1use crate::abortable::{AbortHandle, AbortInner, Aborted};
2use futures_core::future::Future;
3use futures_core::task::{Context, Poll};
4use futures_io::{AsyncBufRead, AsyncWrite};
5use pin_project_lite::pin_project;
6use std::io;
7use std::pin::Pin;
8use std::sync::atomic::Ordering;
9use std::sync::Arc;
10
11/// Creates a future which copies all the bytes from one object to another, with its `AbortHandle`.
12///
13/// The returned future will copy all the bytes read from this `AsyncBufRead` into the
14/// `writer` specified. This future will only complete once abort has been requested or the `reader` has hit
15/// EOF and all bytes have been written to and flushed from the `writer`
16/// provided.
17///
18/// On success the number of bytes is returned. If aborted, `Aborted` is returned. Otherwise, the underlying error is returned.
19///
20/// # Examples
21///
22/// ```
23/// # futures::executor::block_on(async {
24/// use futures::io::{self, AsyncWriteExt, Cursor};
25/// use futures::future::Aborted;
26///
27/// let reader = Cursor::new([1, 2, 3, 4]);
28/// let mut writer = Cursor::new(vec![0u8; 5]);
29///
30/// let (fut, abort_handle) = io::copy_buf_abortable(reader, &mut writer);
31/// let bytes = fut.await;
32/// abort_handle.abort();
33/// writer.close().await.unwrap();
34/// match bytes {
35/// Ok(Ok(n)) => {
36/// assert_eq!(n, 4);
37/// assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]);
38/// Ok(n)
39/// },
40/// Ok(Err(a)) => {
41/// Err::<u64, Aborted>(a)
42/// }
43/// Err(e) => panic!("{}", e)
44/// }
45/// # }).unwrap();
46/// ```
47pub fn copy_buf_abortable<R, W>(
48 reader: R,
49 writer: &mut W,
50) -> (CopyBufAbortable<'_, R, W>, AbortHandle)
51where
52 R: AsyncBufRead,
53 W: AsyncWrite + Unpin + ?Sized,
54{
55 let (handle: AbortHandle, reg: AbortRegistration) = AbortHandle::new_pair();
56 (CopyBufAbortable { reader, writer, amt: 0, inner: reg.inner }, handle)
57}
58
59pin_project! {
60 /// Future for the [`copy_buf_abortable()`] function.
61 #[derive(Debug)]
62 #[must_use = "futures do nothing unless you `.await` or poll them"]
63 pub struct CopyBufAbortable<'a, R, W: ?Sized> {
64 #[pin]
65 reader: R,
66 writer: &'a mut W,
67 amt: u64,
68 inner: Arc<AbortInner>
69 }
70}
71
72macro_rules! ready_or_break {
73 ($e:expr $(,)?) => {
74 match $e {
75 $crate::task::Poll::Ready(t) => t,
76 $crate::task::Poll::Pending => break,
77 }
78 };
79}
80
81impl<R, W> Future for CopyBufAbortable<'_, R, W>
82where
83 R: AsyncBufRead,
84 W: AsyncWrite + Unpin + Sized,
85{
86 type Output = Result<Result<u64, Aborted>, io::Error>;
87
88 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
89 let mut this = self.project();
90 loop {
91 // Check if the task has been aborted
92 if this.inner.aborted.load(Ordering::Relaxed) {
93 return Poll::Ready(Ok(Err(Aborted)));
94 }
95
96 // Read some bytes from the reader, and if we have reached EOF, return total bytes read
97 let buffer = ready_or_break!(this.reader.as_mut().poll_fill_buf(cx))?;
98 if buffer.is_empty() {
99 ready_or_break!(Pin::new(&mut this.writer).poll_flush(cx))?;
100 return Poll::Ready(Ok(Ok(*this.amt)));
101 }
102
103 // Pass the buffer to the writer, and update the amount written
104 let i = ready_or_break!(Pin::new(&mut this.writer).poll_write(cx, buffer))?;
105 if i == 0 {
106 return Poll::Ready(Err(io::ErrorKind::WriteZero.into()));
107 }
108 *this.amt += i as u64;
109 this.reader.as_mut().consume(i);
110 }
111 // Schedule the task to be woken up again.
112 // Never called unless Poll::Pending is returned from io objects.
113 this.inner.waker.register(cx.waker());
114
115 // Check to see if the task was aborted between the first check and
116 // registration.
117 // Checking with `Relaxed` is sufficient because
118 // `register` introduces an `AcqRel` barrier.
119 if this.inner.aborted.load(Ordering::Relaxed) {
120 return Poll::Ready(Ok(Err(Aborted)));
121 }
122 Poll::Pending
123 }
124}
125