From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- vendor/futures-util/src/stream/repeat_with.rs | 93 +++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 vendor/futures-util/src/stream/repeat_with.rs (limited to 'vendor/futures-util/src/stream/repeat_with.rs') diff --git a/vendor/futures-util/src/stream/repeat_with.rs b/vendor/futures-util/src/stream/repeat_with.rs new file mode 100644 index 000000000..f5a81b4ed --- /dev/null +++ b/vendor/futures-util/src/stream/repeat_with.rs @@ -0,0 +1,93 @@ +use super::assert_stream; +use core::pin::Pin; +use futures_core::stream::{FusedStream, Stream}; +use futures_core::task::{Context, Poll}; + +/// An stream that repeats elements of type `A` endlessly by +/// applying the provided closure `F: FnMut() -> A`. +/// +/// This `struct` is created by the [`repeat_with()`] function. +/// See its documentation for more. +#[derive(Debug, Clone)] +#[must_use = "streams do nothing unless polled"] +pub struct RepeatWith { + repeater: F, +} + +impl A> Unpin for RepeatWith {} + +impl A> Stream for RepeatWith { + type Item = A; + + fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll> { + Poll::Ready(Some((&mut self.repeater)())) + } + + fn size_hint(&self) -> (usize, Option) { + (usize::max_value(), None) + } +} + +impl A> FusedStream for RepeatWith { + fn is_terminated(&self) -> bool { + false + } +} + +/// Creates a new stream that repeats elements of type `A` endlessly by +/// applying the provided closure, the repeater, `F: FnMut() -> A`. +/// +/// The `repeat_with()` function calls the repeater over and over again. +/// +/// Infinite stream like `repeat_with()` are often used with adapters like +/// [`stream.take()`], in order to make them finite. +/// +/// If the element type of the stream you need implements [`Clone`], and +/// it is OK to keep the source element in memory, you should instead use +/// the [`stream.repeat()`] function. +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// # futures::executor::block_on(async { +/// use futures::stream::{self, StreamExt}; +/// +/// // let's assume we have some value of a type that is not `Clone` +/// // or which don't want to have in memory just yet because it is expensive: +/// #[derive(PartialEq, Debug)] +/// struct Expensive; +/// +/// // a particular value forever: +/// let mut things = stream::repeat_with(|| Expensive); +/// +/// assert_eq!(Some(Expensive), things.next().await); +/// assert_eq!(Some(Expensive), things.next().await); +/// assert_eq!(Some(Expensive), things.next().await); +/// # }); +/// ``` +/// +/// Using mutation and going finite: +/// +/// ```rust +/// # futures::executor::block_on(async { +/// use futures::stream::{self, StreamExt}; +/// +/// // From the zeroth to the third power of two: +/// let mut curr = 1; +/// let mut pow2 = stream::repeat_with(|| { let tmp = curr; curr *= 2; tmp }) +/// .take(4); +/// +/// assert_eq!(Some(1), pow2.next().await); +/// assert_eq!(Some(2), pow2.next().await); +/// assert_eq!(Some(4), pow2.next().await); +/// assert_eq!(Some(8), pow2.next().await); +/// +/// // ... and now we're done +/// assert_eq!(None, pow2.next().await); +/// # }); +/// ``` +pub fn repeat_with A>(repeater: F) -> RepeatWith { + assert_stream::(RepeatWith { repeater }) +} -- cgit v1.2.3