| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.28/src/stream/stream/flatten_unordered.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>flatten_unordered.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../../normalize.css"><link rel="stylesheet" href="../../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../../ayu.css" disabled><link rel="stylesheet" href="../../../../dark.css" disabled><link rel="stylesheet" href="../../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../../storage.js"></script><script defer src="../../../../source-script.js"></script><script defer src="../../../../source-files.js"></script><script defer src="../../../../main.js"></script><noscript><link rel="stylesheet" href="../../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../../futures_util/index.html"><div class="logo-container"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../futures_util/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| <span id="522">522</span> |
| <span id="523">523</span> |
| <span id="524">524</span> |
| <span id="525">525</span> |
| <span id="526">526</span> |
| <span id="527">527</span> |
| <span id="528">528</span> |
| <span id="529">529</span> |
| <span id="530">530</span> |
| <span id="531">531</span> |
| <span id="532">532</span> |
| <span id="533">533</span> |
| <span id="534">534</span> |
| <span id="535">535</span> |
| <span id="536">536</span> |
| </pre><pre class="rust"><code><span class="kw">use </span>alloc::sync::Arc; |
| <span class="kw">use </span>core::{ |
| cell::UnsafeCell, |
| convert::identity, |
| fmt, |
| marker::PhantomData, |
| num::NonZeroUsize, |
| pin::Pin, |
| sync::atomic::{AtomicU8, Ordering}, |
| }; |
| |
| <span class="kw">use </span>pin_project_lite::pin_project; |
| |
| <span class="kw">use </span>futures_core::{ |
| future::Future, |
| ready, |
| stream::{FusedStream, Stream}, |
| task::{Context, Poll, Waker}, |
| }; |
| <span class="attribute">#[cfg(feature = <span class="string">"sink"</span>)] |
| </span><span class="kw">use </span>futures_sink::Sink; |
| <span class="kw">use </span>futures_task::{waker, ArcWake}; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::stream::FuturesUnordered; |
| |
| <span class="doccomment">/// Stream for the [`flatten_unordered`](super::StreamExt::flatten_unordered) |
| /// method. |
| </span><span class="kw">pub type </span>FlattenUnordered<St> = FlattenUnorderedWithFlowController<St, ()>; |
| |
| <span class="doccomment">/// There is nothing to poll and stream isn't being polled/waking/woken at the moment. |
| </span><span class="kw">const </span>NONE: u8 = <span class="number">0</span>; |
| |
| <span class="doccomment">/// Inner streams need to be polled. |
| </span><span class="kw">const </span>NEED_TO_POLL_INNER_STREAMS: u8 = <span class="number">1</span>; |
| |
| <span class="doccomment">/// The base stream needs to be polled. |
| </span><span class="kw">const </span>NEED_TO_POLL_STREAM: u8 = <span class="number">0b10</span>; |
| |
| <span class="doccomment">/// Both base stream and inner streams need to be polled. |
| </span><span class="kw">const </span>NEED_TO_POLL_ALL: u8 = NEED_TO_POLL_INNER_STREAMS | NEED_TO_POLL_STREAM; |
| |
| <span class="doccomment">/// The current stream is being polled at the moment. |
| </span><span class="kw">const </span>POLLING: u8 = <span class="number">0b100</span>; |
| |
| <span class="doccomment">/// Stream is being woken at the moment. |
| </span><span class="kw">const </span>WAKING: u8 = <span class="number">0b1000</span>; |
| |
| <span class="doccomment">/// The stream was waked and will be polled. |
| </span><span class="kw">const </span>WOKEN: u8 = <span class="number">0b10000</span>; |
| |
| <span class="doccomment">/// Internal polling state of the stream. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">struct </span>SharedPollState { |
| state: Arc<AtomicU8>, |
| } |
| |
| <span class="kw">impl </span>SharedPollState { |
