1 //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file provides a template class that determines if a type is a class or 11 // not. The basic mechanism, based on using the pointer to member function of 12 // a zero argument to a function was "boosted" from the boost type_traits 13 // library. See http://www.boost.org/ for all the gory details. 14 // 15 //===----------------------------------------------------------------------===// 16 17 #ifndef LLVM_SUPPORT_TYPE_TRAITS_H 18 #define LLVM_SUPPORT_TYPE_TRAITS_H 19 20 #include "llvm/Support/DataTypes.h" 21 #include <cstddef> 22 #include <utility> 23 24 // This is actually the conforming implementation which works with abstract 25 // classes. However, enough compilers have trouble with it that most will use 26 // the one in boost/type_traits/object_traits.hpp. This implementation actually 27 // works with VC7.0, but other interactions seem to fail when we use it. 28 29 namespace llvm { 30 31 namespace dont_use 32 { 33 // These two functions should never be used. They are helpers to 34 // the is_class template below. They cannot be located inside 35 // is_class because doing so causes at least GCC to think that 36 // the value of the "value" enumerator is not constant. Placing 37 // them out here (for some strange reason) allows the sizeof 38 // operator against them to magically be constant. This is 39 // important to make the is_class<T>::value idiom zero cost. it 40 // evaluates to a constant 1 or 0 depending on whether the 41 // parameter T is a class or not (respectively). 42 template<typename T> char is_class_helper(void(T::*)()); 43 template<typename T> double is_class_helper(...); 44 } 45 46 template <typename T> 47 struct is_class 48 { 49 // is_class<> metafunction due to Paul Mensonides (leavings (at) attbi.com). For 50 // more details: 51 // http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1 52 public: 53 enum { value = sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)) }; 54 }; 55 56 57 /// isPodLike - This is a type trait that is used to determine whether a given 58 /// type can be copied around with memcpy instead of running ctors etc. 59 template <typename T> 60 struct isPodLike { 61 // If we don't know anything else, we can (at least) assume that all non-class 62 // types are PODs. 63 static const bool value = !is_class<T>::value; 64 }; 65 66 // std::pair's are pod-like if their elements are. 67 template<typename T, typename U> 68 struct isPodLike<std::pair<T, U> > { 69 static const bool value = isPodLike<T>::value && isPodLike<U>::value; 70 }; 71 72 73 template <class T, T v> 74 struct integral_constant { 75 typedef T value_type; 76 static const value_type value = v; 77 typedef integral_constant<T,v> type; 78 operator value_type() { return value; } 79 }; 80 81 typedef integral_constant<bool, true> true_type; 82 typedef integral_constant<bool, false> false_type; 83 84 /// \brief Metafunction that determines whether the two given types are 85 /// equivalent. 86 template<typename T, typename U> struct is_same : public false_type {}; 87 template<typename T> struct is_same<T, T> : public true_type {}; 88 89 /// \brief Metafunction that removes const qualification from a type. 90 template <typename T> struct remove_const { typedef T type; }; 91 template <typename T> struct remove_const<const T> { typedef T type; }; 92 93 /// \brief Metafunction that removes volatile qualification from a type. 94 template <typename T> struct remove_volatile { typedef T type; }; 95 template <typename T> struct remove_volatile<volatile T> { typedef T type; }; 96 97 /// \brief Metafunction that removes both const and volatile qualification from 98 /// a type. 99 template <typename T> struct remove_cv { 100 typedef typename remove_const<typename remove_volatile<T>::type>::type type; 101 }; 102 103 /// \brief Helper to implement is_integral metafunction. 