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use core::fmt::{self, Debug};
use core::pin::Pin;
use futures_core::{Poll, Stream, FusedStream};
use futures_core::task::Context;
use crate::stream::{StreamExt, StreamFuture, FuturesUnordered};
#[must_use = "streams do nothing unless polled"]
pub struct SelectAll<St> {
inner: FuturesUnordered<StreamFuture<St>>,
}
impl<St: Debug> Debug for SelectAll<St> {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "SelectAll {{ ... }}")
}
}
impl<St: Stream + Unpin> SelectAll<St> {
pub fn new() -> SelectAll<St> {
SelectAll { inner: FuturesUnordered::new() }
}
pub fn len(&self) -> usize {
self.inner.len()
}
pub fn is_empty(&self) -> bool {
self.inner.is_empty()
}
pub fn push(&mut self, stream: St) {
self.inner.push(stream.into_future());
}
}
impl<St: Stream + Unpin> Default for SelectAll<St> {
fn default() -> SelectAll<St> {
SelectAll::new()
}
}
impl<St: Stream + Unpin> Stream for SelectAll<St> {
type Item = St::Item;
fn poll_next(
mut self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Option<Self::Item>> {
match self.inner.poll_next_unpin(cx) {
Poll::Pending => Poll::Pending,
Poll::Ready(Some((Some(item), remaining))) => {
self.push(remaining);
Poll::Ready(Some(item))
}
Poll::Ready(Some((None, _))) => {
let _ = self.inner.poll_next_unpin(cx);
Poll::Ready(None)
}
Poll::Ready(_) => Poll::Ready(None),
}
}
}
impl<St: Stream + Unpin> FusedStream for SelectAll<St> {
fn is_terminated(&self) -> bool {
self.inner.is_terminated()
}
}
pub fn select_all<I>(streams: I) -> SelectAll<I::Item>
where I: IntoIterator,
I::Item: Stream + Unpin
{
let mut set = SelectAll::new();
for stream in streams {
set.push(stream);
}
set
}