| <span class="doccomment">/// Constructs new `SharedPollState` with the given state. |
| </span><span class="kw">fn </span>new(value: u8) -> SharedPollState { |
| SharedPollState { state: Arc::new(AtomicU8::new(value)) } |
| } |
| |
| <span class="doccomment">/// Attempts to start polling, returning stored state in case of success. |
| /// Returns `None` if either waker is waking at the moment. |
| </span><span class="kw">fn </span>start_polling( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| ) -> <span class="prelude-ty">Option</span><(u8, PollStateBomb<<span class="lifetime">'_</span>, <span class="kw">impl </span>FnOnce(<span class="kw-2">&</span>SharedPollState) -> u8>)> { |
| <span class="kw">let </span>value = <span class="self">self |
| </span>.state |
| .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |value| { |
| <span class="kw">if </span>value & WAKING == NONE { |
| <span class="prelude-val">Some</span>(POLLING) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| }) |
| .ok()<span class="question-mark">?</span>; |
| <span class="kw">let </span>bomb = PollStateBomb::new(<span class="self">self</span>, SharedPollState::reset); |
| |
| <span class="prelude-val">Some</span>((value, bomb)) |
| } |
| |
| <span class="doccomment">/// Attempts to start the waking process and performs bitwise or with the given value. |
| /// |
| /// If some waker is already in progress or stream is already woken/being polled, waking process won't start, however |
| /// state will be disjuncted with the given value. |
| </span><span class="kw">fn </span>start_waking( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| to_poll: u8, |
| ) -> <span class="prelude-ty">Option</span><(u8, PollStateBomb<<span class="lifetime">'_</span>, <span class="kw">impl </span>FnOnce(<span class="kw-2">&</span>SharedPollState) -> u8>)> { |
| <span class="kw">let </span>value = <span class="self">self |
| </span>.state |
| .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |value| { |
| <span class="kw">let </span><span class="kw-2">mut </span>next_value = value | to_poll; |
| <span class="kw">if </span>value & (WOKEN | POLLING) == NONE { |
| next_value |= WAKING; |
| } |
| |
| <span class="kw">if </span>next_value != value { |
| <span class="prelude-val">Some</span>(next_value) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| }) |
| .ok()<span class="question-mark">?</span>; |
| |
| <span class="comment">// Only start the waking process if we're not in the polling/waking phase and the stream isn't woken already |
| </span><span class="kw">if </span>value & (WOKEN | POLLING | WAKING) == NONE { |
| <span class="kw">let </span>bomb = PollStateBomb::new(<span class="self">self</span>, SharedPollState::stop_waking); |
| |
| <span class="prelude-val">Some</span>((value, bomb)) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| |
| <span class="doccomment">/// Sets current state to |
| /// - `!POLLING` allowing to use wakers |
| /// - `WOKEN` if the state was changed during `POLLING` phase as waker will be called, |
| /// or `will_be_woken` flag supplied |
| /// - `!WAKING` as |
| /// * Wakers called during the `POLLING` phase won't propagate their calls |
| /// * `POLLING` phase can't start if some of the wakers are active |
| /// So no wrapped waker can touch the inner waker's cell, it's safe to poll again. |
| </span><span class="kw">fn </span>stop_polling(<span class="kw-2">&</span><span class="self">self</span>, to_poll: u8, will_be_woken: bool) -> u8 { |
| <span class="self">self</span>.state |
| .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |<span class="kw-2">mut </span>value| { |
| <span class="kw">let </span><span class="kw-2">mut </span>next_value = to_poll; |
| |
| value &= NEED_TO_POLL_ALL; |
| <span class="kw">if </span>value != NONE || will_be_woken { |
| next_value |= WOKEN; |
| } |
| next_value |= value; |
| |
| <span class="prelude-val">Some</span>(next_value & !POLLING & !WAKING) |
