Add AsyncRead::poll_read_buf and AsyncWrite::poll_write_buf

.travis.yml

@@ -128,14 +128,23 @@ matrix:
             --no-default-features
             --features alloc
 
-    - name: cargo check (futures-util)
+    - name: cargo check (sub crates)
       rust: nightly
       script:
         - cargo run --manifest-path ci/remove-dev-dependencies/Cargo.toml */Cargo.toml
 
+        # futures-io
+        # Check default-features, all-features
+        - cargo check --manifest-path futures-io/Cargo.toml
+        - cargo check --manifest-path futures-io/Cargo.toml --all-features
+        # Check each features
+        - cargo check --manifest-path futures-io/Cargo.toml --features bytes,unstable
+
+        # futures-util
+        # Check default-features, all-features
         - cargo check --manifest-path futures-util/Cargo.toml
         - cargo check --manifest-path futures-util/Cargo.toml --all-features
-
+        # Check each features
         - cargo check --manifest-path futures-util/Cargo.toml --features sink
         - cargo check --manifest-path futures-util/Cargo.toml --features io
         - cargo check --manifest-path futures-util/Cargo.toml --features channel
@@ -150,6 +159,7 @@ matrix:
         - cargo check --manifest-path futures-util/Cargo.toml --features sink,bilock,unstable
         - cargo check --manifest-path futures-util/Cargo.toml --features io,bilock,unstable
         - cargo check --manifest-path futures-util/Cargo.toml --features sink,io
+        - cargo check --manifest-path futures-util/Cargo.toml --features bytes,unstable
 
         - cargo check --manifest-path futures-util/Cargo.toml --no-default-features
         - cargo check --manifest-path futures-util/Cargo.toml --no-default-features --features sink

futures-io/Cargo.toml

@@ -18,7 +18,13 @@ name = "futures_io"
 default = ["std"]
 std = []
 
+# Unstable features
+# `bytes` feature is outside of the normal semver guarantees and require the
+# `unstable` feature as an explicit opt-in to unstable API.
+unstable = []
+
 [dependencies]
+bytes = { version = "0.4.7", optional = true }
 
 [dev-dependencies]
 futures-preview = { path = "../futures", version = "=0.3.0-alpha.18" }

futures-io/src/lib.rs

@@ -19,6 +19,9 @@
 
 #![doc(html_root_url = "https://rust-lang-nursery.github.io/futures-api-docs/0.3.0-alpha.18/futures_io")]
 
+#[cfg(all(feature = "bytes", not(feature = "unstable")))]
+compile_error!("The `bytes` feature requires the `unstable` feature as an explicit opt-in to unstable features");
+
 #[cfg(feature = "std")]
 mod if_std {
     use std::cmp;
@@ -40,6 +43,10 @@ mod if_std {
         SeekFrom as SeekFrom,
     };
 
+    #[cfg(feature = "bytes")]
+    #[allow(unreachable_pub)] // https://github.com/rust-lang/rust/issues/57411
+    pub use bytes::{Buf, BufMut};
+
     /// A type used to conditionally initialize buffers passed to `AsyncRead`
     /// methods, modeled after `std`.
     #[derive(Debug)]
@@ -154,6 +161,42 @@ mod if_std {
                 Poll::Ready(Ok(0))
             }
         }
+
+        /// Pull some bytes from this source into the specified `BufMut`, returning
+        /// how many bytes were read.
+        ///
+        /// The `buf` provided will have bytes read into it and the internal cursor
+        /// will be advanced if any bytes were read. Note that this method typically
+        /// will not reallocate the buffer provided.
+        #[cfg(feature = "bytes")]
+        fn poll_read_buf<B: BufMut>(
+            self: Pin<&mut Self>,
+            cx: &mut Context<'_>,
+            buf: &mut B,
+        ) -> Poll<Result<usize>>
+        where
+            Self: Sized,
+        {
+            if !buf.has_remaining_mut() {
+                return Poll::Ready(Ok(0));
+            }
+
+            unsafe {
+                let n = {
+                    let mut b = buf.bytes_mut();
+
+                    self.initializer().initialize(&mut b);
+
+                    match self.poll_read(cx, b)? {
+                        Poll::Ready(n) => n,
+                        Poll::Pending => return Poll::Pending,
+                    }
+                };
+
+                buf.advance_mut(n);
+                Poll::Ready(Ok(n))
+            }
+        }
     }
 
