libstdc++-v3/include/tr1/functional_hash.h

   1 // TR1 functional_hash.h header -*- C++ -*-
   2
   3 // Copyright (C) 2007-2023 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
  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