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use crate::io::AsyncWrite;
use bytes::Buf;
use pin_project_lite::pin_project;
use std::future::Future;
use std::io;
use std::marker::PhantomPinned;
use std::pin::Pin;
use std::task::{Context, Poll};
pin_project! {
/// A future to write some of the buffer to an `AsyncWrite`.
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct WriteBuf<'a, W, B> {
writer: &'a mut W,
buf: &'a mut B,
#[pin]
_pin: PhantomPinned,
}
}
/// Tries to write some bytes from the given `buf` to the writer in an
/// asynchronous manner, returning a future.
pub(crate) fn write_buf<'a, W, B>(writer: &'a mut W, buf: &'a mut B) -> WriteBuf<'a, W, B>
where
W: AsyncWrite + Unpin,
B: Buf,
{
WriteBuf {
writer,
buf,
_pin: PhantomPinned,
}
}
impl<W, B> Future for WriteBuf<'_, W, B>
where
W: AsyncWrite + Unpin,
B: Buf,
{
type Output = io::Result<usize>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
let me = self.project();
if !me.buf.has_remaining() {
return Poll::Ready(Ok(0));
}
let n = ready!(Pin::new(me.writer).poll_write(cx, me.buf.chunk()))?;
me.buf.advance(n);
Poll::Ready(Ok(n))
}
}