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use futures_core::future::Future;
use futures_core::task::{Context, Poll};
use futures_io::{AsyncBufRead, AsyncWrite};
use std::io;
use std::pin::Pin;
use pin_project::{pin_project, project};
pub fn copy_buf<R, W>(reader: R, writer: &mut W) -> CopyBuf<'_, R, W>
where
R: AsyncBufRead,
W: AsyncWrite + Unpin + ?Sized,
{
CopyBuf {
reader,
writer,
amt: 0,
}
}
#[pin_project]
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct CopyBuf<'a, R, W: ?Sized> {
#[pin]
reader: R,
writer: &'a mut W,
amt: u64,
}
impl<R, W> Future for CopyBuf<'_, R, W>
where R: AsyncBufRead,
W: AsyncWrite + Unpin + ?Sized,
{
type Output = io::Result<u64>;
#[project]
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
#[project]
let CopyBuf { mut reader, mut writer, amt } = self.project();
loop {
let buffer = ready!(reader.as_mut().poll_fill_buf(cx))?;
if buffer.is_empty() {
ready!(Pin::new(&mut writer).poll_flush(cx))?;
return Poll::Ready(Ok(*amt));
}
let i = ready!(Pin::new(&mut writer).poll_write(cx, buffer))?;
if i == 0 {
return Poll::Ready(Err(io::ErrorKind::WriteZero.into()))
}
*amt += i as u64;
reader.as_mut().consume(i);
}
}
}