| }) |
| .unwrap() |
| } |
| |
| <span class="doccomment">/// Toggles state to non-waking, allowing to start polling. |
| </span><span class="kw">fn </span>stop_waking(<span class="kw-2">&</span><span class="self">self</span>) -> u8 { |
| <span class="kw">let </span>value = <span class="self">self |
| </span>.state |
| .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |value| { |
| <span class="kw">let </span>next_value = value & !WAKING | WOKEN; |
| |
| <span class="kw">if </span>next_value != value { |
| <span class="prelude-val">Some</span>(next_value) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| }) |
| .unwrap_or_else(identity); |
| |
| <span class="macro">debug_assert!</span>(value & (WOKEN | POLLING | WAKING) == WAKING); |
| value |
| } |
| |
| <span class="doccomment">/// Resets current state allowing to poll the stream and wake up wakers. |
| </span><span class="kw">fn </span>reset(<span class="kw-2">&</span><span class="self">self</span>) -> u8 { |
| <span class="self">self</span>.state.swap(NEED_TO_POLL_ALL, Ordering::SeqCst) |
| } |
| } |
| |
| <span class="doccomment">/// Used to execute some function on the given state when dropped. |
| </span><span class="kw">struct </span>PollStateBomb<<span class="lifetime">'a</span>, F: FnOnce(<span class="kw-2">&</span>SharedPollState) -> u8> { |
| state: <span class="kw-2">&</span><span class="lifetime">'a </span>SharedPollState, |
| drop: <span class="prelude-ty">Option</span><F>, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>, F: FnOnce(<span class="kw-2">&</span>SharedPollState) -> u8> PollStateBomb<<span class="lifetime">'a</span>, F> { |
| <span class="doccomment">/// Constructs new bomb with the given state. |
| </span><span class="kw">fn </span>new(state: <span class="kw-2">&</span><span class="lifetime">'a </span>SharedPollState, drop: F) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ state, drop: <span class="prelude-val">Some</span>(drop) } |
| } |
| |
| <span class="doccomment">/// Deactivates bomb, forces it to not call provided function when dropped. |
| </span><span class="kw">fn </span>deactivate(<span class="kw-2">mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.drop.take(); |
| } |
| } |
| |
| <span class="kw">impl</span><F: FnOnce(<span class="kw-2">&</span>SharedPollState) -> u8> Drop <span class="kw">for </span>PollStateBomb<<span class="lifetime">'_</span>, F> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(drop) = <span class="self">self</span>.drop.take() { |
| (drop)(<span class="self">self</span>.state); |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Will update state with the provided value on `wake_by_ref` call |
| /// and then, if there is a need, call `inner_waker`. |
| </span><span class="kw">struct </span>WrappedWaker { |
| inner_waker: UnsafeCell<<span class="prelude-ty">Option</span><Waker>>, |
| poll_state: SharedPollState, |
| need_to_poll: u8, |
| } |
| |
| <span class="kw">unsafe impl </span>Send <span class="kw">for </span>WrappedWaker {} |
| <span class="kw">unsafe impl </span>Sync <span class="kw">for </span>WrappedWaker {} |
| |
| <span class="kw">impl </span>WrappedWaker { |
| <span class="doccomment">/// Replaces given waker's inner_waker for polling stream/futures which will |
| /// update poll state on `wake_by_ref` call. Use only if you need several |
| /// contexts. |
| /// |
| /// ## Safety |
| /// |
| /// This function will modify waker's `inner_waker` via `UnsafeCell`, so |
| /// it should be used only during `POLLING` phase by one thread at the time. |
| </span><span class="kw">unsafe fn </span>replace_waker(self_arc: <span class="kw-2">&mut </span>Arc<<span class="self">Self</span>>, cx: <span class="kw-2">&</span>Context<<span class="lifetime">'_</span>>) { |
| <span class="kw-2">*</span>self_arc.inner_waker.get() = cx.waker().clone().into(); |
| } |
| |
| <span class="doccomment">/// Attempts to start the waking process for the waker with the given value. |
