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100 lines
3 KiB
Rust
100 lines
3 KiB
Rust
use std::pin::Pin;
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use crate::future::Future;
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use crate::io::{self, BufRead, BufReader, Read, Write};
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use crate::task::{Context, Poll};
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/// Copies the entire contents of a reader into a writer.
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///
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/// This function will continuously read data from `reader` and then
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/// write it into `writer` in a streaming fashion until `reader`
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/// returns EOF.
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///
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/// On success, the total number of bytes that were copied from
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/// `reader` to `writer` is returned.
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///
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/// If you’re wanting to copy the contents of one file to another and you’re
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/// working with filesystem paths, see the [`fs::copy`] function.
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///
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/// This function is an async version of [`std::io::copy`].
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///
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/// [`std::io::copy`]: https://doc.rust-lang.org/std/io/fn.copy.html
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/// [`fs::copy`]: ../fs/fn.copy.html
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///
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/// # Errors
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///
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/// This function will return an error immediately if any call to `read` or
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/// `write` returns an error. All instances of `ErrorKind::Interrupted` are
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/// handled by this function and the underlying operation is retried.
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///
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/// # Examples
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///
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/// ```
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/// # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
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/// #
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/// use async_std::io;
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///
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/// let mut reader: &[u8] = b"hello";
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/// let mut writer = io::stdout();
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///
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/// io::copy(&mut reader, &mut writer).await?;
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/// #
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/// # Ok(()) }) }
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/// ```
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pub async fn copy<R, W>(reader: &mut R, writer: &mut W) -> io::Result<u64>
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where
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R: Read + Unpin + ?Sized,
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W: Write + Unpin + ?Sized,
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{
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pub struct CopyFuture<'a, R, W: ?Sized> {
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reader: R,
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writer: &'a mut W,
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amt: u64,
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}
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impl<R, W: Unpin + ?Sized> CopyFuture<'_, R, W> {
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fn project(self: Pin<&mut Self>) -> (Pin<&mut R>, Pin<&mut W>, &mut u64) {
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unsafe {
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let this = self.get_unchecked_mut();
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(
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Pin::new_unchecked(&mut this.reader),
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Pin::new(&mut *this.writer),
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&mut this.amt,
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)
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}
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}
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}
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impl<R, W> Future for CopyFuture<'_, R, W>
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where
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R: BufRead,
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W: Write + Unpin + ?Sized,
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{
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type Output = io::Result<u64>;
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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let (mut reader, mut writer, amt) = self.project();
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loop {
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let buffer = futures_core::ready!(reader.as_mut().poll_fill_buf(cx))?;
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if buffer.is_empty() {
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futures_core::ready!(writer.as_mut().poll_flush(cx))?;
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return Poll::Ready(Ok(*amt));
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}
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let i = futures_core::ready!(writer.as_mut().poll_write(cx, buffer))?;
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if i == 0 {
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return Poll::Ready(Err(io::ErrorKind::WriteZero.into()));
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}
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*amt += i as u64;
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reader.as_mut().consume(i);
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}
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}
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}
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let future = CopyFuture {
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reader: BufReader::new(reader),
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writer,
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amt: 0,
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};
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future.await
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}
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