net/spdy/hpack_constants.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_SPDY_HPACK_CONSTANTS_H_
   6 #define NET_SPDY_HPACK_CONSTANTS_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "net/base/net_export.h"
  12
  13 // All section references below are to
  14 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08
  15
  16 namespace net {
  17
  18 // An HpackPrefix signifies |bits| stored in the top |bit_size| bits
  19 // of an octet.
  20 struct HpackPrefix {
  21   uint8 bits;
  22   size_t bit_size;
  23 };
  24
  25 // Represents a symbol and its Huffman code (stored in most-significant bits).
  26 struct HpackHuffmanSymbol {
  27   uint32 code;
  28   uint8 length;
  29   uint16 id;
  30 };
  31
  32 // An entry in the static table. Must be a POD in order to avoid static
  33 // initializers, i.e. no user-defined constructors or destructors.
  34 struct HpackStaticEntry {
  35   const char* const name;
  36   const size_t name_len;
  37   const char* const value;
  38   const size_t value_len;
  39 };
  40
  41 class HpackHuffmanTable;
  42 class HpackStaticTable;
  43
  44 const uint32 kDefaultHeaderTableSizeSetting = 4096;
  45
  46 // Largest string literal an HpackDecoder/HpackEncoder will attempt to process
  47 // before returning an error.
  48 const uint32 kDefaultMaxStringLiteralSize = 16 * 1024;
  49
  50 // Maximum amount of encoded header buffer HpackDecoder will retain before
  51 // returning an error.
  52 // TODO(jgraettinger): Remove with SpdyHeadersHandlerInterface switch.
  53 const uint32 kMaxDecodeBufferSize = 32 * 1024;
  54
  55 // 6.2: Flag for a string literal that is stored unmodified (i.e.,
  56 // without Huffman encoding).
  57 const HpackPrefix kStringLiteralIdentityEncoded = { 0x0, 1 };
  58
  59 // 6.2: Flag for a Huffman-coded string literal.
  60 const HpackPrefix kStringLiteralHuffmanEncoded = { 0x1, 1 };
  61
  62 // 7.1: Opcode for an indexed header field.
  63 const HpackPrefix kIndexedOpcode = { 0x1, 1 };
  64
  65 // 7.2.1: Opcode for a literal header field with incremental indexing.
  66 const HpackPrefix kLiteralIncrementalIndexOpcode = { 0x1, 2 };
  67
  68 // 7.2.2: Opcode for a literal header field without indexing.
  69 const HpackPrefix kLiteralNoIndexOpcode = { 0x0, 4 };
  70
  71 // 7.2.3: Opcode for a literal header field which is never indexed.
  72 const HpackPrefix kLiteralNeverIndexOpcode = { 0x1, 4 };
  73
  74 // 7.3: Opcode for maximum header table size update. Begins a varint-encoded
  75 // table size with a 5-bit prefix.
  76 const HpackPrefix kHeaderTableSizeUpdateOpcode = { 0x1, 3 };
  77
  78 // Returns symbol code table from "Appendix C. Huffman Code".
  79 NET_EXPORT_PRIVATE std::vector<HpackHuffmanSymbol> HpackHuffmanCode();
  80
  81 // Returns static table from "Appendix B. Static Table Definition".
  82 NET_EXPORT_PRIVATE std::vector<HpackStaticEntry> HpackStaticTableVector();
  83
  84 // Returns a HpackHuffmanTable instance initialized with |kHpackHuffmanCode|.
  85 // The instance is read-only, has static lifetime, and is safe to share amoung
  86 // threads. This function is thread-safe.
  87 NET_EXPORT_PRIVATE const HpackHuffmanTable& ObtainHpackHuffmanTable();
  88
  89 // Returns a HpackStaticTable instance initialized with |kHpackStaticTable|.
  90 // The instance is read-only, has static lifetime, and is safe to share amoung
  91 // threads. This function is thread-safe.
  92 NET_EXPORT_PRIVATE const HpackStaticTable& ObtainHpackStaticTable();
  93
  94 // Pseudo-headers start with a colon.  (HTTP2 8.1.2.1., HPACK 3.1.)
  95 const char kPseudoHeaderPrefix = ':';
  96
  97 }  // namespace net
  98
  99 #endif  // NET_SPDY_HPACK_CONSTANTS_H_