Bug 848954 - Part 12 - Make sure COM is initialized when calling into WASAPI functions. r=kinetik

media/libcubeb/src/cubeb_wasapi.cpp

@@ -68,6 +68,35 @@ void SafeRelease(T * ptr)
   }
 }
 
+struct auto_com {
+  auto_com()
+  : need_uninit(true) {
+    HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
+    // This is for information purposes only, in anycase, COM is initialized
+    // at the end of the constructor.
+    if (hr == RPC_E_CHANGED_MODE) {
+      // This is an error, COM was not initialized by this function, so it is
+      // not necessary to uninit it.
+      LOG("COM already initialized in STA.");
+      need_uninit = false;
+    } else if (hr == S_FALSE) {
+      // This is not an error. We are allowed to call CoInitializeEx more than
+      // once, as long as it is matches by an CoUninitialize call.
+      // We do that in the dtor which is guaranteed to be called.
+      LOG("COM already initialized in MTA");
+    } else if (hr == S_OK) {
+      LOG("COM initialized.");
+    }
+  }
+  ~auto_com() {
+    if (need_uninit) {
+      CoUninitialize();
+    }
+  }
+private:
+  bool need_uninit;
+};
+
 typedef HANDLE (WINAPI *set_mm_thread_characteristics_function)(
                                       const char* TaskName, LPDWORD TaskIndex);
 typedef BOOL (WINAPI *revert_mm_thread_characteristics_function)(HANDLE handle);
@@ -244,6 +273,7 @@ wasapi_stream_render_loop(LPVOID stream)
   HRESULT hr;
   bool first = true;
   DWORD mmcss_task_index = 0;
+  auto_com com;
 
   /* We could consider using "Pro Audio" here for WebAudio and
    * maybe WebRTC. */
@@ -254,11 +284,6 @@ wasapi_stream_render_loop(LPVOID stream)
     LOG("Unable to use mmcss to bump the render thread priority: %x", GetLastError());
   }
 
-  hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
-  if (FAILED(hr)) {
-    LOG("could not initialize COM in render thread: %x", hr);
-    return hr;
-  }
 
   while (is_playing) {
     DWORD waitResult = WaitForMultipleObjects(ARRAY_LENGTH(wait_array),
@@ -329,7 +354,6 @@ wasapi_stream_render_loop(LPVOID stream)
 
   stm->context->revert_mm_thread_characteristics(mmcss_handle);
 
-  CoUninitialize();
   return 0;
 }
 
@@ -376,12 +400,7 @@ extern "C" {
 int wasapi_init(cubeb ** context, char const * context_name)
 {
   HRESULT hr;
-
-  hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
-  if (FAILED(hr)) {
-    LOG("Could not init COM.");
-    return CUBEB_ERROR;
-  }
+  auto_com com;
 
   /* We don't use the device yet, but need to make sure we can initialize one
      so that this backend is not incorrectly enabled on platforms that don't
@@ -443,13 +462,15 @@ char const* wasapi_get_backend_id(cubeb * context)
 int
 wasapi_get_max_channel_count(cubeb * ctx, uint32_t * max_channels)
 {
+  HRESULT hr;
   IAudioClient * client;
   WAVEFORMATEX * mix_format;
+  auto_com com;
 
   assert(ctx && max_channels);
 
   IMMDevice * device;
-  HRESULT hr = get_default_endpoint(&device);
+  hr = get_default_endpoint(&device);
   if (FAILED(hr)) {
     return CUBEB_ERROR;
   }
@@ -482,10 +503,12 @@ wasapi_get_min_latency(cubeb * ctx, cubeb_stream_params params, uint32_t * laten
   HRESULT hr;
   IAudioClient * client;
   REFERENCE_TIME default_period;
+  auto_com com;
 
   IMMDevice * device;
   hr = get_default_endpoint(&device);
   if (FAILED(hr)) {
+    LOG("Could not get default endpoint:%x.", hr)
     return CUBEB_ERROR;
   }
 
@@ -494,6 +517,7 @@ wasapi_get_min_latency(cubeb * ctx, cubeb_stream_params params, uint32_t * laten
                         NULL, (void **)&client);
   SafeRelease(device);
   if (FAILED(hr)) {
+    LOG("Could not activate device for latency: %x.", hr)
     return CUBEB_ERROR;
   }
 
@@ -501,9 +525,12 @@ wasapi_get_min_latency(cubeb * ctx, cubeb_stream_params params, uint32_t * laten
   hr = client->GetDevicePeriod(&default_period, NULL);
   if (FAILED(hr)) {
     SafeRelease(client);
+    LOG("Could not get device period: %x.", hr)
     return CUBEB_ERROR;
   }
 
+  LOG("default device period: %ld", default_period)
+
   /* According to the docs, the best latency we can achieve is by synchronizing
    * the stream and the engine.
    * http://msdn.microsoft.com/en-us/library/windows/desktop/dd370871%28v=vs.85%29.aspx */
@@ -520,6 +547,7 @@ wasapi_get_preferred_sample_rate(cubeb * ctx, uint32_t * rate)
   HRESULT hr;
   IAudioClient * client;
   WAVEFORMATEX * mix_format;
+  auto_com com;
 
   IMMDevice * device;
   hr = get_default_endpoint(&device);
@@ -627,15 +655,10 @@ wasapi_stream_init(cubeb * context, cubeb_stream ** stream,
 {
   HRESULT hr;
   WAVEFORMATEX * mix_format;
+  auto_com com;
 
   assert(context && stream);
 
-  hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
-  if (FAILED(hr)) {
-    LOG("Could not initialize COM.");
-    return CUBEB_ERROR;
-  }
-
   cubeb_stream * stm = (cubeb_stream *)calloc(1, sizeof(cubeb_stream));
 
   assert(stm);
@@ -808,7 +831,6 @@ void wasapi_stream_destroy(cubeb_stream * stm)
 
   free(stm->mix_buffer);
   free(stm);
-  CoUninitialize();
 }
 
 int wasapi_stream_start(cubeb_stream * stm)