1 | use futures_core::future::Future; |
2 | use futures_core::ready; |
3 | use futures_core::task::{Context, Poll}; |
4 | use futures_io::{AsyncBufRead, AsyncWrite}; |
5 | use pin_project_lite::pin_project; |
6 | use std::io; |
7 | use std::pin::Pin; |
8 | |
9 | /// Creates a future which copies all the bytes from one object to another. |
10 | /// |
11 | /// The returned future will copy all the bytes read from this `AsyncBufRead` into the |
12 | /// `writer` specified. This future will only complete once the `reader` has hit |
13 | /// EOF and all bytes have been written to and flushed from the `writer` |
14 | /// provided. |
15 | /// |
16 | /// On success the number of bytes is returned. |
17 | /// |
18 | /// # Examples |
19 | /// |
20 | /// ``` |
21 | /// # futures::executor::block_on(async { |
22 | /// use futures::io::{self, AsyncWriteExt, Cursor}; |
23 | /// |
24 | /// let reader = Cursor::new([1, 2, 3, 4]); |
25 | /// let mut writer = Cursor::new(vec![0u8; 5]); |
26 | /// |
27 | /// let bytes = io::copy_buf(reader, &mut writer).await?; |
28 | /// writer.close().await?; |
29 | /// |
30 | /// assert_eq!(bytes, 4); |
31 | /// assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]); |
32 | /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap(); |
33 | /// ``` |
34 | pub fn copy_buf<R, W>(reader: R, writer: &mut W) -> CopyBuf<'_, R, W> |
35 | where |
36 | R: AsyncBufRead, |
37 | W: AsyncWrite + Unpin + ?Sized, |
38 | { |
39 | CopyBuf { reader, writer, amt: 0 } |
40 | } |
41 | |
42 | pin_project! { |
43 | /// Future for the [`copy_buf()`] function. |
44 | #[derive(Debug)] |
45 | #[must_use = "futures do nothing unless you `.await` or poll them" ] |
46 | pub struct CopyBuf<'a, R, W: ?Sized> { |
47 | #[pin] |
48 | reader: R, |
49 | writer: &'a mut W, |
50 | amt: u64, |
51 | } |
52 | } |
53 | |
54 | impl<R, W> Future for CopyBuf<'_, R, W> |
55 | where |
56 | R: AsyncBufRead, |
57 | W: AsyncWrite + Unpin + ?Sized, |
58 | { |
59 | type Output = io::Result<u64>; |
60 | |
61 | fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
62 | let mut this: Projection<'_, '_, R, W> = self.project(); |
63 | loop { |
64 | let buffer: &[u8] = ready!(this.reader.as_mut().poll_fill_buf(cx))?; |
65 | if buffer.is_empty() { |
66 | ready!(Pin::new(&mut this.writer).poll_flush(cx))?; |
67 | return Poll::Ready(Ok(*this.amt)); |
68 | } |
69 | |
70 | let i: usize = ready!(Pin::new(&mut this.writer).poll_write(cx, buffer))?; |
71 | if i == 0 { |
72 | return Poll::Ready(Err(io::ErrorKind::WriteZero.into())); |
73 | } |
74 | *this.amt += i as u64; |
75 | this.reader.as_mut().consume(amt:i); |
76 | } |
77 | } |
78 | } |
79 | |