Removing DataSource from Filter hierarchy

media/base/data_source.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_BASE_DATA_SOURCE_H_
+#define MEDIA_BASE_DATA_SOURCE_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class DataSourceHost {

[Ami GONE FROM CHROMIUM, 2011/12/15 18:39:08]

No MEDIA_EXPORT on this and the enum below?

[acolwell GONE FROM CHROMIUM, 2011/12/15 20:57:59]

Didn't appear to be needed for my shared build, but I'll add it to
DataSourceHost just in case.

PipelineStatus doesn't have a MEDIA_EXPORT so I think Preroll should be ok.

+ public:
+  // Set the total size of the media file.
+  virtual void SetTotalBytes(int64 total_bytes) = 0;
+
+  // Sets the total number of bytes that are buffered on the client and ready to
+  // be played.
+  virtual void SetBufferedBytes(int64 buffered_bytes) = 0;
+
+  // Sets the flag to indicate current network activity.
+  virtual void SetNetworkActivity(bool is_downloading_data) = 0;
+
+ protected:
+  virtual ~DataSourceHost() {}

[Ami GONE FROM CHROMIUM, 2011/12/15 18:39:08]

Comment about why?

[acolwell GONE FROM CHROMIUM, 2011/12/15 20:57:59]

I don't have a good reason why so I'm just going to make it 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 WebCore::MediaPlayer::Preload and
+// there will be assertions at compile time if they do not match.
+enum Preload {

[Ami GONE FROM CHROMIUM, 2011/12/15 18:39:08]

I wonder whether this wants to live inside DataSource.

[acolwell GONE FROM CHROMIUM, 2011/12/15 20:57:59]

Actually after further thought, I don't think DataSource is a good home for
this. DataSource only needs to know about it because of how FFmpegDemuxer
implemented the preload behaviors. To me the preload concept is really a demuxer
level or higher concept. For example ChunkDemuxer could implement it's preroll
behaviors but doesn't use DataSource.

Perhaps move this into it's own file? demuxer.h? pipeline.h?

[Ami GONE FROM CHROMIUM, 2011/12/15 22:39:18]

Either of the latter 2 would cause a circular dependency, so bad.
ISTM the _right_ solution here is to have different enums for different points
in the hierarchy, but I guess I don't care enough about it to force any change
here.

+  NONE,
+  METADATA,
+  AUTO,
+};
+
+class MEDIA_EXPORT DataSource : public base::RefCountedThreadSafe<DataSource> {
+ public:
+  typedef base::Callback<void(int64, int64)> StatusCallback;
+  typedef base::Callback<void(size_t)> ReadCallback;
+  static const size_t kReadError;
+
+  virtual void set_host(DataSourceHost* host);
+
+  // Reads |size| bytes from |position| into |data|. And when the read is done
+  // or failed, |read_callback| is called with the number of bytes read or
+  // kReadError in case of error.
+  // TODO(hclam): should change |size| to int! It makes the code so messy
+  // with size_t and int all over the place..
+  virtual void Read(int64 position, size_t size,
+                    uint8* data,
+                    const DataSource::ReadCallback& read_callback) = 0;
+
+  // Notifies the DataSource of a change in the current playback rate.
+  virtual void SetPlaybackRate(float playback_rate);
+
+  // Stops the DataSource. Once this is called all future Read() calls will
+  // return an error.
+  virtual void Stop(const base::Closure& callback) = 0;
+
+  // Returns true and the file size, false if the file size could not be
+  // retrieved.
+  virtual bool GetSize(int64* size_out) = 0;
+
+  // Returns true if we are performing streaming. In this case seeking is
+  // not possible.
+  virtual bool IsStreaming() = 0;
+
+  // Alert the DataSource that the video preload value has been changed.
+  virtual void SetPreload(Preload preload) = 0;
+
+  // Notify the DataSource of the bitrate of the media.
+  // Values of |bitrate| <= 0 are invalid and should be ignored.
+  virtual void SetBitrate(int bitrate) = 0;
+
+ protected:
+  friend class base::RefCountedThreadSafe<DataSource>;

[Ami GONE FROM CHROMIUM, 2011/12/15 18:39:08]

This is necessary?

[acolwell GONE FROM CHROMIUM, 2011/12/15 20:57:59]

Yes. This follows the pattern, in other parts of the media code, of only
allowing the scoped_refptr to delete the object. Added the comment indicating
this that I forgot to copy over.

+
+  DataSource();

[Ami GONE FROM CHROMIUM, 2011/12/15 18:39:08]

doco why these are protected?

(generally, "protected" without a comment explaining the expected contract with
subclassers is raises my suspicions).

[acolwell GONE FROM CHROMIUM, 2011/12/15 20:57:59]

Made this public since a DataSource can't be created on its own.

+  virtual ~DataSource();
+
+  DataSourceHost* host();
+
+ private:
+  DataSourceHost* host_;
+
+  DISALLOW_COPY_AND_ASSIGN(DataSource);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_DATA_SOURCE_H_