futures_util/io/
write_all.rs

use std::io;
use std::mem;

use {Poll, Future, task};

use futures_io::AsyncWrite;

/// A future used to write the entire contents of some data to a stream.
///
/// This is created by the [`write_all`] top-level method.
///
/// [`write_all`]: fn.write_all.html
#[derive(Debug)]
pub struct WriteAll<A, T> {
    state: State<A, T>,
}

#[derive(Debug)]
enum State<A, T> {
    Writing {
        a: A,
        buf: T,
        pos: usize,
    },
    Empty,
}

pub fn write_all<A, T>(a: A, buf: T) -> WriteAll<A, T>
    where A: AsyncWrite,
          T: AsRef<[u8]>,
{
    WriteAll {
        state: State::Writing {
            a: a,
            buf: buf,
            pos: 0,
        },
    }
}

fn zero_write() -> io::Error {
    io::Error::new(io::ErrorKind::WriteZero, "zero-length write")
}

impl<A, T> Future for WriteAll<A, T>
    where A: AsyncWrite,
          T: AsRef<[u8]>,
{
    type Item = (A, T);
    type Error = io::Error;

    fn poll(&mut self, cx: &mut task::Context) -> Poll<(A, T), io::Error> {
        match self.state {
            State::Writing { ref mut a, ref buf, ref mut pos } => {
                let buf = buf.as_ref();
                while *pos < buf.len() {
                    let n = try_ready!(a.poll_write(cx, &buf[*pos..]));
                    *pos += n;
                    if n == 0 {
                        return Err(zero_write())
                    }
                }
            }
            State::Empty => panic!("poll a WriteAll after it's done"),
        }

        match mem::replace(&mut self.state, State::Empty) {
            State::Writing { a, buf, .. } => Ok((a, buf).into()),
            State::Empty => panic!(),
        }
    }
}
futures_util/io/write_all.rs

futures_util/io/
write_all.rs
