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

   1 // functional_hash.h header -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 3, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 /** @file bits/functional_hash.h
  27  *  This is an internal header file, included by other library headers.
  28  *  Do not attempt to use it directly. @headername{functional}
  29  */
  30
  31 #ifndef _FUNCTIONAL_HASH_H
  32 #define _FUNCTIONAL_HASH_H 1
  33
  34 #pragma GCC system_header
  35
  36 #include <bits/hash_bytes.h>
  37
  38 namespace std _GLIBCXX_VISIBILITY(default)
  39 {
  40 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  41
  42   /** @defgroup hashes Hashes
  43    *  @ingroup functors
  44    *
  45    *   Hashing functors taking a variable type and returning a @c std::size_t.
  46    *
  47    *  @{
  48    */
  49
  50   template<typename _Result, typename _Arg>
  51     struct __hash_base
  52     {
  53       typedef _Result     result_type;
  54       typedef _Arg      argument_type;
  55     };
  56
  57   /// Primary class template hash.
  58   template<typename _Tp>
  59     struct hash;
  60
  61   /// Partial specializations for pointer types.
  62   template<typename _Tp>
  63     struct hash<_Tp*> : public __hash_base<size_t, _Tp*>
  64     {
  65       size_t
  66       operator()(_Tp* __p) const noexcept
  67       { return reinterpret_cast<size_t>(__p); }
  68     };
  69
  70   // Explicit specializations for integer types.
  71 #define _Cxx_hashtable_define_trivial_hash(_Tp)         \
  72   template<>                                            \
  73     struct hash<_Tp> : public __hash_base<size_t, _Tp>  \
  74     {                                                   \
  75       size_t                                            \
  76       operator()(_Tp __val) const noexcept              \
  77       { return static_cast<size_t>(__val); }            \
  78     };
  79
  80   /// Explicit specialization for bool.
  81   _Cxx_hashtable_define_trivial_hash(bool)
  82
  83   /// Explicit specialization for char.
  84   _Cxx_hashtable_define_trivial_hash(char)
  85
  86   /// Explicit specialization for signed char.
  87   _Cxx_hashtable_define_trivial_hash(signed char)
  88
  89   /// Explicit specialization for unsigned char.
  90   _Cxx_hashtable_define_trivial_hash(unsigned char)
  91
  92   /// Explicit specialization for wchar_t.
  93   _Cxx_hashtable_define_trivial_hash(wchar_t)
  94
  95   /// Explicit specialization for char16_t.
  96   _Cxx_hashtable_define_trivial_hash(char16_t)
  97
  98   /// Explicit specialization for char32_t.
  99   _Cxx_hashtable_define_trivial_hash(char32_t)
 100
 101   /// Explicit specialization for short.
 102   _Cxx_hashtable_define_trivial_hash(short)
 103
 104   /// Explicit specialization for int.
 105   _Cxx_hashtable_define_trivial_hash(int)
 106
 107   /// Explicit specialization for long.
 108   _Cxx_hashtable_define_trivial_hash(long)
 109
 110   /// Explicit specialization for long long.
 111   _Cxx_hashtable_define_trivial_hash(long long)
 112
 113   /// Explicit specialization for unsigned short.
 114   _Cxx_hashtable_define_trivial_hash(unsigned short)
 115
 116   /// Explicit specialization for unsigned int.
 117   _Cxx_hashtable_define_trivial_hash(unsigned int)
 118
 119   /// Explicit specialization for unsigned long.
 120   _Cxx_hashtable_define_trivial_hash(unsigned long)
 121
 122   /// Explicit specialization for unsigned long long.
 123   _Cxx_hashtable_define_trivial_hash(unsigned long long)
 124
 125 #undef _Cxx_hashtable_define_trivial_hash
 126
 127   struct _Hash_impl
 128   {
 129     static size_t
 130     hash(const void* __ptr, size_t __clength,
 131          size_t __seed = static_cast<size_t>(0xc70f6907UL))
 132     { return _Hash_bytes(__ptr, __clength, __seed); }
 133
 134     template<typename _Tp>
 135       static size_t
 136       hash(const _Tp& __val)
 137       { return hash(&__val, sizeof(__val)); }
 138
 139     template<typename _Tp>
 140       static size_t
 141       __hash_combine(const _Tp& __val, size_t __hash)
 142       { return hash(&__val, sizeof(__val), __hash); }
 143   };
 144
 145   struct _Fnv_hash_impl
 146   {
 147     static size_t
 148     hash(const void* __ptr, size_t __clength,
 149          size_t __seed = static_cast<size_t>(2166136261UL))
 150     { return _Fnv_hash_bytes(__ptr, __clength, __seed); }
 151
 152     template<typename _Tp>
 153       static size_t
 154       hash(const _Tp& __val)
 155       { return hash(&__val, sizeof(__val)); }
 156
 157     template<typename _Tp>
 158       static size_t
 159       __hash_combine(const _Tp& __val, size_t __hash)
 160       { return hash(&__val, sizeof(__val), __hash); }
 161   };
 162
 163   /// Specialization for float.
 164   template<>
 165     struct hash<float> : public __hash_base<size_t, float>
 166     {
 167       size_t
 168       operator()(float __val) const noexcept
 169       {
 170         // 0 and -0 both hash to zero.
 171         return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0;
 172       }
 173     };
 174
 175   /// Specialization for double.
 176   template<>
 177     struct hash<double> : public __hash_base<size_t, double>
 178     {
 179       size_t
 180       operator()(double __val) const noexcept
 181       {
 182         // 0 and -0 both hash to zero.
 183         return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0;
 184       }
 185     };
 186
 187   /// Specialization for long double.
 188   template<>
 189     struct hash<long double>
 190     : public __hash_base<size_t, long double>
 191     {
 192       _GLIBCXX_PURE size_t
 193       operator()(long double __val) const noexcept;
 194     };
 195
 196   // @} group hashes
 197
 198 _GLIBCXX_END_NAMESPACE_VERSION
 199 } // namespace
 200
 201 #endif // _FUNCTIONAL_HASH_H