65 lines
1.8 KiB
Rust
65 lines
1.8 KiB
Rust
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use std::{
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ops::Deref,
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sync::Mutex,
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thread::{self, JoinHandle},
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};
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enum InternalPromiseState<T: Send + Clone> {
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Loading(Option<JoinHandle<Result<T, anyhow::Error>>>),
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Result(Result<T, anyhow::Error>),
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}
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impl<T: Send + Clone> InternalPromiseState<T> {
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fn loading(&mut self) -> Option<JoinHandle<anyhow::Result<T>>> {
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match self {
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Self::Loading(handle) => handle.take(),
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_ => None,
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}
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}
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}
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pub struct Promise<T: Send + Clone> {
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internal: Mutex<InternalPromiseState<T>>,
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}
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impl<T: Send + Clone> Promise<T> {
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pub fn new<F>(f: F) -> Promise<T>
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where
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F: Fn() -> anyhow::Result<T> + Send + 'static,
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T: 'static,
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{
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let thread = thread::spawn(f);
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Promise {
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internal: Mutex::new(InternalPromiseState::Loading(Some(thread))),
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}
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}
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pub fn get(&self) -> T {
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let mut internal = self.internal.lock().expect("promise lock is poisoned");
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if let Some(handle) = internal.loading() {
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let result = handle.join();
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match result {
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Ok(result) => match result {
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Ok(t) => *internal = InternalPromiseState::Result(Ok(t)),
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Err(err) => *internal = InternalPromiseState::Result(Err(err)),
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},
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Err(err) => {
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println!("Promise Thread Join Error: {:?}", err);
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*internal = InternalPromiseState::Result(Err(anyhow::Error::msg(
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"Failed joining thread",
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)))
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}
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}
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}
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match internal.deref() {
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InternalPromiseState::Result(t) => t.as_ref().expect("result error").clone(),
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InternalPromiseState::Loading(_) => unreachable!(),
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}
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}
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}
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