blob: 0ca68496eb6969363122577fae47d4977029f62c [file] [log] [blame]
use {Async, Poll};
use stream::Stream;
/// A stream combinator which returns a maximum number of elements.
///
/// This structure is produced by the `Stream::take` method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Take<S> {
stream: S,
remaining: u64,
}
pub fn new<S>(s: S, amt: u64) -> Take<S>
where S: Stream,
{
Take {
stream: s,
remaining: amt,
}
}
impl<S> Take<S> {
/// 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> ::sink::Sink for Take<S>
where S: ::sink::Sink + Stream
{
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> Stream for Take<S>
where S: Stream,
{
type Item = S::Item;
type Error = S::Error;
fn poll(&mut self) -> Poll<Option<S::Item>, S::Error> {
if self.remaining == 0 {
Ok(Async::Ready(None))
} else {
let next = try_ready!(self.stream.poll());
match next {
Some(_) => self.remaining -= 1,
None => self.remaining = 0,
}
Ok(Async::Ready(next))
}
}
}