仿SGI STL的traits技法
首先是iterator traits，这个是用来萃取迭代器的特性的
1 #ifndef _STL_ITERATOR_H_ 2 #define _STL_ITERATOR_H_ 3 4 5 #include <cstddef> 6 /* 7 ** iterator_traits<Iterator> ----> 负责萃取迭代器的特性 8 */ 9 namespace zstd 10 { 11 struct inpt_iterator_tag{}; 12 struct outpt_iterator_tag{}; 13 struct forward_iterator_tag :public inpt_iterator_tag {}; 14 struct bidirectional_iterator_tag :public forward_iterator_tag {}; 15 struct random_access_iterator_tag :public bidirectional_iterator_tag {}; 16 17 template<class Category, class T, class Distance = ptrdiff_t, 18 class Pointer = T*, class Reference = T&> 19 struct iterator 20 { 21 typedef Category iterator_category; 22 typedef T value_type; 23 typedef Distance difference_type; 24 typedef Pointer pointer; 25 typedef Reference reference; 26 }; 27 28 template<class Iterator> 29 struct iterator_traits 30 { 31 typedef typename Iterator::Category iterator_category; 32 typedef typename Iterator::T value_type; 33 typedef typename Iterator::Distance difference_type; 34 typedef typename Iterator::Pointer pointer; 35 typedef typename Iterator::Reference reference; 36 }; 37 template<class T> 38 struct iterator_traits<T*> 39 { 40 typedef random_access_iterator_tag iterator_category; 41 typedef T value_type; 42 typedef ptrdiff_t difference_type; 43 typedef T* pointer; 44 typedef T& reference; 45 }; 46 template<class T> 47 struct iterator_traits<const T*> 48 { 49 typedef random_access_iterator_tag iterator_category; 50 typedef T value_type; 51 typedef ptrdiff_t difference_type; 52 typedef const T* pointer; 53 typedef const T& reference; 54 }; 55 56 template<class Iterator> 57 inline typename Iterator::iterator_category 58 iterator_category(const Iterator& It) 59 { 60 typedef typename Iterator::iterator_category category; 61 return category(); 62 } 63 template<class Iterator> 64 inline typename Iterator::value_type* 65 value_type(const Iterator& It) 66 { 67 return static_cast<typename iterator_traits<Iterator>::value_type*>(0); 68 } 69 template<class Iterator> 70 inline typename Iterator::difference_type* 71 difference_type(const Iterator& It) 72 { 73 return static_cast<typename iterator_traits<Iterator>::difference_type*>(0); 74 } 75 } 76 #endif
然后是type traits，这个是用来萃取c++语言型别（type）的特性的
1 #ifndef _TYPE_TRAITS_H_ 2 #define _TYPE_TRAITS_H_ 3 4 /* 5 ** _type_traits<T> ----> 负责萃取型别T的特性 6 */ 7 #include <iostream> 8 using namespace std; 9 namespace zstd 10 { 11 struct _true_type { void print(){ cout << "_true_type" << endl; } }; 12 struct _false_type { void print(){ cout << "_false_type" << endl; } }; 13 14 template<class T> 15 struct _type_traits 16 { 17 typedef _false_type has_trivial_default_constructor; 18 typedef _false_type has_trivial_copy_constructor; 19 typedef _false_type has_trivial_assignment_operator; 20 typedef _false_type has_trivial_destructor; 21 typedef _false_type is_POD_type; 22 }; 23 24 template<> 25 struct _type_traits<bool> 26 { 27 typedef _true_type has_trivial_default_constructor; 28 typedef _true_type has_trivial_copy_constructor; 29 typedef _true_type has_trivial_assignment_operator; 30 typedef _true_type has_trivial_destructor; 31 typedef _true_type is_POD_type; 32 }; 33 template<> 34 struct _type_traits<char> 35 { 36 typedef _true_type has_trivial_default_constructor; 37 typedef _true_type has_trivial_copy_constructor; 38 typedef _true_type has_trivial_assignment_operator; 39 typedef _true_type has_trivial_destructor; 40 typedef _true_type is_POD_type; 41 }; 42 template<> 43 struct _type_traits<unsigned char> 44 { 45 typedef _true_type has_trivial_default_constructor; 46 typedef _true_type has_trivial_copy_constructor; 47 typedef _true_type has_trivial_assignment_operator; 48 typedef _true_type has_trivial_destructor; 49 typedef _true_type is_POD_type; 50 }; 51 template<> 52 struct _type_traits<signed char> 53 { 54 typedef _true_type has_trivial_default_constructor; 55 typedef _true_type has_trivial_copy_constructor; 56 typedef _true_type has_trivial_assignment_operator; 57 typedef _true_type has_trivial_destructor; 58 typedef _true_type is_POD_type; 59 }; 60 template<> 61 struct _type_traits<wchar_t> 62 { 63 typedef _true_type has_trivial_default_constructor; 64 typedef _true_type has_trivial_copy_constructor; 65 typedef _true_type has_trivial_assignment_operator; 66 typedef _true_type has_trivial_destructor; 67 typedef _true_type is_POD_type; 68 }; 69 template<> 70 struct _type_traits<short> 71 { 72 typedef _true_type has_trivial_default_constructor; 73 typedef _true_type has_trivial_copy_constructor; 74 typedef _true_type has_trivial_assignment_operator; 75 typedef _true_type has_trivial_destructor; 76 typedef _true_type is_POD_type; 77 }; 78 template<> 79 struct _type_traits<unsigned short> 80 { 81 typedef _true_type has_trivial_default_constructor; 82 typedef _true_type has_trivial_copy_constructor; 83 typedef _true_type has_trivial_assignment_operator; 84 typedef _true_type has_trivial_destructor; 85 typedef _true_type is_POD_type; 86 }; 87 template<> 88 struct _type_traits<int> 89 { 90 typedef _true_type has_trivial_default_constructor; 91 typedef _true_type has_trivial_copy_constructor; 92 typedef _true_type has_trivial_assignment_operator; 93 typedef _true_type has_trivial_destructor; 94 typedef _true_type is_POD_type; 95 }; 96 template<> 97 struct _type_traits<unsigned int> 98 { 99 typedef _true_type has_trivial_default_constructor; 100 typedef _true_type has_trivial_copy_constructor; 101 typedef _true_type has_trivial_assignment_operator; 102 typedef _true_type has_trivial_destructor; 103 typedef _true_type is_POD_type; 104 }; 105 template<> 106 struct _type_traits<long> 107 { 108 typedef _true_type has_trivial_default_constructor; 109 typedef _true_type has_trivial_copy_constructor; 110 typedef _true_type has_trivial_assignment_operator; 111 typedef _true_type has_trivial_destructor; 112 typedef _true_type is_POD_type; 113 }; 114 template<> 115 struct _type_traits<unsigned long> 116 { 117 typedef _true_type has_trivial_default_constructor; 118 typedef _true_type has_trivial_copy_constructor; 119 typedef _true_type has_trivial_assignment_operator; 120 typedef _true_type has_trivial_destructor; 121 typedef _true_type is_POD_type; 122 }; 123 template<> 124 struct _type_traits<long long> 125 { 126 typedef _true_type has_trivial_default_constructor; 127 typedef _true_type has_trivial_copy_constructor; 128 typedef _true_type has_trivial_assignment_operator; 129 typedef _true_type has_trivial_destructor; 130 typedef _true_type is_POD_type; 131 }; 132 template<> 133 struct _type_traits<unsigned long long> 134 { 135 typedef _true_type has_trivial_default_constructor; 136 typedef _true_type has_trivial_copy_constructor; 137 typedef _true_type has_trivial_assignment_operator; 138 typedef _true_type has_trivial_destructor; 139 typedef _true_type is_POD_type; 140 }; 141 template<> 142 struct _type_traits<float> 143 { 144 typedef _true_type has_trivial_default_constructor; 145 typedef _true_type has_trivial_copy_constructor; 146 typedef _true_type has_trivial_assignment_operator; 147 typedef _true_type has_trivial_destructor; 148 typedef _true_type is_POD_type; 149 }; 150 template<> 151 struct _type_traits<double> 152 { 153 typedef _true_type has_trivial_default_constructor; 154 typedef _true_type has_trivial_copy_constructor; 155 typedef _true_type has_trivial_assignment_operator; 156 typedef _true_type has_trivial_destructor; 157 typedef _true_type is_POD_type; 158 }; 159 template<> 160 struct _type_traits<long double> 161 { 162 typedef _true_type has_trivial_default_constructor; 163 typedef _true_type has_trivial_copy_constructor; 164 typedef _true_type has_trivial_assignment_operator; 165 typedef _true_type has_trivial_destructor; 166 typedef _true_type is_POD_type; 167 }; 168 169 template<class T> 170 struct _type_traits<T*> 171 { 172 typedef _true_type has_trivial_default_constructor; 173 typedef _true_type has_trivial_copy_constructor; 174 typedef _true_type has_trivial_assignment_operator; 175 typedef _true_type has_trivial_destructor; 176 typedef _true_type is_POD_type; 177 }; 178 template<class T> 179 struct _type_traits<const T*> 180 { 181 typedef _true_type has_trivial_default_constructor; 182 typedef _true_type has_trivial_copy_constructor; 183 typedef _true_type has_trivial_assignment_operator; 184 typedef _true_type has_trivial_destructor; 185 typedef _true_type is_POD_type; 186 }; 187 template<> 188 struct _type_traits<char*> 189 { 190 typedef _true_type has_trivial_default_constructor; 191 typedef _true_type has_trivial_copy_constructor; 192 typedef _true_type has_trivial_assignment_operator; 193 typedef _true_type has_trivial_destructor; 194 typedef _true_type is_POD_type; 195 }; 196 template<> 197 struct _type_traits<unsigned char*> 198 { 199 typedef _true_type has_trivial_default_constructor; 200 typedef _true_type has_trivial_copy_constructor; 201 typedef _true_type has_trivial_assignment_operator; 202 typedef _true_type has_trivial_destructor; 203 typedef _true_type is_POD_type; 204 }; 205 template<> 206 struct _type_traits<signed char*> 207 { 208 typedef _true_type has_trivial_default_constructor; 209 typedef _true_type has_trivial_copy_constructor; 210 typedef _true_type has_trivial_assignment_operator; 211 typedef _true_type has_trivial_destructor; 212 typedef _true_type is_POD_type; 213 }; 214 template<> 215 struct _type_traits<const char*> 216 { 217 typedef _true_type has_trivial_default_constructor; 218 typedef _true_type has_trivial_copy_constructor; 219 typedef _true_type has_trivial_assignment_operator; 220 typedef _true_type has_trivial_destructor; 221 typedef _true_type is_POD_type; 222 }; 223 template<> 224 struct _type_traits<const unsigned char*> 225 { 226 typedef _true_type has_trivial_default_constructor; 227 typedef _true_type has_trivial_copy_constructor; 228 typedef _true_type has_trivial_assignment_operator; 229 typedef _true_type has_trivial_destructor; 230 typedef _true_type is_POD_type; 231 }; 232 template<> 233 struct _type_traits<const signed char*> 234 { 235 typedef _true_type has_trivial_default_constructor; 236 typedef _true_type has_trivial_copy_constructor; 237 typedef _true_type has_trivial_assignment_operator; 238 typedef _true_type has_trivial_destructor; 239 typedef _true_type is_POD_type; 240 }; 241 } 242 #endif
