diff options
Diffstat (limited to 'tokio-util/src/lib.rs')
-rw-r--r-- | tokio-util/src/lib.rs | 75 |
1 files changed, 70 insertions, 5 deletions
diff --git a/tokio-util/src/lib.rs b/tokio-util/src/lib.rs index c4d80440..15bfc1a2 100644 --- a/tokio-util/src/lib.rs +++ b/tokio-util/src/lib.rs @@ -55,18 +55,18 @@ pub mod time; #[cfg(any(feature = "io", feature = "codec"))] mod util { - use tokio::io::{AsyncRead, ReadBuf}; + use tokio::io::{AsyncRead, AsyncWrite, ReadBuf}; - use bytes::BufMut; + use bytes::{Buf, BufMut}; use futures_core::ready; - use std::io; + use std::io::{self, IoSlice}; use std::mem::MaybeUninit; use std::pin::Pin; use std::task::{Context, Poll}; - /// Try to read data from an `AsyncRead` into an implementer of the [`Buf`] trait. + /// Try to read data from an `AsyncRead` into an implementer of the [`BufMut`] trait. /// - /// [`Buf`]: bytes::Buf + /// [`BufMut`]: bytes::Buf /// /// # Example /// @@ -132,4 +132,69 @@ mod util { Poll::Ready(Ok(n)) } + + /// Try to write data from an implementer of the [`Buf`] trait to an + /// [`AsyncWrite`], advancing the buffer's internal cursor. + /// + /// This function will use [vectored writes] when the [`AsyncWrite`] supports + /// vectored writes. + /// + /// # Examples + /// + /// [`File`] implements [`AsyncWrite`] and [`Cursor<&[u8]>`] implements + /// [`Buf`]: + /// + /// ```no_run + /// use tokio_util::io::poll_write_buf; + /// use tokio::io; + /// use tokio::fs::File; + /// + /// use bytes::Buf; + /// use std::io::Cursor; + /// use std::pin::Pin; + /// use futures::future::poll_fn; + /// + /// #[tokio::main] + /// async fn main() -> io::Result<()> { + /// let mut file = File::create("foo.txt").await?; + /// let mut buf = Cursor::new(b"data to write"); + /// + /// // Loop until the entire contents of the buffer are written to + /// // the file. + /// while buf.has_remaining() { + /// poll_fn(|cx| poll_write_buf(Pin::new(&mut file), cx, &mut buf)).await?; + /// } + /// + /// Ok(()) + /// } + /// ``` + /// + /// [`Buf`]: bytes::Buf + /// [`AsyncWrite`]: tokio::io::AsyncWrite + /// [`File`]: tokio::fs::File + /// [vectored writes]: tokio::io::AsyncWrite::poll_write_vectored + #[cfg_attr(not(feature = "io"), allow(unreachable_pub))] + pub fn poll_write_buf<T: AsyncWrite, B: Buf>( + io: Pin<&mut T>, + cx: &mut Context<'_>, + buf: &mut B, + ) -> Poll<io::Result<usize>> { + const MAX_BUFS: usize = 64; + + if !buf.has_remaining() { + return Poll::Ready(Ok(0)); + } + + let n = if io.is_write_vectored() { + let mut slices = [IoSlice::new(&[]); MAX_BUFS]; + let cnt = buf.bytes_vectored(&mut slices); + ready!(io.poll_write_vectored(cx, &slices[..cnt]))? + } else { + ready!(io.poll_write(cx, buf.bytes()))? + }; + + buf.advance(n); + + Poll::Ready(Ok(n)) + } } |