media/blink/buffered_data_source.h

// Copyright 2013 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_BLINK_BUFFERED_DATA_SOURCE_H_
#define MEDIA_BLINK_BUFFERED_DATA_SOURCE_H_

#include <string>
#include <vector>

#include "base/callback.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/synchronization/lock.h"
#include "media/base/data_source.h"
#include "media/base/media_export.h"
#include "media/base/ranges.h"
#include "media/blink/buffered_resource_loader.h"
#include "url/gurl.h"

namespace base {
class SingleThreadTaskRunner;
}

namespace media {
class MediaLog;

class MEDIA_EXPORT BufferedDataSourceHost {
 public:
  // Notify the host of the total size of the media file.
  virtual void SetTotalBytes(int64 total_bytes) = 0;

  // Notify the host that byte range [start,end] has been buffered.
  // TODO(fischman): remove this method when demuxing is push-based instead of
  // pull-based.  http://crbug.com/131444
  virtual void AddBufferedByteRange(int64 start, int64 end) = 0;

 protected:
  virtual ~BufferedDataSourceHost() {}
};

// A data source capable of loading URLs and buffering the data using an
// in-memory sliding window.
//
// BufferedDataSource must be created and destroyed on the thread associated
// with the |task_runner| passed in the constructor.
class MEDIA_EXPORT BufferedDataSource : public DataSource {
 public:
  // Used to specify video preload states. They are "hints" to the browser about
  // how aggressively the browser should load and buffer data.
  // Please see the HTML5 spec for the descriptions of these values:
  // http://www.w3.org/TR/html5/video.html#attr-media-preload
  //
  // Enum values must match the values in blink::WebMediaPlayer::Preload and
  // there will be assertions at compile time if they do not match.
  enum Preload {
    NONE,
    METADATA,
    AUTO,
  };
  typedef base::Callback<void(bool)> DownloadingCB;

  // |url| and |cors_mode| are passed to the object. Buffered byte range changes
  // will be reported to |host|. |downloading_cb| will be called whenever the
  // downloading/paused state of the source changes.
  BufferedDataSource(
      const GURL& url,
      BufferedResourceLoader::CORSMode cors_mode,
      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
      blink::WebFrame* frame,
      MediaLog* media_log,
      BufferedDataSourceHost* host,
      const DownloadingCB& downloading_cb);
  ~BufferedDataSource() override;

  // Executes |init_cb| with the result of initialization when it has completed.
  //
  // Method called on the render thread.
  typedef base::Callback<void(bool)> InitializeCB;
  void Initialize(const InitializeCB& init_cb);

  // Adjusts the buffering algorithm based on the given preload value.
  void SetPreload(Preload preload);

  // Returns true if the media resource has a single origin, false otherwise.
  // Only valid to call after Initialize() has completed.
  //
  // Method called on the render thread.
  bool HasSingleOrigin();

  // Returns true if the media resource passed a CORS access control check.
  bool DidPassCORSAccessCheck() const;

  // Cancels initialization, any pending loaders, and any pending read calls
  // from the demuxer. The caller is expected to release its reference to this
  // object and never call it again.
  //
  // Method called on the render thread.
  void Abort();

  // Notifies changes in playback state for controlling media buffering
  // behavior.
  void MediaPlaybackRateChanged(float playback_rate);
  void MediaIsPlaying();
  void MediaIsPaused();

  // Returns true if the resource is local.
  bool assume_fully_buffered() { return !url_.SchemeIsHTTPOrHTTPS(); }

  // DataSource implementation.
  // Called from demuxer thread.
  void Stop() override;

  void Read(int64 position,
            int size,
            uint8* data,
            const DataSource::ReadCB& read_cb) override;
  bool GetSize(int64* size_out) override;
  bool IsStreaming() override;
  void SetBitrate(int bitrate) override;

 protected:
  // A factory method to create a BufferedResourceLoader based on the read
  // parameters. We can override this file to object a mock
  // BufferedResourceLoader for testing.
  virtual BufferedResourceLoader* CreateResourceLoader(
      int64 first_byte_position, int64 last_byte_position);

 private:
  friend class BufferedDataSourceTest;

