rust / expert
Snippet
Custom Waker-Driven Future Implementation
Manual Future implementations require thread-safe waker registration and atomic synchronization to notify asynchronous executors when data becomes available without spin-locking.
snippet.rs
rust
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use std::future::Future;use std::pin::Pin;use std::sync::atomic::{AtomicBool, Ordering};use std::sync::Arc;use std::task::{Context, Poll, Waker};pub struct SignalFuture {state: Arc<SignalState>,}struct SignalState {completed: AtomicBool,waker: std::sync::Mutex<Option<Waker>>,}impl Future for SignalFuture {type Output = &'static str;fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {if self.state.completed.load(Ordering::Acquire) {Poll::Ready("Signal received")} else {let mut waker_guard = self.state.waker.lock().unwrap();*waker_guard = Some(cx.waker().clone());Poll::Pending}}}
Breakdown
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pub struct SignalFuture {
Defines a wrapper struct holding a shared atomic state reference across async contexts.
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
Implements the core polling entry point required by the std Future trait.
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if self.state.completed.load(Ordering::Acquire) {
Checks the atomic completion state with Acquire memory ordering.
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*waker_guard = Some(cx.waker().clone());
Registers the reactor Waker inside a Mutex for delayed execution notification.