Use separate WaitableEvents in BlockingUrlProtocol for signalling abort versus read complete.

media/filters/blocking_url_protocol.h

 // Copyright (c) 2012 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_FILTERS_BLOCKING_URL_PROTOCOL_H_
 #define MEDIA_FILTERS_BLOCKING_URL_PROTOCOL_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/synchronization/waitable_event.h"
 #include "media/filters/ffmpeg_glue.h"
 
 namespace media {
 
 class DataSource;
 
 // An implementation of FFmpegURLProtocol that blocks until the underlying
 // asynchronous DataSource::Read() operation completes.
-//
-// TODO(scherkus): Should be more thread-safe as |last_read_bytes_| is updated
-// from multiple threads without any protection.
 class MEDIA_EXPORT BlockingUrlProtocol : public FFmpegURLProtocol {
  public:
   // Implements FFmpegURLProtocol using the given |data_source|. |error_cb| is
   // fired any time DataSource::Read() returns an error.
   //
   // TODO(scherkus): After all blocking operations are isolated on a separate
   // thread we should be able to eliminate |error_cb|.
   BlockingUrlProtocol(const scoped_refptr<DataSource>& data_source,
                       const base::Closure& error_cb);
   virtual ~BlockingUrlProtocol();
 
   // Aborts any pending reads by returning a read error. After this method
   // returns all subsequent calls to Read() will immediately fail.
-  //
-  // TODO(scherkus): Currently this will cause |error_cb| to fire. Fix.
   void Abort();
 
   // FFmpegURLProtocol implementation.
   virtual int Read(int size, uint8* data) OVERRIDE;
   virtual bool GetPosition(int64* position_out) OVERRIDE;
   virtual bool SetPosition(int64 position) OVERRIDE;
   virtual bool GetSize(int64* size_out) OVERRIDE;
   virtual bool IsStreaming() OVERRIDE;
 
  private:
   // Sets |last_read_bytes_| and signals the blocked thread that the read
   // has completed.
   void SignalReadCompleted(int size);
 
   scoped_refptr<DataSource> data_source_;
   base::Closure error_cb_;
 
-  // Used to convert an asynchronous DataSource::Read() into a blocking
-  // FFmpegUrlProtocol::Read().
-  base::WaitableEvent read_event_;
-
-  // Read errors and aborts are unrecoverable. Any subsequent reads will
-  // immediately fail when this is set to true.
-  bool read_has_failed_;
+  // Used to unblock the thread during shutdown and when reads complete.
+  base::WaitableEvent aborted_;
+  base::WaitableEvent read_complete_;
 
   // Cached number of bytes last read from the data source.
   int last_read_bytes_;
 
   // Cached position within the data source.
   int64 read_position_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BlockingUrlProtocol);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_BLOCKING_URL_PROTOCOL_H_