| //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file provides a template class that determines if a type is a class or |
| // not. The basic mechanism, based on using the pointer to member function of |
| // a zero argument to a function was "boosted" from the boost type_traits |
| // library. See http://www.boost.org/ for all the gory details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_TYPE_TRAITS_H |
| #define LLVM_SUPPORT_TYPE_TRAITS_H |
| |
| #include <cstddef> |
| #include <utility> |
| |
| // This is actually the conforming implementation which works with abstract |
| // classes. However, enough compilers have trouble with it that most will use |
| // the one in boost/type_traits/object_traits.hpp. This implementation actually |
| // works with VC7.0, but other interactions seem to fail when we use it. |
| |
| namespace llvm { |
| |
| namespace dont_use |
| { |
| // These two functions should never be used. They are helpers to |
| // the is_class template below. They cannot be located inside |
| // is_class because doing so causes at least GCC to think that |
| // the value of the "value" enumerator is not constant. Placing |
| // them out here (for some strange reason) allows the sizeof |
| // operator against them to magically be constant. This is |
| // important to make the is_class<T>::value idiom zero cost. it |
| // evaluates to a constant 1 or 0 depending on whether the |
| // parameter T is a class or not (respectively). |
| template<typename T> char is_class_helper(void(T::*)()); |
| template<typename T> double is_class_helper(...); |
| } |
| |
| template <typename T> |
| struct is_class |
| { |
| // is_class<> metafunction due to Paul Mensonides (leavings@attbi.com). For |
| // more details: |
| // http://groups.google.com/groups?hl=en&selm=000001c1cc83%24e154d5e0%247772e50c%40c161550a&rnum=1 |
| public: |
| enum { value = sizeof(char) == sizeof(dont_use::is_class_helper<T>(0)) }; |
| }; |
| |
| |
| /// isPodLike - This is a type trait that is used to determine whether a given |
| /// type can be copied around with memcpy instead of running ctors etc. |
| template <typename T> |
| struct isPodLike { |
| // If we don't know anything else, we can (at least) assume that all non-class |
| // types are PODs. |
| static const bool value = !is_class<T>::value; |
| }; |
| |
| // std::pair's are pod-like if their elements are. |
| template<typename T, typename U> |
| struct isPodLike<std::pair<T, U> > { |
| static const bool value = isPodLike<T>::value & isPodLike<U>::value; |
| }; |
| |
| |
| /// \brief Metafunction that determines whether the two given types are |
| /// equivalent. |
| template<typename T, typename U> |
| struct is_same { |
| static const bool value = false; |
| }; |
| |
| template<typename T> |
| struct is_same<T, T> { |
| static const bool value = true; |
| }; |
| |
| // enable_if_c - Enable/disable a template based on a metafunction |
| template<bool Cond, typename T = void> |
| struct enable_if_c { |
| typedef T type; |
| }; |
| |
| template<typename T> struct enable_if_c<false, T> { }; |
| |
| // enable_if - Enable/disable a template based on a metafunction |
| template<typename Cond, typename T = void> |
| struct enable_if : public enable_if_c<Cond::value, T> { }; |
| |
| namespace dont_use { |
| template<typename Base> char base_of_helper(const volatile Base*); |
| template<typename Base> double base_of_helper(...); |
| } |
| |
| /// is_base_of - Metafunction to determine whether one type is a base class of |
| /// (or identical to) another type. |
| template<typename Base, typename Derived> |
| struct is_base_of { |
| static const bool value |
| = is_class<Base>::value && is_class<Derived>::value && |
| sizeof(char) == sizeof(dont_use::base_of_helper<Base>((Derived*)0)); |
| }; |
| |
| // remove_pointer - Metafunction to turn Foo* into Foo. Defined in |
| // C++0x [meta.trans.ptr]. |
| template <typename T> struct remove_pointer { typedef T type; }; |
| template <typename T> struct remove_pointer<T*> { typedef T type; }; |
| template <typename T> struct remove_pointer<T*const> { typedef T type; }; |
| template <typename T> struct remove_pointer<T*volatile> { typedef T type; }; |
| template <typename T> struct remove_pointer<T*const volatile> { |
| typedef T type; }; |
| |
| template <bool, typename T, typename F> |
| struct conditional { typedef T type; }; |
| |
| template <typename T, typename F> |
| struct conditional<false, T, F> { typedef F type; }; |
| |
| } |
| |
| #endif |