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 <utility>
  11 #include <vector>
  12
  13 #include "base/basictypes.h"
  14 #include "base/macros.h"
  15 #include "base/strings/string_piece.h"
  16 #include "net/base/net_export.h"
  17 #include "net/spdy/hpack_header_table.h"
  18 #include "net/spdy/hpack_output_stream.h"
  19
  20 // An HpackEncoder encodes header sets as outlined in
  21 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08
  22
  23 namespace net {
  24
  25 class HpackHuffmanTable;
  26
  27 namespace test {
  28 class HpackEncoderPeer;
  29 }  // namespace test
  30
  31 class NET_EXPORT_PRIVATE HpackEncoder {
  32  public:
  33   friend class test::HpackEncoderPeer;
  34
  35   // |table| is an initialized HPACK Huffman table, having an
  36   // externally-managed lifetime which spans beyond HpackEncoder.
  37   explicit HpackEncoder(const HpackHuffmanTable& table);
  38   ~HpackEncoder();
  39
  40   // Encodes the given header set into the given string. Returns
  41   // whether or not the encoding was successful.
  42   bool EncodeHeaderSet(const std::map<std::string, std::string>& header_set,
  43                        std::string* output);
  44
  45   // Encodes the given header set into the given string. Only non-indexed
  46   // literal representations are emitted, bypassing the header table. Huffman
  47   // coding is also not used. Returns whether the encoding was successful.
  48   // TODO(jgraettinger): Enable Huffman coding once the table as stablized.
  49   bool EncodeHeaderSetWithoutCompression(
  50       const std::map<std::string, std::string>& header_set,
  51       std::string* output);
  52
  53   // Called upon a change to SETTINGS_HEADER_TABLE_SIZE. Specifically, this
  54   // is to be called after receiving (and sending an acknowledgement for) a
  55   // SETTINGS_HEADER_TABLE_SIZE update from the remote decoding endpoint.
  56   void ApplyHeaderTableSizeSetting(size_t size_setting) {
  57     header_table_.SetSettingsHeaderTableSize(size_setting);
  58   }
  59
  60   // Sets externally-owned storage for aggregating character counts of emitted
  61   // literal representations.
  62   void SetCharCountsStorage(std::vector<size_t>* char_counts,
  63                             size_t* total_char_counts);
  64
  65  private:
  66   typedef std::pair<base::StringPiece, base::StringPiece> Representation;
  67   typedef std::vector<Representation> Representations;
  68
  69   // Emits a static/dynamic indexed representation (Section 7.1).
  70   void EmitIndex(const HpackEntry* entry);
  71
  72   // Emits a literal representation (Section 7.2).
  73   void EmitIndexedLiteral(const Representation& representation);
  74   void EmitNonIndexedLiteral(const Representation& representation);
  75   void EmitLiteral(const Representation& representation);
  76
  77   // Emits a Huffman or identity string (whichever is smaller).
  78   void EmitString(base::StringPiece str);
  79
  80   void UpdateCharacterCounts(base::StringPiece str);
  81
  82   // Crumbles a cookie header into sorted, de-duplicated crumbs.
  83   static void CookieToCrumbs(const Representation& cookie,
  84                              Representations* crumbs_out);
  85
  86   // Crumbles other header field values at \0 delimiters.
  87   static void DecomposeRepresentation(const Representation& header_field,
  88                                       Representations* out);
  89
  90   HpackHeaderTable header_table_;
  91   HpackOutputStream output_stream_;
  92
  93   bool allow_huffman_compression_;
  94   const HpackHuffmanTable& huffman_table_;
  95
  96   // Externally-owned, nullable storage for character counts of literals.
  97   std::vector<size_t>* char_counts_;
  98   size_t* total_char_counts_;
  99
 100   DISALLOW_COPY_AND_ASSIGN(HpackEncoder);
 101 };
 102
 103 }  // namespace net
 104
 105 #endif  // NET_SPDY_HPACK_ENCODER_H_