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