1use super::{copy_buf, BufReader, CopyBuf};
2use futures_core::future::Future;
3use futures_core::task::{Context, Poll};
4use futures_io::{AsyncRead, AsyncWrite};
5use pin_project_lite::pin_project;
6use std::io;
7use 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 `AsyncRead` 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(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/// ```
34pub fn copy<R, W>(reader: R, writer: &mut W) -> Copy<'_, R, W>
35where
36 R: AsyncRead,
37 W: AsyncWrite + Unpin + ?Sized,
38{
39 Copy { inner: copy_buf(reader:BufReader::new(inner:reader), writer) }
40}
41
42pin_project! {
43 /// Future for the [`copy()`] function.
44 #[derive(Debug)]
45 #[must_use = "futures do nothing unless you `.await` or poll them"]
46 pub struct Copy<'a, R, W: ?Sized> {
47 #[pin]
48 inner: CopyBuf<'a, BufReader<R>, W>,
49 }
50}
51
52impl<R: AsyncRead, W: AsyncWrite + Unpin + ?Sized> Future for Copy<'_, R, W> {
53 type Output = io::Result<u64>;
54
55 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
56 self.project().inner.poll(cx)
57 }
58}
59