| /// If succeeded, then the stream isn't yet woken and not being polled at the moment. |
| </span><span class="kw">fn </span>start_waking(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><(u8, PollStateBomb<<span class="lifetime">'_</span>, <span class="kw">impl </span>FnOnce(<span class="kw-2">&</span>SharedPollState) -> u8>)> { |
| <span class="self">self</span>.poll_state.start_waking(<span class="self">self</span>.need_to_poll) |
| } |
| } |
| |
| <span class="kw">impl </span>ArcWake <span class="kw">for </span>WrappedWaker { |
| <span class="kw">fn </span>wake_by_ref(self_arc: <span class="kw-2">&</span>Arc<<span class="self">Self</span>>) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>((<span class="kw">_</span>, state_bomb)) = self_arc.start_waking() { |
| <span class="comment">// Safety: now state is not `POLLING` |
| </span><span class="kw">let </span>waker_opt = <span class="kw">unsafe </span>{ self_arc.inner_waker.get().as_ref().unwrap() }; |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(inner_waker) = waker_opt.clone() { |
| <span class="comment">// Stop waking to allow polling stream |
| </span>drop(state_bomb); |
| |
| <span class="comment">// Wake up inner waker |
| </span>inner_waker.wake(); |
| } |
| } |
| } |
| } |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// Future which polls optional inner stream. |
| /// |
| /// If it's `Some`, it will attempt to call `poll_next` on it, |
| /// returning `Some((item, next_item_fut))` in case of `Poll::Ready(Some(...))` |
| /// or `None` in case of `Poll::Ready(None)`. |
| /// |
| /// If `poll_next` will return `Poll::Pending`, it will be forwarded to |
| /// the future and current task will be notified by waker. |
| </span><span class="attribute">#[must_use = <span class="string">"futures do nothing unless you `.await` or poll them"</span>] |
| </span><span class="kw">struct </span>PollStreamFut<St> { |
| <span class="attribute">#[pin] |
| </span>stream: <span class="prelude-ty">Option</span><St>, |
| } |
| } |
| |
| <span class="kw">impl</span><St> PollStreamFut<St> { |
| <span class="doccomment">/// Constructs new `PollStreamFut` using given `stream`. |
| </span><span class="kw">fn </span>new(stream: <span class="kw">impl </span>Into<<span class="prelude-ty">Option</span><St>>) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ stream: stream.into() } |
| } |
| } |
| |
| <span class="kw">impl</span><St: Stream + Unpin> Future <span class="kw">for </span>PollStreamFut<St> { |
| <span class="kw">type </span>Output = <span class="prelude-ty">Option</span><(St::Item, PollStreamFut<St>)>; |
| |
| <span class="kw">fn </span>poll(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="self">Self</span>::Output> { |
| <span class="kw">let </span><span class="kw-2">mut </span>stream = <span class="self">self</span>.project().stream; |
| |
| <span class="kw">let </span>item = <span class="kw">if let </span><span class="prelude-val">Some</span>(stream) = stream.as_mut().as_pin_mut() { |
| <span class="macro">ready!</span>(stream.poll_next(cx)) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>}; |
| <span class="kw">let </span>next_item_fut = PollStreamFut::new(stream.get_mut().take()); |
| <span class="kw">let </span>out = item.map(|item| (item, next_item_fut)); |
| |
| Poll::Ready(out) |
| } |
| } |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// Stream for the [`flatten_unordered`](super::StreamExt::flatten_unordered) |
| /// method with ability to specify flow controller. |
| </span><span class="attribute">#[project = FlattenUnorderedWithFlowControllerProj] |
| #[must_use = <span class="string">"streams do nothing unless polled"</span>] |
| </span><span class="kw">pub struct </span>FlattenUnorderedWithFlowController<St, Fc> <span class="kw">where </span>St: Stream { |
| <span class="attribute">#[pin] |
| </span>inner_streams: FuturesUnordered<PollStreamFut<St::Item>>, |
