libstdc++
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00001 // functional_hash.h header -*- C++ -*- 00002 00003 // Copyright (C) 2007-2016 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file bits/functional_hash.h 00026 * This is an internal header file, included by other library headers. 00027 * Do not attempt to use it directly. @headername{functional} 00028 */ 00029 00030 #ifndef _FUNCTIONAL_HASH_H 00031 #define _FUNCTIONAL_HASH_H 1 00032 00033 #pragma GCC system_header 00034 00035 #include <bits/hash_bytes.h> 00036 00037 namespace std _GLIBCXX_VISIBILITY(default) 00038 { 00039 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00040 00041 /** @defgroup hashes Hashes 00042 * @ingroup functors 00043 * 00044 * Hashing functors taking a variable type and returning a @c std::size_t. 00045 * 00046 * @{ 00047 */ 00048 00049 template<typename _Result, typename _Arg> 00050 struct __hash_base 00051 { 00052 typedef _Result result_type; 00053 typedef _Arg argument_type; 00054 }; 00055 00056 /// Primary class template hash. 00057 template<typename _Tp> 00058 struct hash; 00059 00060 // Helper struct for SFINAE-poisoning non-enum types. 00061 template<typename _Tp, bool = is_enum<_Tp>::value> 00062 struct __hash_enum 00063 { 00064 private: 00065 // Private rather than deleted to be non-trivially-copyable. 00066 __hash_enum(__hash_enum&&); 00067 ~__hash_enum(); 00068 }; 00069 00070 // Helper struct for hash with enum types. 00071 template<typename _Tp> 00072 struct __hash_enum<_Tp, true> : public __hash_base<size_t, _Tp> 00073 { 00074 size_t 00075 operator()(_Tp __val) const noexcept 00076 { 00077 using __type = typename underlying_type<_Tp>::type; 00078 return hash<__type>{}(static_cast<__type>(__val)); 00079 } 00080 }; 00081 00082 /// Primary class template hash, usable for enum types only. 00083 // Use with non-enum types still SFINAES. 00084 template<typename _Tp> 00085 struct hash : __hash_enum<_Tp> 00086 { }; 00087 00088 /// Partial specializations for pointer types. 00089 template<typename _Tp> 00090 struct hash<_Tp*> : public __hash_base<size_t, _Tp*> 00091 { 00092 size_t 00093 operator()(_Tp* __p) const noexcept 00094 { return reinterpret_cast<size_t>(__p); } 00095 }; 00096 00097 // Explicit specializations for integer types. 00098 #define _Cxx_hashtable_define_trivial_hash(_Tp) \ 00099 template<> \ 00100 struct hash<_Tp> : public __hash_base<size_t, _Tp> \ 00101 { \ 00102 size_t \ 00103 operator()(_Tp __val) const noexcept \ 00104 { return static_cast<size_t>(__val); } \ 00105 }; 00106 00107 /// Explicit specialization for bool. 00108 _Cxx_hashtable_define_trivial_hash(bool) 00109 00110 /// Explicit specialization for char. 00111 _Cxx_hashtable_define_trivial_hash(char) 00112 00113 /// Explicit specialization for signed char. 00114 _Cxx_hashtable_define_trivial_hash(signed char) 00115 00116 /// Explicit specialization for unsigned char. 00117 _Cxx_hashtable_define_trivial_hash(unsigned char) 00118 00119 /// Explicit specialization for wchar_t. 00120 _Cxx_hashtable_define_trivial_hash(wchar_t) 00121 00122 /// Explicit specialization for char16_t. 00123 _Cxx_hashtable_define_trivial_hash(char16_t) 00124 00125 /// Explicit specialization for char32_t. 00126 _Cxx_hashtable_define_trivial_hash(char32_t) 00127 00128 /// Explicit specialization for short. 00129 _Cxx_hashtable_define_trivial_hash(short) 00130 00131 /// Explicit specialization for int. 00132 _Cxx_hashtable_define_trivial_hash(int) 00133 00134 /// Explicit specialization for long. 00135 _Cxx_hashtable_define_trivial_hash(long) 00136 00137 /// Explicit specialization for long long. 00138 _Cxx_hashtable_define_trivial_hash(long long) 00139 00140 /// Explicit specialization for unsigned short. 