1 files changed, 102 insertions, 0 deletions
diff --git a/dom/media/Tracing.h b/dom/media/Tracing.h
new file mode 100644
index 0000000000..ab9fcb440e
--- /dev/null
+++ b/dom/media/Tracing.h
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 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 TRACING_H
+#define TRACING_H
+
+#include <algorithm>
+#include <cstdint>
+#include <cstdio>
+
+#include "AsyncLogger.h"
+
+#include "mozilla/Attributes.h"
+#include "mozilla/UniquePtr.h"
+
+#if defined(_MSC_VER)
+// MSVC
+#  define FUNCTION_SIGNATURE __FUNCSIG__
+#elif defined(__GNUC__)
+// gcc, clang
+#  define FUNCTION_SIGNATURE __PRETTY_FUNCTION__
+#endif
+
+extern mozilla::AsyncLogger gAudioCallbackTraceLogger;
+
+// This is no-op if tracing is not enabled, and is idempotent.
+void StartAudioCallbackTracing();
+void StopAudioCallbackTracing();
+
+#ifdef MOZ_REAL_TIME_TRACING
+#  define TRACE(aName) AutoTracer trace(gAudioCallbackTraceLogger, aName);
+#  define TRACE_COMMENT(aName, aFmt, ...)              \
+    AutoTracer trace(gAudioCallbackTraceLogger, aName, \
+                     AutoTracer::EventType::DURATION, aFmt, ##__VA_ARGS__);
+#  define TRACE_AUDIO_CALLBACK_BUDGET(aLocation, aFrames, aSampleRate) \
+    AutoTracer budget(gAudioCallbackTraceLogger, aLocation,            \
+                      AutoTracer::EventType::BUDGET, aFrames, aSampleRate);
+#else
+#  define TRACE(aName)
+#  define TRACE_COMMENT(aFmt, ...)
+#  define TRACE_AUDIO_CALLBACK_BUDGET(aLocation, aFrames, aSampleRate)
+#endif
+
+class MOZ_RAII AutoTracer {
+ public:
+  static const int32_t BUFFER_SIZE = 256;
+
+  enum class EventType { DURATION, BUDGET };
+
+  AutoTracer(mozilla::AsyncLogger& aLogger, const char* aLocation,
+             EventType aEventType = EventType::DURATION,
+             const char* aComment = nullptr);
+
+  template <typename... Args>
+  AutoTracer(mozilla::AsyncLogger& aLogger, const char* aLocation,
+             EventType aEventType, const char* aFormat, Args... aArgs)
+      : mLogger(aLogger),
+        mLocation(aLocation),
+        mComment(mBuffer),
+        mEventType(aEventType) {
+    MOZ_ASSERT(aEventType == EventType::DURATION);
+    if (aLogger.Enabled()) {
+      int32_t size = snprintf(mBuffer, BUFFER_SIZE, aFormat, aArgs...);
+      size = std::min(size, BUFFER_SIZE - 1);
+      mBuffer[size] = 0;
+      PrintEvent(aLocation, "perf", mComment,
+                 mozilla::AsyncLogger::TracingPhase::BEGIN);
+    }
+  }
+
+  AutoTracer(mozilla::AsyncLogger& aLogger, const char* aLocation,
+             EventType aEventType, uint64_t aFrames, uint64_t aSampleRate);
+
+  ~AutoTracer();
+
+ private:
+  void PrintEvent(const char* aName, const char* aCategory,
+                  const char* aComment,
+                  mozilla::AsyncLogger::TracingPhase aPhase);
+
+  void PrintBudget(const char* aName, const char* aCategory, uint64_t aDuration,
+                   uint64_t aFrames, uint64_t aSampleRate);
+
+  // The logger to use. It musdt have a lifetime longer than the block an
+  // instance of this class traces.
+  mozilla::AsyncLogger& mLogger;
+  // The location for this trace point, arbitrary string literal, often the
+  // name of the calling function, with a static lifetime.
+  const char* mLocation;
+  // A comment for this trace point, abitrary string literal with a static
+  // lifetime.
+  const char* mComment;
+  // A buffer used to hold string-formatted traces.
+  char mBuffer[BUFFER_SIZE];
+  // The event type, for now either a budget or a duration.
+  const EventType mEventType;
+};
+
+#endif /* TRACING_H */