futures_util/io/
split.rs

1use crate::lock::BiLock;
2use core::fmt;
3use futures_core::ready;
4use futures_core::task::{Context, Poll};
5use futures_io::{AsyncRead, AsyncWrite, IoSlice, IoSliceMut};
6use std::io;
7use std::pin::Pin;
8
9/// The readable half of an object returned from `AsyncRead::split`.
10#[derive(Debug)]
11pub struct ReadHalf<T> {
12    handle: BiLock<T>,
13}
14
15/// The writable half of an object returned from `AsyncRead::split`.
16#[derive(Debug)]
17pub struct WriteHalf<T> {
18    handle: BiLock<T>,
19}
20
21fn lock_and_then<T, U, E, F>(lock: &BiLock<T>, cx: &mut Context<'_>, f: F) -> Poll<Result<U, E>>
22where
23    F: FnOnce(Pin<&mut T>, &mut Context<'_>) -> Poll<Result<U, E>>,
24{
25    let mut l = ready!(lock.poll_lock(cx));
26    f(l.as_pin_mut(), cx)
27}
28
29pub(super) fn split<T: AsyncRead + AsyncWrite>(t: T) -> (ReadHalf<T>, WriteHalf<T>) {
30    let (a, b) = BiLock::new(t);
31    (ReadHalf { handle: a }, WriteHalf { handle: b })
32}
33
34impl<T: Unpin> ReadHalf<T> {
35    /// Attempts to put the two "halves" of a split `AsyncRead + AsyncWrite` back
36    /// together. Succeeds only if the `ReadHalf<T>` and `WriteHalf<T>` are
37    /// a matching pair originating from the same call to `AsyncReadExt::split`.
38    pub fn reunite(self, other: WriteHalf<T>) -> Result<T, ReuniteError<T>> {
39        self.handle
40            .reunite(other.handle)
41            .map_err(|err| ReuniteError(ReadHalf { handle: err.0 }, WriteHalf { handle: err.1 }))
42    }
43}
44
45impl<T: Unpin> WriteHalf<T> {
46    /// Attempts to put the two "halves" of a split `AsyncRead + AsyncWrite` back
47    /// together. Succeeds only if the `ReadHalf<T>` and `WriteHalf<T>` are
48    /// a matching pair originating from the same call to `AsyncReadExt::split`.
49    pub fn reunite(self, other: ReadHalf<T>) -> Result<T, ReuniteError<T>> {
50        other.reunite(self)
51    }
52}
53
54impl<R: AsyncRead> AsyncRead for ReadHalf<R> {
55    fn poll_read(
56        self: Pin<&mut Self>,
57        cx: &mut Context<'_>,
58        buf: &mut [u8],
59    ) -> Poll<io::Result<usize>> {
60        lock_and_then(&self.handle, cx, |l, cx| l.poll_read(cx, buf))
61    }
62
63    fn poll_read_vectored(
64        self: Pin<&mut Self>,
65        cx: &mut Context<'_>,
66        bufs: &mut [IoSliceMut<'_>],
67    ) -> Poll<io::Result<usize>> {
68        lock_and_then(&self.handle, cx, |l, cx| l.poll_read_vectored(cx, bufs))
69    }
70}
71
72impl<W: AsyncWrite> AsyncWrite for WriteHalf<W> {
73    fn poll_write(
74        self: Pin<&mut Self>,
75        cx: &mut Context<'_>,
76        buf: &[u8],
77    ) -> Poll<io::Result<usize>> {
78        lock_and_then(&self.handle, cx, |l, cx| l.poll_write(cx, buf))
79    }
80
81    fn poll_write_vectored(
82        self: Pin<&mut Self>,
83        cx: &mut Context<'_>,
84        bufs: &[IoSlice<'_>],
85    ) -> Poll<io::Result<usize>> {
86        lock_and_then(&self.handle, cx, |l, cx| l.poll_write_vectored(cx, bufs))
87    }
88
89    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
90        lock_and_then(&self.handle, cx, |l, cx| l.poll_flush(cx))
91    }
92
93    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
94        lock_and_then(&self.handle, cx, |l, cx| l.poll_close(cx))
95    }
96}
97
98/// Error indicating a `ReadHalf<T>` and `WriteHalf<T>` were not two halves
99/// of a `AsyncRead + AsyncWrite`, and thus could not be `reunite`d.
100pub struct ReuniteError<T>(pub ReadHalf<T>, pub WriteHalf<T>);
101
102impl<T> fmt::Debug for ReuniteError<T> {
103    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
104        f.debug_tuple("ReuniteError").field(&"...").finish()
105    }
106}
107
108impl<T> fmt::Display for ReuniteError<T> {
109    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
110        write!(f, "tried to reunite a ReadHalf and WriteHalf that don't form a pair")
111    }
112}
113
114#[cfg(feature = "std")]
115impl<T: core::any::Any> std::error::Error for ReuniteError<T> {}
futures_util/io/split.rs

futures_util/io/
split.rs
