe_drop_on_as_ref_panic() {
+    let buf: [u8; 10] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+    let drop_counter = SharedAtomicCounter::new();
+    let mut owner = OwnedTester::new(buf, drop_counter.clone());
+    owner.panic_as_ref = true;
+
+    let result = panic::catch_unwind(AssertUnwindSafe(|| {
+        let _ = Bytes::from_owner(owner);
+    }));
+
+    assert!(result.is_err());
+    assert_eq!(drop_counter.get(), 1);
+}

tests/test_bytes_vec_alloc.rs

@@ -1,3 +1,4 @@
+#![cfg(not(miri))]
 use std::alloc::{GlobalAlloc, Layout, System};
 use std::ptr::null_mut;
 use std::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
@@ -7,7 +8,7 @@ use bytes::{Buf, Bytes};
 #[global_allocator]
 static LEDGER: Ledger = Ledger::new();
 
-const LEDGER_LENGTH: usize = 2048;
+const LEDGER_LENGTH: usize = 1024 * 1024;
 
 struct Ledger {
     alloc_table: [(AtomicPtr<u8>, AtomicUsize); LEDGER_LENGTH],
@@ -31,9 +32,11 @@ impl Ledger {
                 .is_ok()
             {
                 entry_size.store(size, Ordering::SeqCst);
-                break;
+                return;
             }
         }
+
+        panic!("Ledger ran out of space.");
     }
 
     fn remove(&self, ptr: *mut u8) -> usize {

tests/test_take.rs

@@ -30,3 +30,55 @@ fn take_copy_to_bytes_panics() {
     let abcd = Bytes::copy_from_slice(b"abcd");
     abcd.take(2).copy_to_bytes(3);
 }
+
+#[cfg(feature = "std")]
+#[test]
+fn take_chunks_vectored() {
+    fn chain() -> impl Buf {
+        Bytes::from([1, 2, 3].to_vec()).chain(Bytes::from([4, 5, 6].to_vec()))
+    }
+
+    {
+        let mut dst = [std::io::IoSlice::new(&[]); 2];
+        let take = chain().take(0);
+        assert_eq!(take.chunks_vectored(&mut dst), 0);
+    }
+
+    {
+        let mut dst = [std::io::IoSlice::new(&[]); 2];
+        let take = chain().take(1);
+        assert_eq!(take.chunks_vectored(&mut dst), 1);
+        assert_eq!(&*dst[0], &[1]);
+    }
+
+    {
+        let mut dst = [std::io::IoSlice::new(&[]); 2];
+        let take = chain().take(3);
+        assert_eq!(take.chunks_vectored(&mut dst), 1);
+        assert_eq!(&*dst[0], &[1, 2, 3]);
+    }
+
+    {
+        let mut dst = [std::io::IoSlice::new(&[]); 2];
+        let take = chain().take(4);
+        assert_eq!(take.chunks_vectored(&mut dst), 2);
+        assert_eq!(&*dst[0], &[1, 2, 3]);
+        assert_eq!(&*dst[1], &[4]);
+    }
+
+    {
+        let mut dst = [std::io::IoSlice::new(&[]); 2];
+        let take = chain().take(6);
+        assert_eq!(take.chunks_vectored(&mut dst), 2);
+        assert_eq!(&*dst[0], &[1, 2, 3]);
+        assert_eq!(&*dst[1], &[4, 5, 6]);
+    }
+
+    {
+        let mut dst = [std::io::IoSlice::new(&[]); 2];
+        let take = chain().take(7);
+        assert_eq!(take.chunks_vectored(&mut dst), 2);
+        assert_eq!(&*dst[0], &[1, 2, 3]);
+        assert_eq!(&*dst[1], &[4, 5, 6]);
+    }
+}