Add metronome interface
Change-Id: Iea2f8ddb21a5d5a6880912f63a81cd4be408bb09
Bug: webrtc:13560, chromium:1253787
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/249380
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Evan Shrubsole <eshr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35844}
diff --git a/api/metronome/BUILD.gn b/api/metronome/BUILD.gn
new file mode 100644
index 0000000..3d3d876
--- /dev/null
+++ b/api/metronome/BUILD.gn
@@ -0,0 +1,19 @@
+# Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS. All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+import("../../webrtc.gni")
+
+rtc_source_set("metronome") {
+ visibility = [ "*" ]
+ sources = [ "metronome.h" ]
+ deps = [
+ "../../rtc_base/system:rtc_export",
+ "../task_queue",
+ "../units:time_delta",
+ ]
+}
diff --git a/api/metronome/metronome.h b/api/metronome/metronome.h
new file mode 100644
index 0000000..fc5f350
--- /dev/null
+++ b/api/metronome/metronome.h
@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef API_METRONOME_METRONOME_H_
+#define API_METRONOME_METRONOME_H_
+
+#include "api/task_queue/task_queue_base.h"
+#include "api/units/time_delta.h"
+#include "rtc_base/system/rtc_export.h"
+
+namespace webrtc {
+
+// The Metronome posts OnTick() on task queues provided by its listeners' task
+// queue periodically. The metronome can be used as an alternative to using
+// PostDelayedTask on a thread or task queue for coalescing work and reducing
+// the number of idle-wakeups.
+//
+// Listeners can be added and removed from any sequence, but it is illegal to
+// remove a listener from an OnTick invocation.
+//
+// The metronome concept is still under experimentation, and may not be availble
+// in all platforms or applications. See https://crbug.com/1253787 for more
+// details.
+//
+// Metronome implementations must be thread-safe.
+class RTC_EXPORT Metronome {
+ public:
+ class RTC_EXPORT TickListener {
+ public:
+ virtual ~TickListener() = default;
+
+ // OnTick is run on the task queue provided by OnTickTaskQueue each time the
+ // metronome ticks.
+ virtual void OnTick() = 0;
+
+ // The task queue that OnTick will run on. Must not be null.
+ virtual TaskQueueBase* OnTickTaskQueue() = 0;
+ };
+
+ virtual ~Metronome() = default;
+
+ // Adds a tick listener to the metronome. Once this method has returned
+ // OnTick will be invoked on each metronome tick. A listener may
+ // only be added to the metronome once.
+ virtual void AddListener(TickListener* listener) = 0;
+
+ // Removes the tick listener from the metronome. Once this method has returned
+ // OnTick will never be called again. This method must not be called from
+ // within OnTick.
+ virtual void RemoveListener(TickListener* listener) = 0;
+
+ // Returns the current tick period of the metronome.
+ virtual TimeDelta TickPeriod() const = 0;
+};
+
+} // namespace webrtc
+
+#endif // API_METRONOME_METRONOME_H_