  // Task posted to perform actual reading on the render thread.
  void ReadTask();

  // Cancels oustanding callbacks and sets |stop_signal_received_|. Safe to call
  // from any thread.
  void StopInternal_Locked();

  // Stops |loader_| if present. Used by Abort() and Stop().
  void StopLoader();

  // Tells |loader_| the bitrate of the media.
  void SetBitrateTask(int bitrate);

  // The method that performs actual read. This method can only be executed on
  // the render thread.
  void ReadInternal();

  // BufferedResourceLoader::Start() callback for initial load.
  void StartCallback(BufferedResourceLoader::Status status);

  // BufferedResourceLoader::Start() callback for subsequent loads (i.e.,
  // when accessing ranges that are outside initial buffered region).
  void PartialReadStartCallback(BufferedResourceLoader::Status status);

  // BufferedResourceLoader callbacks.
  void ReadCallback(BufferedResourceLoader::Status status, int bytes_read);
  void LoadingStateChangedCallback(BufferedResourceLoader::LoadingState state);
  void ProgressCallback(int64 position);

  // Update |loader_|'s deferring strategy in response to a play/pause, or
  // change in playback rate.
  void UpdateDeferStrategy(bool paused);

  // URL of the resource requested.
  GURL url_;
  // crossorigin attribute on the corresponding HTML media element, if any.
  BufferedResourceLoader::CORSMode cors_mode_;

  // The total size of the resource. Set during StartCallback() if the size is
  // known, otherwise it will remain kPositionNotSpecified until the size is
  // determined by reaching EOF.
  int64 total_bytes_;

  // This value will be true if this data source can only support streaming.
  // i.e. range request is not supported.
  bool streaming_;

  // A webframe for loading.
  blink::WebFrame* frame_;

  // A resource loader for the media resource.
  scoped_ptr<BufferedResourceLoader> loader_;

  // Callback method from the pipeline for initialization.
  InitializeCB init_cb_;

  // Read parameters received from the Read() method call. Must be accessed
  // under |lock_|.
  class ReadOperation;
  scoped_ptr<ReadOperation> read_op_;

  // This buffer is intermediate, we use it for BufferedResourceLoader to write
  // to. And when read in BufferedResourceLoader is done, we copy data from
  // this buffer to |read_buffer_|. The reason for an additional copy is that
  // we don't own |read_buffer_|. But since the read operation is asynchronous,
  // |read_buffer| can be destroyed at any time, so we only copy into
  // |read_buffer| in the final step when it is safe.
  // Memory is allocated for this member during initialization of this object
  // because we want buffer to be passed into BufferedResourceLoader to be
  // always non-null. And by initializing this member with a default size we can
  // avoid creating zero-sized buffered if the first read has zero size.
  std::vector<uint8> intermediate_read_buffer_;

  // The task runner of the render thread.
  const scoped_refptr<base::SingleThreadTaskRunner> render_task_runner_;

  // Protects |stop_signal_received_| and |read_op_|.
  base::Lock lock_;

  // Whether we've been told to stop via Abort() or Stop().
  bool stop_signal_received_;

  // This variable is true when the user has requested the video to play at
  // least once.
  bool media_has_played_;

  // This variable holds the value of the preload attribute for the video
  // element.
  Preload preload_;

  // Bitrate of the content, 0 if unknown.
  int bitrate_;

  // Current playback rate.
  float playback_rate_;

  scoped_refptr<MediaLog> media_log_;

  // Host object to report buffered byte range changes to.
  BufferedDataSourceHost* host_;

  DownloadingCB downloading_cb_;

  // NOTE: Weak pointers must be invalidated before all other member variables.
  base::WeakPtrFactory<BufferedDataSource> weak_factory_;

  // Disallow rebinding WeakReference ownership to a different thread by keeping
  // a persistent reference. This avoids problems with the thread-safety of
  // reaching into this class from multiple threads to attain a WeakPtr.
  const base::WeakPtr<BufferedDataSource> weak_ptr_;

  DISALLOW_COPY_AND_ASSIGN(BufferedDataSource);
};

}  // namespace media

#endif  // MEDIA_BLINK_BUFFERED_DATA_SOURCE_H_