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use std::io;
use std::mem;
use futures::{Poll, Future};
use AsyncRead;
#[derive(Debug)]
pub struct ReadExact<A, T> {
state: State<A, T>,
}
#[derive(Debug)]
enum State<A, T> {
Reading {
a: A,
buf: T,
pos: usize,
},
Empty,
}
pub fn read_exact<A, T>(a: A, buf: T) -> ReadExact<A, T>
where A: AsyncRead,
T: AsMut<[u8]>,
{
ReadExact {
state: State::Reading {
a: a,
buf: buf,
pos: 0,
},
}
}
fn eof() -> io::Error {
io::Error::new(io::ErrorKind::UnexpectedEof, "early eof")
}
impl<A, T> Future for ReadExact<A, T>
where A: AsyncRead,
T: AsMut<[u8]>,
{
type Item = (A, T);
type Error = io::Error;
fn poll(&mut self) -> Poll<(A, T), 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 {
return Err(eof())
}
}
}
State::Empty => panic!("poll a ReadExact after it's done"),
}
match mem::replace(&mut self.state, State::Empty) {
State::Reading { a, buf, .. } => Ok((a, buf).into()),
State::Empty => panic!(),
}
}
}