Add QuicFramer and friends.

net/quic/quic_data_writer.h

Index: net/quic/quic_data_writer.h
diff --git a/net/quic/quic_data_writer.h b/net/quic/quic_data_writer.h
new file mode 100644
index 0000000000000000000000000000000000000000..57ef79bf7db30a97320be8a6990201d461372dc5
--- /dev/null
+++ b/net/quic/quic_data_writer.h
@@ -0,0 +1,93 @@
+// 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 NET_QUIC_QUIC_DATA_WRITER_H_
+#define NET_QUIC_QUIC_DATA_WRITER_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "net/quic/quic_protocol.h"
+#include "net/quic/uint128.h"
+#include "base/string_piece.h"
+
+namespace net {
+
+// This class provides facilities for packing QUIC data.
+//
+// The QuicDataWriter supports appending primitive values (int, string, etc)
+// to a frame instance.  The QuicDataWriter grows its internal memory buffer
+// dynamically to hold the sequence of primitive values.   The internal memory
+// buffer is exposed as the "data" of the QuicDataWriter.
+class QuicDataWriter {
+ public:
+  ~QuicDataWriter();
+
+  explicit QuicDataWriter(size_t length);

[jar (doing other things), 2012/10/14 23:04:38]

nit: constructors then destructors.

[Ryan Hamilton, 2012/10/15 21:22:08]

Done.

+
+  // Returns the size of the QuicDataWriter's data.
+  size_t length() const { return length_; }
+
+  // Takes the buffer from the QuicDataWriter.
+  char* take() {
+    char* rv = buffer_;

[jar (doing other things), 2012/10/14 23:04:38]

nit: Usually we try not to put much code in the header files.  I think the goal
is to reduce compile times.

Is there a good reason for doing this here?  It looks like optimization... but
most of these would be handled by the compiler optimizations (I think).

[Ryan Hamilton, 2012/10/15 21:22:08]

This code mostly came from the SPDY equivalent and preserved the inlined
methods.  Added a TODO to move the code.

+    buffer_ = NULL;
+    capacity_ = 0;
+    length_ = 0;
+    return rv;
+  }
+
+  // Methods for adding to the payload.  These values are appended to the end
+  // of the QuicDataWriter payload. Note - binary integers are written in
+  // host byte order (little endian) not network byte order (big endian).
+  bool WriteUInt8(uint8 value) {
+    return WriteBytes(&value, sizeof(value));
+  }
+  bool WriteUInt16(uint16 value) {
+    return WriteBytes(&value, sizeof(value));
+  }
+  bool WriteUInt32(uint32 value) {
+    return WriteBytes(&value, sizeof(value));
+  }
+  bool WriteUInt48(uint64 value) {
+    uint32 hi = value >> 32;
+    uint32 lo = value & 0x00000000FFFFFFFF;
+    return WriteUInt32(lo) && WriteUInt16(hi);
+  }
+  bool WriteUInt64(uint64 value) {
+    return WriteBytes(&value, sizeof(value));
+  }
+  bool WriteUInt128(uint128 value) {
+    return WriteUInt64(value.lo) && WriteUInt64(value.hi);
+  }
+
+  bool AdvancePointer(uint32 len);
+
+  bool WriteBytes(const void* data, uint32 data_len);
+
+  static void WriteUint64ToBuffer(uint64 value, char* buffer);
+  static void WriteUint128ToBuffer(uint128 value, char* buffer);

[jar (doing other things), 2012/10/14 23:04:38]

This API is a bit scary (no way to check).  Is this used for writing back into
the quic_data_writer?... and if so... can we use a non-static method, and bounds
check the target?

[Ryan Hamilton, 2012/10/15 21:22:08]

I believe these methods are used for tweaking fields in already constructed
packets.  It's possible that with the recent change to get rid of
re-transmission that they will not be needed, but currently they are used. 
Happy to revisit once we nuke retransmission.

+
+  size_t capacity() const {
+    return capacity_;
+  }
+
+ protected:
+  const char* end_of_payload() const { return buffer_ + length_; }
+
+ private:
+  // Returns the location that the data should be written at, or NULL if there
+  // is not enough room. Call EndWrite with the returned offset and the given
+  // length to pad out for the next write.
+  char* BeginWrite(size_t length);
+
+  char* buffer_;
+  size_t capacity_;  // Allocation size of payload (or -1 if buffer is const).
+  size_t length_;    // current length of the buffer

[jar (doing other things), 2012/10/14 23:04:38]

nit: Capital and period.

[Ryan Hamilton, 2012/10/15 21:22:08]

Done.

+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_QUIC_DATA_WRITER_H_