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

   1 // functional_hash.h header -*- C++ -*-
   2
   3 // Copyright (C) 2007-2015 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/hash_bytes.h>
  36
  37 namespace std _GLIBCXX_VISIBILITY(default)
  38 {
  39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  40
  41   /** @defgroup hashes Hashes
  42    *  @ingroup functors
  43    *
  44    *   Hashing functors taking a variable type and returning a @c std::size_t.
  45    *
  46    *  @{
  47    */
  48
  49   template<typename _Result, typename _Arg>
  50     struct __hash_base
  51     {
  52       typedef _Result     result_type;
  53       typedef _Arg      argument_type;
  54     };
  55
  56   /// Primary class template hash.
  57   template<typename _Tp>
  58     struct hash;
  59
  60   /// Partial specializations for pointer types.
  61   template<typename _Tp>
  62     struct hash<_Tp*> : public __hash_base<size_t, _Tp*>
  63     {
  64       size_t
  65       operator()(_Tp* __p) const noexcept
  66       { return reinterpret_cast<size_t>(__p); }
  67     };
  68
  69   // Explicit specializations for integer types.
  70 #define _Cxx_hashtable_define_trivial_hash(_Tp)         \
  71   template<>                                            \
  72     struct hash<_Tp> : public __hash_base<size_t, _Tp>  \
  73     {                                                   \
  74       size_t                                            \
  75       operator()(_Tp __val) const noexcept              \
  76       { return static_cast<size_t>(__val); }            \
  77     };
  78
  79   /// Explicit specialization for bool.
  80   _Cxx_hashtable_define_trivial_hash(bool)
  81
  82   /// Explicit specialization for char.
  83   _Cxx_hashtable_define_trivial_hash(char)
  84
  85   /// Explicit specialization for signed char.
  86   _Cxx_hashtable_define_trivial_hash(signed char)
  87
  88   /// Explicit specialization for unsigned char.
  89   _Cxx_hashtable_define_trivial_hash(unsigned char)
  90
  91   /// Explicit specialization for wchar_t.
  92   _Cxx_hashtable_define_trivial_hash(wchar_t)
  93
  94   /// Explicit specialization for char16_t.
  95   _Cxx_hashtable_define_trivial_hash(char16_t)
  96
  97   /// Explicit specialization for char32_t.
  98   _Cxx_hashtable_define_trivial_hash(char32_t)
  99
 100   /// Explicit specialization for short.
 101   _Cxx_hashtable_define_trivial_hash(short)
 102
 103   /// Explicit specialization for int.
 104   _Cxx_hashtable_define_trivial_hash(int)
 105
 106   /// Explicit specialization for long.
 107   _Cxx_hashtable_define_trivial_hash(long)
 108
 109   /// Explicit specialization for long long.
 110   _Cxx_hashtable_define_trivial_hash(long long)
 111
 112   /// Explicit specialization for unsigned short.
 113   _Cxx_hashtable_define_trivial_hash(unsigned short)
 114
 115   /// Explicit specialization for unsigned int.
 116   _Cxx_hashtable_define_trivial_hash(unsigned int)
 117
 118   /// Explicit specialization for unsigned long.
 119   _Cxx_hashtable_define_trivial_hash(unsigned long)
 120
 121   /// Explicit specialization for unsigned long long.
 122   _Cxx_hashtable_define_trivial_hash(unsigned long long)
 123
 124 #ifdef __GLIBCXX_TYPE_INT_N_0
 125   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0)
 126   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0 unsigned)
 127 #endif
 128 #ifdef __GLIBCXX_TYPE_INT_N_1
 129   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1)
 130   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1 unsigned)
 131 #endif
 132 #ifdef __GLIBCXX_TYPE_INT_N_2
 133   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2)
 134   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2 unsigned)
 135 #endif
 136 #ifdef __GLIBCXX_TYPE_INT_N_3
 137   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3)
 138   _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3 unsigned)
 139 #endif
 140
 141 #undef _Cxx_hashtable_define_trivial_hash
 142
 143   struct _Hash_impl
 144   {
 145     static size_t
 146     hash(const void* __ptr, size_t __clength,
 147          size_t __seed = static_cast<size_t>(0xc70f6907UL))
 148     { return _Hash_bytes(__ptr, __clength, __seed); }
 149
 150     template<typename _Tp>
 151       static size_t
 152       hash(const _Tp& __val)
 153       { return hash(&__val, sizeof(__val)); }
 154
 155     template<typename _Tp>
 156       static size_t
 157       __hash_combine(const _Tp& __val, size_t __hash)
 158       { return hash(&__val, sizeof(__val), __hash); }
 159   };
 160
 161   struct _Fnv_hash_impl
 162   {
 163     static size_t
 164     hash(const void* __ptr, size_t __clength,
 165          size_t __seed = static_cast<size_t>(2166136261UL))
 166     { return _Fnv_hash_bytes(__ptr, __clength, __seed); }
 167
 168     template<typename _Tp>
 169       static size_t
 170       hash(const _Tp& __val)
 171       { return hash(&__val, sizeof(__val)); }
 172
 173     template<typename _Tp>
 174       static size_t
 175       __hash_combine(const _Tp& __val, size_t __hash)
 176       { return hash(&__val, sizeof(__val), __hash); }
 177   };
 178
 179   /// Specialization for float.
 180   template<>
 181     struct hash<float> : public __hash_base<size_t, float>
 182     {
 183       size_t
 184       operator()(float __val) const noexcept
 185       {
 186         // 0 and -0 both hash to zero.
 187         return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0;
 188       }
 189     };
 190
 191   /// Specialization for double.
 192   template<>
 193     struct hash<double> : public __hash_base<size_t, double>
 194     {
 195       size_t
 196       operator()(double __val) const noexcept
 197       {
 198         // 0 and -0 both hash to zero.
 199         return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0;
 200       }
 201     };
 202
 203   /// Specialization for long double.
 204   template<>
 205     struct hash<long double>
 206     : public __hash_base<size_t, long double>
 207     {
 208       _GLIBCXX_PURE size_t
 209       operator()(long double __val) const noexcept;
 210     };
 211
 212   // @} group hashes
 213
 214   // Hint about performance of hash functor. If not fast the hash based
 215   // containers will cache the hash code.
 216   // Default behavior is to consider that hasher are fast unless specified
 217   // otherwise.
 218   template<typename _Hash>
 219     struct __is_fast_hash : public std::true_type
 220     { };
 221
 222   template<>
 223     struct __is_fast_hash<hash<long double>> : public std::false_type
 224     { };
 225
 226 _GLIBCXX_END_NAMESPACE_VERSION
 227 } // namespace
 228
 229 #endif // _FUNCTIONAL_HASH_H