tokio_io/io/
write_all.rs

1use std::io;
2use std::mem;
3
4use futures::{Future, Poll};
5
6use AsyncWrite;
7
8/// A future used to write the entire contents of some data to a stream.
9///
10/// This is created by the [`write_all`] top-level method.
11///
12/// [`write_all`]: fn.write_all.html
13#[derive(Debug)]
14pub struct WriteAll<A, T> {
15    state: State<A, T>,
16}
17
18#[derive(Debug)]
19enum State<A, T> {
20    Writing { a: A, buf: T, pos: usize },
21    Empty,
22}
23
24/// Creates a future that will write the entire contents of the buffer `buf` to
25/// the stream `a` provided.
26///
27/// The returned future will not return until all the data has been written, and
28/// the future will resolve to the stream as well as the buffer (for reuse if
29/// needed).
30///
31/// Any error which happens during writing will cause both the stream and the
32/// buffer to get destroyed.
33///
34/// The `buf` parameter here only requires the `AsRef<[u8]>` trait, which should
35/// be broadly applicable to accepting data which can be converted to a slice.
36/// The `Window` struct is also available in this crate to provide a different
37/// window into a slice if necessary.
38pub fn write_all<A, T>(a: A, buf: T) -> WriteAll<A, T>
39where
40    A: AsyncWrite,
41    T: AsRef<[u8]>,
42{
43    WriteAll {
44        state: State::Writing {
45            a: a,
46            buf: buf,
47            pos: 0,
48        },
49    }
50}
51
52fn zero_write() -> io::Error {
53    io::Error::new(io::ErrorKind::WriteZero, "zero-length write")
54}
55
56impl<A, T> Future for WriteAll<A, T>
57where
58    A: AsyncWrite,
59    T: AsRef<[u8]>,
60{
61    type Item = (A, T);
62    type Error = io::Error;
63
64    fn poll(&mut self) -> Poll<(A, T), io::Error> {
65        match self.state {
66            State::Writing {
67                ref mut a,
68                ref buf,
69                ref mut pos,
70            } => {
71                let buf = buf.as_ref();
72                while *pos < buf.len() {
73                    let n = try_ready!(a.poll_write(&buf[*pos..]));
74                    *pos += n;
75                    if n == 0 {
76                        return Err(zero_write());
77                    }
78                }
79            }
80            State::Empty => panic!("poll a WriteAll after it's done"),
81        }
82
83        match mem::replace(&mut self.state, State::Empty) {
84            State::Writing { a, buf, .. } => Ok((a, buf).into()),
85            State::Empty => panic!(),
86        }
87    }
88}
tokio_io/io/write_all.rs

tokio_io/io/
write_all.rs
