1 // TR1 functional_hash.h header -*- C++ -*-
2
3 // Copyright (C) 2007-2017 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 namespace tr1
38 {
39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
40
41 /// Class template hash.
42 // Declaration of default hash functor std::tr1::hash. The types for
43 // which std::tr1::hash<T> is well-defined is in clause 6.3.3. of the PDTR.
44 template<typename _Tp>
45 struct hash : public std::unary_function<_Tp, size_t>
46 {
47 size_t
48 operator()(_Tp __val) const;
49 };
50
51 /// Partial specializations for pointer types.
52 template<typename _Tp>
53 struct hash<_Tp*> : public std::unary_function<_Tp*, size_t>
54 {
55 size_t
56 operator()(_Tp* __p) const
57 { return reinterpret_cast<size_t>(__p); }
58 };
59
60 /// Explicit specializations for integer types.
61 #define _TR1_hashtable_define_trivial_hash(_Tp) \
62 template<> \
63 inline size_t \
64 hash<_Tp>::operator()(_Tp __val) const \
65 { return static_cast<size_t>(__val); }
66
67 _TR1_hashtable_define_trivial_hash(bool);
68 _TR1_hashtable_define_trivial_hash(char);
69 _TR1_hashtable_define_trivial_hash(signed char);
70 _TR1_hashtable_define_trivial_hash(unsigned char);
71 _TR1_hashtable_define_trivial_hash(wchar_t);
72 _TR1_hashtable_define_trivial_hash(short);
73 _TR1_hashtable_define_trivial_hash(int);
74 _TR1_hashtable_define_trivial_hash(long);
75 _TR1_hashtable_define_trivial_hash(long long);
76 _TR1_hashtable_define_trivial_hash(unsigned short);
77 _TR1_hashtable_define_trivial_hash(unsigned int);
78 _TR1_hashtable_define_trivial_hash(unsigned long);
79 _TR1_hashtable_define_trivial_hash(unsigned long long);
80
81 #undef _TR1_hashtable_define_trivial_hash
82
83 // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
84 // (Used by the next specializations of std::tr1::hash.)
85
86 // N.B. These functions should work on unsigned char, otherwise they do not
87 // correctly implement the FNV-1a algorithm (see PR59406).
88 // The existing behaviour is retained for backwards compatibility.
89
90 /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
91 template<size_t>
92 struct _Fnv_hash_base
93 {
94 template<typename _Tp>
95 static size_t
96 hash(const _Tp* __ptr, size_t __clength)
97 {
98 size_t __result = 0;
99 const char* __cptr = reinterpret_cast<const char*>(__ptr);
100 for (; __clength; --__clength)
101 __result = (__result * 131) + *__cptr++;
102 return __result;
103 }
104 };
105
106 template<>
107 struct _Fnv_hash_base<4>
108 {
109 template<typename _Tp>
110 static size_t
111 hash(const _Tp* __ptr, size_t __clength)
112 {
113 size_t __result = static_cast<size_t>(2166136261UL);
114 const char* __cptr = reinterpret_cast<const char*>(__ptr);
115 for (; __clength; --__clength)
116 {
117 __result ^= static_cast<size_t>(*__cptr++);
118 __result *= static_cast<size_t>(16777619UL);
119 }
120 return __result;
121 }
122 };
123
124 template<>
125 struct _Fnv_hash_base<8>
126 {
127 template<typename _Tp>
128 static size_t
129 hash(const _Tp* __ptr, size_t __clength)
130 {
131 size_t __result
132 = static_cast<size_t>(14695981039346656037ULL);
133 const char* __cptr = reinterpret_cast<const char*>(__ptr);
134 for (; __clength; --__clength)
135 {
136 __result ^= static_cast<size_t>(*__cptr++);
137 __result *= static_cast<size_t>(1099511628211ULL);
138 }
139 return __result;
140 }
141 };
142
143 struct _Fnv_hash
144 : public _Fnv_hash_base<sizeof(size_t)>
145 {
146 using _Fnv_hash_base<sizeof(size_t)>::hash;
147
148 template<typename _Tp>
149 static size_t
150 hash(const _Tp& __val)
151 { return hash(&__val, sizeof(__val)); }
152 };
153
154 /// Explicit specializations for float.
155 template<>
156 inline size_t
157 hash<float>::operator()(float __val) const
158 {
159 // 0 and -0 both hash to zero.
160 return __val != 0.0f ? std::tr1::_Fnv_hash::hash(__val) : 0;
161 }
162
163 /// Explicit specializations for double.
164 template<>
165 inline size_t
166 hash<double>::operator()(double __val) const
167 {
168 // 0 and -0 both hash to zero.
169 return __val != 0.0 ? std::tr1::_Fnv_hash::hash(__val) : 0;
170 }
171
172 /// Explicit specializations for long double.
173 template<>
174 _GLIBCXX_PURE size_t
175 hash<long double>::operator()(long double __val) const;
176
177 /// Explicit specialization of member operator for non-builtin types.
178 template<>
179 _GLIBCXX_PURE size_t
180 hash<string>::operator()(string) const;
181
182 template<>
183 _GLIBCXX_PURE size_t
184 hash<const string&>::operator()(const string&) const;
185
186 #ifdef _GLIBCXX_USE_WCHAR_T
187 template<>
188 _GLIBCXX_PURE size_t
189 hash<wstring>::operator()(wstring) const;
190
191 template<>
192 _GLIBCXX_PURE size_t
193 hash<const wstring&>::operator()(const wstring&) const;
194 #endif
195
196 _GLIBCXX_END_NAMESPACE_VERSION
197 }
198 }
199
200 #endif // _GLIBCXX_TR1_FUNCTIONAL_HASH_H
201