     /// Write bytes asynchronously.
@@ -250,6 +293,31 @@ mod if_std {
         /// `Poll::Pending` and either internally retry or convert
         /// `Interrupted` into another error kind.
         fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<()>>;
+
+        /// Write a `Buf` into this value, returning how many bytes were written.
+        ///
+        /// Note that this method will advance the `buf` provided automatically by
+        /// the number of bytes written.
+        #[cfg(feature = "bytes")]
+        fn poll_write_buf<B: Buf>(
+            self: Pin<&mut Self>,
+            cx: &mut Context<'_>,
+            buf: &mut B,
+        ) -> Poll<Result<usize>>
+        where
+            Self: Sized,
+        {
+            if !buf.has_remaining() {
+                return Poll::Ready(Ok(0));
+            }
+
+            let n = match self.poll_write(cx, buf.bytes())? {
+                Poll::Ready(n) => n,
+                Poll::Pending => return Poll::Pending,
+            };
+            buf.advance(n);
+            Poll::Ready(Ok(n))
+        }
     }
 
     /// Seek bytes asynchronously.

futures-util/Cargo.toml

@@ -33,6 +33,7 @@ select-macro = ["async-await", "futures-select-macro-preview", "proc-macro-hack"
 unstable = ["futures-core-preview/unstable"]
 cfg-target-has-atomic = ["futures-core-preview/cfg-target-has-atomic"]
 bilock = []
+bytes = ["io", "futures-io-preview/bytes", "futures-io-preview/unstable"]
 
 [dependencies]
 futures-core-preview = { path = "../futures-core", version = "=0.3.0-alpha.18", default-features = false }

futures-util/src/io/mod.rs

@@ -13,6 +13,8 @@ pub use futures_io::{
     AsyncRead, AsyncWrite, AsyncSeek, AsyncBufRead, Error, ErrorKind,
     IoSlice, IoSliceMut, Result, SeekFrom,
 };
+#[cfg(feature = "bytes")]
+pub use futures_io::{Buf, BufMut};
 
 #[cfg(feature = "io-compat")] use crate::compat::Compat;
 
@@ -61,6 +63,11 @@ pub use self::read::Read;
 mod read_vectored;
 pub use self::read_vectored::ReadVectored;
 
+#[cfg(feature = "bytes")]
+mod read_buf;
+#[cfg(feature = "bytes")]
+pub use self::read_buf::ReadBuf;
+
 mod read_exact;
 pub use self::read_exact::ReadExact;
 
@@ -100,6 +107,11 @@ pub use self::write::Write;
 mod write_vectored;
 pub use self::write_vectored::WriteVectored;
 
+#[cfg(feature = "bytes")]
+mod write_buf;
+#[cfg(feature = "bytes")]
+pub use self::write_buf::WriteBuf;
+
 mod write_all;
 pub use self::write_all::WriteAll;
 
@@ -213,6 +225,17 @@ pub trait AsyncReadExt: AsyncRead {
         ReadVectored::new(self, bufs)
     }
 
+    /// Creates a future which will read from the `AsyncRead` into `buf`.
+    ///
+    /// The returned future will resolve to the number of bytes read once the read
+    /// operation is completed.
+    #[cfg(feature = "bytes")]
+    fn read_buf<'a, B: BufMut>(&'a mut self, buf: &'a mut B) -> ReadBuf<'a, Self, B>
+        where Self: Unpin,
+    {
+        ReadBuf::new(self, buf)
+    }
+
     /// Creates a future which will read exactly enough bytes to fill `buf`,
     /// returning an error if end of file (EOF) is hit sooner.
     ///
@@ -455,6 +478,17 @@ pub trait AsyncWriteExt: AsyncWrite {
         WriteVectored::new(self, bufs)
     }
 
+    /// Creates a future which will write bytes from `buf` into the object.
+    ///
+    /// The returned future will resolve to the number of bytes written once the write
+    /// operation is completed.
+    #[cfg(feature = "bytes")]
+    fn write_buf<'a, B: Buf>(&'a mut self, buf: &'a mut B) -> WriteBuf<'a, Self, B>
+        where Self: Unpin,
+    {
+        WriteBuf::new(self, buf)
+    }
+
     /// Write data into this object.
     ///
     /// Creates a future that will write the entire contents of the buffer `buf` into

futures-util/src/io/read_buf.rs

@@ -0,0 +1,30 @@
+use futures_core::future::Future;
+use futures_core::task::{Context, Poll};
+use futures_io::{AsyncRead, BufMut};
+use std::io;
+use std::pin::Pin;
+
+/// Future for the [`read_buf`](super::AsyncReadExt::read_buf) method.
+#[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+pub struct ReadBuf<'a, R: ?Sized + Unpin, B> {
+    reader: &'a mut R,
+    buf: &'a mut B,
+}
+
+impl<R: ?Sized + Unpin, B> Unpin for ReadBuf<'_, R, B> {}
+
+impl<'a, R: AsyncRead + ?Sized + Unpin, B: BufMut> ReadBuf<'a, R, B> {
+    pub(super) fn new(reader: &'a mut R, buf: &'a mut B) -> Self {
+        Self { reader, buf }
+    }
+}
+
+impl<R: AsyncRead + ?Sized + Unpin, B: BufMut> Future for ReadBuf<'_, R, B> {
+    type Output = io::Result<usize>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = &mut *self;
+        Pin::new(&mut this.reader).poll_read_buf(cx, this.buf)
+    }
+}

