1 // functional_hash.h header -*- C++ -*- 2 3 // Copyright (C) 2007, 2008, 2009, 2010, 2011 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 : public __hash_base<size_t, _Tp> 59 { 60 static_assert(sizeof(_Tp) < 0, 61 "std::hash is not specialized for this type"); 62 size_t operator()(const _Tp&) const noexcept; 63 }; 64 65 /// Partial specializations for pointer types. 66 template<typename _Tp> 67 struct hash<_Tp*> : public __hash_base<size_t, _Tp*> 68 { 69 size_t 70 operator()(_Tp* __p) const noexcept 71 { return reinterpret_cast<size_t>(__p); } 72 }; 73 74 // Explicit specializations for integer types. 75 #define _Cxx_hashtable_define_trivial_hash(_Tp) \ 76 template<> \ 77 struct hash<_Tp> : public __hash_base<size_t, _Tp> \ 78 { \ 79 size_t \ 80 operator()(_Tp __val) const noexcept \ 81 { return static_cast<size_t>(__val); } \ 82 }; 83 84 /// Explicit specialization for bool. 85 _Cxx_hashtable_define_trivial_hash(bool) 86 87 /// Explicit specialization for char. 88 _Cxx_hashtable_define_trivial_hash(char) 89 90 /// Explicit specialization for signed char. 91 _Cxx_hashtable_define_trivial_hash(signed char) 92 93 /// Explicit specialization for unsigned char. 94 _Cxx_hashtable_define_trivial_hash(unsigned char) 95 96 /// Explicit specialization for wchar_t. 97 _Cxx_hashtable_define_trivial_hash(wchar_t) 98 99 /// Explicit specialization for char16_t. 100 _Cxx_hashtable_define_trivial_hash(char16_t) 101 102 /// Explicit specialization for char32_t. 103 _Cxx_hashtable_define_trivial_hash(char32_t) 104 105 /// Explicit specialization for short. 106 _Cxx_hashtable_define_trivial_hash(short) 107 108 /// Explicit specialization for int. 109 _Cxx_hashtable_define_trivial_hash(int) 110 111 /// Explicit specialization for long. 112 _Cxx_hashtable_define_trivial_hash(long) 113 114 /// Explicit specialization for long long. 115 _Cxx_hashtable_define_trivial_hash(long long) 116 117 /// Explicit specialization for unsigned short. 118 _Cxx_hashtable_define_trivial_hash(unsigned short) 119 120 /// Explicit specialization for unsigned int. 121 _Cxx_hashtable_define_trivial_hash(unsigned int) 122 123 /// Explicit specialization for unsigned long. 124 _Cxx_hashtable_define_trivial_hash(unsigned long) 125 126 /// Explicit specialization for unsigned long long. 127 _Cxx_hashtable_define_trivial_hash(unsigned long long) 128 129 #undef _Cxx_hashtable_define_trivial_hash 130 131 struct _Hash_impl 132 { 133 static size_t 134 hash(const void* __ptr, size_t __clength, 135 size_t __seed = static_cast<size_t>(0xc70f6907UL)) 136 { return _Hash_bytes(__ptr, __clength, __seed); } 137 138 template<typename _Tp> 139 static size_t 140 hash(const _Tp& __val) 141 { return hash(&__val, sizeof(__val)); } 142 143 template<typename _Tp> 144 static size_t 145 __hash_combine(const _Tp& __val, size_t __hash) 146 { return hash(&__val, sizeof(__val), __hash); } 147 }; 148 149 struct _Fnv_hash_impl 150 { 151 static size_t 152 hash(const void* __ptr, size_t __clength, 153 size_t __seed = static_cast<size_t>(2166136261UL)) 154 { return _Fnv_hash_bytes(__ptr, __clength, __seed); } 155 156 template<typename _Tp> 157 static size_t 158 hash(const _Tp& __val) 159 { return hash(&__val, sizeof(__val)); } 160 161 template<typename _Tp> 162 static size_t 163 __hash_combine(const _Tp& __val, size_t __hash) 164 { return hash(&__val, sizeof(__val), __hash); } 165 }; 166 167 /// Specialization for float. 168 template<> 169 struct hash<float> : public __hash_base<size_t, float> 170 { 171 size_t 172 operator()(float __val) const noexcept 173 { 174 // 0 and -0 both hash to zero. 175 return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0; 176 } 177 }; 178 179 /// Specialization for double. 180 template<> 181 struct hash<double> : public __hash_base<size_t, double> 182 { 183 size_t 184 operator()(double __val) const noexcept 185 { 186 // 0 and -0 both hash to zero. 187 return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0; 188 } 189 }; 190 191 /// Specialization for long double. 192 template<> 193 struct hash<long double> 194 : public __hash_base<size_t, long double> 195 { 196 _GLIBCXX_PURE size_t 197 operator()(long double __val) const noexcept; 198 }; 199 200 // @} group hashes 201 202 _GLIBCXX_END_NAMESPACE_VERSION 203 } // namespace 204 205 #endif // _FUNCTIONAL_HASH_H 206
