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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_TEMPLATE_UTIL_H_
+#define BASE_TEMPLATE_UTIL_H_
+#pragma once
+
+#include <cstddef> // For size_t.
+
+#include "build/build_config.h"
+
+namespace base {
+
+// template definitions from tr1
+
+template<class T, T v>
+struct integral_constant {
+ static const T value = v;
+ typedef T value_type;
+ typedef integral_constant<T, v> type;
+};
+
+template <class T, T v> const T integral_constant<T, v>::value;
+
+typedef integral_constant<bool, true> true_type;
+typedef integral_constant<bool, false> false_type;
+
+template <class T> struct is_pointer : false_type {};
+template <class T> struct is_pointer<T*> : true_type {};
+
+template <class T, class U> struct is_same : public false_type {};
+template <class T> struct is_same<T,T> : true_type {};
+
+template<class> struct is_array : public false_type {};
+template<class T, size_t n> struct is_array<T[n]> : public true_type {};
+template<class T> struct is_array<T[]> : public true_type {};
+
+template <class T> struct is_non_const_reference : false_type {};
+template <class T> struct is_non_const_reference<T&> : true_type {};
+template <class T> struct is_non_const_reference<const T&> : false_type {};
+
+template <class T> struct is_void : false_type {};
+template <> struct is_void<void> : true_type {};
+
+namespace internal {
+
+// Types YesType and NoType are guaranteed such that sizeof(YesType) <
+// sizeof(NoType).
+typedef char YesType;
+
+struct NoType {
+ YesType dummy[2];
+};
+
+// This class is an implementation detail for is_convertible, and you
+// don't need to know how it works to use is_convertible. For those
+// who care: we declare two different functions, one whose argument is
+// of type To and one with a variadic argument list. We give them
+// return types of different size, so we can use sizeof to trick the
+// compiler into telling us which function it would have chosen if we
+// had called it with an argument of type From. See Alexandrescu's
+// _Modern C++ Design_ for more details on this sort of trick.
+
+struct ConvertHelper {
+ template <typename To>
+ static YesType Test(To);
+
+ template <typename To>
+ static NoType Test(...);
+
+ template <typename From>
+ static From Create();
+};
+
+// Used to determine if a type is a struct/union/class. Inspired by Boost's
+// is_class type_trait implementation.
+struct IsClassHelper {
+ template <typename C>
+ static YesType Test(void(C::*)(void));
+
+ template <typename C>
+ static NoType Test(...);
+};
+
+} // namespace internal
+
+// Inherits from true_type if From is convertible to To, false_type otherwise.
+//
+// Note that if the type is convertible, this will be a true_type REGARDLESS
+// of whether or not the conversion would emit a warning.
+template <typename From, typename To>
+struct is_convertible
+ : integral_constant<bool,
+ sizeof(internal::ConvertHelper::Test<To>(
+ internal::ConvertHelper::Create<From>())) ==
+ sizeof(internal::YesType)> {
+};
+
+template <typename T>
+struct is_class
+ : integral_constant<bool,
+ sizeof(internal::IsClassHelper::Test<T>(0)) ==
+ sizeof(internal::YesType)> {
+};
+
+} // namespace base
+
+#endif // BASE_TEMPLATE_UTIL_H_