1use crate::io::{AsyncBufRead, AsyncWrite};
2use std::future::Future;
3use std::io;
4use std::pin::Pin;
5use std::task::{ready, Context, Poll};
6
7cfg_io_util! {
8 /// A future that asynchronously copies the entire contents of a reader into a
9 /// writer.
10 ///
11 /// This struct is generally created by calling [`copy_buf`][copy_buf]. Please
12 /// see the documentation of `copy_buf()` for more details.
13 ///
14 /// [copy_buf]: copy_buf()
15 #[derive(Debug)]
16 #[must_use = "futures do nothing unless you `.await` or poll them"]
17 struct CopyBuf<'a, R: ?Sized, W: ?Sized> {
18 reader: &'a mut R,
19 writer: &'a mut W,
20 amt: u64,
21 }
22
23 /// Asynchronously copies the entire contents of a reader into a writer.
24 ///
25 /// This function returns a future that will continuously read data from
26 /// `reader` and then write it into `writer` in a streaming fashion until
27 /// `reader` returns EOF or fails.
28 ///
29 /// On success, the total number of bytes that were copied from `reader` to
30 /// `writer` is returned.
31 ///
32 /// This is a [`tokio::io::copy`] alternative for [`AsyncBufRead`] readers
33 /// with no extra buffer allocation, since [`AsyncBufRead`] allow access
34 /// to the reader's inner buffer.
35 ///
36 /// [`tokio::io::copy`]: crate::io::copy
37 /// [`AsyncBufRead`]: crate::io::AsyncBufRead
38 ///
39 /// # Errors
40 ///
41 /// The returned future will finish with an error will return an error
42 /// immediately if any call to `poll_fill_buf` or `poll_write` returns an
43 /// error.
44 ///
45 /// # Examples
46 ///
47 /// ```
48 /// use tokio::io;
49 ///
50 /// # async fn dox() -> std::io::Result<()> {
51 /// let mut reader: &[u8] = b"hello";
52 /// let mut writer: Vec<u8> = vec![];
53 ///
54 /// io::copy_buf(&mut reader, &mut writer).await?;
55 ///
56 /// assert_eq!(b"hello", &writer[..]);
57 /// # Ok(())
58 /// # }
59 /// ```
60 pub async fn copy_buf<'a, R, W>(reader: &'a mut R, writer: &'a mut W) -> io::Result<u64>
61 where
62 R: AsyncBufRead + Unpin + ?Sized,
63 W: AsyncWrite + Unpin + ?Sized,
64 {
65 CopyBuf {
66 reader,
67 writer,
68 amt: 0,
69 }.await
70 }
71}
72
73impl<R, W> Future for CopyBuf<'_, R, W>
74where
75 R: AsyncBufRead + Unpin + ?Sized,
76 W: AsyncWrite + Unpin + ?Sized,
77{
78 type Output = io::Result<u64>;
79
80 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
81 loop {
82 let me: &mut CopyBuf<'_, R, W> = &mut *self;
83 let buffer: &[u8] = ready!(Pin::new(&mut *me.reader).poll_fill_buf(cx))?;
84 if buffer.is_empty() {
85 ready!(Pin::new(&mut self.writer).poll_flush(cx))?;
86 return Poll::Ready(Ok(self.amt));
87 }
88
89 let i: usize = ready!(Pin::new(&mut *me.writer).poll_write(cx, buffer))?;
90 if i == 0 {
91 return Poll::Ready(Err(std::io::ErrorKind::WriteZero.into()));
92 }
93 self.amt += i as u64;
94 Pin::new(&mut *self.reader).consume(amt:i);
95 }
96 }
97}
98
99#[cfg(test)]
100mod tests {
101 use super::*;
102
103 #[test]
104 fn assert_unpin() {
105 use std::marker::PhantomPinned;
106 crate::is_unpin::<CopyBuf<'_, PhantomPinned, PhantomPinned>>();
107 }
108}
109