net/spdy/hpack_entry.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_ENTRY_H_
   6 #define NET_SPDY_HPACK_ENTRY_H_
   7
   8 #include <cstddef>
   9 #include <deque>
  10 #include <string>
  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
  18 namespace net {
  19
  20 // All section references below are to
  21 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-05
  22 // .
  23
  24 // A structure for an entry in the header table (3.1.2) and the
  25 // reference set (3.1.3). This structure also keeps track of how many
  26 // times the entry has been 'touched', which is useful for both
  27 // encoding and decoding.
  28 class NET_EXPORT_PRIVATE HpackEntry {
  29  public:
  30   // The constant amount added to name().size() and value().size() to
  31   // get the size of an HpackEntry as defined in 3.3.1.
  32   static const uint32 kSizeOverhead;
  33
  34   // The constant returned by touch_count() if an entry hasn't been
  35   // touched (which is distinct from an entry having a touch count of
  36   // 0).
  37   //
  38   // TODO(akalin): The distinction between untouched and having a
  39   // touch count of 0 is confusing. Think of a better way to represent
  40   // this state.
  41   static const uint32 kUntouched;
  42
  43   // Creates an entry with empty name a value. Only defined so that
  44   // entries can be stored in STL containers.
  45   HpackEntry();
  46
  47   // Creates an entry with a copy is made of the given name and value.
  48   //
  49   // TODO(akalin): Add option to not make a copy (for static table
  50   // entries).
  51   HpackEntry(base::StringPiece name, base::StringPiece value);
  52
  53   // Copy constructor and assignment operator welcome.
  54
  55   // The name() and value() StringPieces have the same lifetime as
  56   // this entry.
  57
  58   base::StringPiece name() const { return base::StringPiece(name_); }
  59   base::StringPiece value() const { return base::StringPiece(value_); }
  60
  61   // Returns whether or not this entry is in the reference set.
  62   bool IsReferenced() const;
  63
  64   // Returns how many touches this entry has, or kUntouched if this
  65   // entry hasn't been touched at all. The meaning of the touch count
  66   // is defined by whatever is calling
  67   // AddTouchCount()/ClearTouchCount() (i.e., the encoder or decoder).
  68   uint32 TouchCount() const;
  69
  70   // Returns the size of an entry as defined in 3.3.1. The returned
  71   // value may not necessarily fit in 32 bits.
  72   size_t Size() const;
  73
  74   std::string GetDebugString() const;
  75
  76   // Returns whether this entry has the same name, value, referenced
  77   // state, and touch count as the given one.
  78   bool Equals(const HpackEntry& other) const;
  79
  80   void SetReferenced(bool referenced);
  81
  82   // Adds the given number of touches to this entry (see
  83   // TouchCount()). The total number of touches must not exceed 2^31 -
  84   // 2. It is guaranteed that this entry's touch count will not equal
  85   // kUntouched after this function is called (even if touch_count ==
  86   // 0).
  87   void AddTouches(uint32 additional_touch_count);
  88
  89   // Sets the touch count of this entry to kUntouched.
  90   void ClearTouches();
  91
  92  private:
  93   std::string name_;
  94   std::string value_;
  95
  96   // The high bit stores 'referenced' and the rest stores the touch
  97   // count.
  98   uint32 referenced_and_touch_count_;
  99 };
 100
 101 }  // namespace net
 102
 103 #endif  // NET_SPDY_HPACK_ENTRY_H_