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diff --git a/netwerk/ipc/ChannelEventQueue.h b/netwerk/ipc/ChannelEventQueue.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set sw=2 ts=8 et tw=80 :
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+#ifndef mozilla_net_ChannelEventQueue_h
+#define mozilla_net_ChannelEventQueue_h
+
+#include "nsTArray.h"
+#include "nsAutoPtr.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/UniquePtr.h"
+
+class nsISupports;
+class nsIEventTarget;
+
+namespace mozilla {
+namespace net {
+
+class ChannelEvent
+{
+ public:
+ ChannelEvent() { MOZ_COUNT_CTOR(ChannelEvent); }
+ virtual ~ChannelEvent() { MOZ_COUNT_DTOR(ChannelEvent); }
+ virtual void Run() = 0;
+};
+
+// Workaround for Necko re-entrancy dangers. We buffer IPDL messages in a
+// queue if still dispatching previous one(s) to listeners/observers.
+// Otherwise synchronous XMLHttpRequests and/or other code that spins the
+// event loop (ex: IPDL rpc) could cause listener->OnDataAvailable (for
+// instance) to be dispatched and called before mListener->OnStartRequest has
+// completed.
+
+class ChannelEventQueue final
+{
+ NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ChannelEventQueue)
+
+ public:
+ explicit ChannelEventQueue(nsISupports *owner)
+ : mSuspendCount(0)
+ , mSuspended(false)
+ , mForced(false)
+ , mFlushing(false)
+ , mOwner(owner)
+ , mMutex("ChannelEventQueue::mMutex")
+ {}
+
+ // Puts IPDL-generated channel event into queue, to be run later
+ // automatically when EndForcedQueueing and/or Resume is called.
+ //
+ // @param aCallback - the ChannelEvent
+ // @param aAssertionWhenNotQueued - this optional param will be used in an
+ // assertion when the event is executed directly.
+ inline void RunOrEnqueue(ChannelEvent* aCallback,
+ bool aAssertionWhenNotQueued = false);
+ inline nsresult PrependEvents(nsTArray<UniquePtr<ChannelEvent>>& aEvents);
+
+ // After StartForcedQueueing is called, RunOrEnqueue() will start enqueuing
+ // events that will be run/flushed when EndForcedQueueing is called.
+ // - Note: queueing may still be required after EndForcedQueueing() (if the
+ // queue is suspended, etc): always call RunOrEnqueue() to avoid race
+ // conditions.
+ inline void StartForcedQueueing();
+ inline void EndForcedQueueing();
+
+ // Suspend/resume event queue. RunOrEnqueue() will start enqueuing
+ // events and they will be run/flushed when resume is called. These should be
+ // called when the channel owning the event queue is suspended/resumed.
+ inline void Suspend();
+ // Resume flushes the queue asynchronously, i.e. items in queue will be
+ // dispatched in a new event on the current thread.
+ void Resume();
+
+ // Retargets delivery of events to the target thread specified.
+ nsresult RetargetDeliveryTo(nsIEventTarget* aTargetThread);
+
+ private:
+ // Private destructor, to discourage deletion outside of Release():
+ ~ChannelEventQueue()
+ {
+ }
+
+ inline void MaybeFlushQueue();
+ void FlushQueue();
+ inline void CompleteResume();
+
+ ChannelEvent* TakeEvent();
+
+ nsTArray<UniquePtr<ChannelEvent>> mEventQueue;
+
+ uint32_t mSuspendCount;
+ bool mSuspended;
+ bool mForced;
+ bool mFlushing;
+
+ // Keep ptr to avoid refcount cycle: only grab ref during flushing.
+ nsISupports *mOwner;
+
+ Mutex mMutex;
+
+ // EventTarget for delivery of events to the correct thread.
+ nsCOMPtr<nsIEventTarget> mTargetThread;
+
+ friend class AutoEventEnqueuer;
+};
+
+inline void
+ChannelEventQueue::RunOrEnqueue(ChannelEvent* aCallback,
+ bool aAssertionWhenNotQueued)
+{
+ MOZ_ASSERT(aCallback);
+
+ // To avoid leaks.
+ UniquePtr<ChannelEvent> event(aCallback);
+
+ {
+ MutexAutoLock lock(mMutex);
+
+ bool enqueue = mForced || mSuspended || mFlushing;
+ MOZ_ASSERT(enqueue == true || mEventQueue.IsEmpty(),
+ "Should always enqueue if ChannelEventQueue not empty");
+
+ if (enqueue) {
+ mEventQueue.AppendElement(Move(event));
+ return;
+ }
+ }
+
+ MOZ_RELEASE_ASSERT(!aAssertionWhenNotQueued);
+ event->Run();
+}
+
+inline void
+ChannelEventQueue::StartForcedQueueing()
+{
+ MutexAutoLock lock(mMutex);
+ mForced = true;
+}
+
+inline void
+ChannelEventQueue::EndForcedQueueing()
+{
+ {
+ MutexAutoLock lock(mMutex);
+ mForced = false;
+ }
+
+ MaybeFlushQueue();
+}
+
+inline nsresult
+ChannelEventQueue::PrependEvents(nsTArray<UniquePtr<ChannelEvent>>& aEvents)
+{
+ MutexAutoLock lock(mMutex);
+
+ UniquePtr<ChannelEvent>* newEvents =
+ mEventQueue.InsertElementsAt(0, aEvents.Length());
+ if (!newEvents) {
+ return NS_ERROR_OUT_OF_MEMORY;
+ }
+
+ for (uint32_t i = 0; i < aEvents.Length(); i++) {
+ newEvents[i] = Move(aEvents[i]);
+ }
+
+ return NS_OK;
+}
+
+inline void
+ChannelEventQueue::Suspend()
+{
+ MutexAutoLock lock(mMutex);
+
+ mSuspended = true;
+ mSuspendCount++;
+}
+
+inline void
+ChannelEventQueue::CompleteResume()
+{
+ {
+ MutexAutoLock lock(mMutex);
+
+ // channel may have been suspended again since Resume fired event to call
+ // this.
+ if (!mSuspendCount) {
+ // we need to remain logically suspended (for purposes of queuing incoming
+ // messages) until this point, else new incoming messages could run before
+ // queued ones.
+ mSuspended = false;
+ }
+ }
+
+ MaybeFlushQueue();
+}
+
+inline void
+ChannelEventQueue::MaybeFlushQueue()
+{
+ // Don't flush if forced queuing on, we're already being flushed, or
+ // suspended, or there's nothing to flush
+ bool flushQueue = false;
+
+ {
+ MutexAutoLock lock(mMutex);
+ flushQueue = !mForced && !mFlushing && !mSuspended &&
+ !mEventQueue.IsEmpty();
+ }
+
+ if (flushQueue) {
+ FlushQueue();
+ }
+}
+
+// Ensures that RunOrEnqueue() will be collecting events during its lifetime
+// (letting caller know incoming IPDL msgs should be queued). Flushes the queue
+// when it goes out of scope.
+class MOZ_STACK_CLASS AutoEventEnqueuer
+{
+ public:
+ explicit AutoEventEnqueuer(ChannelEventQueue *queue) : mEventQueue(queue) {
+ mEventQueue->StartForcedQueueing();
+ }
+ ~AutoEventEnqueuer() {
+ mEventQueue->EndForcedQueueing();
+ }
+ private:
+ RefPtr<ChannelEventQueue> mEventQueue;
+};
+
+} // namespace net
+} // namespace mozilla
+
+#endif