[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.

[Randy Smith (Not in Mondays), 2016/03/09 23:03:56]

suggestion: Put these last two requirements in terms of the methods on the
class?  I think that means "Note that it is an error to drain more bytes than
are available in the BlockBuffer (i.e. calling WasDrained() with |filled_bytes >
bytes_left()|) or to refill the BlockBuffer when its previous block is not
completely drained (|hasMoreBytes()| is true).

[xunjieli, 2016/04/20 19:16:09]

Done.

+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(); }

[Randy Smith (Not in Mondays), 2016/03/09 23:03:55]

I think it's important to document the distinction between bytes() and buffer().
 I presume that bytes() points to the next byte that may be read/drained from
the buffer, and buffer() to the full buffer (that will be written into on
filling)?

[xunjieli, 2016/04/20 19:16:08]

Done.

+
+ private:
+  scoped_refptr<IOBuffer> buffer_;
+  char* bytes_;
+  size_t bytes_left_;
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_BLOCK_BUFFER_H