ceph/src/rapidjson/include/rapidjson/internal/meta.h

   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 #define RAPIDJSON_REMOVEFPTR_(type) \
 152     typename ::RAPIDJSON_NAMESPACE::internal::RemoveSfinaeTag \
 153         < ::RAPIDJSON_NAMESPACE::internal::SfinaeTag&(*) type>::Type
 154
 155 #define RAPIDJSON_ENABLEIF(cond) \
 156     typename ::RAPIDJSON_NAMESPACE::internal::EnableIf \
 157         <RAPIDJSON_REMOVEFPTR_(cond)>::Type * = NULL
 158
 159 #define RAPIDJSON_DISABLEIF(cond) \
 160     typename ::RAPIDJSON_NAMESPACE::internal::DisableIf \
 161         <RAPIDJSON_REMOVEFPTR_(cond)>::Type * = NULL
 162
 163 #define RAPIDJSON_ENABLEIF_RETURN(cond,returntype) \
 164     typename ::RAPIDJSON_NAMESPACE::internal::EnableIf \
 165         <RAPIDJSON_REMOVEFPTR_(cond), \
 166          RAPIDJSON_REMOVEFPTR_(returntype)>::Type
 167
 168 #define RAPIDJSON_DISABLEIF_RETURN(cond,returntype) \
 169     typename ::RAPIDJSON_NAMESPACE::internal::DisableIf \
 170         <RAPIDJSON_REMOVEFPTR_(cond), \
 171          RAPIDJSON_REMOVEFPTR_(returntype)>::Type
 172
 173 } // namespace internal
 174 RAPIDJSON_NAMESPACE_END
 175 //@endcond
 176
 177 #if defined(__GNUC__) || defined(_MSC_VER)
 178 RAPIDJSON_DIAG_POP
 179 #endif
 180
 181 #endif // RAPIDJSON_INTERNAL_META_H_