template_util.h revision a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7
15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Copyright (c) 2011 The Chromium Authors. All rights reserved. 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// found in the LICENSE file. 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#ifndef BASE_TEMPLATE_UTIL_H_ 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#define BASE_TEMPLATE_UTIL_H_ 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include <cstddef> // For size_t. 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "build/build_config.h" 115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)namespace base { 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// template definitions from tr1 155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template<class T, T v> 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)struct integral_constant { 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static const T value = v; 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) typedef T value_type; 205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) typedef integral_constant<T, v> type; 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T, T v> const T integral_constant<T, v>::value; 245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)typedef integral_constant<bool, true> true_type; 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)typedef integral_constant<bool, false> false_type; 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_pointer : false_type {}; 295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_pointer<T*> : true_type {}; 305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 31a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)// Member function pointer detection up to four params. Add more as needed 32a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)// below. This is built-in to C++ 11, and we can remove this when we switch. 33a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template<typename T> 34a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer : false_type {}; 35a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 36a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z> 37a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)()> : true_type {}; 38a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z> 39a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)() const> : true_type {}; 40a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 41a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A> 42a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A)> : true_type {}; 43a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A> 44a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A) const> : true_type {}; 45a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 46a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A, typename B> 47a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A, B)> : true_type {}; 48a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A, typename B> 49a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A, B) const> : true_type {}; 50a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 51a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A, typename B, typename C> 52a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A, B, C)> : true_type {}; 53a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A, typename B, typename C> 54a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A, B, C) const> : true_type {}; 55a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 56a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A, typename B, typename C, 57a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) typename D> 58a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A, B, C, D)> : true_type {}; 59a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)template <typename R, typename Z, typename A, typename B, typename C, 60a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) typename D> 61a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles)struct is_member_function_pointer<R(Z::*)(A, B, C, D) const> : true_type {}; 62a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 63a3f6a49ab37290eeeb8db0f41ec0f1cb74a68be7Torne (Richard Coles) 645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T, class U> struct is_same : public false_type {}; 655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_same<T,T> : true_type {}; 665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template<class> struct is_array : public false_type {}; 685821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template<class T, size_t n> struct is_array<T[n]> : public true_type {}; 695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template<class T> struct is_array<T[]> : public true_type {}; 705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_non_const_reference : false_type {}; 725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_non_const_reference<T&> : true_type {}; 735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_non_const_reference<const T&> : false_type {}; 745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 758bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles)template <class T> struct is_const : false_type {}; 768bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles)template <class T> struct is_const<const T> : true_type {}; 778bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles) 785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <class T> struct is_void : false_type {}; 795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <> struct is_void<void> : true_type {}; 805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 815821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)namespace internal { 825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Types YesType and NoType are guaranteed such that sizeof(YesType) < 845821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// sizeof(NoType). 855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)typedef char YesType; 865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)struct NoType { 885821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) YesType dummy[2]; 895821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 905821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 915821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This class is an implementation detail for is_convertible, and you 925821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// don't need to know how it works to use is_convertible. For those 935821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// who care: we declare two different functions, one whose argument is 945821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// of type To and one with a variadic argument list. We give them 955821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// return types of different size, so we can use sizeof to trick the 965821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// compiler into telling us which function it would have chosen if we 975821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// had called it with an argument of type From. See Alexandrescu's 985821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// _Modern C++ Design_ for more details on this sort of trick. 995821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1005821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)struct ConvertHelper { 1015821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) template <typename To> 1025821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static YesType Test(To); 1035821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1045821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) template <typename To> 1055821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static NoType Test(...); 1065821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1075821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) template <typename From> 1085821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static From& Create(); 1095821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 1105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Used to determine if a type is a struct/union/class. Inspired by Boost's 1125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// is_class type_trait implementation. 1135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)struct IsClassHelper { 1145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) template <typename C> 1155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static YesType Test(void(C::*)(void)); 1165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) template <typename C> 1185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) static NoType Test(...); 1195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 1205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} // namespace internal 1225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Inherits from true_type if From is convertible to To, false_type otherwise. 1245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 1255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// Note that if the type is convertible, this will be a true_type REGARDLESS 1265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// of whether or not the conversion would emit a warning. 1275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <typename From, typename To> 1285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)struct is_convertible 1295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) : integral_constant<bool, 1305821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) sizeof(internal::ConvertHelper::Test<To>( 1315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) internal::ConvertHelper::Create<From>())) == 1325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) sizeof(internal::YesType)> { 1335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 1345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)template <typename T> 1365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)struct is_class 1375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) : integral_constant<bool, 1385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) sizeof(internal::IsClassHelper::Test<T>(0)) == 1395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) sizeof(internal::YesType)> { 1405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)}; 1415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1428bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles)template<bool B, class T = void> 1438bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles)struct enable_if {}; 1448bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles) 1458bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles)template<class T> 1468bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles)struct enable_if<true, T> { typedef T type; }; 1478bcbed890bc3ce4d7a057a8f32cab53fa534672eTorne (Richard Coles) 1485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} // namespace base 1495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 1505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#endif // BASE_TEMPLATE_UTIL_H_ 151