1 // Tencent is pleased to support the open source community by making RapidJSON available. 2 // 3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved. 4 // 5 // Licensed under the MIT License (the "License"); you may not use this file except 6 // in compliance with the License. You may obtain a copy of the License at 7 // 8 // http://opensource.org/licenses/MIT 9 // 10 // Unless required by applicable law or agreed to in writing, software distributed 11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the 13 // specific language governing permissions and limitations under the License. 14 15 #ifndef RAPIDJSON_INTERNAL_META_H_ 16 #define RAPIDJSON_INTERNAL_META_H_ 17 18 #include "../rapidjson.h" 19 20 #ifdef __GNUC__ 21 RAPIDJSON_DIAG_PUSH 22 RAPIDJSON_DIAG_OFF(effc++) 23 #endif 24 #if defined(_MSC_VER) 25 RAPIDJSON_DIAG_PUSH 26 RAPIDJSON_DIAG_OFF(6334) 27 #endif 28 29 #if RAPIDJSON_HAS_CXX11_TYPETRAITS 30 #include <type_traits> 31 #endif 32 33 //@cond RAPIDJSON_INTERNAL 34 RAPIDJSON_NAMESPACE_BEGIN 35 namespace internal { 36 37 // Helper to wrap/convert arbitrary types to void, useful for arbitrary type matching 38 template <typename T> struct Void { typedef void Type; }; 39 40 /////////////////////////////////////////////////////////////////////////////// 41 // BoolType, TrueType, FalseType 42 // 43 template <bool Cond> struct BoolType { 44 static const bool Value = Cond; 45 typedef BoolType Type; 46 }; 47 typedef BoolType<true> TrueType; 48 typedef BoolType<false> FalseType; 49 50 51 /////////////////////////////////////////////////////////////////////////////// 52 // SelectIf, BoolExpr, NotExpr, AndExpr, OrExpr 53 // 54 55 template <bool C> struct SelectIfImpl { template <typename T1, typename T2> struct Apply { typedef T1 Type; }; }; 56 template <> struct SelectIfImpl<false> { template <typename T1, typename T2> struct Apply { typedef T2 Type; }; }; 57 template <bool C, typename T1, typename T2> struct SelectIfCond : SelectIfImpl<C>::template Apply<T1,T2> {}; 58 template <typename C, typename T1, typename T2> struct SelectIf : SelectIfCond<C::Value, T1, T2> {}; 59 60 template <bool Cond1, bool Cond2> struct AndExprCond : FalseType {}; 61 template <> struct AndExprCond<true, true> : TrueType {}; 62 template <bool Cond1, bool Cond2> struct OrExprCond : TrueType {}; 63 template <> struct OrExprCond<false, false> : FalseType {}; 64 65 template <typename C> struct BoolExpr : SelectIf<C,TrueType,FalseType>::Type {}; 66 template <typename C> struct NotExpr : SelectIf<C,FalseType,TrueType>::Type {}; 67 template <typename C1, typename C2> struct AndExpr : AndExprCond<C1::Value, C2::Value>::Type {}; 68 template <typename C1, typename C2> struct OrExpr : OrExprCond<C1::Value, C2::Value>::Type {}; 69 70 71 /////////////////////////////////////////////////////////////////////////////// 72 // AddConst, MaybeAddConst, RemoveConst 73 template <typename T> struct AddConst { typedef const T Type; }; 74 template <bool Constify, typename T> struct MaybeAddConst : SelectIfCond<Constify, const T, T> {}; 75 template <typename T> struct RemoveConst { typedef T Type; }; 76 template <typename T> struct RemoveConst<const T> { typedef T Type; }; 77 78 79 /////////////////////////////////////////////////////////////////////////////// 80 // IsSame, IsConst, IsMoreConst, IsPointer 81 // 82 template <typename T, typename U> struct IsSame : FalseType {}; 83 template <typename T> struct IsSame<T, T> : TrueType {}; 84 85 template <typename T> struct IsConst : FalseType {}; 