libstdc++
functional_hash.h
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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 
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  size_t
61  operator()(_Tp __val) const;
62  };
63 
64  /// Partial specializations for pointer types.
65  template<typename _Tp>
66  struct hash<_Tp*> : public __hash_base<size_t, _Tp*>
67  {
68  size_t
69  operator()(_Tp* __p) const
70  { return reinterpret_cast<size_t>(__p); }
71  };
72 
73  // Explicit specializations for integer types.
74 #define _Cxx_hashtable_define_trivial_hash(_Tp) \
75  template<> \
76  inline size_t \
77  hash<_Tp>::operator()(_Tp __val) const \
78  { return static_cast<size_t>(__val); }
79 
80  /// Explicit specialization for bool.
81  _Cxx_hashtable_define_trivial_hash(bool);
82 
83  /// Explicit specialization for char.
84  _Cxx_hashtable_define_trivial_hash(char);
85 
86  /// Explicit specialization for signed char.
87  _Cxx_hashtable_define_trivial_hash(signed char);
88 
89  /// Explicit specialization for unsigned char.
90  _Cxx_hashtable_define_trivial_hash(unsigned char);
91 
92  /// Explicit specialization for wchar_t.
93  _Cxx_hashtable_define_trivial_hash(wchar_t);
94 
95  /// Explicit specialization for char16_t.
96  _Cxx_hashtable_define_trivial_hash(char16_t);
97 
98  /// Explicit specialization for char32_t.
99  _Cxx_hashtable_define_trivial_hash(char32_t);
100 
101  /// Explicit specialization for short.
102  _Cxx_hashtable_define_trivial_hash(short);
103 
104  /// Explicit specialization for int.
105  _Cxx_hashtable_define_trivial_hash(int);
106 
107  /// Explicit specialization for long.
108  _Cxx_hashtable_define_trivial_hash(long);
109 
110  /// Explicit specialization for long long.
111  _Cxx_hashtable_define_trivial_hash(long long);
112 
113  /// Explicit specialization for unsigned short.
114  _Cxx_hashtable_define_trivial_hash(unsigned short);
115 
116  /// Explicit specialization for unsigned int.
117  _Cxx_hashtable_define_trivial_hash(unsigned int);
118 
119  /// Explicit specialization for unsigned long.
120  _Cxx_hashtable_define_trivial_hash(unsigned long);
121 
122  /// Explicit specialization for unsigned long long.
123  _Cxx_hashtable_define_trivial_hash(unsigned long long);
124 
125 #undef _Cxx_hashtable_define_trivial_hash
126 
127  struct _Hash_impl
128  {
129  static size_t
130  hash(const void* __ptr, size_t __clength,
131  size_t __seed = static_cast<size_t>(0xc70f6907UL))
132  { return _Hash_bytes(__ptr, __clength, __seed); }
133 
134  template<typename _Tp>
135  static size_t
136  hash(const _Tp& __val)
137  { return hash(&__val, sizeof(__val)); }
138 
139  template<typename _Tp>
140  static size_t
141  __hash_combine(const _Tp& __val, size_t __hash)
142  { return hash(&__val, sizeof(__val), __hash); }
143  };
144 
145  struct _Fnv_hash_impl
146  {
147  static size_t
148  hash(const void* __ptr, size_t __clength,
149  size_t __seed = static_cast<size_t>(2166136261UL))
150  { return _Fnv_hash_bytes(__ptr, __clength, __seed); }
151 
152  template<typename _Tp>
153  static size_t
154  hash(const _Tp& __val)
155  { return hash(&__val, sizeof(__val)); }
156 
157  template<typename _Tp>
158  static size_t
159  __hash_combine(const _Tp& __val, size_t __hash)
160  { return hash(&__val, sizeof(__val), __hash); }
161  };
162 
163  /// Specialization for float.
164  template<>
165  inline size_t
166  hash<float>::operator()(float __val) const
167  {
168  // 0 and -0 both hash to zero.
169  return __val != 0.0f ? std::_Hash_impl::hash(__val) : 0;
170  }
171 
172  /// Specialization for double.
173  template<>
174  inline size_t
175  hash<double>::operator()(double __val) const
176  {
177  // 0 and -0 both hash to zero.
178  return __val != 0.0 ? std::_Hash_impl::hash(__val) : 0;
179  }
180 
181  /// Specialization for long double.
182  template<>
183  _GLIBCXX_PURE size_t
184  hash<long double>::operator()(long double __val) const;
185 
186  // @} group hashes
187 
188 _GLIBCXX_END_NAMESPACE_VERSION
189 } // namespace
190 
191 #endif // _FUNCTIONAL_HASH_H
Primary class template hash.
Definition: system_error:112