use crate::stream::{StreamExt, Fuse};
use core::cmp;
use core::pin::Pin;
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{Context, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct Zip<St1: Stream, St2: Stream> {
stream1: Fuse<St1>,
stream2: Fuse<St2>,
queued1: Option<St1::Item>,
queued2: Option<St2::Item>,
}
#[allow(clippy::type_repetition_in_bounds)] impl<St1, St2> Unpin for Zip<St1, St2>
where
St1: Stream,
Fuse<St1>: Unpin,
St2: Stream,
Fuse<St2>: Unpin,
{}
impl<St1: Stream, St2: Stream> Zip<St1, St2> {
unsafe_pinned!(stream1: Fuse<St1>);
unsafe_pinned!(stream2: Fuse<St2>);
unsafe_unpinned!(queued1: Option<St1::Item>);
unsafe_unpinned!(queued2: Option<St2::Item>);
pub(super) fn new(stream1: St1, stream2: St2) -> Zip<St1, St2> {
Zip {
stream1: stream1.fuse(),
stream2: stream2.fuse(),
queued1: None,
queued2: None,
}
}
pub fn get_ref(&self) -> (&St1, &St2) {
(self.stream1.get_ref(), self.stream2.get_ref())
}
pub fn get_mut(&mut self) -> (&mut St1, &mut St2) {
(self.stream1.get_mut(), self.stream2.get_mut())
}
pub fn get_pin_mut(self: Pin<&mut Self>) -> (Pin<&mut St1>, Pin<&mut St2>) {
unsafe {
let Self { stream1, stream2, .. } = self.get_unchecked_mut();
(Pin::new_unchecked(stream1).get_pin_mut(), Pin::new_unchecked(stream2).get_pin_mut())
}
}
pub fn into_inner(self) -> (St1, St2) {
(self.stream1.into_inner(), self.stream2.into_inner())
}
}
impl<St1, St2> FusedStream for Zip<St1, St2>
where St1: Stream, St2: Stream,
{
fn is_terminated(&self) -> bool {
self.stream1.is_terminated() && self.stream2.is_terminated()
}
}
impl<St1, St2> Stream for Zip<St1, St2>
where St1: Stream, St2: Stream
{
type Item = (St1::Item, St2::Item);
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Self::Item>> {
if self.queued1.is_none() {
match self.as_mut().stream1().poll_next(cx) {
Poll::Ready(Some(item1)) => *self.as_mut().queued1() = Some(item1),
Poll::Ready(None) | Poll::Pending => {}
}
}
if self.queued2.is_none() {
match self.as_mut().stream2().poll_next(cx) {
Poll::Ready(Some(item2)) => *self.as_mut().queued2() = Some(item2),
Poll::Ready(None) | Poll::Pending => {}
}
}
if self.queued1.is_some() && self.queued2.is_some() {
let pair = (self.as_mut().queued1().take().unwrap(),
self.as_mut().queued2().take().unwrap());
Poll::Ready(Some(pair))
} else if self.stream1.is_done() || self.stream2.is_done() {
Poll::Ready(None)
} else {
Poll::Pending
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let queued1_len = if self.queued1.is_some() { 1 } else { 0 };
let queued2_len = if self.queued2.is_some() { 1 } else { 0 };
let (stream1_lower, stream1_upper) = self.stream1.size_hint();
let (stream2_lower, stream2_upper) = self.stream2.size_hint();
let stream1_lower = stream1_lower.saturating_add(queued1_len);
let stream2_lower = stream2_lower.saturating_add(queued2_len);
let lower = cmp::min(stream1_lower, stream2_lower);
let upper = match (stream1_upper, stream2_upper) {
(Some(x), Some(y)) => {
let x = x.saturating_add(queued1_len);
let y = y.saturating_add(queued2_len);
Some(cmp::min(x, y))
}
(Some(x), None) => x.checked_add(queued1_len),
(None, Some(y)) => y.checked_add(queued2_len),
(None, None) => None
};
(lower, upper)
}
}