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use futures::{Async, Poll, Sink, StartSend, Stream};
/// A stream combinator which combines the yields the current item
/// plus its count starting from 0.
///
/// This structure is produced by the `Stream::enumerate` method.
#[derive(Debug)]
#[must_use = "Does nothing unless polled"]
pub struct Enumerate<T> {
inner: T,
count: usize,
}
impl<T> Enumerate<T> {
pub(crate) fn new(stream: T) -> Self {
Self {
inner: stream,
count: 0,
}
}
/// Acquires a reference to the underlying stream that this combinator is
/// pulling from.
pub fn get_ref(&self) -> &T {
&self.inner
}
/// 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 T {
&mut self.inner
}
/// 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) -> T {
self.inner
}
}
impl<T> Stream for Enumerate<T>
where
T: Stream,
{
type Item = (usize, T::Item);
type Error = T::Error;
fn poll(&mut self) -> Poll<Option<Self::Item>, T::Error> {
match try_ready!(self.inner.poll()) {
Some(item) => {
let ret = Some((self.count, item));
self.count += 1;
Ok(Async::Ready(ret))
}
None => return Ok(Async::Ready(None)),
}
}
}
// Forwarding impl of Sink from the underlying stream
impl<T> Sink for Enumerate<T>
where
T: Sink,
{
type SinkItem = T::SinkItem;
type SinkError = T::SinkError;
fn start_send(&mut self, item: T::SinkItem) -> StartSend<T::SinkItem, T::SinkError> {
self.inner.start_send(item)
}
fn poll_complete(&mut self) -> Poll<(), T::SinkError> {
self.inner.poll_complete()
}
fn close(&mut self) -> Poll<(), T::SinkError> {
self.inner.close()
}
}
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