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-rw-r--r--dom/media/MediaTimer.cpp184
1 files changed, 184 insertions, 0 deletions
diff --git a/dom/media/MediaTimer.cpp b/dom/media/MediaTimer.cpp
new file mode 100644
index 000000000..1420d6aca
--- /dev/null
+++ b/dom/media/MediaTimer.cpp
@@ -0,0 +1,184 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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/. */
+
+#include "MediaTimer.h"
+
+#include <math.h>
+
+#include "nsComponentManagerUtils.h"
+#include "nsThreadUtils.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/SharedThreadPool.h"
+
+namespace mozilla {
+
+NS_IMPL_ADDREF(MediaTimer)
+NS_IMPL_RELEASE_WITH_DESTROY(MediaTimer, DispatchDestroy())
+
+MediaTimer::MediaTimer()
+ : mMonitor("MediaTimer Monitor")
+ , mTimer(do_CreateInstance("@mozilla.org/timer;1"))
+ , mCreationTimeStamp(TimeStamp::Now())
+ , mUpdateScheduled(false)
+{
+ TIMER_LOG("MediaTimer::MediaTimer");
+
+ // Use the SharedThreadPool to create an nsIThreadPool with a maximum of one
+ // thread, which is equivalent to an nsIThread for our purposes.
+ RefPtr<SharedThreadPool> threadPool(
+ SharedThreadPool::Get(NS_LITERAL_CSTRING("MediaTimer"), 1));
+ mThread = threadPool.get();
+ mTimer->SetTarget(mThread);
+}
+
+void
+MediaTimer::DispatchDestroy()
+{
+ // Hold a strong reference to the thread so that it doesn't get deleted in
+ // Destroy(), which may run completely before the stack if Dispatch() begins
+ // to unwind.
+ nsCOMPtr<nsIEventTarget> thread = mThread;
+ nsresult rv = thread->Dispatch(NewNonOwningRunnableMethod(this, &MediaTimer::Destroy),
+ NS_DISPATCH_NORMAL);
+ MOZ_DIAGNOSTIC_ASSERT(NS_SUCCEEDED(rv));
+ (void) rv;
+}
+
+void
+MediaTimer::Destroy()
+{
+ MOZ_ASSERT(OnMediaTimerThread());
+ TIMER_LOG("MediaTimer::Destroy");
+
+ // Reject any outstanding entries. There's no need to acquire the monitor
+ // here, because we're on the timer thread and all other references to us
+ // must be gone.
+ while (!mEntries.empty()) {
+ mEntries.top().mPromise->Reject(false, __func__);
+ mEntries.pop();
+ }
+
+ // Cancel the timer if necessary.
+ CancelTimerIfArmed();
+
+ delete this;
+}
+
+bool
+MediaTimer::OnMediaTimerThread()
+{
+ bool rv = false;
+ mThread->IsOnCurrentThread(&rv);
+ return rv;
+}
+
+RefPtr<MediaTimerPromise>
+MediaTimer::WaitUntil(const TimeStamp& aTimeStamp, const char* aCallSite)
+{
+ MonitorAutoLock mon(mMonitor);
+ TIMER_LOG("MediaTimer::WaitUntil %lld", RelativeMicroseconds(aTimeStamp));
+ Entry e(aTimeStamp, aCallSite);
+ RefPtr<MediaTimerPromise> p = e.mPromise.get();
+ mEntries.push(e);
+ ScheduleUpdate();
+ return p;
+}
+
+void
+MediaTimer::ScheduleUpdate()
+{
+ mMonitor.AssertCurrentThreadOwns();
+ if (mUpdateScheduled) {
+ return;
+ }
+ mUpdateScheduled = true;
+
+ nsresult rv = mThread->Dispatch(NewRunnableMethod(this, &MediaTimer::Update),
+ NS_DISPATCH_NORMAL);
+ MOZ_DIAGNOSTIC_ASSERT(NS_SUCCEEDED(rv));
+ (void) rv;
+}
+
+void
+MediaTimer::Update()
+{
+ MonitorAutoLock mon(mMonitor);
+ UpdateLocked();
+}
+
+void
+MediaTimer::UpdateLocked()
+{
+ MOZ_ASSERT(OnMediaTimerThread());
+ mMonitor.AssertCurrentThreadOwns();
+ mUpdateScheduled = false;
+
+ TIMER_LOG("MediaTimer::UpdateLocked");
+
+ // Resolve all the promises whose time is up.
+ TimeStamp now = TimeStamp::Now();
+ while (!mEntries.empty() && mEntries.top().mTimeStamp <= now) {
+ mEntries.top().mPromise->Resolve(true, __func__);
+ DebugOnly<TimeStamp> poppedTimeStamp = mEntries.top().mTimeStamp;
+ mEntries.pop();
+ MOZ_ASSERT_IF(!mEntries.empty(), *&poppedTimeStamp <= mEntries.top().mTimeStamp);
+ }
+
+ // If we've got no more entries, cancel any pending timer and bail out.
+ if (mEntries.empty()) {
+ CancelTimerIfArmed();
+ return;
+ }
+
+ // We've got more entries - (re)arm the timer for the soonest one.
+ if (!TimerIsArmed() || mEntries.top().mTimeStamp < mCurrentTimerTarget) {
+ CancelTimerIfArmed();
+ ArmTimer(mEntries.top().mTimeStamp, now);
+ }
+}
+
+/*
+ * We use a callback function, rather than a callback method, to ensure that
+ * the nsITimer does not artifically keep the refcount of the MediaTimer above
+ * zero. When the MediaTimer is destroyed, it safely cancels the nsITimer so that
+ * we never fire against a dangling closure.
+ */
+
+/* static */ void
+MediaTimer::TimerCallback(nsITimer* aTimer, void* aClosure)
+{
+ static_cast<MediaTimer*>(aClosure)->TimerFired();
+}
+
+void
+MediaTimer::TimerFired()
+{
+ MonitorAutoLock mon(mMonitor);
+ MOZ_ASSERT(OnMediaTimerThread());
+ mCurrentTimerTarget = TimeStamp();
+ UpdateLocked();
+}
+
+void
+MediaTimer::ArmTimer(const TimeStamp& aTarget, const TimeStamp& aNow)
+{
+ MOZ_DIAGNOSTIC_ASSERT(!TimerIsArmed());
+ MOZ_DIAGNOSTIC_ASSERT(aTarget > aNow);
+
+ // XPCOM timer resolution is in milliseconds. It's important to never resolve
+ // a timer when mTarget might compare < now (even if very close), so round up.
+ unsigned long delay = std::ceil((aTarget - aNow).ToMilliseconds());
+ TIMER_LOG("MediaTimer::ArmTimer delay=%lu", delay);
+ mCurrentTimerTarget = aTarget;
+ nsresult rv = mTimer->InitWithNamedFuncCallback(&TimerCallback, this, delay,
+ nsITimer::TYPE_ONE_SHOT,
+ "MediaTimer::TimerCallback");
+ MOZ_DIAGNOSTIC_ASSERT(NS_SUCCEEDED(rv));
+ (void) rv;
+}
+
+} // namespace mozilla