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-06
  22
  23 // A structure for an entry in the header table (3.1.2) and the
  24 // reference set (3.1.3). This structure also keeps track of how many
  25 // times the entry has been 'touched', which is useful for both
  26 // encoding and decoding.
  27 class NET_EXPORT_PRIVATE HpackEntry {
  28  public:
  29   // The constant amount added to name().size() and value().size() to
  30   // get the size of an HpackEntry as defined in 3.3.1.
  31   static const uint32 kSizeOverhead;
  32
  33   // The constant returned by touch_count() if an entry hasn't been
  34   // touched (which is distinct from an entry having a touch count of
  35   // 0).
  36   //
  37   // TODO(akalin): The distinction between untouched and having a
  38   // touch count of 0 is confusing. Think of a better way to represent
  39   // this state.
  40   static const uint32 kUntouched;
  41
  42   // Creates an entry with empty name a value. Only defined so that
  43   // entries can be stored in STL containers.
  44   HpackEntry();
  45
  46   // Creates an entry with a copy is made of the given name and value.
  47   //
  48   // TODO(akalin): Add option to not make a copy (for static table
  49   // entries).
  50   HpackEntry(base::StringPiece name, base::StringPiece value);
  51
  52   // Copy constructor and assignment operator welcome.
  53
  54   // The name() and value() StringPieces have the same lifetime as
  55   // this entry.
  56
  57   base::StringPiece name() const { return base::StringPiece(name_); }
  58   base::StringPiece value() const { return base::StringPiece(value_); }
  59
  60   // Returns whether or not this entry is in the reference set.
  61   bool IsReferenced() const;
  62
  63   // Returns how many touches this entry has, or kUntouched if this
  64   // entry hasn't been touched at all. The meaning of the touch count
  65   // is defined by whatever is calling
  66   // AddTouchCount()/ClearTouchCount() (i.e., the encoder or decoder).
  67   uint32 TouchCount() const;
  68
  69   // Returns the size of an entry as defined in 3.3.1. The returned
  70   // value may not necessarily fit in 32 bits.
  71   size_t Size() const;
  72
  73   std::string GetDebugString() const;
  74
  75   // Returns whether this entry has the same name, value, referenced
  76   // state, and touch count as the given one.
  77   bool Equals(const HpackEntry& other) const;
  78
  79   void SetReferenced(bool referenced);
  80
  81   // Adds the given number of touches to this entry (see
  82   // TouchCount()). The total number of touches must not exceed 2^31 -
  83   // 2. It is guaranteed that this entry's touch count will not equal
  84   // kUntouched after this function is called (even if touch_count ==
  85   // 0).
  86   void AddTouches(uint32 additional_touch_count);
  87
  88   // Sets the touch count of this entry to kUntouched.
  89   void ClearTouches();
  90
  91  private:
  92   std::string name_;
  93   std::string value_;
  94
  95   // The high bit stores 'referenced' and the rest stores the touch
  96   // count.
  97   uint32 referenced_and_touch_count_;
  98 };
  99
 100 }  // namespace net
 101
 102 #endif  // NET_SPDY_HPACK_ENTRY_H_