blob: 732ae855deebbaf87b898f66c1e6062211af06d9 [file] [log] [blame]
use {Async, Poll, IntoFuture, Future};
use stream::Stream;
/// A stream combinator which takes elements from a stream while a predicate
/// holds.
///
/// This structure is produced by the `Stream::take_while` method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TakeWhile<S, P, R> where S: Stream, R: IntoFuture {
stream: S,
pred: P,
pending: Option<(R::Future, S::Item)>,
done_taking: bool,
}
pub fn new<S, P, R>(s: S, p: P) -> TakeWhile<S, P, R>
where S: Stream,
P: FnMut(&S::Item) -> R,
R: IntoFuture<Item=bool, Error=S::Error>,
{
TakeWhile {
stream: s,
pred: p,
pending: None,
done_taking: false,
}
}
impl<S, P, R> TakeWhile<S, P, R> where S: Stream, R: IntoFuture {
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &S {
&self.stream
}
/// 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 {
&mut self.stream
}
/// 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
}
}
// Forwarding impl of Sink from the underlying stream
impl<S, P, R> ::sink::Sink for TakeWhile<S, P, R>
where S: ::sink::Sink + Stream, R: 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()
}
}
impl<S, P, R> Stream for TakeWhile<S, P, R>
where S: Stream,
P: FnMut(&S::Item) -> R,
R: IntoFuture<Item=bool, Error=S::Error>,
{
type Item = S::Item;
type Error = S::Error;
fn poll(&mut self) -> Poll<Option<S::Item>, S::Error> {
if self.done_taking {
return Ok(Async::Ready(None));
}
if self.pending.is_none() {
let item = match try_ready!(self.stream.poll()) {
Some(e) => e,
None => return Ok(Async::Ready(None)),
};
self.pending = Some(((self.pred)(&item).into_future(), item));
}
assert!(self.pending.is_some());
match self.pending.as_mut().unwrap().0.poll() {
Ok(Async::Ready(true)) => {
let (_, item) = self.pending.take().unwrap();
Ok(Async::Ready(Some(item)))
},
Ok(Async::Ready(false)) => {
self.done_taking = true;
Ok(Async::Ready(None))
}
Ok(Async::NotReady) => Ok(Async::NotReady),
Err(e) => {
self.pending = None;
Err(e)
}
}
}
}