| <span class="attribute">#[pin] |
| </span>stream: St, |
| poll_state: SharedPollState, |
| limit: <span class="prelude-ty">Option</span><NonZeroUsize>, |
| is_stream_done: bool, |
| inner_streams_waker: Arc<WrappedWaker>, |
| stream_waker: Arc<WrappedWaker>, |
| flow_controller: PhantomData<Fc> |
| } |
| } |
| |
| <span class="kw">impl</span><St, Fc> fmt::Debug <span class="kw">for </span>FlattenUnorderedWithFlowController<St, Fc> |
| <span class="kw">where |
| </span>St: Stream + fmt::Debug, |
| St::Item: Stream + fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"FlattenUnorderedWithFlowController"</span>) |
| .field(<span class="string">"poll_state"</span>, <span class="kw-2">&</span><span class="self">self</span>.poll_state) |
| .field(<span class="string">"inner_streams"</span>, <span class="kw-2">&</span><span class="self">self</span>.inner_streams) |
| .field(<span class="string">"limit"</span>, <span class="kw-2">&</span><span class="self">self</span>.limit) |
| .field(<span class="string">"stream"</span>, <span class="kw-2">&</span><span class="self">self</span>.stream) |
| .field(<span class="string">"is_stream_done"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_stream_done) |
| .field(<span class="string">"flow_controller"</span>, <span class="kw-2">&</span><span class="self">self</span>.flow_controller) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl</span><St, Fc> FlattenUnorderedWithFlowController<St, Fc> |
| <span class="kw">where |
| </span>St: Stream, |
| Fc: FlowController<St::Item, <St::Item <span class="kw">as </span>Stream>::Item>, |
| St::Item: Stream + Unpin, |
| { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new( |
| stream: St, |
| limit: <span class="prelude-ty">Option</span><usize>, |
| ) -> FlattenUnorderedWithFlowController<St, Fc> { |
| <span class="kw">let </span>poll_state = SharedPollState::new(NEED_TO_POLL_STREAM); |
| |
| FlattenUnorderedWithFlowController { |
| inner_streams: FuturesUnordered::new(), |
| stream, |
| is_stream_done: <span class="bool-val">false</span>, |
| limit: limit.and_then(NonZeroUsize::new), |
| inner_streams_waker: Arc::new(WrappedWaker { |
| inner_waker: UnsafeCell::new(<span class="prelude-val">None</span>), |
| poll_state: poll_state.clone(), |
| need_to_poll: NEED_TO_POLL_INNER_STREAMS, |
| }), |
| stream_waker: Arc::new(WrappedWaker { |
| inner_waker: UnsafeCell::new(<span class="prelude-val">None</span>), |
| poll_state: poll_state.clone(), |
| need_to_poll: NEED_TO_POLL_STREAM, |
| }), |
| poll_state, |
| flow_controller: PhantomData, |
| } |
| } |
| |
| <span class="macro">delegate_access_inner!</span>(stream, St, ()); |
| } |
| |
| <span class="doccomment">/// Returns the next flow step based on the received item. |
| </span><span class="kw">pub trait </span>FlowController<I, O> { |
| <span class="doccomment">/// Handles an item producing `FlowStep` describing the next flow step. |
| </span><span class="kw">fn </span>next_step(item: I) -> FlowStep<I, O>; |
| } |
| |
| <span class="kw">impl</span><I, O> FlowController<I, O> <span class="kw">for </span>() { |
| <span class="kw">fn </span>next_step(item: I) -> FlowStep<I, O> { |
| FlowStep::Continue(item) |
| } |
| } |
| |
| <span class="doccomment">/// Describes the next flow step. |
| </span><span class="attribute">#[derive(Debug, Clone)] |
| </span><span class="kw">pub enum </span>FlowStep<C, R> { |
| <span class="doccomment">/// Just yields an item and continues standard flow. |
| </span>Continue(C), |
| <span class="doccomment">/// Immediately returns an underlying item from the function. |
| </span>Return(R), |
| } |
| |
| <span class="kw">impl</span><St, Fc> FlattenUnorderedWithFlowControllerProj<<span class="lifetime">'_</span>, St, Fc> |
| <span class="kw">where |
| </span>St: Stream, |
| { |
| <span class="doccomment">/// Checks if current `inner_streams` bucket size is greater than optional limit. |
