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-rw-r--r--third_party/rust/futures-util/src/stream/select_all.rs254
1 files changed, 254 insertions, 0 deletions
diff --git a/third_party/rust/futures-util/src/stream/select_all.rs b/third_party/rust/futures-util/src/stream/select_all.rs
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+//! An unbounded set of streams
+
+use core::fmt::{self, Debug};
+use core::iter::FromIterator;
+use core::pin::Pin;
+
+use futures_core::ready;
+use futures_core::stream::{FusedStream, Stream};
+use futures_core::task::{Context, Poll};
+
+use pin_project_lite::pin_project;
+
+use super::assert_stream;
+use crate::stream::{futures_unordered, FuturesUnordered, StreamExt, StreamFuture};
+
+pin_project! {
+ /// An unbounded set of streams
+ ///
+ /// This "combinator" provides the ability to maintain a set of streams
+ /// and drive them all to completion.
+ ///
+ /// Streams are pushed into this set and their realized values are
+ /// yielded as they become ready. Streams will only be polled when they
+ /// generate notifications. This allows to coordinate a large number of streams.
+ ///
+ /// Note that you can create a ready-made `SelectAll` via the
+ /// `select_all` function in the `stream` module, or you can start with an
+ /// empty set with the `SelectAll::new` constructor.
+ #[must_use = "streams do nothing unless polled"]
+ pub struct SelectAll<St> {
+ #[pin]
+ inner: FuturesUnordered<StreamFuture<St>>,
+ }
+}
+
+impl<St: Debug> Debug for SelectAll<St> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ write!(f, "SelectAll {{ ... }}")
+ }
+}
+
+impl<St: Stream + Unpin> SelectAll<St> {
+ /// Constructs a new, empty `SelectAll`
+ ///
+ /// The returned `SelectAll` does not contain any streams and, in this
+ /// state, `SelectAll::poll` will return `Poll::Ready(None)`.
+ pub fn new() -> Self {
+ Self { inner: FuturesUnordered::new() }
+ }
+
+ /// Returns the number of streams contained in the set.
+ ///
+ /// This represents the total number of in-flight streams.
+ pub fn len(&self) -> usize {
+ self.inner.len()
+ }
+
+ /// Returns `true` if the set contains no streams
+ pub fn is_empty(&self) -> bool {
+ self.inner.is_empty()
+ }
+
+ /// Push a stream into the set.
+ ///
+ /// This function submits the given stream to the set for managing. This
+ /// function will not call `poll` on the submitted stream. The caller must
+ /// ensure that `SelectAll::poll` is called in order to receive task
+ /// notifications.
+ pub fn push(&mut self, stream: St) {
+ self.inner.push(stream.into_future());
+ }
+
+ /// Returns an iterator that allows inspecting each stream in the set.
+ pub fn iter(&self) -> Iter<'_, St> {
+ Iter(self.inner.iter())
+ }
+
+ /// Returns an iterator that allows modifying each stream in the set.
+ pub fn iter_mut(&mut self) -> IterMut<'_, St> {
+ IterMut(self.inner.iter_mut())
+ }
+
+ /// Clears the set, removing all streams.
+ pub fn clear(&mut self) {
+ self.inner.clear()
+ }
+}
+
+impl<St: Stream + Unpin> Default for SelectAll<St> {
+ fn default() -> Self {
+ Self::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>> {
+ loop {
+ match ready!(self.inner.poll_next_unpin(cx)) {
+ Some((Some(item), remaining)) => {
+ self.push(remaining);
+ return Poll::Ready(Some(item));
+ }
+ Some((None, _)) => {
+ // `FuturesUnordered` thinks it isn't terminated
+ // because it yielded a Some.
+ // We do not return, but poll `FuturesUnordered`
+ // in the next loop iteration.
