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
37namespace 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