1 // functional_hash.h header -*- C++ -*-
2
3 // Copyright (C) 2007-2016 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
_GLIBCXX_VISIBILITY(default)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 // Helper struct for SFINAE-poisoning non-enum types.
61 template<typename _Tp, bool = is_enum<_Tp>::value>
62 struct __hash_enum
63 {
64 private:
65 // Private rather than deleted to be non-trivially-copyable.
66 __hash_enum(__hash_enum&&);
67 ~__hash_enum();
68 };
69
70 // Helper struct for hash with enum types.
71 template<typename _Tp>
72 struct __hash_enum<_Tp, true> : public __hash_base<size_t, _Tp>
73 {
74 size_t
75 operator()(_Tp __val) const noexcept
76 {
77 using __type = typename underlying_type<_Tp>::type;
78 return hash<__type>{}(static_cast<__type>(__val));
79 }
80 };
81
82 /// Primary class template hash, usable for enum types only.
83 // Use with non-enum types still SFINAES.
84 template<typename _Tp>
85 struct hash : __hash_enum<_Tp>
86 { };
87
88 /// Partial specializations for pointer types.
89 template<typename _Tp>
90 struct hash<_Tp*> : public __hash_base<size_t, _Tp*>
91 {
92 size_t
93 operator()(_Tp* __p) const noexcept
94 { return reinterpret_cast<size_t>(__p); }
95 };
96
97 // Explicit specializations for integer types.
98 #define _Cxx_hashtable_define_trivial_hash(_Tp) \
99 template<> \
100 struct hash<_Tp> : public __hash_base<size_t, _Tp> \
101 { \
102 size_t \
103 operator()(_Tp __val) const noexcept \
104 { return static_cast<size_t>(__val); } \
105 };
106
107 /// Explicit specialization for bool.
108 _Cxx_hashtable_define_trivial_hash(bool)
109
110 /// Explicit specialization for char.
111 _Cxx_hashtable_define_trivial_hash(char)
112
113 /// Explicit specialization for signed char.
114 _Cxx_hashtable_define_trivial_hash(signed char)
115
116 /// Explicit specialization for unsigned char.
117 _Cxx_hashtable_define_trivial_hash(unsigned char)
118
119 /// Explicit specialization for wchar_t.
120 _Cxx_hashtable_define_trivial_hash(wchar_t)
121
122 /// Explicit specialization for char16_t.
123 _Cxx_hashtable_define_trivial_hash(char16_t)
124
125 /// Explicit specialization for char32_t.
126 _Cxx_hashtable_define_trivial_hash(char32_t)
127
128 /// Explicit specialization for short.
129 _Cxx_hashtable_define_trivial_hash(short)
130
131 /// Explicit specialization for int.
132 _Cxx_hashtable_define_trivial_hash(int)
133
134 /// Explicit specialization for long.
135 _Cxx_hashtable_define_trivial_hash(long)
136
137 /// Explicit specialization for long long.
138 _Cxx_hashtable_define_trivial_hash(long long)
139
140 /// Explicit specialization for unsigned short.
141 _Cxx_hashtable_define_trivial_hash(unsigned short)
142
143 /// Explicit specialization for unsigned int.
144 _Cxx_hashtable_define_trivial_hash(unsigned int)
145
146 /// Explicit specialization for unsigned long.
147 _Cxx_hashtable_define_trivial_hash(unsigned long)
148
149 /// Explicit specialization for unsigned long long.
150 _Cxx_hashtable_define_trivial_hash(unsigned long long)
151
152 #ifdef __GLIBCXX_TYPE_INT_N_0
153 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0)
154 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_0 unsigned)
155 #endif
156 #ifdef __GLIBCXX_TYPE_INT_N_1
157 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1)
158 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_1 unsigned)
159 #endif
160 #ifdef __GLIBCXX_TYPE_INT_N_2
161 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2)
162 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_2 unsigned)
163 #endif
164 #ifdef __GLIBCXX_TYPE_INT_N_3
165 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3)
166 _Cxx_hashtable_define_trivial_hash(__GLIBCXX_TYPE_INT_N_3 unsigned)
167 #endif
168
169 #undef _Cxx_hashtable_define_trivial_hash
170
171 struct _Hash_impl
172 {
173 static size_t
174 hash(const void* __ptr, size_t __clength,
175 size_t __seed = static_cast<size_t>(0xc70f6907UL))
176 { return _Hash_bytes(__ptr, __clength, __seed); }
177
178 template<typename _Tp>
179 static size_t
180 hash(const _Tp& __val)
181 { return hash(&__val, sizeof(__val)); }
182
183 template<typename _Tp>
184 static size_t
185 __hash_combine(const _Tp& __val, size_t __hash)
186 { return hash(&__val, sizeof(__val), __hash); }
187 };
188
189 struct _Fnv_hash_impl
190 {
191 static size_t
192 hash(const void* __ptr, size_t __clength,
193 size_t __seed = static_cast<size_t>(2166136261UL))
194 { return _Fnv_hash_bytes(__ptr, __clength, __seed); }
195
196 template<typename _Tp>
197 static size_t
198 hash(const _Tp& __val)
199 { return hash(&__val, sizeof(__val)); }
200
201 template<typename _Tp>
202 static size_t
203 __hash_combine(const _Tp& __val, size_t __hash)
204 { return hash(&__val, sizeof(__val), __hash); }
205 };
206
207 /// Specialization for float.
208 template<>
209 struct hash<float> : public __hash_base<size_t, float>
210 {
211 size_t
212 operator()(float __val) const noexcept
213 {
214 // 0 and -0 both hash to zero.
215 return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0;
216 }
217 };
218
219 /// Specialization for double.
220 template<>
221 struct hash<double> : public __hash_base<size_t, double>
222 {
223 size_t
224 operator()(double __val) const noexcept
225 {
226 // 0 and -0 both hash to zero.
227 return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0;
228 }
229 };
230
231 /// Specialization for long double.
232 template<>
233 struct hash<long double>
234 : public __hash_base<size_t, long double>
235 {
236 _GLIBCXX_PURE size_t
237 operator()(long double __val) const noexcept;
238 };
239
240 // @} group hashes
241
242 // Hint about performance of hash functor. If not fast the hash-based
243 // containers will cache the hash code.
244 // Default behavior is to consider that hashers are fast unless specified
245 // otherwise.
246 template<typename _Hash>
247 struct __is_fast_hash : public std::true_type
248 { };
249
250 template<>
251 struct __is_fast_hash<hash<long double>> : public std::false_type
252 { };
253
254 _GLIBCXX_END_NAMESPACE_VERSION
255 } // namespace
256
257 #endif // _FUNCTIONAL_HASH_H
258