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
_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 : 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