introduce a generic worker event-loop

components/script/dom/abstractworkerglobalscope.rs

@@ -2,11 +2,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use devtools_traits::DevtoolScriptControlMsg;
 use dom::abstractworker::WorkerScriptMsg;
-use dom::dedicatedworkerglobalscope::DedicatedWorkerScriptMsg;
+use dom::bindings::conversions::DerivedFrom;
+use dom::bindings::reflector::DomObject;
+use dom::dedicatedworkerglobalscope::{AutoWorkerReset, DedicatedWorkerScriptMsg};
+use dom::globalscope::GlobalScope;
 use dom::worker::TrustedWorkerAddress;
+use dom::workerglobalscope::WorkerGlobalScope;
 use script_runtime::{ScriptChan, CommonScriptMsg, ScriptPort};
-use std::sync::mpsc::{Receiver, Sender};
+use std::sync::mpsc::{Receiver, Select, Sender};
+use task_queue::{QueuedTaskConversion, TaskQueue};
 
 /// A ScriptChan that can be cloned freely and will silently send a TrustedWorkerAddress with
 /// common event loop messages. While this SendableWorkerScriptChan is alive, the associated
@@ -69,3 +75,87 @@ impl ScriptPort for Receiver<DedicatedWorkerScriptMsg> {
         }
     }
 }
+
+pub trait WorkerEventLoopMethods {
+    type TimerMsg: Send;
+    type WorkerMsg: QueuedTaskConversion + Send;
+    type Event;
+    fn timer_event_port(&self) -> &Receiver<Self::TimerMsg>;
+    fn task_queue(&self) -> &TaskQueue<Self::WorkerMsg>;
+    fn handle_event(&self, event: Self::Event);
+    fn handle_worker_post_event(&self, worker: &TrustedWorkerAddress) -> Option<AutoWorkerReset>;
+    fn from_worker_msg(&self, msg: Self::WorkerMsg) -> Self::Event;
+    fn from_timer_msg(&self, msg: Self::TimerMsg) -> Self::Event;
+    fn from_devtools_msg(&self, msg: DevtoolScriptControlMsg) -> Self::Event;
+}
+
+#[allow(unsafe_code)]
+// https://html.spec.whatwg.org/multipage/#worker-event-loop
+pub fn run_worker_event_loop<T, TimerMsg, WorkerMsg, Event>(worker_scope: &T,
+                                                            worker: Option<&TrustedWorkerAddress>)
+where
+    TimerMsg: Send,
+    WorkerMsg: QueuedTaskConversion + Send,
+    T: WorkerEventLoopMethods<TimerMsg = TimerMsg,  WorkerMsg = WorkerMsg, Event = Event>
+    + DerivedFrom<WorkerGlobalScope> + DerivedFrom<GlobalScope>
+    + DomObject {
+    let scope = worker_scope.upcast::<WorkerGlobalScope>();
+    let timer_event_port = worker_scope.timer_event_port();
+    let devtools_port = scope.from_devtools_receiver();
+    let task_queue = worker_scope.task_queue();
+    let sel = Select::new();
+    let mut worker_handle = sel.handle(task_queue.select());
+    let mut timer_event_handle = sel.handle(timer_event_port);
+    let mut devtools_handle = sel.handle(devtools_port);
+    unsafe {
+        worker_handle.add();
+        timer_event_handle.add();
+        if scope.from_devtools_sender().is_some() {
+            devtools_handle.add();
+        }
+    }
+    let ret = sel.wait();
+    let event = {
+        if ret == worker_handle.id() {
+            task_queue.take_tasks();
+            worker_scope.from_worker_msg(task_queue.recv().unwrap())
+        } else if ret == timer_event_handle.id() {
+            worker_scope.from_timer_msg(timer_event_port.recv().unwrap())
+        } else if ret == devtools_handle.id() {
+            worker_scope.from_devtools_msg(devtools_port.recv().unwrap())
+        } else {
+            panic!("unexpected select result!")
+        }
+    };
+    let mut sequential = vec![];
+    sequential.push(event);
+    // https://html.spec.whatwg.org/multipage/#worker-event-loop
+    // Once the WorkerGlobalScope's closing flag is set to true,
+    // the event loop's task queues must discard any further tasks
+    // that would be added to them
+    // (tasks already on the queue are unaffected except where otherwise specified).
+    while !scope.is_closing() {
+        // Batch all events that are ready.
+        // The task queue will throttle non-priority tasks if necessary.
+        match task_queue.try_recv() {
+            Err(_) => match timer_event_port.try_recv() {
+                Err(_) => match devtools_port.try_recv() {
+                    Err(_) => break,
+                    Ok(ev) => sequential.push(worker_scope.from_devtools_msg(ev)),
+                },
+                Ok(ev) => sequential.push(worker_scope.from_timer_msg(ev)),
+            },
+            Ok(ev) => sequential.push(worker_scope.from_worker_msg(ev)),
+        }
+    }
+    // Step 3
+    for event in sequential {
+        worker_scope.handle_event(event);
+        // Step 6
+        let _ar = match worker {
+            Some(worker) => worker_scope.handle_worker_post_event(worker),
+            None => None
+        };
+        worker_scope.upcast::<GlobalScope>().perform_a_microtask_checkpoint();
+    }
+}