termion/src/async.rs

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2016-03-15 19:32:25 +00:00
use std::io::{self, Read};
use std::sync::mpsc;
use std::thread;
/// Construct an asynchronous handle to the standard input.
///
/// This allows you to read from standard input _without blocking_ the current thread.
/// Specifically, it works by firing up another thread to handle the event stream, which will then
/// be buffered in a mpsc queue, which will eventually be read by the current thread.
///
/// Note that this will acquire the Mutex lock on the standard input, making all future stdin
/// construction hang the program.
pub fn async_stdin() -> AsyncReader {
let (send, recv) = mpsc::channel();
thread::spawn(move || {
let stdin = io::stdin();
for i in stdin.lock().bytes() {
if send.send(i).is_err() {
return;
}
}
});
AsyncReader {
recv: recv,
}
}
/// An asynchronous reader.
pub struct AsyncReader {
/// The underlying mpsc receiver.
#[doc(hidden)]
pub recv: mpsc::Receiver<io::Result<u8>>,
}
impl Read for AsyncReader {
/// Read from the byte stream.
///
/// This will never block, but try to drain the event queue until empty. If the total number of
/// bytes written is lower than the buffer's length, the event queue is empty or that the event
/// stream halted.
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let mut total = 0;
loop {
match self.recv.try_recv() {
Ok(Ok(b)) => {
buf[total] = b;
total += 1;
if total == buf.len() {
break;
}
},
Ok(Err(e)) => return Err(e),
Err(_) => break,
}
}
Ok(total)
}
}
#[cfg(test)]
mod test {
use super::*;
use std::io::Read;
#[test]
fn test_async_stdin() {
let stdin = async_stdin();
stdin.bytes().next();
}
}