Created
February 13, 2024 13:51
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Tiny async raw demo
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use core::{ | |
future::Future, | |
pin::Pin, | |
task::{Context, Poll, RawWaker, RawWakerVTable, Waker}, | |
}; | |
use std::collections::VecDeque; | |
fn dummy_raw_waker() -> RawWaker { | |
fn no_op(_: *const ()) {} | |
fn clone(_: *const ()) -> RawWaker { | |
dummy_raw_waker() | |
} | |
let vtable = &RawWakerVTable::new(clone, no_op, no_op, no_op); | |
RawWaker::new(0 as *const (), vtable) | |
} | |
fn dummy_waker() -> Waker { | |
unsafe { Waker::from_raw(dummy_raw_waker()) } | |
} | |
pub struct SimpleExecutor { | |
task_queue: VecDeque<Task>, | |
} | |
impl SimpleExecutor { | |
pub fn new() -> SimpleExecutor { | |
SimpleExecutor { | |
task_queue: VecDeque::new(), | |
} | |
} | |
pub fn spawn(&mut self, task: Task) { | |
self.task_queue.push_back(task) | |
} | |
pub fn run(&mut self) { | |
while let Some(mut task) = self.task_queue.pop_front() { | |
let waker = dummy_waker(); | |
let mut context = Context::from_waker(&waker); | |
match task.poll(&mut context) { | |
Poll::Ready(()) => {} // task done | |
Poll::Pending => self.task_queue.push_back(task), | |
} | |
} | |
} | |
} | |
pub struct Task { | |
future: Pin<Box<dyn Future<Output = ()>>>, | |
} | |
impl Task { | |
pub fn new(future: impl Future<Output = ()> + 'static) -> Task { | |
Task { | |
future: Box::pin(future), | |
} | |
} | |
fn poll(&mut self, context: &mut Context) -> Poll<()> { | |
self.future.as_mut().poll(context) | |
} | |
} | |
async fn async_number() -> u32 { | |
42 | |
} | |
async fn example_task() { | |
let number = async_number().await; | |
println!("async number: {}", number); | |
} | |
fn main() { | |
let mut executor = SimpleExecutor::new(); | |
executor.spawn(Task::new(example_task())); | |
executor.run(); | |
} |
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