+ }
+ None => return Poll::Ready(None),
+ }
+ }
+ }
+}
+
+impl<St: Stream + Unpin> FusedStream for SelectAll<St> {
+ fn is_terminated(&self) -> bool {
+ self.inner.is_terminated()
+ }
+}
+
+/// Convert a list of streams into a `Stream` of results from the streams.
+///
+/// This essentially takes a list of streams (e.g. a vector, an iterator, etc.)
+/// and bundles them together into a single stream.
+/// The stream will yield items as they become available on the underlying
+/// streams internally, in the order they become available.
+///
+/// Note that the returned set can also be used to dynamically push more
+/// streams into the set as they become available.
+///
+/// This function is only available when the `std` or `alloc` feature of this
+/// library is activated, and it is activated by default.
+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);
+ }
+
+ assert_stream::<<I::Item as Stream>::Item, _>(set)
+}
+
+impl<St: Stream + Unpin> FromIterator<St> for SelectAll<St> {
+ fn from_iter<T: IntoIterator<Item = St>>(iter: T) -> Self {
+ select_all(iter)
+ }
+}
+
+impl<St: Stream + Unpin> Extend<St> for SelectAll<St> {
+ fn extend<T: IntoIterator<Item = St>>(&mut self, iter: T) {
+ for st in iter {
+ self.push(st)
+ }
+ }
+}
+
+impl<St: Stream + Unpin> IntoIterator for SelectAll<St> {
+ type Item = St;
+ type IntoIter = IntoIter<St>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ IntoIter(self.inner.into_iter())
+ }
+}
+
+impl<'a, St: Stream + Unpin> IntoIterator for &'a SelectAll<St> {
+ type Item = &'a St;
+ type IntoIter = Iter<'a, St>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ self.iter()
+ }
+}
+
+impl<'a, St: Stream + Unpin> IntoIterator for &'a mut SelectAll<St> {
+ type Item = &'a mut St;
+ type IntoIter = IterMut<'a, St>;
+
+ fn into_iter(self) -> Self::IntoIter {
+ self.iter_mut()
+ }
+}
+
+/// Immutable iterator over all streams in the unordered set.
+#[derive(Debug)]
+pub struct Iter<'a, St: Unpin>(futures_unordered::Iter<'a, StreamFuture<St>>);
+
+/// Mutable iterator over all streams in the unordered set.
+#[derive(Debug)]
+pub struct IterMut<'a, St: Unpin>(futures_unordered::IterMut<'a, StreamFuture<St>>);
+
+/// Owned iterator over all streams in the unordered set.
+#[derive(Debug)]
+pub struct IntoIter<St: Unpin>(futures_unordered::IntoIter<StreamFuture<St>>);
+
+impl<'a, St: Stream + Unpin> Iterator for Iter<'a, St> {
+ type Item = &'a St;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let st = self.0.next()?;
+ let next = st.get_ref();
+ // This should always be true because FuturesUnordered removes completed futures.
+ debug_assert!(next.is_some());
+ next
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.0.size_hint()
+ }
+}
+
+impl<St: Stream + Unpin> ExactSizeIterator for Iter<'_, St> {}
+
+impl<'a, St: Stream + Unpin> Iterator for IterMut<'a, St> {
+ type Item = &'a mut St;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let st = self.0.next()?;
+ let next = st.get_mut();
+ // This should always be true because FuturesUnordered removes completed futures.
+ debug_assert!(next.is_some());
+ next
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.0.size_hint()
+ }
+}
+
+impl<St: Stream + Unpin> ExactSizeIterator for IterMut<'_, St> {}
+
+impl<St: Stream + Unpin> Iterator for IntoIter<St> {
+ type Item = St;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let st = self.0.next()?;
+ let next = st.into_inner();
+ // This should always be true because FuturesUnordered removes completed futures.
+ debug_assert!(next.is_some());
+ next
+ }
+
+ fn size_hint(&self) -> (usize, Option<usize>) {
+ self.0.size_hint()
+ }
+}
+
+impl<St: Stream + Unpin> ExactSizeIterator for IntoIter<St> {}