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meta.h: add IsBaseOf meta function

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In order to match GenericValue and its derived classes for the
SFINAE-implementation of some of the operators/functions, this
meta-function matches all types equal to or derived from a given
class.  See std::is_base_of<B,D> available in C++11.

Define RAPIDJSON_HAS_CXX_TYPETRAITS to use the C++11 implementation.
This commit is contained in:
Philipp A. Hartmann 2014-08-30 13:14:07 +02:00
parent ed282b8141
commit f076faca3d
1 changed files with 40 additions and 1 deletions
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41
include/rapidjson/internal/meta.h
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@ -25,6 +25,14 @@
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(effc++)
#endif
#if defined(_MSC_VER)
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(6334)
#endif
#ifdef RAPIDJSON_HAS_CXX11_TYPETRAITS
#include <type_traits>
#endif
//@cond RAPIDJSON_INTERNAL
namespace rapidjson {
@ -87,9 +95,40 @@ struct IsMoreConst
template <typename T> struct IsPointer : FalseType {};
template <typename T> struct IsPointer<T*> : TrueType {};
///////////////////////////////////////////////////////////////////////////////
// IsBaseOf
//
#ifdef 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
@ -137,7 +176,7 @@ template <typename T> struct RemoveSfinaeTag<SfinaeTag&(*)(T)> { typedef T Type;
} // namespace rapidjson
//@endcond
#ifdef __GNUC__
#if defined(__GNUC__) || defined(_MSC_VER)
RAPIDJSON_DIAG_POP
#endif