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

   1 // TR1 functional_hash.h header -*- 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/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 #ifndef _GLIBCXX_TR1_FUNCTIONAL_HASH_H
  31 #define _GLIBCXX_TR1_FUNCTIONAL_HASH_H 1
  32
  33 #pragma GCC system_header
  34
  35 namespace std
  36 {
  37 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   _TR1_hashtable_define_trivial_hash(short);
  71   _TR1_hashtable_define_trivial_hash(int);
  72   _TR1_hashtable_define_trivial_hash(long);
  73   _TR1_hashtable_define_trivial_hash(long long);
  74   _TR1_hashtable_define_trivial_hash(unsigned short);
  75   _TR1_hashtable_define_trivial_hash(unsigned int);
  76   _TR1_hashtable_define_trivial_hash(unsigned long);
  77   _TR1_hashtable_define_trivial_hash(unsigned long long);
  78
  79 #undef _TR1_hashtable_define_trivial_hash
  80
  81   // Fowler / Noll / Vo (FNV) Hash (type FNV-1a)
  82   // (Used by the next specializations of std::tr1::hash.)
  83
  84   /// Dummy generic implementation (for sizeof(size_t) != 4, 8).
  85   template<size_t = sizeof(size_t)>
  86     struct _Fnv_hash
  87     {
  88       static size_t
  89       hash(const char* __first, size_t __length)
  90       {
  91         size_t __result = 0;
  92         for (; __length > 0; --__length)
  93           __result = (__result * 131) + *__first++;
  94         return __result;
  95       }
  96     };
  97
  98   template<>
  99     struct _Fnv_hash<4>
 100     {
 101       static size_t
 102       hash(const char* __first, size_t __length)
 103       {
 104         size_t __result = static_cast<size_t>(2166136261UL);
 105         for (; __length > 0; --__length)
 106           {
 107             __result ^= static_cast<size_t>(*__first++);
 108             __result *= static_cast<size_t>(16777619UL);
 109           }
 110         return __result;
 111       }
 112     };
 113
 114   template<>
 115     struct _Fnv_hash<8>
 116     {
 117       static size_t
 118       hash(const char* __first, size_t __length)
 119       {
 120         size_t __result =
 121           static_cast<size_t>(14695981039346656037ULL);
 122         for (; __length > 0; --__length)
 123           {
 124             __result ^= static_cast<size_t>(*__first++);
 125             __result *= static_cast<size_t>(1099511628211ULL);
 126           }
 127         return __result;
 128       }
 129     };
 130
 131   /// Explicit specializations for float.
 132   template<>
 133     inline size_t
 134     hash<float>::operator()(float __val) const
 135     {
 136       size_t __result = 0;
 137
 138       // 0 and -0 both hash to zero.
 139       if (__val != 0.0f)
 140         __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
 141                                      sizeof(__val));
 142       return __result;
 143     };
 144
 145   /// Explicit specializations for double.
 146   template<>
 147     inline size_t
 148     hash<double>::operator()(double __val) const
 149     {
 150         size_t __result = 0;
 151
 152         // 0 and -0 both hash to zero.
 153         if (__val != 0.0)
 154           __result = _Fnv_hash<>::hash(reinterpret_cast<const char*>(&__val),
 155                                        sizeof(__val));
 156         return __result;
 157     };
 158
 159   /// Explicit specializations for long double.
 160   template<>
 161     _GLIBCXX_PURE size_t
 162     hash<long double>::operator()(long double __val) const;
 163
 164   /// Explicit specialization of member operator for non-builtin types.
 165   template<>
 166     _GLIBCXX_PURE size_t
 167     hash<string>::operator()(string) const;
 168
 169   template<>
 170     _GLIBCXX_PURE size_t
 171     hash<const string&>::operator()(const string&) const;
 172
 173 #ifdef _GLIBCXX_USE_WCHAR_T
 174   template<>
 175     _GLIBCXX_PURE size_t
 176     hash<wstring>::operator()(wstring) const;
 177
 178   template<>
 179     _GLIBCXX_PURE size_t
 180     hash<const wstring&>::operator()(const wstring&) const;
 181 #endif
 182 }
 183 }
 184
 185 #endif // _GLIBCXX_TR1_FUNCTIONAL_HASH_H