87 lines
2.6 KiB
Rust
87 lines
2.6 KiB
Rust
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use failure::*;
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use std::sync::{Mutex, Arc};
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use futures::*;
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use tokio::sync::oneshot;
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struct BroadcastData<T> {
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result: Option<Result<T, String>>,
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listeners: Vec<oneshot::Sender<Result<T, Error>>>,
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source: Option<Box<Future<Item=T, Error=Error> + Send >>,
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}
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/// Broadcast future results to registered listeners
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pub struct BroadcastFuture<T> {
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inner: Arc<Mutex<BroadcastData<T>>>,
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}
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impl <T: Clone + Send + 'static> BroadcastFuture<T> {
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/// Create instance for specified source future.
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///
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/// The result of the future is sent to all registered listeners.
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pub fn new(source: Box<Future<Item=T, Error=Error> + Send>) -> Self {
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let data = BroadcastData {
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result: None,
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listeners: vec![],
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source: Some(source),
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};
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Self { inner: Arc::new(Mutex::new(data)) }
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}
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fn update(inner: Arc<Mutex<BroadcastData<T>>>, result: Result<T, String>) {
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let mut data = inner.lock().unwrap();
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data.result = Some(result.clone());
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loop {
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match data.listeners.pop() {
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None => { break; },
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Some(ch) => {
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match &result {
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Ok(result) => { let _ = ch.send(Ok(result.clone())); },
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Err(err) => { let _ = ch.send(Err(format_err!("{}", err))); },
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}
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},
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}
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}
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}
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fn spawn(inner: Arc<Mutex<BroadcastData<T>>>) -> impl Future<Item=T, Error=Error> {
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let mut data = inner.lock().unwrap();
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match &data.result {
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None => {},
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Some(Ok(result)) => return futures::future::Either::A(futures::future::ok(result.clone())),
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Some(Err(err)) => return futures::future::Either::A(futures::future::err(format_err!("{}", err))),
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}
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let (tx, rx) = oneshot::channel::<Result<T, Error>>();
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data.listeners.push(tx);
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if let Some(source) = data.source.take() {
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let inner1 = inner.clone();
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let task = source.then(move |value| {
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match value {
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Ok(value) => Self::update(inner1, Ok(value.clone())),
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Err(err) => Self::update(inner1, Err(err.to_string())),
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}
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Ok(())
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});
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tokio::spawn(task);
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}
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futures::future::Either::B(rx.map_err(Error::from).and_then(|result| { result }))
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}
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/// Register a listener
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pub fn listen(&self) -> impl Future<Item=T, Error=Error> {
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let inner2 = self.inner.clone();
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futures::future::lazy(move || { Self::spawn(inner2) })
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}
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}
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