Refactor FFmpegURLProtocol code from FFmpegDemuxer into BlockingUrlProtocol.

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/compiler_specific.h"

[DaleCurtis, 2012/11/13 03:42:28]

Needed?

[scherkus (not reviewing), 2012/11/13 18:19:13]

Done.

+#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 and use ConditionVariable+Lock as

[DaleCurtis, 2012/11/13 03:42:28]

WaitableEvent uses CV under the hood, so I think this TODO is redundant.

[scherkus (not reviewing), 2012/11/13 18:19:13]

WEs are implemented using OS primitives (e.g., HANDLE on windows) and CVs are
implemented using events when the OS does not provide a primitive (e.g., WinXP
implementation of a CV)

Anyway, I updated the TODO to describe the problem as opposed to a potential
solution

[DaleCurtis, 2012/11/13 21:44:07]

Whoops, I was looking at the internal posix SyncWaiter implementation. You're
correct.

+// opposed to a WaitableEvent.
+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 methods.
+  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_;
+
+  // 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_