Implementation of 'AudioContext.getOutputTimestamp' method

third_party/WebKit/Source/modules/webaudio/AudioContext.cpp

Index: third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
index f7cc9c928a7f3b814c40749e345b535337eaaf75..7a85589686fb1d1e2ad66e82365db7f7cf51ebb2 100644
--- a/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
@@ -9,7 +9,11 @@
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/ExceptionCode.h"
+#include "core/frame/LocalDOMWindow.h"
+#include "core/timing/DOMWindowPerformance.h"
+#include "core/timing/Performance.h"
 #include "modules/webaudio/AudioBufferCallback.h"
+#include "modules/webaudio/AudioTimestamp.h"
 #include "platform/Histogram.h"
 #include "platform/audio/AudioUtilities.h"
 
@@ -80,6 +84,7 @@ AbstractAudioContext* AudioContext::create(Document& document, ExceptionState& e
 AudioContext::AudioContext(Document& document)
     : AbstractAudioContext(&document)
     , m_contextId(s_contextId++)
+    , m_outputTimestampFramesOrigin(0)
 {
 }
 
@@ -138,8 +143,10 @@ ScriptPromise AudioContext::resumeContext(ScriptState* scriptState)
     ScriptPromise promise = resolver->promise();
 
     // Restart the destination node to pull on the audio graph.
-    if (destination())
+    if (destination()) {
+        m_outputTimestampFramesOrigin = currentSampleFrame();
         startRendering();
+    }
 
     // Save the resolver which will get resolved when the destination node starts pulling on the
     // graph again.
@@ -151,6 +158,40 @@ ScriptPromise AudioContext::resumeContext(ScriptState* scriptState)
     return promise;
 }
 
+static double toPerformanceTime(ExecutionContext* context, double seconds)
+{
+    if (!context)
+        return 0.0;
+
+    LocalDOMWindow* window = context->executingWindow();
+    if (!window)
+        return 0.0;
+
+    Performance* performance = DOMWindowPerformance::performance(*window);
+    if (!performance)
+        return 0.0;
+
+    return performance->monotonicTimeToDOMHighResTimeStamp(seconds);
+}
+
+void AudioContext::getOutputTimestamp(AudioTimestamp& result)
+{
+    DCHECK(isMainThread());
+    if (!destination()) {
+        result.setContextTime(0.0);
+        result.setPerformanceTime(0.0);
+        return;
+    }
+
+    WebAudioTimestamp timestamp = outputTimestamp();
+    double sampleRate = destination()->audioDestinationHandler().sampleRate();
+    double contextTime = (m_outputTimestampFramesOrigin + timestamp.frames) / sampleRate;
+    double performanceTime = timestamp.seconds ? toPerformanceTime(getExecutionContext(), timestamp.seconds) : 0.0;
+
+    result.setContextTime(contextTime);
+    result.setPerformanceTime(performanceTime);
+}
+
 ScriptPromise AudioContext::closeContext(ScriptState* scriptState)
 {
     if (isContextClosed()) {