103 lines
2.9 KiB
Rust
103 lines
2.9 KiB
Rust
/*!
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* Primitive Async/Wait implementation.
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*
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* To create an Async promise, create an AsyncBuilder. Ask for its channel receiver/sender with
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* `tx` and `rx` methods to pass them in your worker's closure. Build an `Async<T>` with your
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* `JoinHandle<T>`. The thread must communicate with the `Async<T>` object via `AsyncStatus`
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* messages.
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*
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* When `Async<T>` receives `AsyncStatus::Finished` it joins the thread and takes its value which
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* can be extracted with `extract`.
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*/
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use chan;
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use std::thread;
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/// Messages to pass between `Async<T>` owner and its worker thread.
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#[derive(Debug)]
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pub enum AsyncStatus {
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NoUpdate,
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Finished,
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///The number may hold whatever meaning the user chooses.
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ProgressReport(usize),
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}
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/// A builder object for `Async<T>`
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#[derive(Debug)]
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pub struct AsyncBuilder {
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tx: chan::Sender<AsyncStatus>,
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rx: chan::Receiver<AsyncStatus>,
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}
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#[derive(Debug)]
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pub struct Async<T> {
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value: Option<T>,
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worker: Option<thread::JoinHandle<T>>,
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tx: chan::Sender<AsyncStatus>,
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rx: chan::Receiver<AsyncStatus>,
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}
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impl AsyncBuilder {
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pub fn new() -> Self {
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let (sender, receiver) = chan::sync(::std::mem::size_of::<AsyncStatus>());
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AsyncBuilder {
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tx: sender,
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rx: receiver,
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}
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}
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/// Returns the sender object of the promise's channel.
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pub fn tx(&mut self) -> chan::Sender<AsyncStatus> {
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self.tx.clone()
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}
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/// Returns the receiver object of the promise's channel.
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pub fn rx(&mut self) -> chan::Receiver<AsyncStatus> {
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self.rx.clone()
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}
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/// Returns an `Async<T>` object that contains a `Thread` join handle that returns a `T`
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pub fn build<T: Clone>(self, worker: thread::JoinHandle<T>) -> Async<T> {
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Async {
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worker: Some(worker),
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value: None,
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tx: self.tx,
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rx: self.rx,
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}
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}
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}
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impl<T> Async<T> {
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/// Consumes `self` and returns the computed value. Will panic if computation hasn't finished.
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pub fn extract(self) -> T {
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self.value.unwrap()
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}
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/// Polls worker thread and returns result.
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pub fn poll(&mut self) -> Result<AsyncStatus, ()> {
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if self.value.is_some() {
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return Ok(AsyncStatus::Finished);
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}
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//self.tx.send(true);
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let rx = &self.rx;
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chan_select! {
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default => {
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return Ok(AsyncStatus::NoUpdate);
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},
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rx.recv() -> r => {
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match r {
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Some(AsyncStatus::Finished) => {
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},
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Some(a) => {
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return Ok(a);
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}
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_ => {
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return Err(());
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},
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}
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},
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}
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let v = self.worker.take().unwrap().join().unwrap();
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self.value = Some(v);
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return Ok(AsyncStatus::Finished);
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}
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}
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