net/spdy/hpack_encoder.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_ENCODER_H_
   6 #define NET_SPDY_HPACK_ENCODER_H_
   7
   8 #include <map>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/basictypes.h"
  13 #include "base/macros.h"
  14 #include "base/strings/string_piece.h"
  15 #include "net/base/net_export.h"
  16 #include "net/spdy/hpack_header_table.h"
  17 #include "net/spdy/hpack_output_stream.h"
  18
  19 // An HpackEncoder encodes header sets as outlined in
  20 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08
  21
  22 namespace net {
  23
  24 class HpackHuffmanTable;
  25
  26 namespace test {
  27 class HpackEncoderPeer;
  28 }  // namespace test
  29
  30 class NET_EXPORT_PRIVATE HpackEncoder {
  31  public:
  32   friend class test::HpackEncoderPeer;
  33
  34   // |table| is an initialized HPACK Huffman table, having an
  35   // externally-managed lifetime which spans beyond HpackEncoder.
  36   explicit HpackEncoder(const HpackHuffmanTable& table);
  37   ~HpackEncoder();
  38
  39   // Encodes the given header set into the given string. Returns
  40   // whether or not the encoding was successful.
  41   bool EncodeHeaderSet(const std::map<std::string, std::string>& header_set,
  42                        std::string* output);
  43
  44   // Encodes the given header set into the given string. Only non-indexed
  45   // literal representations are emitted, bypassing the header table. Huffman
  46   // coding is also not used. Returns whether the encoding was successful.
  47   // TODO(jgraettinger): Enable Huffman coding once the table as stablized.
  48   bool EncodeHeaderSetWithoutCompression(
  49       const std::map<std::string, std::string>& header_set,
  50       std::string* output);
  51
  52   // Called upon a change to SETTINGS_HEADER_TABLE_SIZE. Specifically, this
  53   // is to be called after receiving (and sending an acknowledgement for) a
  54   // SETTINGS_HEADER_TABLE_SIZE update from the remote decoding endpoint.
  55   void ApplyHeaderTableSizeSetting(size_t size_setting) {
  56     header_table_.SetSettingsHeaderTableSize(size_setting);
  57   }
  58
  59   // Sets externally-owned storage for aggregating character counts of emitted
  60   // literal representations.
  61   void SetCharCountsStorage(std::vector<size_t>* char_counts,
  62                             size_t* total_char_counts);
  63
  64  private:
  65   typedef std::pair<base::StringPiece, base::StringPiece> Representation;
  66   typedef std::vector<Representation> Representations;
  67
  68   // Emits a static/dynamic indexed representation (Section 7.1).
  69   void EmitIndex(HpackEntry* entry);
  70
  71   // Emits a literal representation (Section 7.2).
  72   void EmitIndexedLiteral(const Representation& representation);
  73   void EmitNonIndexedLiteral(const Representation& representation);
  74   void EmitLiteral(const Representation& representation);
  75
  76   // Emits a Huffman or identity string (whichever is smaller).
  77   void EmitString(base::StringPiece str);
  78
  79   void UpdateCharacterCounts(base::StringPiece str);
  80
  81   // Crumbles a cookie header into sorted, de-duplicated crumbs.
  82   static void CookieToCrumbs(const Representation& cookie,
  83                              Representations* crumbs_out);
  84
  85   HpackHeaderTable header_table_;
  86   HpackOutputStream output_stream_;
  87
  88   bool allow_huffman_compression_;
  89   const HpackHuffmanTable& huffman_table_;
  90
  91   // Externally-owned, nullable storage for character counts of literals.
  92   std::vector<size_t>* char_counts_;
  93   size_t* total_char_counts_;
  94
  95   DISALLOW_COPY_AND_ASSIGN(HpackEncoder);
  96 };
  97
  98 }  // namespace net
  99
 100 #endif  // NET_SPDY_HPACK_ENCODER_H_