104 template <typename T> struct is_integral_impl : false_type {}; 105 template <> struct is_integral_impl< bool> : true_type {}; 106 template <> struct is_integral_impl< char> : true_type {}; 107 template <> struct is_integral_impl< signed char> : true_type {}; 108 template <> struct is_integral_impl<unsigned char> : true_type {}; 109 template <> struct is_integral_impl< wchar_t> : true_type {}; 110 template <> struct is_integral_impl< short> : true_type {}; 111 template <> struct is_integral_impl<unsigned short> : true_type {}; 112 template <> struct is_integral_impl< int> : true_type {}; 113 template <> struct is_integral_impl<unsigned int> : true_type {}; 114 template <> struct is_integral_impl< long> : true_type {}; 115 template <> struct is_integral_impl<unsigned long> : true_type {}; 116 template <> struct is_integral_impl< long long> : true_type {}; 117 template <> struct is_integral_impl<unsigned long long> : true_type {}; 118 119 /// \brief Metafunction that determines whether the given type is an integral 120 /// type. 121 template <typename T> 122 struct is_integral : is_integral_impl<T> {}; 123 124 /// \brief Metafunction to remove reference from a type. 125 template <typename T> struct remove_reference { typedef T type; }; 126 template <typename T> struct remove_reference<T&> { typedef T type; }; 127 128 /// \brief Metafunction that determines whether the given type is a pointer 129 /// type. 130 template <typename T> struct is_pointer : false_type {}; 131 template <typename T> struct is_pointer<T*> : true_type {}; 132 template <typename T> struct is_pointer<T* const> : true_type {}; 133 template <typename T> struct is_pointer<T* volatile> : true_type {}; 134 template <typename T> struct is_pointer<T* const volatile> : true_type {}; 135 136 /// \brief Metafunction that determines whether the given type is either an 137 /// integral type or an enumeration type. 138 /// 139 /// Note that this accepts potentially more integral types than we whitelist 140 /// above for is_integral because it is based on merely being convertible 141 /// implicitly to an integral type. 142 template <typename T> class is_integral_or_enum { 143 // Provide an overload which can be called with anything implicitly 144 // convertible to an unsigned long long. This should catch integer types and 145 // enumeration types at least. We blacklist classes with conversion operators 146 // below. 147 static double check_int_convertible(unsigned long long); 148 static char check_int_convertible(...); 149 150 typedef typename remove_reference<T>::type UnderlyingT; 151 static UnderlyingT &nonce_instance; 152 153 public: 154 enum { 155 value = (!is_class<UnderlyingT>::value && !is_pointer<UnderlyingT>::value && 156 !is_same<UnderlyingT, float>::value && 157 !is_same<UnderlyingT, double>::value && 158 sizeof(char) != sizeof(check_int_convertible(nonce_instance))) 159 }; 160 }; 161 162 // enable_if_c - Enable/disable a template based on a metafunction 163 template<bool Cond, typename T = void> 164 struct enable_if_c { 165 typedef T type; 166 }; 167 168 template<typename T> struct enable_if_c<false, T> { }; 169 170 // enable_if - Enable/disable a template based on a metafunction 171 template<typename Cond, typename T = void> 172 struct enable_if : public enable_if_c<Cond::value, T> { }; 173 174 namespace dont_use { 175 template<typename Base> char base_of_helper(const volatile Base*); 176 template<typename Base> double base_of_helper(...); 177 } 178 179 /// is_base_of - Metafunction to determine whether one type is a base class of 180 /// (or identical to) another type. 181 template<typename Base, typename Derived> 182 struct is_base_of { 183 static const bool value 184 = is_class<Base>::value && is_class<Derived>::value && 185 sizeof(char) == sizeof(dont_use::base_of_helper<Base>((Derived*)0)); 186 }; 187 188 // remove_pointer - Metafunction to turn Foo* into Foo. Defined in 189 // C++0x [meta.trans.ptr]. 190 template <typename T> struct remove_pointer { typedef T type; }; 191 template <typename T> struct remove_pointer<T*> { typedef T type; }; 192 template <typename T> struct remove_pointer<T*const> { typedef T type; }; 193 template <typename T> struct remove_pointer<T*volatile> { typedef T type; }; 194 template <typename T> struct remove_pointer<T*const volatile> { 195 typedef T type; }; 196 197 template <bool, typename T, typename F> 198 struct conditional { typedef T type; }; 199 200 template <typename T, typename F> 201 struct conditional<false, T, F> { typedef F type; }; 202 203 } 204 205 #endif 206
