media/filters/blocking_url_protocol.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_FILTERS_BLOCKING_URL_PROTOCOL_H_
   6 #define MEDIA_FILTERS_BLOCKING_URL_PROTOCOL_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/callback.h"
  10 #include "base/synchronization/waitable_event.h"
  11 #include "media/filters/ffmpeg_glue.h"
  12
  13 namespace media {
  14
  15 class DataSource;
  16
  17 // An implementation of FFmpegURLProtocol that blocks until the underlying
  18 // asynchronous DataSource::Read() operation completes.
  19 class MEDIA_EXPORT BlockingUrlProtocol : public FFmpegURLProtocol {
  20  public:
  21   // Implements FFmpegURLProtocol using the given |data_source|. |error_cb| is
  22   // fired any time DataSource::Read() returns an error.
  23   //
  24   // TODO(scherkus): After all blocking operations are isolated on a separate
  25   // thread we should be able to eliminate |error_cb|.
  26   BlockingUrlProtocol(DataSource* data_source, const base::Closure& error_cb);
  27   virtual ~BlockingUrlProtocol();
  28
  29   // Aborts any pending reads by returning a read error. After this method
  30   // returns all subsequent calls to Read() will immediately fail.
  31   void Abort();
  32
  33   // FFmpegURLProtocol implementation.
  34   virtual int Read(int size, uint8* data) OVERRIDE;
  35   virtual bool GetPosition(int64* position_out) OVERRIDE;
  36   virtual bool SetPosition(int64 position) OVERRIDE;
  37   virtual bool GetSize(int64* size_out) OVERRIDE;
  38   virtual bool IsStreaming() OVERRIDE;
  39
  40  private:
  41   // Sets |last_read_bytes_| and signals the blocked thread that the read
  42   // has completed.
  43   void SignalReadCompleted(int size);
  44
  45   DataSource* data_source_;
  46   base::Closure error_cb_;
  47
  48   // Used to unblock the thread during shutdown and when reads complete.
  49   base::WaitableEvent aborted_;
  50   base::WaitableEvent read_complete_;
  51
  52   // Cached number of bytes last read from the data source.
  53   int last_read_bytes_;
  54
  55   // Cached position within the data source.
  56   int64 read_position_;
  57
  58   DISALLOW_IMPLICIT_CONSTRUCTORS(BlockingUrlProtocol);
  59 };
  60
  61 }  // namespace media
  62
  63 #endif  // MEDIA_FILTERS_BLOCKING_URL_PROTOCOL_H_