86 template <typename T> struct IsConst<const T> : TrueType {}; 87 88 template <typename CT, typename T> 89 struct IsMoreConst 90 : AndExpr<IsSame<typename RemoveConst<CT>::Type, typename RemoveConst<T>::Type>, 91 BoolType<IsConst<CT>::Value >= IsConst<T>::Value> >::Type {}; 92 93 template <typename T> struct IsPointer : FalseType {}; 94 template <typename T> struct IsPointer<T*> : TrueType {}; 95 96 /////////////////////////////////////////////////////////////////////////////// 97 // IsBaseOf 98 // 99 #if RAPIDJSON_HAS_CXX11_TYPETRAITS 100 101 template <typename B, typename D> struct IsBaseOf 102 : BoolType< ::std::is_base_of<B,D>::value> {}; 103 104 #else // simplified version adopted from Boost 105 106 template<typename B, typename D> struct IsBaseOfImpl { 107 RAPIDJSON_STATIC_ASSERT(sizeof(B) != 0); 108 RAPIDJSON_STATIC_ASSERT(sizeof(D) != 0); 109 110 typedef char (&Yes)[1]; 111 typedef char (&No) [2]; 112 113 template <typename T> 114 static Yes Check(const D*, T); 115 static No Check(const B*, int); 116 117 struct Host { 118 operator const B*() const; 119 operator const D*(); 120 }; 121 122 enum { Value = (sizeof(Check(Host(), 0)) == sizeof(Yes)) }; 123 }; 124 125 template <typename B, typename D> struct IsBaseOf 126 : OrExpr<IsSame<B, D>, BoolExpr<IsBaseOfImpl<B, D> > >::Type {}; 127 128 #endif // RAPIDJSON_HAS_CXX11_TYPETRAITS 129 130 131 ////////////////////////////////////////////////////////////////////////// 132 // EnableIf / DisableIf 133 // 134 template <bool Condition, typename T = void> struct EnableIfCond { typedef T Type; }; 135 template <typename T> struct EnableIfCond<false, T> { /* empty */ }; 136 137 template <bool Condition, typename T = void> struct DisableIfCond { typedef T Type; }; 138 template <typename T> struct DisableIfCond<true, T> { /* empty */ }; 139 140 template <typename Condition, typename T = void> 141 struct EnableIf : EnableIfCond<Condition::Value, T> {}; 142 143 template <typename Condition, typename T = void> 144 struct DisableIf : DisableIfCond<Condition::Value, T> {}; 145 146 // SFINAE helpers 147 struct SfinaeTag {}; 148 template <typename T> struct RemoveSfinaeTag; 149 template <typename T> struct RemoveSfinaeTag<SfinaeTag&(*)(T)> { typedef T Type; }; 150 151 // NOLINT: Do not add parentheses around 'type'. 152 #define RAPIDJSON_REMOVEFPTR_(type) \ 153 typename ::RAPIDJSON_NAMESPACE::internal::RemoveSfinaeTag \ 154 < ::RAPIDJSON_NAMESPACE::internal::SfinaeTag&(*) type>::Type // NOLINT 155 156 // NOLINT: Do not add parentheses around a statement. 157 #define RAPIDJSON_ENABLEIF(cond) \ 158 typename ::RAPIDJSON_NAMESPACE::internal::EnableIf \ 159 <RAPIDJSON_REMOVEFPTR_(cond)>::Type * = NULL // NOLINT 160 161 // NOLINT: Do not add parentheses around a statement. 162 #define RAPIDJSON_DISABLEIF(cond) \ 163 typename ::RAPIDJSON_NAMESPACE::internal::DisableIf \ 164 <RAPIDJSON_REMOVEFPTR_(cond)>::Type * = NULL // NOLINT 165 166 #define RAPIDJSON_ENABLEIF_RETURN(cond,returntype) \ 167 typename ::RAPIDJSON_NAMESPACE::internal::EnableIf \ 168 <RAPIDJSON_REMOVEFPTR_(cond), \ 169 RAPIDJSON_REMOVEFPTR_(returntype)>::Type 170 171 #define RAPIDJSON_DISABLEIF_RETURN(cond,returntype) \ 172 typename ::RAPIDJSON_NAMESPACE::internal::DisableIf \ 173 <RAPIDJSON_REMOVEFPTR_(cond), \ 174 RAPIDJSON_REMOVEFPTR_(returntype)>::Type 175 176 } // namespace internal 177 RAPIDJSON_NAMESPACE_END 178 //@endcond 179 180 #if defined(__GNUC__) || defined(_MSC_VER) 181 RAPIDJSON_DIAG_POP 182 #endif 183 184 #endif // RAPIDJSON_INTERNAL_META_H_ 185