Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 57 insertions, 0 deletions

diff --git a/third_party/rust/futures-util/src/stream/poll_fn.rs b/third_party/rust/futures-util/src/stream/poll_fn.rs
new file mode 100644
index 0000000000..b9bd7d1664
--- /dev/null
+++ b/third_party/rust/futures-util/src/stream/poll_fn.rs
@@ -0,0 +1,57 @@
+//! Definition of the `PollFn` combinator
+
+use super::assert_stream;
+use core::fmt;
+use core::pin::Pin;
+use futures_core::stream::Stream;
+use futures_core::task::{Context, Poll};
+
+/// Stream for the [`poll_fn`] function.
+#[must_use = "streams do nothing unless polled"]
+pub struct PollFn<F> {
+    f: F,
+}
+
+impl<F> Unpin for PollFn<F> {}
+
+impl<F> fmt::Debug for PollFn<F> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("PollFn").finish()
+    }
+}
+
+/// Creates a new stream wrapping a function returning `Poll<Option<T>>`.
+///
+/// Polling the returned stream calls the wrapped function.
+///
+/// # Examples
+///
+/// ```
+/// use futures::stream::poll_fn;
+/// use futures::task::Poll;
+///
+/// let mut counter = 1usize;
+///
+/// let read_stream = poll_fn(move |_| -> Poll<Option<String>> {
+///     if counter == 0 { return Poll::Ready(None); }
+///     counter -= 1;
+///     Poll::Ready(Some("Hello, World!".to_owned()))
+/// });
+/// ```
+pub fn poll_fn<T, F>(f: F) -> PollFn<F>
+where
+    F: FnMut(&mut Context<'_>) -> Poll<Option<T>>,
+{
+    assert_stream::<T, _>(PollFn { f })
+}
+
+impl<T, F> Stream for PollFn<F>
+where
+    F: FnMut(&mut Context<'_>) -> Poll<Option<T>>,
+{
+    type Item = T;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
+        (&mut self.f)(cx)
+    }
+}