libstdc++-v3/include/tr1_impl/functional_hash.h

   1 // TR1 functional -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008 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 2, 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 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING.  If not, write to the Free
  18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19 // USA.
  20
  21 // As a special exception, you may use this file as part of a free software
  22 // library without restriction.  Specifically, if other files instantiate
  23 // templates or use macros or inline functions from this file, or you compile
  24 // this file and link it with other files to produce an executable, this
  25 // file does not by itself cause the resulting executable to be covered by
  26 // the GNU General Public License.  This exception does not however
  27 // invalidate any other reasons why the executable file might be covered by
  28 // the GNU General Public License.
  29
  30 /** @file tr1_impl/functional_hash.h
  31  *  This is an internal header file, included by other library headers.
  32  *  You should not attempt to use it directly.
  33  */
  34
  35 namespace std
  36 {
  37 _GLIBCXX_BEGIN_NAMESPACE_TR1
  38
  39   /// Class template hash.
  40   // Declaration of default hash functor std::tr1::hash.  The types for
  41   // which std::tr1::hash<T> is well-defined is in clause 6.3.3. of the PDTR.
  42   template<typename _Tp>
  43     struct hash : public std::unary_function<_Tp, size_t>
  44     {
  45       size_t
  46       operator()(_Tp __val) const;
  47     };
  48
  49   /// Partial specializations for pointer types.
  50   template<typename _Tp>
  51     struct hash<_Tp*> : public std::unary_function<_Tp*, size_t>
  52     {
  53       size_t
  54       operator()(_Tp* __p) const
  55       { return reinterpret_cast<size_t>(__p); }
  56     };
  57
  58   /// Explicit specializations for integer types.
  59 #define _TR1_hashtable_define_trivial_hash(_Tp)         \
  60   template<>                                            \
  61     inline size_t                                       \
  62     hash<_Tp>::operator()(_Tp __val) const              \
  63     { return static_cast<size_t>(__val); }
  64
  65   _TR1_hashtable_define_trivial_hash(bool);
  66   _TR1_hashtable_define_trivial_hash(char);
  67   _TR1_hashtable_define_trivial_hash(signed char);
  68   _TR1_hashtable_define_trivial_hash(unsigned char);
  69   _TR1_hashtable_define_trivial_hash(wchar_t);
  70 #ifdef _GLIBCXX_INCLUDE_AS_CXX0X
  71   _TR1_hashtable_define_trivial_hash(char16_t);
  72   _TR1_hashtable_define_trivial_hash(char32_t);
  73 #endif
  74   _TR1_hashtable_define_trivial_hash(short);
  75   _TR1_hashtable_define_trivial_hash(int);
  76   _TR1_hashtable_define_trivial_hash(long);
  77   _TR1_hashtable_define_trivial_hash(long long);
  78   _TR1_hashtable_define_trivial_hash(unsigned short);
  79   _TR1_hashtable_define_trivial_hash(unsigned int);
  80   _TR1_hashtable_define_trivial_hash(unsigned long);
  81   _TR1_hashtable_define_trivial_hash(unsigned long long);
  82
  83 #undef _TR1_hashtable_define_trivial_hash
  84
  85   // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
  86   // (Used by the next specializations of std::tr1::hash.)
  87
  88   /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
  89   template<size_t = sizeof(size_t)>
  90     struct _Fnv_hash
  91     {
  92       static size_t
  93       hash(const char* __first, size_t __length)
  94       {
  95         size_t __result = 0;
  96         for (; __length > 0; --__length)
  97           __result = (__result * 131) + *__first++;
  98         return __result;
  99       }
 100     };
 101
 102   template<>
 103     struct _Fnv_hash<4>
 104     {
 105       static size_t
 106       hash(const char* __first, size_t __length)
 107       {
 108         size_t __result = static_cast<size_t>(2166136261UL);
 109         for (; __length > 0; --__length)
 110           {
 111             __result ^= static_cast<size_t>(*__first++);
 112             __result *= static_cast<size_t>(16777619UL);
 113           }
 114         return __result;
 115       }
 116     };
 117
 118   template<>
 119     struct _Fnv_hash<8>
 120     {
 121       static size_t
 122       hash(const char* __first, size_t __length)
 123       {
 124         size_t __result =
 125           static_cast<size_t>(14695981039346656037ULL);
 126         for (; __length > 0; --__length)
 127           {
 128             __result ^= static_cast<size_t>(*__first++);
 129             __result *= static_cast<size_t>(1099511628211ULL);
 130           }
 131         return __result;
 132       }
 133     };
 134
 135   /// Explicit specializations for float.
 136   template<>
 137     inline size_t
 138     hash<float>::operator()(float __val) const
 139     {
 140       size_t __result = 0;
 141
 142       // 0 and -0 both hash to zero.
 143       if (__val != 0.0f)
 144         __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
 145                                      sizeof(__val));
 146       return __result;
 147     };
 148
 149   /// Explicit specializations for double.
 150   template<>
 151     inline size_t
 152     hash<double>::operator()(double __val) const
 153     {
 154         size_t __result = 0;
 155
 156         // 0 and -0 both hash to zero.
 157         if (__val != 0.0)
 158           __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
 159                                        sizeof(__val));
 160         return __result;
 161     };
 162
 163   /// Explicit specializations for long double.
 164   template<>
 165     size_t
 166     hash<long double>::operator()(long double __val) const;
 167
 168   /// Explicit specialization of member operator for non-builtin types.
 169   template<>
 170     size_t
 171     hash<string>::operator()(string) const;
 172
 173   template<>
 174     size_t
 175     hash<const string&>::operator()(const string&) const;
 176
 177 #ifdef _GLIBCXX_USE_WCHAR_T
 178   template<>
 179     size_t
 180     hash<wstring>::operator()(wstring) const;
 181
 182   template<>
 183     size_t
 184     hash<const wstring&>::operator()(const wstring&) const;
 185 #endif
 186
 187 _GLIBCXX_END_NAMESPACE_TR1
 188 }