Deduplicate JsFuture definitions

Turns out it's the exact same for both before and after atomics, so
let's use the same definition!
This commit is contained in:
Alex Crichton 2019-07-18 13:59:14 -07:00
parent cde9684e4b
commit d590a9e053
3 changed files with 92 additions and 85 deletions

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@ -1,29 +1,13 @@
use std::cell::RefCell;
use std::fmt;
use std::rc::Rc;
use std::sync::atomic::{AtomicI32, Ordering};
use std::sync::Arc;
use futures::executor::{self, Notify, Spawn};
use futures::future;
use futures::prelude::*;
use futures::sync::oneshot;
use js_sys::Function;
use wasm_bindgen::prelude::*;
use wasm_bindgen::JsCast;
/// A Rust `Future` backed by a JavaScript `Promise`.
///
/// This type is constructed with a JavaScript `Promise` object and translates
/// it to a Rust `Future`. This type implements the `Future` trait from the
/// `futures` crate and will either succeed or fail depending on what happens
/// with the JavaScript `Promise`.
///
/// Currently this type is constructed with `JsFuture::from`.
pub struct JsFuture {
rx: oneshot::Receiver<Result<JsValue, JsValue>>,
}
// Duplicate a bit here because `then` takes a `JsValue` instead of a `Closure`.
#[wasm_bindgen]
extern "C" {
@ -38,75 +22,6 @@ extern "C" {
fn get_wait_async() -> JsValue;
}
impl fmt::Debug for JsFuture {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "JsFuture {{ ... }}")
}
}
impl From<js_sys::Promise> for JsFuture {
fn from(js: js_sys::Promise) -> JsFuture {
// Use the `then` method to schedule two callbacks, one for the
// resolved value and one for the rejected value. We're currently
// assuming that JS engines will unconditionally invoke precisely one of
// these callbacks, no matter what.
//
// Ideally we'd have a way to cancel the callbacks getting invoked and
// free up state ourselves when this `JsFuture` is dropped. We don't
// have that, though, and one of the callbacks is likely always going to
// be invoked.
//
// As a result we need to make sure that no matter when the callbacks
// are invoked they are valid to be called at any time, which means they
// have to be self-contained. Through the `Closure::once` and some
// `Rc`-trickery we can arrange for both instances of `Closure`, and the
// `Rc`, to all be destroyed once the first one is called.
let (tx, rx) = oneshot::channel();
let state = Rc::new(RefCell::new(None));
let state2 = state.clone();
let resolve = Closure::once(move |val| finish(&state2, Ok(val)));
let state2 = state.clone();
let reject = Closure::once(move |val| finish(&state2, Err(val)));
js.then2(&resolve, &reject);
*state.borrow_mut() = Some((tx, resolve, reject));
return JsFuture { rx };
fn finish(
state: &RefCell<
Option<(
oneshot::Sender<Result<JsValue, JsValue>>,
Closure<dyn FnMut(JsValue)>,
Closure<dyn FnMut(JsValue)>,
)>,
>,
val: Result<JsValue, JsValue>,
) {
match state.borrow_mut().take() {
// We don't have any guarantee that anyone's still listening at this
// point (the Rust `JsFuture` could have been dropped) so simply
// ignore any errors here.
Some((tx, _, _)) => drop(tx.send(val)),
None => wasm_bindgen::throw_str("cannot finish twice"),
}
}
}
}
impl Future for JsFuture {
type Item = JsValue;
type Error = JsValue;
fn poll(&mut self) -> Poll<JsValue, JsValue> {
match self.rx.poll() {
Ok(Async::Ready(val)) => val.map(Async::Ready),
Ok(Async::NotReady) => Ok(Async::NotReady),
Err(_) => wasm_bindgen::throw_str("cannot cancel"),
}
}
}
/// Converts a Rust `Future` into a JavaScript `Promise`.
///
/// This function will take any future in Rust and schedule it to be executed,

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@ -0,0 +1,89 @@
use std::cell::RefCell;
use std::fmt;
use std::rc::Rc;
use futures::prelude::*;
use futures::sync::oneshot;
use js_sys::Promise;
use wasm_bindgen::prelude::*;
/// A Rust `Future` backed by a JavaScript `Promise`.
///
/// This type is constructed with a JavaScript `Promise` object and translates
/// it to a Rust `Future`. This type implements the `Future` trait from the
/// `futures` crate and will either succeed or fail depending on what happens
/// with the JavaScript `Promise`.
///
/// Currently this type is constructed with `JsFuture::from`.
pub struct JsFuture {
rx: oneshot::Receiver<Result<JsValue, JsValue>>,
}
impl fmt::Debug for JsFuture {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "JsFuture {{ ... }}")
}
}
impl From<Promise> for JsFuture {
fn from(js: Promise) -> JsFuture {
// Use the `then` method to schedule two callbacks, one for the
// resolved value and one for the rejected value. We're currently
// assuming that JS engines will unconditionally invoke precisely one of
// these callbacks, no matter what.
//
// Ideally we'd have a way to cancel the callbacks getting invoked and
// free up state ourselves when this `JsFuture` is dropped. We don't
// have that, though, and one of the callbacks is likely always going to
// be invoked.
//
// As a result we need to make sure that no matter when the callbacks
// are invoked they are valid to be called at any time, which means they
// have to be self-contained. Through the `Closure::once` and some
// `Rc`-trickery we can arrange for both instances of `Closure`, and the
// `Rc`, to all be destroyed once the first one is called.
let (tx, rx) = oneshot::channel();
let state = Rc::new(RefCell::new(None));
let state2 = state.clone();
let resolve = Closure::once(move |val| finish(&state2, Ok(val)));
let state2 = state.clone();
let reject = Closure::once(move |val| finish(&state2, Err(val)));
js.then2(&resolve, &reject);
*state.borrow_mut() = Some((tx, resolve, reject));
return JsFuture { rx };
fn finish(
state: &RefCell<
Option<(
oneshot::Sender<Result<JsValue, JsValue>>,
Closure<dyn FnMut(JsValue)>,
Closure<dyn FnMut(JsValue)>,
)>,
>,
val: Result<JsValue, JsValue>,
) {
match state.borrow_mut().take() {
// We don't have any guarantee that anyone's still listening at this
// point (the Rust `JsFuture` could have been dropped) so simply
// ignore any errors here.
Some((tx, _, _)) => drop(tx.send(val)),
None => wasm_bindgen::throw_str("cannot finish twice"),
}
}
}
}
impl Future for JsFuture {
type Item = JsValue;
type Error = JsValue;
fn poll(&mut self) -> Poll<JsValue, JsValue> {
match self.rx.poll() {
Ok(Async::Ready(val)) => val.map(Async::Ready),
Ok(Async::NotReady) => Ok(Async::NotReady),
Err(_) => wasm_bindgen::throw_str("cannot cancel"),
}
}
}

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@ -106,6 +106,9 @@
use cfg_if::cfg_if;
mod legacy_js2rust;
pub use legacy_js2rust::*;
cfg_if! {
if #[cfg(target_feature = "atomics")] {
/// Contains a thread-safe version of this crate, with Futures 0.1