libstdc++
tr1_impl/functional_hash.h
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1 // TR1 functional -*- C++ -*-
2 
3 // Copyright (C) 2007, 2008, 2009 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_impl/functional_hash.h
26  * This is an internal header file, included by other library headers.
27  * You should not attempt to use it directly.
28  */
29 
30 namespace std
31 {
32 _GLIBCXX_BEGIN_NAMESPACE_TR1
33 
34  /// Class template hash.
35  // Declaration of default hash functor std::tr1::hash. The types for
36  // which std::tr1::hash<T> is well-defined is in clause 6.3.3. of the PDTR.
37  template<typename _Tp>
38  struct hash : public std::unary_function<_Tp, size_t>
39  {
40  size_t
41  operator()(_Tp __val) const;
42  };
43 
44  /// Partial specializations for pointer types.
45  template<typename _Tp>
47  {
48  size_t
49  operator()(_Tp* __p) const
50  { return reinterpret_cast<size_t>(__p); }
51  };
52 
53  /// Explicit specializations for integer types.
54 #define _TR1_hashtable_define_trivial_hash(_Tp) \
55  template<> \
56  inline size_t \
57  hash<_Tp>::operator()(_Tp __val) const \
58  { return static_cast<size_t>(__val); }
59 
65 #ifdef _GLIBCXX_INCLUDE_AS_CXX0X
68 #endif
73  _TR1_hashtable_define_trivial_hash(unsigned short);
76  _TR1_hashtable_define_trivial_hash(unsigned long long);
77 
78 #undef _TR1_hashtable_define_trivial_hash
79 
80  // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
81  // (Used by the next specializations of std::tr1::hash.)
82 
83  /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
84  template<size_t = sizeof(size_t)>
85  struct _Fnv_hash
86  {
87  static size_t
88  hash(const char* __first, size_t __length)
89  {
90  size_t __result = 0;
91  for (; __length > 0; --__length)
92  __result = (__result * 131) + *__first++;
93  return __result;
94  }
95  };
96 
97  template<>
98  struct _Fnv_hash<4>
99  {
100  static size_t
101  hash(const char* __first, size_t __length)
102  {
103  size_t __result = static_cast<size_t>(2166136261UL);
104  for (; __length > 0; --__length)
105  {
106  __result ^= static_cast<size_t>(*__first++);
107  __result *= static_cast<size_t>(16777619UL);
108  }
109  return __result;
110  }
111  };
112 
113  template<>
114  struct _Fnv_hash<8>
115  {
116  static size_t
117  hash(const char* __first, size_t __length)
118  {
119  size_t __result =
120  static_cast<size_t>(14695981039346656037ULL);
121  for (; __length > 0; --__length)
122  {
123  __result ^= static_cast<size_t>(*__first++);
124  __result *= static_cast<size_t>(1099511628211ULL);
125  }
126  return __result;
127  }
128  };
129 
130  /// Explicit specializations for float.
131  template<>
132  inline size_t
133  hash<float>::operator()(float __val) const
134  {
135  size_t __result = 0;
136 
137  // 0 and -0 both hash to zero.
138  if (__val != 0.0f)
139  __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
140  sizeof(__val));
141  return __result;
142  };
143 
144  /// Explicit specializations for double.
145  template<>
146  inline size_t
147  hash<double>::operator()(double __val) const
148  {
149  size_t __result = 0;
150 
151  // 0 and -0 both hash to zero.
152  if (__val != 0.0)
153  __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
154  sizeof(__val));
155  return __result;
156  };
157 
158  /// Explicit specializations for long double.
159  template<>
160  size_t
161  hash<long double>::operator()(long double __val) const;
162 
163  /// Explicit specialization of member operator for non-builtin types.
164  template<>
165  size_t
166  hash<string>::operator()(string) const;
167 
168  template<>
169  size_t
170  hash<const string&>::operator()(const string&) const;
171 
172 #ifdef _GLIBCXX_USE_WCHAR_T
173  template<>
174  size_t
175  hash<wstring>::operator()(wstring) const;
176 
177  template<>
178  size_t
179  hash<const wstring&>::operator()(const wstring&) const;
180 #endif
181 
182 _GLIBCXX_END_NAMESPACE_TR1
183 }
Dummy generic implementation (for sizeof(size_t) != 4, 8).
#define _TR1_hashtable_define_trivial_hash(_Tp)
Explicit specializations for integer types.
Class template hash.