00141 _Cxx_hashtable_define_trivial_hash(unsigned short) 00142 00143 /// Explicit specialization for unsigned int. 00144 _Cxx_hashtable_define_trivial_hash(unsigned int) 00145 00146 /// Explicit specialization for unsigned long. 00147 _Cxx_hashtable_define_trivial_hash(unsigned long) 00148 00149 /// Explicit specialization for unsigned long long. 00150 _Cxx_hashtable_define_trivial_hash(unsigned long long) 00151 00152 #ifdef __GLIBCXX_TYPE_INT_N_0 00153 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0) 00154 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0 unsigned) 00155 #endif 00156 #ifdef __GLIBCXX_TYPE_INT_N_1 00157 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1) 00158 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1 unsigned) 00159 #endif 00160 #ifdef __GLIBCXX_TYPE_INT_N_2 00161 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2) 00162 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2 unsigned) 00163 #endif 00164 #ifdef __GLIBCXX_TYPE_INT_N_3 00165 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3) 00166 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3 unsigned) 00167 #endif 00168 00169 #undef _Cxx_hashtable_define_trivial_hash 00170 00171 struct _Hash_impl 00172 { 00173 static size_t 00174 hash(const void* __ptr, size_t __clength, 00175 size_t __seed = static_cast<size_t>(0xc70f6907UL)) 00176 { return _Hash_bytes(__ptr, __clength, __seed); } 00177 00178 template<typename _Tp> 00179 static size_t 00180 hash(const _Tp& __val) 00181 { return hash(&__val, sizeof(__val)); } 00182 00183 template<typename _Tp> 00184 static size_t 00185 __hash_combine(const _Tp& __val, size_t __hash) 00186 { return hash(&__val, sizeof(__val), __hash); } 00187 }; 00188 00189 struct _Fnv_hash_impl 00190 { 00191 static size_t 00192 hash(const void* __ptr, size_t __clength, 00193 size_t __seed = static_cast<size_t>(2166136261UL)) 00194 { return _Fnv_hash_bytes(__ptr, __clength, __seed); } 00195 00196 template<typename _Tp> 00197 static size_t 00198 hash(const _Tp& __val) 00199 { return hash(&__val, sizeof(__val)); } 00200 00201 template<typename _Tp> 00202 static size_t 00203 __hash_combine(const _Tp& __val, size_t __hash) 00204 { return hash(&__val, sizeof(__val), __hash); } 00205 }; 00206 00207 /// Specialization for float. 00208 template<> 00209 struct hash<float> : public __hash_base<size_t, float> 00210 { 00211 size_t 00212 operator()(float __val) const noexcept 00213 { 00214 // 0 and -0 both hash to zero. 00215 return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0; 00216 } 00217 }; 00218 00219 /// Specialization for double. 00220 template<> 00221 struct hash<double> : public __hash_base<size_t, double> 00222 { 00223 size_t 00224 operator()(double __val) const noexcept 00225 { 00226 // 0 and -0 both hash to zero. 00227 return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0; 00228 } 00229 }; 00230 00231 /// Specialization for long double. 00232 template<> 00233 struct hash<long double> 00234 : public __hash_base<size_t, long double> 00235 { 00236 _GLIBCXX_PURE size_t 00237 operator()(long double __val) const noexcept; 00238 }; 00239 00240 // @} group hashes 00241 00242 // Hint about performance of hash functor. If not fast the hash-based 00243 // containers will cache the hash code. 00244 // Default behavior is to consider that hashers are fast unless specified 00245 // otherwise. 00246 template<typename _Hash> 00247 struct __is_fast_hash : public std::true_type 00248 { }; 00249 00250 template<> 00251 struct __is_fast_hash<hash<long double>> : public std::false_type 00252 { }; 00253 00254 _GLIBCXX_END_NAMESPACE_VERSION 00255 } // namespace 00256 00257 #endif // _FUNCTIONAL_HASH_H