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use std::io;
use std::mem;
use futures::{Future, Poll};
use tokio_io::AsyncRead;
#[derive(Debug)]
pub struct TryReadFull<A, T> {
state: State<A, T>,
}
#[derive(Debug)]
enum State<A, T> {
Reading { a: A, buf: T, pos: usize },
Empty,
}
pub fn try_read_full<A, T>(a: A, buf: T) -> TryReadFull<A, T>
where
A: AsyncRead,
T: AsMut<[u8]>,
{
TryReadFull {
state: State::Reading { a, buf, pos: 0 },
}
}
impl<A, T> Future for TryReadFull<A, T>
where
A: AsyncRead,
T: AsMut<[u8]>,
{
type Item = (A, T, usize);
type Error = io::Error;
fn poll(&mut self) -> Poll<(A, T, usize), io::Error> {
match self.state {
State::Reading {
ref mut a,
ref mut buf,
ref mut pos,
} => {
let buf = buf.as_mut();
while *pos < buf.len() {
let n = try_nb!(a.read(&mut buf[*pos..]));
*pos += n;
if n == 0 {
break;
}
}
}
State::Empty => panic!("poll a TryReadFull after it's done"),
}
match mem::replace(&mut self.state, State::Empty) {
State::Reading { a, buf, pos } => Ok((a, buf, pos).into()),
State::Empty => panic!(),
}
}
}