| </span><span class="kw">fn </span>is_exceeded_limit(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.limit.map_or(<span class="bool-val">false</span>, |limit| <span class="self">self</span>.inner_streams.len() >= limit.get()) |
| } |
| } |
| |
| <span class="kw">impl</span><St, Fc> FusedStream <span class="kw">for </span>FlattenUnorderedWithFlowController<St, Fc> |
| <span class="kw">where |
| </span>St: FusedStream, |
| Fc: FlowController<St::Item, <St::Item <span class="kw">as </span>Stream>::Item>, |
| St::Item: Stream + Unpin, |
| { |
| <span class="kw">fn </span>is_terminated(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.stream.is_terminated() && <span class="self">self</span>.inner_streams.is_empty() |
| } |
| } |
| |
| <span class="kw">impl</span><St, Fc> Stream <span class="kw">for </span>FlattenUnorderedWithFlowController<St, Fc> |
| <span class="kw">where |
| </span>St: Stream, |
| Fc: FlowController<St::Item, <St::Item <span class="kw">as </span>Stream>::Item>, |
| St::Item: Stream + Unpin, |
| { |
| <span class="kw">type </span>Item = <St::Item <span class="kw">as </span>Stream>::Item; |
| |
| <span class="kw">fn </span>poll_next(<span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Option</span><<span class="self">Self</span>::Item>> { |
| <span class="kw">let </span><span class="kw-2">mut </span>next_item = <span class="prelude-val">None</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>need_to_poll_next = NONE; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>this = <span class="self">self</span>.as_mut().project(); |
| |
| <span class="comment">// Attempt to start polling, in case some waker is holding the lock, wait in loop |
| </span><span class="kw">let </span>(<span class="kw-2">mut </span>poll_state_value, state_bomb) = <span class="kw">loop </span>{ |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(value) = this.poll_state.start_polling() { |
| <span class="kw">break </span>value; |
| } |
| }; |
| |
| <span class="comment">// Safety: now state is `POLLING`. |
| </span><span class="kw">unsafe </span>{ |
| WrappedWaker::replace_waker(this.stream_waker, cx); |
| WrappedWaker::replace_waker(this.inner_streams_waker, cx) |
| }; |
| |
| <span class="kw">if </span>poll_state_value & NEED_TO_POLL_STREAM != NONE { |
| <span class="kw">let </span><span class="kw-2">mut </span>stream_waker = <span class="prelude-val">None</span>; |
| |
| <span class="comment">// Here we need to poll the base stream. |
| // |
| // To improve performance, we will attempt to place as many items as we can |
| // to the `FuturesUnordered` bucket before polling inner streams |
| </span><span class="kw">loop </span>{ |
| <span class="kw">if </span>this.is_exceeded_limit() || <span class="kw-2">*</span>this.is_stream_done { |
| <span class="comment">// We either exceeded the limit or the stream is exhausted |
| </span><span class="kw">if </span>!<span class="kw-2">*</span>this.is_stream_done { |
| <span class="comment">// The stream needs to be polled in the next iteration |
| </span>need_to_poll_next |= NEED_TO_POLL_STREAM; |
| } |
| |
| <span class="kw">break</span>; |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span><span class="kw-2">mut </span>cx = Context::from_waker( |
| stream_waker.get_or_insert_with(|| waker(this.stream_waker.clone())), |
| ); |
| |
| <span class="kw">match </span>this.stream.as_mut().poll_next(<span class="kw-2">&mut </span>cx) { |
| Poll::Ready(<span class="prelude-val">Some</span>(item)) => { |
| <span class="kw">let </span>next_item_fut = <span class="kw">match </span>Fc::next_step(item) { |
| <span class="comment">// Propagates an item immediately (the main use-case is for errors) |
| </span>FlowStep::Return(item) => { |
| need_to_poll_next |= NEED_TO_POLL_STREAM |
| | (poll_state_value & NEED_TO_POLL_INNER_STREAMS); |
| poll_state_value &= !NEED_TO_POLL_INNER_STREAMS; |
| |
| next_item = <span class="prelude-val">Some</span>(item); |
| |
| <span class="kw">break</span>; |
