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 <set>
  10 #include <string>
  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
  17 // All section references below are to
  18 // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-06
  19
  20 namespace net {
  21
  22 // A structure for an entry in the header table (3.1.2) and the
  23 // reference set (3.1.3).
  24 class NET_EXPORT_PRIVATE HpackEntry {
  25  public:
  26   // The constant amount added to name().size() and value().size() to
  27   // get the size of an HpackEntry as defined in 3.3.1.
  28   static const size_t kSizeOverhead;
  29
  30   // Implements a total ordering of HpackEntry on name(), value(), then Index()
  31   // ascending. Note that Index() may change over the lifetime of an HpackEntry,
  32   // but the relative Index() order of two entries will not. This comparator is
  33   // composed with the 'lookup' HpackEntry constructor to allow for efficient
  34   // lower-bounding of matching entries.
  35   struct NET_EXPORT_PRIVATE Comparator {
  36     bool operator() (const HpackEntry* lhs, const HpackEntry* rhs) const;
  37   };
  38   typedef std::set<HpackEntry*, Comparator> OrderedSet;
  39
  40   // Creates an entry. Preconditions:
  41   // - |is_static| captures whether this entry is a member of the static
  42   //   or dynamic header table.
  43   // - |insertion_index| is this entry's index in the total set of entries ever
  44   //   inserted into the header table (including static entries).
  45   // - |total_table_insertions_or_current_size| references an externally-
  46   //   updated count of either the total number of header insertions (if
  47   //   !|is_static|), or the current size of the header table (if |is_static|).
  48   //
  49   // The combination of |is_static|, |insertion_index|, and
  50   // |total_table_insertions_or_current_size| allows an HpackEntry to determine
  51   // its current table index in O(1) time.
  52   HpackEntry(base::StringPiece name,
  53              base::StringPiece value,
  54              bool is_static,
  55              size_t insertion_index,
  56              const size_t* total_table_insertions_or_current_size);
  57
  58   // Create a 'lookup' entry (only) suitable for querying a HpackEntrySet. The
  59   // instance Index() always returns 0, and will lower-bound all entries
  60   // matching |name| & |value| in an OrderedSet.
  61   HpackEntry(base::StringPiece name, base::StringPiece value);
  62
  63   // Creates an entry with empty name a value. Only defined so that
  64   // entries can be stored in STL containers.
  65   HpackEntry();
  66
  67   ~HpackEntry();
  68
  69   const std::string& name() const { return name_; }
  70   const std::string& value() const { return value_; }
  71
  72   // Returns whether this entry is a member of the static (as opposed to
  73   // dynamic) table.
  74   bool IsStatic() const { return is_static_; }
  75
  76   // Returns and sets the state of the entry, or zero if never set.
  77   // The semantics of |state| are specific to the encoder or decoder.
  78   uint8 state() const { return state_; }
  79   void set_state(uint8 state) { state_ = state; }
  80
  81   // Returns the entry's current index in the header table.
  82   size_t Index() const;
  83
  84   // Returns the size of an entry as defined in 3.3.1.
  85   static size_t Size(base::StringPiece name, base::StringPiece value);
  86   size_t Size() const;
  87
  88   std::string GetDebugString() const;
  89
  90  private:
  91   // TODO(jgraettinger): Reduce copies, possibly via SpdyPinnableBufferPiece.
  92   std::string name_;
  93   std::string value_;
  94
  95   bool is_static_;
  96   uint8 state_;
  97
  98   // The entry's index in the total set of entries ever inserted into the header
  99   // table.
 100   size_t insertion_index_;
 101
 102   // If |is_static_|, references the current size of the headers table.
 103   // Else, references the total number of header insertions which have occurred.
 104   const size_t* total_insertions_or_size_;
 105 };
 106
 107 }  // namespace net
 108
 109 #endif  // NET_SPDY_HPACK_ENTRY_H_