meta.h
// Tencent is pleased to support the open source community by making RapidJSON available.
//
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
// http://opensource.org/licenses/MIT
//
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.
#ifndef RAPIDJSON_INTERNAL_META_H_
#define RAPIDJSON_INTERNAL_META_H_
#include "../rapidjson.h"
#ifdef __GNUC__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(effc++)
#endif
#if defined(_MSC_VER)
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(6334)
#endif
#if RAPIDJSON_HAS_CXX11_TYPETRAITS
#include <type_traits>
#endif
//@cond RAPIDJSON_INTERNAL
RAPIDJSON_NAMESPACE_BEGIN
namespace internal {
// Helper to wrap/convert arbitrary types to void, useful for arbitrary type matching
template <typename T> struct Void { typedef void Type; };
///////////////////////////////////////////////////////////////////////////////
// BoolType, TrueType, FalseType
//
template <bool Cond> struct BoolType {
static const bool Value = Cond;
typedef BoolType Type;
};
typedef BoolType<true> TrueType;
typedef BoolType<false> FalseType;
///////////////////////////////////////////////////////////////////////////////
// SelectIf, BoolExpr, NotExpr, AndExpr, OrExpr
//
template <bool C> struct SelectIfImpl { template <typename T1, typename T2> struct Apply { typedef T1 Type; }; };
template <> struct SelectIfImpl<false> { template <typename T1, typename T2> struct Apply { typedef T2 Type; }; };
template <bool C, typename T1, typename T2> struct SelectIfCond : SelectIfImpl<C>::template Apply<T1,T2> {};
template <typename C, typename T1, typename T2> struct SelectIf : SelectIfCond<C::Value, T1, T2> {};
template <bool Cond1, bool Cond2> struct AndExprCond : FalseType {};
template <> struct AndExprCond<true, true> : TrueType {};
template <bool Cond1, bool Cond2> struct OrExprCond : TrueType {};
template <> struct OrExprCond<false, false> : FalseType {};
template <typename C> struct BoolExpr : SelectIf<C,TrueType,FalseType>::Type {};
template <typename C> struct NotExpr : SelectIf<C,FalseType,TrueType>::Type {};
template <typename C1, typename C2> struct AndExpr : AndExprCond<C1::Value, C2::Value>::Type {};
template <typename C1, typename C2> struct OrExpr : OrExprCond<C1::Value, C2::Value>::Type {};
///////////////////////////////////////////////////////////////////////////////
// AddConst, MaybeAddConst, RemoveConst
template <typename T> struct AddConst { typedef const T Type; };
template <bool Constify, typename T> struct MaybeAddConst : SelectIfCond<Constify, const T, T> {};
template <typename T> struct RemoveConst { typedef T Type; };
template <typename T> struct RemoveConst<const T> { typedef T Type; };
///////////////////////////////////////////////////////////////////////////////
// IsSame, IsConst, IsMoreConst, IsPointer
//
template <typename T, typename U> struct IsSame : FalseType {};
template <typename T> struct IsSame<T, T> : TrueType {};
template <typename T> struct IsConst : FalseType {};
template <typename T> struct IsConst<const T> : TrueType {};
template <typename CT, typename T>
struct IsMoreConst
: AndExpr<IsSame<typename RemoveConst<CT>::Type, typename RemoveConst<T>::Type>,
BoolType<IsConst<CT>::Value >= IsConst<T>::Value> >::Type {};
template <typename T> struct IsPointer : FalseType {};
template <typename T> struct IsPointer<T*> : TrueType {};
///////////////////////////////////////////////////////////////////////////////
// IsBaseOf
//
#if RAPIDJSON_HAS_CXX11_TYPETRAITS
template <typename B, typename D> struct IsBaseOf
: BoolType< ::std::is_base_of<B,D>::value> {};
#else // simplified version adopted from Boost
template<typename B, typename D> struct IsBaseOfImpl {
RAPIDJSON_STATIC_ASSERT(sizeof(B) != 0);
RAPIDJSON_STATIC_ASSERT(sizeof(D) != 0);
typedef char (&Yes)[1];
typedef char (&No) [2];
template <typename T>
static Yes Check(const D*, T);
static No Check(const B*, int);
struct Host {
operator const B*() const;
operator const D*();
};
enum { Value = (sizeof(Check(Host(), 0)) == sizeof(Yes)) };
};
template <typename B, typename D> struct IsBaseOf
: OrExpr<IsSame<B, D>, BoolExpr<IsBaseOfImpl<B, D> > >::Type {};
#endif // RAPIDJSON_HAS_CXX11_TYPETRAITS
//////////////////////////////////////////////////////////////////////////
// EnableIf / DisableIf
//
template <bool Condition, typename T = void> struct EnableIfCond { typedef T Type; };
template <typename T> struct EnableIfCond<false, T> { /* empty */ };
template <bool Condition, typename T = void> struct DisableIfCond { typedef T Type; };
template <typename T> struct DisableIfCond<true, T> { /* empty */ };
template <typename Condition, typename T = void>
struct EnableIf : EnableIfCond<Condition::Value, T> {};
template <typename Condition, typename T = void>
struct DisableIf : DisableIfCond<Condition::Value, T> {};
// SFINAE helpers
struct SfinaeTag {};
template <typename T> struct RemoveSfinaeTag;
template <typename T> struct RemoveSfinaeTag<SfinaeTag&(*)(T)> { typedef T Type; };
#define RAPIDJSON_REMOVEFPTR_(type) \
typename ::RAPIDJSON_NAMESPACE::internal::RemoveSfinaeTag \
< ::RAPIDJSON_NAMESPACE::internal::SfinaeTag&(*) type>::Type
#define RAPIDJSON_ENABLEIF(cond) \
typename ::RAPIDJSON_NAMESPACE::internal::EnableIf \
<RAPIDJSON_REMOVEFPTR_(cond)>::Type * = NULL
#define RAPIDJSON_DISABLEIF(cond) \
typename ::RAPIDJSON_NAMESPACE::internal::DisableIf \
<RAPIDJSON_REMOVEFPTR_(cond)>::Type * = NULL
#define RAPIDJSON_ENABLEIF_RETURN(cond,returntype) \
typename ::RAPIDJSON_NAMESPACE::internal::EnableIf \
<RAPIDJSON_REMOVEFPTR_(cond), \
RAPIDJSON_REMOVEFPTR_(returntype)>::Type
#define RAPIDJSON_DISABLEIF_RETURN(cond,returntype) \
typename ::RAPIDJSON_NAMESPACE::internal::DisableIf \
<RAPIDJSON_REMOVEFPTR_(cond), \
RAPIDJSON_REMOVEFPTR_(returntype)>::Type
} // namespace internal
RAPIDJSON_NAMESPACE_END
//@endcond
#if defined(__GNUC__) || defined(_MSC_VER)
RAPIDJSON_DIAG_POP
#endif
#endif // RAPIDJSON_INTERNAL_META_H_
rapidjson::Type
Type
Type of JSON value
Definition: rapidjson.h:603
rapidjson::Value
GenericValue< UTF8<> > Value
GenericValue with UTF8 encoding
Definition: document.h:2010
RAPIDJSON_STATIC_ASSERT
#define RAPIDJSON_STATIC_ASSERT(x)
(Internal) macro to check for conditions at compile-time
Definition: rapidjson.h:437