blob: 3011108cf39a9b88a59fd7b7478d3f4c8a407f6a [file] [log] [blame]
use std::fmt;
use {Async, IntoFuture, Poll};
use stream::{Stream, Fuse, FuturesUnordered};
/// An adaptor for a stream of futures to execute the futures concurrently, if
/// possible, delivering results as they become available.
///
/// This adaptor will buffer up a list of pending futures, and then return their
/// results in the order that they complete. This is created by the
/// `Stream::buffer_unordered` method.
#[must_use = "streams do nothing unless polled"]
pub struct BufferUnordered<S>
where S: Stream,
S::Item: IntoFuture,
{
stream: Fuse<S>,
queue: FuturesUnordered<<S::Item as IntoFuture>::Future>,
max: usize,
}
impl<S> fmt::Debug for BufferUnordered<S>
where S: Stream + fmt::Debug,
S::Item: IntoFuture,
<<S as Stream>::Item as IntoFuture>::Future: fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("BufferUnordered")
.field("stream", &self.stream)
.field("queue", &self.queue)
.field("max", &self.max)
.finish()
}
}
pub fn new<S>(s: S, amt: usize) -> BufferUnordered<S>
where S: Stream,
S::Item: IntoFuture<Error=<S as Stream>::Error>,
{
BufferUnordered {
stream: super::fuse::new(s),
queue: FuturesUnordered::new(),
max: amt,
}
}
impl<S> BufferUnordered<S>
where S: Stream,
S::Item: IntoFuture<Error=<S as Stream>::Error>,
{
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &S {
self.stream.get_ref()
}
/// Acquires a mutable reference to the underlying stream that this
/// combinator is pulling from.
///
/// Note that care must be taken to avoid tampering with the state of the
/// stream which may otherwise confuse this combinator.
pub fn get_mut(&mut self) -> &mut S {
self.stream.get_mut()
}
/// Consumes this combinator, returning the underlying stream.
///
/// Note that this may discard intermediate state of this combinator, so
/// care should be taken to avoid losing resources when this is called.
pub fn into_inner(self) -> S {
self.stream.into_inner()
}
}
impl<S> Stream for BufferUnordered<S>
where S: Stream,
S::Item: IntoFuture<Error=<S as Stream>::Error>,
{
type Item = <S::Item as IntoFuture>::Item;
type Error = <S as Stream>::Error;
fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
// First up, try to spawn off as many futures as possible by filling up
// our slab of futures.
while self.queue.len() < self.max {
let future = match self.stream.poll()? {
Async::Ready(Some(s)) => s.into_future(),
Async::Ready(None) |
Async::NotReady => break,
};
self.queue.push(future);
}
// Try polling a new future
if let Some(val) = try_ready!(self.queue.poll()) {
return Ok(Async::Ready(Some(val)));
}
// If we've gotten this far, then there are no events for us to process
// and nothing was ready, so figure out if we're not done yet or if
// we've reached the end.
if self.stream.is_done() {
Ok(Async::Ready(None))
} else {
Ok(Async::NotReady)
}
}
}
// Forwarding impl of Sink from the underlying stream
impl<S> ::sink::Sink for BufferUnordered<S>
where S: ::sink::Sink + Stream,
S::Item: IntoFuture,
{
type SinkItem = S::SinkItem;
type SinkError = S::SinkError;
fn start_send(&mut self, item: S::SinkItem) -> ::StartSend<S::SinkItem, S::SinkError> {
self.stream.start_send(item)
}
fn poll_complete(&mut self) -> Poll<(), S::SinkError> {
self.stream.poll_complete()
}
fn close(&mut self) -> Poll<(), S::SinkError> {
self.stream.close()
}
}