Notify audio host that audio rendering in Pepper plugin is done.

BUG=120837
TEST=See bug


Review URL: http://codereview.chromium.org/9921006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@132746 0039d316-1c4b-4281-b951-d872f2087c98

ppapi/shared_impl/ppb_audio_shared.cc

@@ -6,8 +6,31 @@
 
 #include "base/logging.h"
 
+using base::subtle::Atomic32;
+
 namespace ppapi {
 
+// FIXME: The following two functions (TotalSharedMemorySizeInBytes,
+// SetActualDataSizeInBytes) are copied from audio_util.cc.
+// Remove these functions once a minimal media library is provided for them.
+// code.google.com/p/chromium/issues/detail?id=123203
+
+uint32 TotalSharedMemorySizeInBytes(uint32 packet_size) {
+  // Need to reserve extra 4 bytes for size of data.
+  return packet_size + sizeof(Atomic32);
+}
+
+void SetActualDataSizeInBytes(base::SharedMemory* shared_memory,
+                              uint32 shared_memory_size,
+                              uint32 actual_data_size) {
+  char* ptr = static_cast<char*>(shared_memory->memory()) + shared_memory_size;
+  DCHECK_EQ(0u, reinterpret_cast<size_t>(ptr) & 3);
+
+  // Set actual data size at the end of the buffer.
+  base::subtle::Release_Store(reinterpret_cast<volatile Atomic32*>(ptr),
+                              actual_data_size);
+}
+
 const int PPB_Audio_Shared::kPauseMark = -1;
 
 PPB_Audio_Shared::PPB_Audio_Shared()
@@ -66,7 +89,8 @@ void PPB_Audio_Shared::SetStreamInfo(
   shared_memory_size_ = shared_memory_size;
 
   if (callback_) {
-    shared_memory_->Map(shared_memory_size_);
+    shared_memory_->Map(TotalSharedMemorySizeInBytes(
+        shared_memory_size_));
 
     // In common case StartPlayback() was called before StreamCreated().
     if (playing_)
@@ -90,6 +114,10 @@ void PPB_Audio_Shared::Run() {
       socket_->Receive(&pending_data, sizeof(pending_data)) &&
       pending_data != kPauseMark) {
     callback_(buffer, shared_memory_size_, user_data_);
+
+    // Let the host know we are done.
+    SetActualDataSizeInBytes(shared_memory_.get(), shared_memory_size_,
+        shared_memory_size_);
   }
 }