| } |
| <span class="comment">// Yields an item and continues processing (normal case) |
| </span>FlowStep::Continue(inner_stream) => { |
| PollStreamFut::new(inner_stream) |
| } |
| }; |
| <span class="comment">// Add new stream to the inner streams bucket |
| </span>this.inner_streams.as_mut().push(next_item_fut); |
| <span class="comment">// Inner streams must be polled afterward |
| </span>poll_state_value |= NEED_TO_POLL_INNER_STREAMS; |
| } |
| Poll::Ready(<span class="prelude-val">None</span>) => { |
| <span class="comment">// Mark the base stream as done |
| </span><span class="kw-2">*</span>this.is_stream_done = <span class="bool-val">true</span>; |
| } |
| Poll::Pending => { |
| <span class="kw">break</span>; |
| } |
| } |
| } |
| } |
| } |
| |
| <span class="kw">if </span>poll_state_value & NEED_TO_POLL_INNER_STREAMS != NONE { |
| <span class="kw">let </span>inner_streams_waker = waker(this.inner_streams_waker.clone()); |
| <span class="kw">let </span><span class="kw-2">mut </span>cx = Context::from_waker(<span class="kw-2">&</span>inner_streams_waker); |
| |
| <span class="kw">match </span>this.inner_streams.as_mut().poll_next(<span class="kw-2">&mut </span>cx) { |
| Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Some</span>((item, next_item_fut)))) => { |
| <span class="comment">// Push next inner stream item future to the list of inner streams futures |
| </span>this.inner_streams.as_mut().push(next_item_fut); |
| <span class="comment">// Take the received item |
| </span>next_item = <span class="prelude-val">Some</span>(item); |
| <span class="comment">// On the next iteration, inner streams must be polled again |
| </span>need_to_poll_next |= NEED_TO_POLL_INNER_STREAMS; |
| } |
| Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">None</span>)) => { |
| <span class="comment">// On the next iteration, inner streams must be polled again |
| </span>need_to_poll_next |= NEED_TO_POLL_INNER_STREAMS; |
| } |
| <span class="kw">_ </span>=> {} |
| } |
| } |
| |
| <span class="comment">// We didn't have any `poll_next` panic, so it's time to deactivate the bomb |
| </span>state_bomb.deactivate(); |
| |
| <span class="comment">// Call the waker at the end of polling if |
| </span><span class="kw">let </span><span class="kw-2">mut </span>force_wake = |
| <span class="comment">// we need to poll the stream and didn't reach the limit yet |
| </span>need_to_poll_next & NEED_TO_POLL_STREAM != NONE && !this.is_exceeded_limit() |
| <span class="comment">// or we need to poll the inner streams again |
| </span>|| need_to_poll_next & NEED_TO_POLL_INNER_STREAMS != NONE; |
| |
| <span class="comment">// Stop polling and swap the latest state |
| </span>poll_state_value = this.poll_state.stop_polling(need_to_poll_next, force_wake); |
| <span class="comment">// If state was changed during `POLLING` phase, we also need to manually call a waker |
| </span>force_wake |= poll_state_value & NEED_TO_POLL_ALL != NONE; |
| |
| <span class="kw">let </span>is_done = <span class="kw-2">*</span>this.is_stream_done && this.inner_streams.is_empty(); |
| |
| <span class="kw">if </span>next_item.is_some() || is_done { |
| Poll::Ready(next_item) |
| } <span class="kw">else </span>{ |
| <span class="kw">if </span>force_wake { |
| cx.waker().wake_by_ref(); |
| } |
| |
| Poll::Pending |
| } |
| } |
| } |
| |
| <span class="comment">// Forwarding impl of Sink from the underlying stream |
| </span><span class="attribute">#[cfg(feature = <span class="string">"sink"</span>)] |
| </span><span class="kw">impl</span><St, Item, Fc> Sink<Item> <span class="kw">for </span>FlattenUnorderedWithFlowController<St, Fc> |
| <span class="kw">where |
| </span>St: Stream + Sink<Item>, |
| { |
| <span class="kw">type </span>Error = St::Error; |
| |
| <span class="macro">delegate_sink!</span>(stream, Item); |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="futures_util" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |