composable_kernel/include/rapidjson/internal/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.
//
// 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) && !defined(__clang__)
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(_MSC_VER) && !defined(__clang__)
RAPIDJSON_DIAG_POP
#endif

#ifdef __GNUC__
RAPIDJSON_DIAG_POP
#endif

#endif // RAPIDJSON_INTERNAL_META_H_