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denoland-deno/cli/tokio_write.rs
Ryan Dahl fa3c35301a
Rename //src/ to //cli/ (#1962)
To better distinguish the deno_core crate from the executable deno,
which will now be called "the cli" internally.
2019-03-19 12:18:05 -04:00

62 lines
1.4 KiB
Rust

// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
// TODO Submit this file upstream into tokio-io/src/io/write.rs
use std::io;
use std::mem;
use futures::{Future, Poll};
use tokio::io::AsyncWrite;
/// A future used to write some data to a stream.
///
/// This is created by the [`write`] top-level method.
///
/// [`write`]: fn.write.html
#[derive(Debug)]
pub struct Write<A, T> {
state: State<A, T>,
}
#[derive(Debug)]
enum State<A, T> {
Pending { a: A, buf: T },
Empty,
}
/// Creates a future that will write some of the buffer `buf` to
/// the stream `a` provided.
///
/// Any error which happens during writing will cause both the stream and the
/// buffer to get destroyed.
pub fn write<A, T>(a: A, buf: T) -> Write<A, T>
where
A: AsyncWrite,
T: AsRef<[u8]>,
{
Write {
state: State::Pending { a, buf },
}
}
impl<A, T> Future for Write<A, T>
where
A: AsyncWrite,
T: AsRef<[u8]>,
{
type Item = (A, T, usize);
type Error = io::Error;
fn poll(&mut self) -> Poll<(A, T, usize), io::Error> {
let nwritten = match self.state {
State::Pending {
ref mut a,
ref mut buf,
} => try_ready!(a.poll_write(buf.as_ref())),
State::Empty => panic!("poll a Read after it's done"),
};
match mem::replace(&mut self.state, State::Empty) {
State::Pending { a, buf } => Ok((a, buf, nwritten).into()),
State::Empty => panic!("invalid internal state"),
}
}
}