[ON HOLD] Implement pull-based design for content decoding

net/filter/block_buffer.h

+// Copyright 2015 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 NET_FILTER_BLOCK_BUFFER_H
+#define NET_FILTER_BLOCK_BUFFER_H
+
+#include "base/memory/scoped_ptr.h"
+#include "net/base/io_buffer.h"
+
+namespace net {
+
+// A refillable input buffer, wrapping an IOBuffer.
+// The |WasRefilled| and |WasDrained| methods are responsible for maintaining
+// this class's state machine. A client class should call |WasDrained| when
+// bytes are drained from the buffer, and |WasRefilled| when new bytes are
+// placed in the underlying IOBuffer. Note that it is an error to drain more
+// bytes than are available in the BlockBuffer or to refill the BlockBuffer when
+// its previous block is not completely drained.
+class BlockBuffer {
+ public:
+  BlockBuffer();
+  ~BlockBuffer();
+
+  bool HasMoreBytes() const;
+  void WasRefilled(size_t filled_bytes);
+  void WasDrained(size_t drained_bytes);
+
+  size_t size() const;
+  char* bytes() const { return bytes_; }
+  size_t bytes_left() const { return bytes_left_; }
+  IOBuffer* buffer() { return buffer_.get(); }
+
+ private:
+  scoped_refptr<IOBuffer> buffer_;
+  char* bytes_;
+  size_t bytes_left_;
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_BLOCK_BUFFER_H