1 // functional_hash.h header -*- C++ -*- 2 3 // Copyright (C) 2007-2013 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 #undef _Cxx_hashtable_define_trivial_hash 125 126 struct _Hash_impl 127 { 128 static size_t 129 hash(const void* __ptr, size_t __clength, 130 size_t __seed = static_cast<size_t>(0xc70f6907UL)) 131 { return _Hash_bytes(__ptr, __clength, __seed); } 132 133 template<typename _Tp> 134 static size_t 135 hash(const _Tp& __val) 136 { return hash(&__val, sizeof(__val)); } 137 138 template<typename _Tp> 139 static size_t 140 __hash_combine(const _Tp& __val, size_t __hash) 141 { return hash(&__val, sizeof(__val), __hash); } 142 }; 143 144 struct _Fnv_hash_impl 145 { 146 static size_t 147 hash(const void* __ptr, size_t __clength, 148 size_t __seed = static_cast<size_t>(2166136261UL)) 149 { return _Fnv_hash_bytes(__ptr, __clength, __seed); } 150 151 template<typename _Tp> 152 static size_t 153 hash(const _Tp& __val) 154 { return hash(&__val, sizeof(__val)); } 155 156 template<typename _Tp> 157 static size_t 158 __hash_combine(const _Tp& __val, size_t __hash) 159 { return hash(&__val, sizeof(__val), __hash); } 160 }; 161 162 /// Specialization for float. 163 template<> 164 struct hash<float> : public __hash_base<size_t, float> 165 { 166 size_t 167 operator()(float __val) const noexcept 168 { 169 // 0 and -0 both hash to zero. 170 return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0; 171 } 172 }; 173 174 /// Specialization for double. 175 template<> 176 struct hash<double> : public __hash_base<size_t, double> 177 { 178 size_t 179 operator()(double __val) const noexcept 180 { 181 // 0 and -0 both hash to zero. 182 return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0; 183 } 184 }; 185 186 /// Specialization for long double. 187 template<> 188 struct hash<long double> 189 : public __hash_base<size_t, long double> 190 { 191 _GLIBCXX_PURE size_t 192 operator()(long double __val) const noexcept; 193 }; 194 195 // @} group hashes 196 197 // Hint about performance of hash functor. If not fast the hash based 198 // containers will cache the hash code. 199 // Default behavior is to consider that hasher are fast unless specified 200 // otherwise. 201 template<typename _Hash> 202 struct __is_fast_hash : public std::true_type 203 { }; 204 205 template<> 206 struct __is_fast_hash<hash<long double>> : public std::false_type 207 { }; 208 209 _GLIBCXX_END_NAMESPACE_VERSION 210 } // namespace 211 212 #endif // _FUNCTIONAL_HASH_H 213
