net/spdy/hpack_constants.h


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// Copyright 2014 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_HPACK_CONSTANTS_H_
#define NET_SPDY_HPACK_CONSTANTS_H_

#include <vector>

#include "base/basictypes.h"
#include "net/base/net_export.h"

// All section references below are to
// http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-06

namespace net {

// An HpackPrefix signifies |bits| stored in the top |bit_size| bits
// of an octet.
struct HpackPrefix {
  uint8 bits;
  size_t bit_size;
};

// Represents a symbol and its Huffman code (stored in most-significant bits).
struct HpackHuffmanSymbol {
  uint32 code;
  uint8 length;
  uint16 id;
};

// The marker for a string literal that is stored unmodified (i.e.,
// without Huffman encoding) (from 4.1.2).
const HpackPrefix kStringLiteralIdentityEncoded = { 0x0, 1 };

// The marker for a string literal that is stored with Huffman
// encoding (from 4.1.2).
const HpackPrefix kStringLiteralHuffmanEncoded = { 0x1, 1 };

// The opcode for an indexed header field (from 4.2).
const HpackPrefix kIndexedOpcode = { 0x1, 1 };

// The opcode for a literal header field without indexing (from
// 4.3.1).
const HpackPrefix kLiteralNoIndexOpcode = { 0x01, 2 };

// The opcode for a literal header field with incremental indexing
// (from 4.3.2).
const HpackPrefix kLiteralIncrementalIndexOpcode = { 0x00, 2 };

// Returns symbol code table from "Appendix C. Huffman Codes".
NET_EXPORT_PRIVATE std::vector<HpackHuffmanSymbol> HpackHuffmanCode();

}  // namespace net

#endif  // NET_SPDY_HPACK_CONSTANTS_H_