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use crate::{AsyncRead, AsyncWrite};
use futures_core::ready;
use std::future::Future;
use std::io;
use std::pin::Pin;
use std::task::{Context, Poll};
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub struct Copy<'a, R: ?Sized, W: ?Sized> {
reader: &'a mut R,
read_done: bool,
writer: &'a mut W,
pos: usize,
cap: usize,
amt: u64,
buf: Box<[u8]>,
}
pub(crate) fn copy<'a, R, W>(reader: &'a mut R, writer: &'a mut W) -> Copy<'a, R, W>
where
R: AsyncRead + Unpin + ?Sized,
W: AsyncWrite + Unpin + ?Sized,
{
Copy {
reader,
read_done: false,
writer,
amt: 0,
pos: 0,
cap: 0,
buf: Box::new([0; 2048]),
}
}
impl<R, W> Future for Copy<'_, R, W>
where
R: AsyncRead + Unpin + ?Sized,
W: AsyncWrite + Unpin + ?Sized,
{
type Output = io::Result<u64>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<u64>> {
loop {
// If our buffer is empty, then we need to read some data to
// continue.
if self.pos == self.cap && !self.read_done {
let me = &mut *self;
let n = ready!(Pin::new(&mut *me.reader).poll_read(cx, &mut me.buf))?;
if n == 0 {
self.read_done = true;
} else {
self.pos = 0;
self.cap = n;
}
}
// If our buffer has some data, let's write it out!
while self.pos < self.cap {
let me = &mut *self;
let i = ready!(Pin::new(&mut *me.writer).poll_write(cx, &me.buf[me.pos..me.cap]))?;
if i == 0 {
return Poll::Ready(Err(io::Error::new(
io::ErrorKind::WriteZero,
"write zero byte into writer",
)));
} else {
self.pos += i;
self.amt += i as u64;
}
}
// If we've written al the data and we've seen EOF, flush out the
// data and finish the transfer.
// done with the entire transfer.
if self.pos == self.cap && self.read_done {
let me = &mut *self;
ready!(Pin::new(&mut *me.writer).poll_flush(cx))?;
return Poll::Ready(Ok(self.amt));
}
}
}
}
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