objc4-493.9.tar.gz

[apple/objc4.git] / runtime / llvm-type_traits.h

diff --git a/runtime/llvm-type_traits.h b/runtime/llvm-type_traits.h
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+//===- 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 <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 objc {
+  
+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