use super::ReadBuf;
use std::io;
use std::ops::DerefMut;
use std::pin::Pin;
use std::task::{Context, Poll};
pub trait AsyncRead {
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>>;
}
macro_rules! deref_async_read {
() => {
fn poll_read(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
Pin::new(&mut **self).poll_read(cx, buf)
}
};
}
impl<T: ?Sized + AsyncRead + Unpin> AsyncRead for Box<T> {
deref_async_read!();
}
impl<T: ?Sized + AsyncRead + Unpin> AsyncRead for &mut T {
deref_async_read!();
}
impl<P> AsyncRead for Pin<P>
where
P: DerefMut + Unpin,
P::Target: AsyncRead,
{
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
self.get_mut().as_mut().poll_read(cx, buf)
}
}
impl AsyncRead for &[u8] {
fn poll_read(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
let amt = std::cmp::min(self.len(), buf.remaining());
let (a, b) = self.split_at(amt);
buf.put_slice(a);
*self = b;
Poll::Ready(Ok(()))
}
}
impl<T: AsRef<[u8]> + Unpin> AsyncRead for io::Cursor<T> {
fn poll_read(
mut self: Pin<&mut Self>,
_cx: &mut Context<'_>,
buf: &mut ReadBuf<'_>,
) -> Poll<io::Result<()>> {
let pos = self.position();
let slice: &[u8] = (*self).get_ref().as_ref();
if pos > slice.len() as u64 {
return Poll::Ready(Ok(()));
}
let start = pos as usize;
let amt = std::cmp::min(slice.len() - start, buf.remaining());
let end = start + amt;
buf.put_slice(&slice[start..end]);
self.set_position(end as u64);
Poll::Ready(Ok(()))
}
}