Revert 112147 - Did not get LGTM from all reviewers.

media/audio/win/waveout_output_win.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
 #define MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_
 #pragma once
 
 #include <windows.h>
 #include <mmsystem.h>
 #include <mmreg.h>
 
 #include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/synchronization/lock.h"
 #include "base/win/scoped_handle.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_parameters.h"
 
 class AudioManagerWin;
 
 // Implements PCM audio output support for Windows using the WaveXXX API.
 // While not as nice as the DirectSound-based API, it should work in all target
 // operating systems regardless or DirectX version installed. It is known that
 // in some machines WaveXXX based audio is better while in others DirectSound
 // is better.
 //
 // Important: the OnXXXX functions in AudioSourceCallback are called by more
 // than one thread so it is important to have some form of synchronization if
 // you are keeping state in it.
 class PCMWaveOutAudioOutputStream : public AudioOutputStream {
  public:
-  // The ctor takes all the usual parameters, plus |manager| which is the the
-  // audio manager who is creating this object and |device_id| which is provided
-  // by the operating system.
+  // The ctor takes all the usual parameters, plus |manager| which is the
+  // the audio manager who is creating this object and |device_id| which
+  // is provided by the operating system.
   PCMWaveOutAudioOutputStream(AudioManagerWin* manager,
                               const AudioParameters& params,
                               int num_buffers,
                               UINT device_id);
   virtual ~PCMWaveOutAudioOutputStream();
 
   // Implementation of AudioOutputStream.
   virtual bool Open();
   virtual void Close();
   virtual void Start(AudioSourceCallback* callback);
   virtual void Stop();
   virtual void SetVolume(double volume);
   virtual void GetVolume(double* volume);
 
   // Sends a buffer to the audio driver for playback.
   void QueueNextPacket(WAVEHDR* buffer);
 
  private:
   enum State {
     PCMA_BRAND_NEW,    // Initial state.
     PCMA_READY,        // Device obtained and ready to play.
     PCMA_PLAYING,      // Playing audio.
-    PCMA_STOPPING,     // Audio is stopping, do not "feed" data to Windows.
     PCMA_CLOSED        // Device has been released.
   };
 
-  // Returns pointer to the n-th buffer.
-  inline WAVEHDR* GetBuffer(int n) const;
-
-  // Size of one buffer in bytes, rounded up if necessary.
-  inline size_t BufferSize() const;
-
-  // Windows calls us back asking for more data when buffer_event_ signalled.
-  // See MSDN for help on RegisterWaitForSingleObject() and waveOutOpen().
-  static void NTAPI BufferCallback(PVOID lpParameter, BOOLEAN);
+  // Windows calls us back to feed more data to the device here. See msdn
+  // documentation for 'waveOutProc' for details about the parameters.
+  static void CALLBACK WaveCallback(HWAVEOUT hwo, UINT msg, DWORD_PTR instance,
+                                    DWORD_PTR param1, DWORD_PTR param2);
 
   // If windows reports an error this function handles it and passes it to
   // the attached AudioSourceCallback::OnError().
   void HandleError(MMRESULT error);
-
-  // Allocates and prepares the memory that will be used for playback.
+  // Allocates and prepares the memory that will be used for playback. Only
+  // two buffers are created.
   void SetupBuffers();
-
   // Deallocates the memory allocated in SetupBuffers.
   void FreeBuffers();
 
   // Reader beware. Visual C has stronger guarantees on volatile vars than
   // most people expect. In fact, it has release semantics on write and
   // acquire semantics on reads. See the msdn documentation.
   volatile State state_;
 
   // The audio manager that created this output stream. We notify it when
   // we close so it can release its own resources.
@@ skipping 20 matching lines @@
   // The id assigned by the operating system to the selected wave output
   // hardware device. Usually this is just -1 which means 'default device'.
   UINT device_id_;
 
   // Windows native structure to encode the format parameters.
   WAVEFORMATPCMEX format_;
 
   // Handle to the instance of the wave device.
   HWAVEOUT waveout_;
 
-  // Handle to the buffer event.
-  base::win::ScopedHandle buffer_event_;
+  // Pointer to the first allocated audio buffer. This object owns it.
+  WAVEHDR* buffer_;
 
-  // Handle returned by RegisterWaitForSingleObject().
-  base::win::ScopedHandle waiting_handle_;
-
-  // Pointer to the allocated audio buffers, we allocate all buffers in one big
-  // chunk. This object owns them.
-  scoped_array<char> buffers_;
-
-  // Lock used to avoid the conflict when callbacks are called simultaneously.
-  base::Lock lock_;
+  // Lock used to prevent stopping the hardware callback thread while it is
+  // pending for data or feeding it to audio driver, because doing that causes
+  // the deadlock. Main thread gets that lock before stopping the playback.
+  // Callback tries to acquire that lock before entering critical code. If
+  // acquire fails then main thread is stopping the playback, callback should
+  // immediately return.
+  // Use Windows-specific lock, not Chrome one, because there is limited set of
+  // functions callback can use.
+  CRITICAL_SECTION lock_;
 
   DISALLOW_COPY_AND_ASSIGN(PCMWaveOutAudioOutputStream);
 };
 
 #endif  // MEDIA_AUDIO_WIN_WAVEOUT_OUTPUT_WIN_H_