Media Galleries API Metadata: SafeMediaMetadataParser and IPCTunnelDataReader.

chrome/utility/media_galleries/media_metadata_parser.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 CHROME_UTILITY_MEDIA_GALLERIES_MEDIA_METADATA_PARSER_H_
 #define CHROME_UTILITY_MEDIA_GALLERIES_MEDIA_METADATA_PARSER_H_
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/common/extensions/api/media_galleries.h"
 
+namespace media {
+class DataSource;
+}
+
 namespace metadata {
 
-// This interface provides bytes needed by MediaMetadataParser.
-class DataReader {
- public:
-  typedef base::Callback<void(const std::string& bytes)> ReadBytesCallback;
-
-  virtual ~DataReader() {}
-
-  // Called on the utility thread.
-  virtual void ReadBytes(int64 offset, int64 length,
-                         const ReadBytesCallback& callback) = 0;
-};
-
 // This class takes a MIME type and data source and parses its metadata. It
 // handles audio, video, and images. It delegates its operations to FFMPEG,
 // libexif, etc. This class lives and operates on the utility thread of the
 // utility process, as we wish to sandbox potentially dangerous operations
 // on user-provided data.
 class MediaMetadataParser {
  public:
   typedef extensions::api::media_galleries::MediaMetadata MediaMetadata;
   typedef base::Callback<void(scoped_ptr<MediaMetadata>)> MetadataCallback;
 
-  // Takes ownership of |reader|. The MIME type is always sniffed in the browser
-  // process, as it's faster (and safe enough) to sniff it there. When the user
-  // wants more metadata than just the MIME type, this class provides it.
-  MediaMetadataParser(DataReader* reader, const std::string& mime_type);
+  // Does not take ownership of |source|. The MIME type is sniffed in the

[vandebo (ex-Chrome), 2014/01/07 18:34:59]

You should say more explicitly that the caller is responsible for ensuring that
source outlives MediaMetadataParser

[tommycli, 2014/01/07 20:23:31]

Done.

+  // browser process, as it's faster (and safe enough). When the user wants

[vandebo (ex-Chrome), 2014/01/07 18:34:59]

I think you can omit the stuff about mime type - this API doesn't care about
how/why it is parsed by the user of the API.

[tommycli, 2014/01/07 20:23:31]

Done.

+  // more metadata than just the MIME type, this class provides it.
+  MediaMetadataParser(media::DataSource* source, const std::string& mime_type);
 
   ~MediaMetadataParser();
 
   // |callback| is called on same message loop.
   void Start(const MetadataCallback& callback);
 
  private:
-  scoped_ptr<DataReader> reader_;
+  media::DataSource* source_;
 
   MetadataCallback callback_;
 
   scoped_ptr<MediaMetadata> metadata_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaMetadataParser);
 };
 
 }  // namespace metadata
 
 #endif  // CHROME_UTILITY_MEDIA_GALLERIES_MEDIA_METADATA_PARSER_H_