196 lines
6.8 KiB
Rust
196 lines
6.8 KiB
Rust
use core::ops::DerefMut;
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use core::pin::Pin;
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use core::task::{Context, Poll};
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#[cfg(feature = "alloc")]
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use alloc::boxed::Box;
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#[cfg(feature = "std")]
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use futures::io as std_io;
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use super::error::Result;
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/// Read bytes asynchronously.
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///
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/// This trait is analogous to the `std::io::BufRead` trait, but integrates
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/// with the asynchronous task system. In particular, the `poll_fill_buf`
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/// method, unlike `BufRead::fill_buf`, will automatically queue the current task
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/// for wakeup and return if data is not yet available, rather than blocking
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/// the calling thread.
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pub trait AsyncBufRead {
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/// Attempt to return the contents of the internal buffer, filling it with more data
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/// from the inner reader if it is empty.
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///
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/// On success, returns `Poll::Ready(Ok(buf))`.
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///
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/// If no data is available for reading, the method returns
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/// `Poll::Pending` and arranges for the current task (via
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/// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
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/// readable or is closed.
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///
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/// This function is a lower-level call. It needs to be paired with the
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/// [`consume`] method to function properly. When calling this
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/// method, none of the contents will be "read" in the sense that later
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/// calling [`poll_read`] may return the same contents. As such, [`consume`] must
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/// be called with the number of bytes that are consumed from this buffer to
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/// ensure that the bytes are never returned twice.
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///
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/// [`poll_read`]: AsyncBufRead::poll_read
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/// [`consume`]: AsyncBufRead::consume
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///
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/// An empty buffer returned indicates that the stream has reached EOF.
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///
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/// # Implementation
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///
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/// This function may not return errors of kind `WouldBlock` or
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/// `Interrupted`. Implementations must convert `WouldBlock` into
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/// `Poll::Pending` and either internally retry or convert
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/// `Interrupted` into another error kind.
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fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>>;
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/// Tells this buffer that `amt` bytes have been consumed from the buffer,
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/// so they should no longer be returned in calls to [`poll_read`].
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///
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/// This function is a lower-level call. It needs to be paired with the
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/// [`poll_fill_buf`] method to function properly. This function does
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/// not perform any I/O, it simply informs this object that some amount of
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/// its buffer, returned from [`poll_fill_buf`], has been consumed and should
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/// no longer be returned. As such, this function may do odd things if
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/// [`poll_fill_buf`] isn't called before calling it.
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///
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/// The `amt` must be `<=` the number of bytes in the buffer returned by
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/// [`poll_fill_buf`].
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///
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/// [`poll_read`]: AsyncBufRead::poll_read
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/// [`poll_fill_buf`]: AsyncBufRead::poll_fill_buf
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fn consume(self: Pin<&mut Self>, amt: usize);
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}
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/// Write bytes asynchronously.
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///
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/// This trait is analogous to the `core::io::Write` trait, but integrates
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/// with the asynchronous task system. In particular, the `poll_write`
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/// method, unlike `Write::write`, will automatically queue the current task
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/// for wakeup and return if the writer cannot take more data, rather than blocking
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/// the calling thread.
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pub trait AsyncWrite {
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/// Attempt to write bytes from `buf` into the object.
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///
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/// On success, returns `Poll::Ready(Ok(num_bytes_written))`.
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///
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/// If the object is not ready for writing, the method returns
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/// `Poll::Pending` and arranges for the current task (via
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/// `cx.waker().wake_by_ref()`) to receive a notification when the object becomes
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/// writable or is closed.
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///
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/// # Implementation
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///
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/// This function may not return errors of kind `WouldBlock` or
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/// `Interrupted`. Implementations must convert `WouldBlock` into
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/// `Poll::Pending` and either internally retry or convert
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/// `Interrupted` into another error kind.
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///
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/// `poll_write` must try to make progress by flushing the underlying object if
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/// that is the only way the underlying object can become writable again.
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fn poll_write(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8]) -> Poll<Result<usize>>;
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}
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macro_rules! defer_async_read {
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() => {
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fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
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Pin::new(&mut **self.get_mut()).poll_fill_buf(cx)
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}
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fn consume(mut self: Pin<&mut Self>, amt: usize) {
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Pin::new(&mut **self).consume(amt)
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}
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};
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}
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#[cfg(feature = "alloc")]
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impl<T: ?Sized + AsyncBufRead + Unpin> AsyncBufRead for Box<T> {
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defer_async_read!();
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}
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impl<T: ?Sized + AsyncBufRead + Unpin> AsyncBufRead for &mut T {
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defer_async_read!();
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}
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impl<P> AsyncBufRead for Pin<P>
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where
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P: DerefMut + Unpin,
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P::Target: AsyncBufRead,
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{
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fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
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self.get_mut().as_mut().poll_fill_buf(cx)
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}
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fn consume(self: Pin<&mut Self>, amt: usize) {
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self.get_mut().as_mut().consume(amt)
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}
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}
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macro_rules! deref_async_write {
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() => {
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fn poll_write(
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mut self: Pin<&mut Self>,
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cx: &mut Context<'_>,
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buf: &[u8],
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) -> Poll<Result<usize>> {
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Pin::new(&mut **self).poll_write(cx, buf)
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}
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};
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}
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#[cfg(feature = "alloc")]
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impl<T: ?Sized + AsyncWrite + Unpin> AsyncWrite for Box<T> {
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deref_async_write!();
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}
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impl<T: ?Sized + AsyncWrite + Unpin> AsyncWrite for &mut T {
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deref_async_write!();
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}
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impl<P> AsyncWrite for Pin<P>
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where
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P: DerefMut + Unpin,
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P::Target: AsyncWrite,
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{
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fn poll_write(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8]) -> Poll<Result<usize>> {
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self.get_mut().as_mut().poll_write(cx, buf)
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}
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}
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#[cfg(feature = "std")]
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pub struct FromStdIo<T>(T);
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#[cfg(feature = "std")]
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impl<T> FromStdIo<T> {
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pub fn new(inner: T) -> Self {
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Self(inner)
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}
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}
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#[cfg(feature = "std")]
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impl<T: std_io::AsyncBufRead> AsyncBufRead for FromStdIo<T> {
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fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<&[u8]>> {
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let Self(inner) = unsafe { self.get_unchecked_mut() };
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unsafe { Pin::new_unchecked(inner) }
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.poll_fill_buf(cx)
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.map_err(|e| e.into())
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}
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fn consume(self: Pin<&mut Self>, amt: usize) {
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let Self(inner) = unsafe { self.get_unchecked_mut() };
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unsafe { Pin::new_unchecked(inner) }.consume(amt)
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}
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}
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#[cfg(feature = "std")]
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impl<T: std_io::AsyncWrite> AsyncWrite for FromStdIo<T> {
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fn poll_write(self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &[u8]) -> Poll<Result<usize>> {
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let Self(inner) = unsafe { self.get_unchecked_mut() };
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unsafe { Pin::new_unchecked(inner) }
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.poll_write(cx, buf)
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.map_err(|e| e.into())
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}
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}
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