[SPDY] Replace SpdyIOBuffer with new SpdyBuffer class

net/spdy/spdy_buffer.h

+// Copyright (c) 2013 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_SPDY_SPDY_BUFFER_H_
+#define NET_SPDY_SPDY_BUFFER_H_
+
+#include <cstddef>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+class IOBuffer;
+class SpdyFrame;
+
+// SpdyBuffer is a class to hold data read from or to be written to a
+// SPDY connection. It is similar to a DrainableIOBuffer.

[Ryan Hamilton, 2013/04/16 18:44:25]

nit: Can you add a comment which explains why it is different (and why it is not
an IOBuffer subclass)?

[akalin, 2013/04/16 23:01:46]

Done.

+class NET_EXPORT_PRIVATE SpdyBuffer {
+ public:
+  // Construct with the data in the given frame. Assumes that data is
+  // owned by |frame| or outlives it.
+  explicit SpdyBuffer(scoped_ptr<SpdyFrame> frame);
+
+  // Construct with a copy of the given raw data. |data| must be
+  // non-NULL and |size| must be non-zero.
+  SpdyBuffer(const char* data, size_t size);
+
+  ~SpdyBuffer();
+
+  // Returns the remaining (unconsumed) data.
+  const char* GetRemainingData() const;
+
+  // Returns the number of remaining (unconsumed) bytes.
+  size_t GetRemainingSize() const;
+
+  // Consume the given number of bytes, which must be positive but not
+  // greater than GetRemainingSize().
+  //
+  // TODO(akalin): Add a way to get called back when Consume() is

[Ryan Hamilton, 2013/04/16 18:44:25]

Who should be called back when Consume is called?  The session, I guess?

[akalin, 2013/04/16 23:01:46]

The session and the stream. CL coming!

+  // called.
+  void Consume(size_t consume_size);
+
+  // Returns an IOBuffer pointing to the data starting at
+  // GetRemainingData(). Use with care; the returned IOBuffer must not
+  // be used past the lifetime of this object, and it is not updated
+  // when Consume() is called.
+  IOBuffer* GetIOBufferForRemainingData();

[Ryan Hamilton, 2013/04/16 18:44:25]

Interesting.  IOBuffers are refcounted, right?  It seems dangerous to stick a
refcounted buffer on top of a non-refcounted buffer.

[akalin, 2013/04/16 23:01:46]

It is, but it's unavoidable. :/ It's only used in one place; the call to
socket->Write() in SpdySession. We keep around the buffer (in
in_flight_write_buffer_) until OnWriteComplete is called, so I think it's safe
enough to assume that the socket doesn't hold onto the IOBuffer past that.

[Ryan Hamilton, 2013/04/16 23:34:11]

Sounds good.  Can you add a comment in SpdySession where
GetIOBufferForRemainingData is called that make it clear how long the buffer
needs to live?

+
+ private:
+  const scoped_ptr<SpdyFrame> frame_;
+  size_t offset_;
+
+  DISALLOW_COPY_AND_ASSIGN(SpdyBuffer);
+};
+
+}  // namespace net
+
+#endif  // NET_SPDY_SPDY_BUFFER_H_