Audio output debug recording.

media/audio/audio_debug_file_writer.h

 // Copyright 2015 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_AUDIO_DEBUG_FILE_WRITER_H_
 #define MEDIA_AUDIO_AUDIO_DEBUG_FILE_WRITER_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/files/file.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequence_checker.h"
 #include "base/single_thread_task_runner.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 class AudioBus;
 
-// Writes audio data used for debugging purposes. All operations are
-// non-blocking.
+// Writes audio data to a 16 bit PCM WAVE file used for debugging purposes. All
+// operations are non-blocking.
+// Functions are virtual for the purpose of test mocking.
 class MEDIA_EXPORT AudioDebugFileWriter {
  public:
+  // Number of channels and sample rate are used from |params|, the other
+  // parameters are ignored. The number of channels in the data passed to
+  // Write() must match |params|.
   AudioDebugFileWriter(
       const AudioParameters& params,
       scoped_refptr<base::SingleThreadTaskRunner> file_task_runner);
-  ~AudioDebugFileWriter();
+
+  virtual ~AudioDebugFileWriter();
 
   // Must be called before calling Write() for the first time after creation or
   // Stop() call. Can be called on any sequence; Write() and Stop() must be
   // called on the same sequence as Start().
-  void Start(const base::FilePath& file);
+  virtual void Start(const base::FilePath& file);
 
   // Must be called to finish recording. Each call to Start() requires a call to
   // Stop(). Will be automatically called on destruction.
-  void Stop();
+  virtual void Stop();
 
   // Write |data| to file.
-  void Write(std::unique_ptr<AudioBus> data);
+  virtual void Write(std::unique_ptr<AudioBus> data);
 
   // Returns true if Write() call scheduled at this point will most likely write
   // data to the file, and false if it most likely will be a no-op. The result
   // may be ambigulous if Start() or Stop() is executed at the moment. Can be
   // called from any sequence.
-  bool WillWrite();
+  virtual bool WillWrite();
+
+  // Gets the extension for the file type the as a string, for example "wav".
+  // Can be called before calling Start() to add the appropriate extension to
+  // the filename.
+  virtual const base::FilePath::CharType* GetFileNameExtension();
+
+ protected:
+  const AudioParameters params_;
 
  private:
   class AudioFileWriter;
 
   // Deleter for AudioFileWriter.
   struct OnThreadDeleter {
    public:
     OnThreadDeleter();
     OnThreadDeleter(const OnThreadDeleter& other);
     OnThreadDeleter(scoped_refptr<base::SingleThreadTaskRunner> task_runner);
     ~OnThreadDeleter();
     void operator()(AudioFileWriter* ptr) const;
 
    private:
     scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   };
 
   using AudioFileWriterUniquePtr =
       std::unique_ptr<AudioFileWriter, OnThreadDeleter>;
 
   AudioFileWriterUniquePtr file_writer_;
-  const AudioParameters params_;
   base::SequenceChecker client_sequence_checker_;
 
   // The task runner to do file output operations on.
   scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDebugFileWriter);
 };
 
 }  // namspace media
 
 #endif  // MEDIA_AUDIO_AUDIO_DEBUG_FILE_WRITER_H_