Shared more betwee legacy with/without atomics

Author: alexcrichton

crates/futures/src/legacy.rs

@@ -1,96 +1,11 @@
-use std::cell::{Cell, RefCell};
-use std::fmt;
-use std::rc::Rc;
-use std::sync::Arc;
-
 use futures::executor::{self, Notify, Spawn};
-use futures::future;
 use futures::prelude::*;
-use futures::sync::oneshot;
 use js_sys::{Function, Promise};
+use std::cell::{Cell, RefCell};
+use std::rc::Rc;
+use std::sync::Arc;
 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"),
-        }
-    }
-}
-
 /// Converts a Rust `Future` into a JavaScript `Promise`.
 ///
 /// This function will take any future in Rust and schedule it to be executed,
@@ -112,8 +27,8 @@ impl Future for JsFuture {
 /// resolve**. Instead it will be a leaked promise. This is an unfortunate
 /// limitation of wasm currently that's hoped to be fixed one day!
 pub fn future_to_promise<F>(future: F) -> Promise
-    where
-        F: Future<Item = JsValue, Error = JsValue> + 'static,
+where
+    F: Future<Item = JsValue, Error = JsValue> + 'static,
 {
     _future_to_promise(Box::new(future))
 }
@@ -287,22 +202,3 @@ fn _future_to_promise(future: Box<dyn Future<Item = JsValue, Error = JsValue>>)
         }
     }
 }
-
-/// Converts a Rust `Future` on a local task queue.
-///
-/// The `future` provided must adhere to `'static` because it'll be scheduled
-/// to run in the background and cannot contain any stack references.
-///
-/// # Panics
-///
-/// This function has the same panic behavior as `future_to_promise`.
-pub fn spawn_local<F>(future: F)
-    where
-        F: Future<Item = (), Error = ()> + 'static,
-{
-    future_to_promise(
-        future
-            .map(|()| JsValue::undefined())
-            .or_else(|()| future::ok::<JsValue, JsValue>(JsValue::undefined())),
-    );
-}

crates/futures/src/legacy_atomics.rs

@@ -1,10 +1,8 @@
-use std::sync::atomic::{AtomicI32, Ordering};
-use std::sync::Arc;
-
 use futures::executor::{self, Notify, Spawn};
-use futures::future;
 use futures::prelude::*;
 use js_sys::Function;
+use std::sync::atomic::{AtomicI32, Ordering};
+use std::sync::Arc;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
 
@@ -165,24 +163,4 @@ fn wait_async(ptr: &AtomicI32, val: i32) -> js_sys::Promise {
         let mem = wasm_bindgen::memory().unchecked_into::<js_sys::WebAssembly::Memory>();
         Atomics::wait_async(&mem.buffer(), ptr as *const AtomicI32 as i32 / 4, val)
     }
-
-}
-
-/// Converts a Rust `Future` on a local task queue.
-///
-/// The `future` provided must adhere to `'static` because it'll be scheduled
-/// to run in the background and cannot contain any stack references.
-///
-/// # Panics
-///
-/// This function has the same panic behavior as `future_to_promise`.
-pub fn spawn_local<F>(future: F)
-where
-    F: Future<Item = (), Error = ()> + 'static,
-{
-    future_to_promise(
-        future
-            .map(|()| JsValue::undefined())
-            .or_else(|()| future::ok::<JsValue, JsValue>(JsValue::undefined())),
-    );
 }

crates/futures/src/legacy_js2rust.rs renamed to crates/futures/src/legacy_shared.rs

@@ -1,7 +1,7 @@
 use std::cell::RefCell;
+use futures::future;
 use std::fmt;
 use std::rc::Rc;
-
 use futures::prelude::*;
 use futures::sync::oneshot;
 use js_sys::Promise;
@@ -87,3 +87,22 @@ impl Future for JsFuture {
         }
     }
 }
+
+/// Converts a Rust `Future` on a local task queue.
+///
+/// The `future` provided must adhere to `'static` because it'll be scheduled
+/// to run in the background and cannot contain any stack references.
+///
+/// # Panics
+///
+/// This function has the same panic behavior as `future_to_promise`.
+pub fn spawn_local<F>(future: F)
+where
+    F: Future<Item = (), Error = ()> + 'static,
+{
+    crate::future_to_promise(
+        future
+            .map(|()| JsValue::undefined())
+            .or_else(|()| future::ok::<JsValue, JsValue>(JsValue::undefined())),
+    );
+}

crates/futures/src/lib.rs

@@ -106,18 +106,17 @@
 
 use cfg_if::cfg_if;
 
-mod legacy_js2rust;
-pub use legacy_js2rust::*;
+mod legacy_shared;
+pub use legacy_shared::*;
 
 cfg_if! {
     if #[cfg(target_feature = "atomics")] {
         /// Contains a thread-safe version of this crate, with Futures 0.1
         mod legacy_atomics;
+        pub use legacy_atomics::*;
 
         /// Polyfill for `Atomics.waitAsync` function
         mod wait_async_polyfill;
-
-        pub use legacy_atomics::*;
     } else {
         mod legacy;
         pub use legacy::*;