mirror of
https://github.com/classilla/tenfourfox.git
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193 lines
5.3 KiB
C++
193 lines
5.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* vim: set sw=2 ts=8 et tw=80 :
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*/
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_net_ChannelEventQueue_h
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#define mozilla_net_ChannelEventQueue_h
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#include <nsTArray.h>
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#include <nsAutoPtr.h>
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class nsISupports;
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class nsIEventTarget;
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namespace mozilla {
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namespace net {
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class ChannelEvent
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{
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public:
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ChannelEvent() { MOZ_COUNT_CTOR(ChannelEvent); }
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virtual ~ChannelEvent() { MOZ_COUNT_DTOR(ChannelEvent); }
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virtual void Run() = 0;
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};
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// Workaround for Necko re-entrancy dangers. We buffer IPDL messages in a
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// queue if still dispatching previous one(s) to listeners/observers.
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// Otherwise synchronous XMLHttpRequests and/or other code that spins the
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// event loop (ex: IPDL rpc) could cause listener->OnDataAvailable (for
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// instance) to be dispatched and called before mListener->OnStartRequest has
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// completed.
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class ChannelEventQueue final
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{
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NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ChannelEventQueue)
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public:
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explicit ChannelEventQueue(nsISupports *owner)
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: mSuspendCount(0)
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, mSuspended(false)
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, mForced(false)
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, mFlushing(false)
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, mOwner(owner) {}
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// Checks to determine if an IPDL-generated channel event can be processed
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// immediately, or needs to be queued using Enqueue().
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inline bool ShouldEnqueue();
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// Puts IPDL-generated channel event into queue, to be run later
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// automatically when EndForcedQueueing and/or Resume is called.
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inline void Enqueue(ChannelEvent* callback);
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inline nsresult PrependEvents(nsTArray<nsAutoPtr<ChannelEvent> >& aEvents);
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// After StartForcedQueueing is called, ShouldEnqueue() will return true and
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// no events will be run/flushed until EndForcedQueueing is called.
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// - Note: queueing may still be required after EndForcedQueueing() (if the
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// queue is suspended, etc): always call ShouldEnqueue() to determine
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// whether queueing is needed.
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inline void StartForcedQueueing();
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inline void EndForcedQueueing();
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// Suspend/resume event queue. ShouldEnqueue() will return true and no events
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// will be run/flushed until resume is called. These should be called when
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// the channel owning the event queue is suspended/resumed.
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inline void Suspend();
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// Resume flushes the queue asynchronously, i.e. items in queue will be
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// dispatched in a new event on the current thread.
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void Resume();
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// Retargets delivery of events to the target thread specified.
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nsresult RetargetDeliveryTo(nsIEventTarget* aTargetThread);
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private:
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// Private destructor, to discourage deletion outside of Release():
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~ChannelEventQueue()
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{
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}
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inline void MaybeFlushQueue();
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void FlushQueue();
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inline void CompleteResume();
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nsTArray<nsAutoPtr<ChannelEvent> > mEventQueue;
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uint32_t mSuspendCount;
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bool mSuspended;
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bool mForced;
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bool mFlushing;
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// Keep ptr to avoid refcount cycle: only grab ref during flushing.
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nsISupports *mOwner;
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// EventTarget for delivery of events to the correct thread.
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nsCOMPtr<nsIEventTarget> mTargetThread;
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friend class AutoEventEnqueuer;
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};
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inline bool
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ChannelEventQueue::ShouldEnqueue()
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{
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bool answer = mForced || mSuspended || mFlushing;
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MOZ_ASSERT(answer == true || mEventQueue.IsEmpty(),
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"Should always enqueue if ChannelEventQueue not empty");
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return answer;
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}
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inline void
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ChannelEventQueue::Enqueue(ChannelEvent* callback)
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{
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mEventQueue.AppendElement(callback);
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}
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inline void
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ChannelEventQueue::StartForcedQueueing()
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{
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mForced = true;
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}
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inline void
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ChannelEventQueue::EndForcedQueueing()
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{
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mForced = false;
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MaybeFlushQueue();
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}
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inline nsresult
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ChannelEventQueue::PrependEvents(nsTArray<nsAutoPtr<ChannelEvent> >& aEvents)
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{
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if (!mEventQueue.InsertElementsAt(0, aEvents.Length())) {
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return NS_ERROR_OUT_OF_MEMORY;
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}
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for (uint32_t i = 0; i < aEvents.Length(); i++) {
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mEventQueue.ReplaceElementAt(i, aEvents[i].forget());
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}
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return NS_OK;
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}
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inline void
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ChannelEventQueue::Suspend()
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{
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mSuspended = true;
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mSuspendCount++;
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}
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inline void
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ChannelEventQueue::CompleteResume()
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{
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// channel may have been suspended again since Resume fired event to call this.
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if (!mSuspendCount) {
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// we need to remain logically suspended (for purposes of queuing incoming
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// messages) until this point, else new incoming messages could run before
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// queued ones.
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mSuspended = false;
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MaybeFlushQueue();
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}
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}
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inline void
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ChannelEventQueue::MaybeFlushQueue()
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{
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// Don't flush if forced queuing on, we're already being flushed, or
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// suspended, or there's nothing to flush
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if (!mForced && !mFlushing && !mSuspended && !mEventQueue.IsEmpty())
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FlushQueue();
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}
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// Ensures that ShouldEnqueue() will be true during its lifetime (letting
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// caller know incoming IPDL msgs should be queued). Flushes the queue when it
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// goes out of scope.
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class MOZ_STACK_CLASS AutoEventEnqueuer
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{
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public:
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explicit AutoEventEnqueuer(ChannelEventQueue *queue) : mEventQueue(queue) {
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mEventQueue->StartForcedQueueing();
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}
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~AutoEventEnqueuer() {
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mEventQueue->EndForcedQueueing();
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}
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private:
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RefPtr<ChannelEventQueue> mEventQueue;
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};
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} // namespace net
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} // namespace mozilla
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#endif
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