1 // TR1 functional_hash.h header -*- C++ -*-
2
3 // Copyright (C) 2007-2022 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 tr1/functional_hash.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{tr1/functional}
28 */
29
30 #ifndef _GLIBCXX_TR1_FUNCTIONAL_HASH_H
31 #define _GLIBCXX_TR1_FUNCTIONAL_HASH_H 1
32
33 #pragma GCC system_header
34
_GLIBCXX_VISIBILITY(default)35 namespace std _GLIBCXX_VISIBILITY(default)
36 {
37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
38
39 namespace tr1
40 {
41 // Ignore warnings about std::unary_function and std::binary_function.
42 #pragma GCC diagnostic push
43 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
44
45 /// Class template hash.
46 // Declaration of default hash functor std::tr1::hash. The types for
47 // which std::tr1::hash<T> is well-defined is in clause 6.3.3. of the PDTR.
48 template<typename _Tp>
49 struct hash : public std::unary_function<_Tp, size_t>
50 {
51 size_t
52 operator()(_Tp __val) const;
53 };
54
55 /// Partial specializations for pointer types.
56 template<typename _Tp>
57 struct hash<_Tp*> : public std::unary_function<_Tp*, size_t>
58 {
59 size_t
60 operator()(_Tp* __p) const
61 { return reinterpret_cast<size_t>(__p); }
62 };
63 #pragma GCC diagnostic pop
64
65 /// Explicit specializations for integer types.
66 #define _TR1_hashtable_define_trivial_hash(_Tp) \
67 template<> \
68 inline size_t \
69 hash<_Tp>::operator()(_Tp __val) const \
70 { return static_cast<size_t>(__val); }
71
72 _TR1_hashtable_define_trivial_hash(bool);
73 _TR1_hashtable_define_trivial_hash(char);
74 _TR1_hashtable_define_trivial_hash(signed char);
75 _TR1_hashtable_define_trivial_hash(unsigned char);
76 _TR1_hashtable_define_trivial_hash(wchar_t);
77 _TR1_hashtable_define_trivial_hash(short);
78 _TR1_hashtable_define_trivial_hash(int);
79 _TR1_hashtable_define_trivial_hash(long);
80 _TR1_hashtable_define_trivial_hash(long long);
81 _TR1_hashtable_define_trivial_hash(unsigned short);
82 _TR1_hashtable_define_trivial_hash(unsigned int);
83 _TR1_hashtable_define_trivial_hash(unsigned long);
84 _TR1_hashtable_define_trivial_hash(unsigned long long);
85
86 #undef _TR1_hashtable_define_trivial_hash
87
88 // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
89 // (Used by the next specializations of std::tr1::hash.)
90
91 // N.B. These functions should work on unsigned char, otherwise they do not
92 // correctly implement the FNV-1a algorithm (see PR59406).
93 // The existing behaviour is retained for backwards compatibility.
94
95 /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
96 template<size_t>
97 struct _Fnv_hash_base
98 {
99 template<typename _Tp>
100 static size_t
101 hash(const _Tp* __ptr, size_t __clength)
102 {
103 size_t __result = 0;
104 const char* __cptr = reinterpret_cast<const char*>(__ptr);
105 for (; __clength; --__clength)
106 __result = (__result * 131) + *__cptr++;
107 return __result;
108 }
109 };
110
111 template<>
112 struct _Fnv_hash_base<4>
113 {
114 template<typename _Tp>
115 static size_t
116 hash(const _Tp* __ptr, size_t __clength)
117 {
118 size_t __result = static_cast<size_t>(2166136261UL);
119 const char* __cptr = reinterpret_cast<const char*>(__ptr);
120 for (; __clength; --__clength)
121 {
122 __result ^= static_cast<size_t>(*__cptr++);
123 __result *= static_cast<size_t>(16777619UL);
124 }
125 return __result;
126 }
127 };
128
129 template<>
130 struct _Fnv_hash_base<8>
131 {
132 template<typename _Tp>
133 static size_t
134 hash(const _Tp* __ptr, size_t __clength)
135 {
136 size_t __result
137 = static_cast<size_t>(14695981039346656037ULL);
138 const char* __cptr = reinterpret_cast<const char*>(__ptr);
139 for (; __clength; --__clength)
140 {
141 __result ^= static_cast<size_t>(*__cptr++);
142 __result *= static_cast<size_t>(1099511628211ULL);
143 }
144 return __result;
145 }
146 };
147
148 struct _Fnv_hash
149 : public _Fnv_hash_base<sizeof(size_t)>
150 {
151 using _Fnv_hash_base<sizeof(size_t)>::hash;
152
153 template<typename _Tp>
154 static size_t
155 hash(const _Tp& __val)
156 { return hash(&__val, sizeof(__val)); }
157 };
158
159 /// Explicit specializations for float.
160 template<>
161 inline size_t
162 hash<float>::operator()(float __val) const
163 {
164 // 0 and -0 both hash to zero.
165 return __val != 0.0f ? std::tr1::_Fnv_hash::hash(__val) : 0;
166 }
167
168 /// Explicit specializations for double.
169 template<>
170 inline size_t
171 hash<double>::operator()(double __val) const
172 {
173 // 0 and -0 both hash to zero.
174 return __val != 0.0 ? std::tr1::_Fnv_hash::hash(__val) : 0;
175 }
176
177 /// Explicit specializations for long double.
178 template<>
179 _GLIBCXX_PURE size_t
180 hash<long double>::operator()(long double __val) const;
181
182 /// Explicit specialization of member operator for non-builtin types.
183 template<>
184 _GLIBCXX_PURE size_t
185 hash<string>::operator()(string) const;
186
187 template<>
188 _GLIBCXX_PURE size_t
189 hash<const string&>::operator()(const string&) const;
190
191 #ifdef _GLIBCXX_USE_WCHAR_T
192 template<>
193 _GLIBCXX_PURE size_t
194 hash<wstring>::operator()(wstring) const;
195
196 template<>
197 _GLIBCXX_PURE size_t
198 hash<const wstring&>::operator()(const wstring&) const;
199 #endif
200 }
201
202 _GLIBCXX_END_NAMESPACE_VERSION
203 }
204
205 #endif // _GLIBCXX_TR1_FUNCTIONAL_HASH_H
206