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use bytes::{Bytes, BytesMut};
use futures::sink::{Sink, Wait};
use futures::sync::mpsc::Sender;
use std::io::{Error, ErrorKind, Result, Write};
/// Adapter to implement the `std::io::Write` trait on a `Sender<Bytes>` from a futures channel.
///
/// It uses an intermediate buffer to transfer packets.
pub struct Pipe {
// Wrapping the sender in `Wait` makes it blocking, so we can implement blocking-style
// io::Write over the async-style Sender.
dest: Wait<Sender<Bytes>>,
bytes: BytesMut,
}
impl Pipe {
/// Wrap the given sender in a `Pipe`.
pub fn new(destination: Sender<Bytes>) -> Self {
Pipe {
dest: destination.wait(),
bytes: BytesMut::new(),
}
}
}
impl Drop for Pipe {
fn drop(&mut self) {
// This is the correct thing to do, but is not super important since the `Sink`
// implementation of `Sender` just returns `Ok` without doing anything else.
let _ = self.dest.close();
}
}
impl Write for Pipe {
fn write(&mut self, buf: &[u8]) -> Result<usize> {
// We are given a slice of bytes we do not own, so we must start by copying it.
self.bytes.extend_from_slice(buf);
// Then, take the buffer and send it in the channel.
self.dest
.send(self.bytes.take().into())
.map_err(|e| Error::new(ErrorKind::UnexpectedEof, e))?;
// Return how much we sent - all of it.
Ok(buf.len())
}
fn flush(&mut self) -> Result<()> {
self.dest
.flush()
.map_err(|e| Error::new(ErrorKind::UnexpectedEof, e))
}
}
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