Motown: New wrapper classes for ffmpeg format context and io context

services/media/framework_ffmpeg/av_io_context.h

+// Copyright 2016 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 SERVICES_MEDIA_FRAMEWORK_FFMPEG_AV_IO_CONTEXT_H_
+#define SERVICES_MEDIA_FRAMEWORK_FFMPEG_AV_IO_CONTEXT_H_
+
+#include "services/media/framework/parts/reader.h"
+extern "C" {
+#include "third_party/ffmpeg/libavformat/avio.h"
+}
+
+namespace mojo {
+namespace media {
+
+struct AVIOContextDeleter {
+  void operator()(AVIOContext* context) const;
+};
+
+using AvIoContextPtr = std::unique_ptr<AVIOContext, AVIOContextDeleter>;
+
+struct AvIoContext {
+  // Creates an ffmpeg avio_context for a given reader.
+  static AvIoContextPtr Create(std::shared_ptr<Reader> reader);
+
+  // Performs a read operation using the signature required for avio.
+  static int Read(void* opaque, uint8_t* buf, int buf_size);
+
+  // Performs a seek operation using the signature required for avio.
+  static int64_t Seek(void* opaque, int64_t offset, int whence);
+
+  ~AvIoContext();
+
+ private:
+  AvIoContext(std::shared_ptr<Reader> reader);
+
+  int Read(uint8_t* buffer, size_t bytes_to_read);
+
+  int64_t Seek(int64_t offset, int whence);
+
+  std::shared_ptr<Reader> reader_;
+  bool can_seek_;
+  int64_t size_;
+  int64_t position_ = 0;
+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif // SERVICES_MEDIA_FRAMEWORK_FFMPEG_AV_IO_CONTEXT_H_