futures-util/src/io/write_buf.rs

@@ -0,0 +1,30 @@
+use futures_core::future::Future;
+use futures_core::task::{Context, Poll};
+use futures_io::{AsyncWrite, Buf};
+use std::io;
+use std::pin::Pin;
+
+/// Future for the [`write_buf`](super::AsyncWriteExt::write_buf) method.
+#[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+pub struct WriteBuf<'a, W: ?Sized + Unpin, B> {
+    writer: &'a mut W,
+    buf: &'a mut B,
+}
+
+impl<W: ?Sized + Unpin, B> Unpin for WriteBuf<'_, W, B> {}
+
+impl<'a, W: AsyncWrite + ?Sized + Unpin, B: Buf> WriteBuf<'a, W, B> {
+    pub(super) fn new(writer: &'a mut W, buf: &'a mut B) -> Self {
+        Self { writer, buf }
+    }
+}
+
+impl<W: AsyncWrite + ?Sized + Unpin, B: Buf> Future for WriteBuf<'_, W, B> {
+    type Output = io::Result<usize>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = &mut *self;
+        Pin::new(&mut this.writer).poll_write_buf(cx, this.buf)
+    }
+}

futures-util/src/lib.rs

@@ -19,6 +19,9 @@ compile_error!("The `cfg-target-has-atomic` feature requires the `unstable` feat
 #[cfg(all(feature = "bilock", not(feature = "unstable")))]
 compile_error!("The `bilock` feature requires the `unstable` feature as an explicit opt-in to unstable features");
 
+#[cfg(all(feature = "bytes", not(feature = "unstable")))]
+compile_error!("The `bytes` feature requires the `unstable` feature as an explicit opt-in to unstable features");
+
 #[cfg(feature = "alloc")]
 extern crate alloc;
 

futures/Cargo.toml

@@ -34,6 +34,7 @@ pin-utils = "0.1.0-alpha.4"
 futures-test-preview = { path = "../futures-test", version = "=0.3.0-alpha.18" }
 tokio = "0.1.11"
 assert_matches = "1.3.0"
+bytes_crate = { version = "0.4.7", package = "bytes" }
 
 [features]
 default = ["std"]
@@ -46,9 +47,10 @@ io-compat = ["compat", "futures-util-preview/io-compat"]
 # Unstable features
 # These features are outside of the normal semver guarantees and require the
 # `unstable` feature as an explicit opt-in to unstable API.
-unstable = ["futures-core-preview/unstable", "futures-channel-preview/unstable", "futures-util-preview/unstable"]
+unstable = ["futures-core-preview/unstable", "futures-channel-preview/unstable", "futures-io-preview/unstable", "futures-util-preview/unstable"]
 cfg-target-has-atomic = ["futures-core-preview/cfg-target-has-atomic", "futures-channel-preview/cfg-target-has-atomic", "futures-util-preview/cfg-target-has-atomic"]
 bilock = ["futures-util-preview/bilock"]
+bytes = ["futures-io-preview/bytes", "futures-util-preview/bytes"]
 
 [package.metadata.docs.rs]
 all-features = true

futures/src/lib.rs

@@ -40,6 +40,9 @@ compile_error!("The `cfg-target-has-atomic` feature requires the `unstable` feat
 #[cfg(all(feature = "bilock", not(feature = "unstable")))]
 compile_error!("The `bilock` feature requires the `unstable` feature as an explicit opt-in to unstable features");
 
+#[cfg(all(feature = "bytes", not(feature = "unstable")))]
+compile_error!("The `bytes` feature requires the `unstable` feature as an explicit opt-in to unstable features");
+
 #[doc(hidden)] pub use futures_core::core_reexport;
 
 #[doc(hidden)] pub use futures_core::future::Future;
@@ -308,6 +311,12 @@ pub mod io {
         ReadToString, ReadUntil, ReadVectored, repeat, Repeat, Seek, sink, Sink,
         Take, Window, Write, WriteAll, WriteHalf, WriteVectored,
     };
+
+    #[cfg(feature = "bytes")]
+    pub use futures_io::{Buf, BufMut};
+
+    #[cfg(feature = "bytes")]
+    pub use futures_util::io::{ReadBuf, WriteBuf};
 }
 
 #[cfg_attr(