ajwong@chromium.org | c711b82 | 2011-05-17 07:35:14 +0900 | [diff] [blame] | 1 | // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
willchan@chromium.org | b9b021a | 2010-06-16 04:39:24 +0900 | [diff] [blame] | 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef BASE_TEMPLATE_UTIL_H_ |
| 6 | #define BASE_TEMPLATE_UTIL_H_ |
willchan@chromium.org | b9b021a | 2010-06-16 04:39:24 +0900 | [diff] [blame] | 7 | |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 8 | #include <cstddef> // For size_t. |
| 9 | |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 10 | #include "build/build_config.h" |
| 11 | |
willchan@chromium.org | b9b021a | 2010-06-16 04:39:24 +0900 | [diff] [blame] | 12 | namespace base { |
| 13 | |
| 14 | // template definitions from tr1 |
| 15 | |
| 16 | template<class T, T v> |
| 17 | struct integral_constant { |
| 18 | static const T value = v; |
| 19 | typedef T value_type; |
| 20 | typedef integral_constant<T, v> type; |
| 21 | }; |
| 22 | |
| 23 | template <class T, T v> const T integral_constant<T, v>::value; |
| 24 | |
| 25 | typedef integral_constant<bool, true> true_type; |
| 26 | typedef integral_constant<bool, false> false_type; |
| 27 | |
| 28 | template <class T> struct is_pointer : false_type {}; |
| 29 | template <class T> struct is_pointer<T*> : true_type {}; |
| 30 | |
aa@chromium.org | d05701e | 2013-12-06 15:55:25 +0900 | [diff] [blame] | 31 | // Member function pointer detection up to four params. Add more as needed |
| 32 | // below. This is built-in to C++ 11, and we can remove this when we switch. |
| 33 | template<typename T> |
| 34 | struct is_member_function_pointer : false_type {}; |
| 35 | |
| 36 | template <typename R, typename Z> |
| 37 | struct is_member_function_pointer<R(Z::*)()> : true_type {}; |
| 38 | template <typename R, typename Z> |
| 39 | struct is_member_function_pointer<R(Z::*)() const> : true_type {}; |
| 40 | |
| 41 | template <typename R, typename Z, typename A> |
| 42 | struct is_member_function_pointer<R(Z::*)(A)> : true_type {}; |
| 43 | template <typename R, typename Z, typename A> |
| 44 | struct is_member_function_pointer<R(Z::*)(A) const> : true_type {}; |
| 45 | |
| 46 | template <typename R, typename Z, typename A, typename B> |
| 47 | struct is_member_function_pointer<R(Z::*)(A, B)> : true_type {}; |
| 48 | template <typename R, typename Z, typename A, typename B> |
| 49 | struct is_member_function_pointer<R(Z::*)(A, B) const> : true_type {}; |
| 50 | |
| 51 | template <typename R, typename Z, typename A, typename B, typename C> |
| 52 | struct is_member_function_pointer<R(Z::*)(A, B, C)> : true_type {}; |
| 53 | template <typename R, typename Z, typename A, typename B, typename C> |
| 54 | struct is_member_function_pointer<R(Z::*)(A, B, C) const> : true_type {}; |
| 55 | |
| 56 | template <typename R, typename Z, typename A, typename B, typename C, |
| 57 | typename D> |
| 58 | struct is_member_function_pointer<R(Z::*)(A, B, C, D)> : true_type {}; |
| 59 | template <typename R, typename Z, typename A, typename B, typename C, |
| 60 | typename D> |
| 61 | struct is_member_function_pointer<R(Z::*)(A, B, C, D) const> : true_type {}; |
| 62 | |
| 63 | |
ajwong@chromium.org | ec1750a | 2011-06-27 01:22:50 +0900 | [diff] [blame] | 64 | template <class T, class U> struct is_same : public false_type {}; |
| 65 | template <class T> struct is_same<T,T> : true_type {}; |
| 66 | |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 67 | template<class> struct is_array : public false_type {}; |
| 68 | template<class T, size_t n> struct is_array<T[n]> : public true_type {}; |
| 69 | template<class T> struct is_array<T[]> : public true_type {}; |
| 70 | |
| 71 | template <class T> struct is_non_const_reference : false_type {}; |
| 72 | template <class T> struct is_non_const_reference<T&> : true_type {}; |
| 73 | template <class T> struct is_non_const_reference<const T&> : false_type {}; |
| 74 | |
kinuko@chromium.org | 288f27a | 2013-10-22 18:18:20 +0900 | [diff] [blame] | 75 | template <class T> struct is_const : false_type {}; |
| 76 | template <class T> struct is_const<const T> : true_type {}; |
| 77 | |
ajwong@chromium.org | c711b82 | 2011-05-17 07:35:14 +0900 | [diff] [blame] | 78 | template <class T> struct is_void : false_type {}; |
| 79 | template <> struct is_void<void> : true_type {}; |
| 80 | |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 81 | namespace internal { |
| 82 | |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 83 | // Types YesType and NoType are guaranteed such that sizeof(YesType) < |
| 84 | // sizeof(NoType). |
| 85 | typedef char YesType; |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 86 | |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 87 | struct NoType { |
| 88 | YesType dummy[2]; |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 89 | }; |
| 90 | |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 91 | // This class is an implementation detail for is_convertible, and you |
| 92 | // don't need to know how it works to use is_convertible. For those |
| 93 | // who care: we declare two different functions, one whose argument is |
| 94 | // of type To and one with a variadic argument list. We give them |
| 95 | // return types of different size, so we can use sizeof to trick the |
| 96 | // compiler into telling us which function it would have chosen if we |
| 97 | // had called it with an argument of type From. See Alexandrescu's |
| 98 | // _Modern C++ Design_ for more details on this sort of trick. |
| 99 | |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 100 | struct ConvertHelper { |
ajwong@chromium.org | d5f6111 | 2011-02-17 07:37:58 +0900 | [diff] [blame] | 101 | template <typename To> |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 102 | static YesType Test(To); |
ajwong@chromium.org | d5f6111 | 2011-02-17 07:37:58 +0900 | [diff] [blame] | 103 | |
| 104 | template <typename To> |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 105 | static NoType Test(...); |
ajwong@chromium.org | d5f6111 | 2011-02-17 07:37:58 +0900 | [diff] [blame] | 106 | |
| 107 | template <typename From> |
ajwong@chromium.org | c9c79af | 2011-11-22 04:23:44 +0900 | [diff] [blame] | 108 | static From& Create(); |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 109 | }; |
| 110 | |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 111 | // Used to determine if a type is a struct/union/class. Inspired by Boost's |
| 112 | // is_class type_trait implementation. |
| 113 | struct IsClassHelper { |
| 114 | template <typename C> |
| 115 | static YesType Test(void(C::*)(void)); |
| 116 | |
| 117 | template <typename C> |
| 118 | static NoType Test(...); |
| 119 | }; |
| 120 | |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 121 | } // namespace internal |
| 122 | |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 123 | // Inherits from true_type if From is convertible to To, false_type otherwise. |
ajwong@chromium.org | d5f6111 | 2011-02-17 07:37:58 +0900 | [diff] [blame] | 124 | // |
| 125 | // Note that if the type is convertible, this will be a true_type REGARDLESS |
| 126 | // of whether or not the conversion would emit a warning. |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 127 | template <typename From, typename To> |
| 128 | struct is_convertible |
| 129 | : integral_constant<bool, |
ajwong@chromium.org | d5f6111 | 2011-02-17 07:37:58 +0900 | [diff] [blame] | 130 | sizeof(internal::ConvertHelper::Test<To>( |
| 131 | internal::ConvertHelper::Create<From>())) == |
| 132 | sizeof(internal::YesType)> { |
willchan@chromium.org | 97d688c | 2010-12-15 18:55:35 +0900 | [diff] [blame] | 133 | }; |
| 134 | |
ajwong@chromium.org | e2cca63 | 2011-02-15 10:27:38 +0900 | [diff] [blame] | 135 | template <typename T> |
| 136 | struct is_class |
| 137 | : integral_constant<bool, |
| 138 | sizeof(internal::IsClassHelper::Test<T>(0)) == |
| 139 | sizeof(internal::YesType)> { |
| 140 | }; |
| 141 | |
kinuko@chromium.org | 288f27a | 2013-10-22 18:18:20 +0900 | [diff] [blame] | 142 | template<bool B, class T = void> |
| 143 | struct enable_if {}; |
| 144 | |
| 145 | template<class T> |
| 146 | struct enable_if<true, T> { typedef T type; }; |
| 147 | |
willchan@chromium.org | b9b021a | 2010-06-16 04:39:24 +0900 | [diff] [blame] | 148 | } // namespace base |
| 149 | |
dpolukhin@chromium.org | 21b228d | 2010-09-16 16:59:27 +0900 | [diff] [blame] | 150 | #endif // BASE_TEMPLATE_UTIL_H_ |