32 lines
1.2 KiB
Rust
32 lines
1.2 KiB
Rust
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use core::future::Future;
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use core::pin::Pin;
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use core::ptr;
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use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
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static VTABLE: RawWakerVTable = RawWakerVTable::new(|_| RawWaker::new(ptr::null(), &VTABLE), |_| {}, |_| {}, |_| {});
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/// Run a future to completion using a busy loop.
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///
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/// This calls `.poll()` on the future in a busy loop, which blocks
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/// the current thread at 100% cpu usage until the future is done. The
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/// future's `Waker` mechanism is not used.
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///
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/// It's suitable for systems with no or limited concurrency and without
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/// strict requirements around power consumption. For more complex use
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/// cases, prefer using a "real" executor like `embassy-executor`, which
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/// supports multiple tasks, and putting the core to sleep when no task
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/// needs to do work.
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pub fn block_on<F: Future>(mut fut: F) -> F::Output {
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// safety: we don't move the future after this line.
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let mut fut = unsafe { Pin::new_unchecked(&mut fut) };
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let raw_waker = RawWaker::new(ptr::null(), &VTABLE);
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let waker = unsafe { Waker::from_raw(raw_waker) };
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let mut cx = Context::from_waker(&waker);
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loop {
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if let Poll::Ready(res) = fut.as_mut().poll(&mut cx) {
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return res;
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}
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}
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}
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