libstdc++-v3/include/bits/functional_hash.h

   1 // functional_hash.h header -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file bits/functional_hash.h
  26  *  This is an internal header file, included by other library headers.
  27  *  Do not attempt to use it directly. @headername{functional}
  28  */
  29
  30 #ifndef _FUNCTIONAL_HASH_H
  31 #define _FUNCTIONAL_HASH_H 1
  32
  33 #pragma GCC system_header
  34
  35 #include <bits/c++config.h>
  36
  37 namespace std
  38 {
  39   /** @defgroup hashes Hashes
  40    *  @ingroup functors
  41    *
  42    *   Hashing functors taking a variable type and returning a @c std::size_t.
  43    *
  44    *  @{
  45    */
  46
  47   template<typename _Result, typename _Arg>
  48     struct __hash_base
  49     {
  50       typedef _Result     result_type;
  51       typedef _Arg      argument_type;
  52     };
  53
  54   /// Primary class template hash.
  55   template<typename _Tp>
  56     struct hash : public __hash_base<size_t, _Tp>
  57     {
  58       size_t
  59       operator()(_Tp __val) const;
  60     };
  61
  62   /// Partial specializations for pointer types.
  63   template<typename _Tp>
  64     struct hash<_Tp*> : public __hash_base<size_t, _Tp*>
  65     {
  66       size_t
  67       operator()(_Tp* __p) const
  68       { return reinterpret_cast<size_t>(__p); }
  69     };
  70
  71   // Explicit specializations for integer types.
  72 #define _Cxx_hashtable_define_trivial_hash(_Tp)         \
  73   template<>                                            \
  74     inline size_t                                       \
  75     hash<_Tp>::operator()(_Tp __val) const              \
  76     { return static_cast<size_t>(__val); }
  77
  78   /// Explicit specialization for bool.
  79   _Cxx_hashtable_define_trivial_hash(bool);
  80
  81   /// Explicit specialization for char.
  82   _Cxx_hashtable_define_trivial_hash(char);
  83
  84   /// Explicit specialization for signed char.
  85   _Cxx_hashtable_define_trivial_hash(signed char);
  86
  87   /// Explicit specialization for unsigned char.
  88   _Cxx_hashtable_define_trivial_hash(unsigned char);
  89
  90   /// Explicit specialization for wchar_t.
  91   _Cxx_hashtable_define_trivial_hash(wchar_t);
  92
  93   /// Explicit specialization for char16_t.
  94   _Cxx_hashtable_define_trivial_hash(char16_t);
  95
  96   /// Explicit specialization for char32_t.
  97   _Cxx_hashtable_define_trivial_hash(char32_t);
  98
  99   /// Explicit specialization for short.
 100   _Cxx_hashtable_define_trivial_hash(short);
 101
 102   /// Explicit specialization for int.
 103   _Cxx_hashtable_define_trivial_hash(int);
 104
 105   /// Explicit specialization for long.
 106   _Cxx_hashtable_define_trivial_hash(long);
 107
 108   /// Explicit specialization for long long.
 109   _Cxx_hashtable_define_trivial_hash(long long);
 110
 111   /// Explicit specialization for unsigned short.
 112   _Cxx_hashtable_define_trivial_hash(unsigned short);
 113
 114   /// Explicit specialization for unsigned int.
 115   _Cxx_hashtable_define_trivial_hash(unsigned int);
 116
 117   /// Explicit specialization for unsigned long.
 118   _Cxx_hashtable_define_trivial_hash(unsigned long);
 119
 120   /// Explicit specialization for unsigned long long.
 121   _Cxx_hashtable_define_trivial_hash(unsigned long long);
 122
 123 #undef _Cxx_hashtable_define_trivial_hash
 124
 125   // Hash function implementation for the nontrivial specialization.
 126   // All of them are based on a primitive that hashes a pointer to
 127   // a byte array. The actual hash algorithm is not guaranteed to
 128   // stay the same from release to release -- it may be updated or
 129   // tuned to improve hash quality or speed.
 130   size_t
 131   _Hash_bytes(const void* __ptr, size_t __len, size_t __seed);
 132
 133   // A similar hash primitive, using the FNV hash algorithm. This
 134   // algorithm is guaranteed to stay the same from release to release.
 135   // (although it might not produce the same values on different machines.)
 136   size_t
 137   _Fnv_hash_bytes(const void* __ptr, size_t __len, size_t __seed);
 138
 139   struct _Hash_impl
 140   {
 141     static size_t
 142     hash(const void* __ptr, size_t __clength,
 143          size_t __seed = static_cast<size_t>(0xc70f6907UL))
 144     { return _Hash_bytes(__ptr, __clength, __seed); }
 145
 146     template<typename _Tp>
 147       static size_t
 148       hash(const _Tp& __val)
 149       { return hash(&__val, sizeof(__val)); }
 150
 151     template<typename _Tp>
 152       static size_t
 153       __hash_combine(const _Tp& __val, size_t __hash)
 154       { return hash(&__val, sizeof(__val), __hash); }
 155   };
 156
 157   struct _Fnv_hash_impl
 158   {
 159     static size_t
 160     hash(const void* __ptr, size_t __clength,
 161          size_t __seed = static_cast<size_t>(2166136261UL))
 162     { return _Fnv_hash_bytes(__ptr, __clength, __seed); }
 163
 164     template<typename _Tp>
 165       static size_t
 166       hash(const _Tp& __val)
 167       { return hash(&__val, sizeof(__val)); }
 168
 169     template<typename _Tp>
 170       static size_t
 171       __hash_combine(const _Tp& __val, size_t __hash)
 172       { return hash(&__val, sizeof(__val), __hash); }
 173   };
 174
 175   /// Specialization for float.
 176   template<>
 177     inline size_t
 178     hash<float>::operator()(float __val) const
 179     {
 180       // 0 and -0 both hash to zero.
 181       return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0;
 182     }
 183
 184   /// Specialization for double.
 185   template<>
 186     inline size_t
 187     hash<double>::operator()(double __val) const
 188     {
 189       // 0 and -0 both hash to zero.
 190       return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0;
 191     }
 192
 193   /// Specialization for long double.
 194   template<>
 195     _GLIBCXX_PURE size_t
 196     hash<long double>::operator()(long double __val) const;
 197
 198   // @} group hashes
 199 }
 200
 201 #endif // _FUNCTIONAL_HASH_H