#include <iostream>
#include <typeinfo>
#include <sys/time.h>
#include <stdint.h>
using namespace std;
// Type Lists
template< typename T, T v = T() >
struct Value
{
enum { val = v };
typedef T value_type;
};
struct NullItem
{
static void Print() { std::cout << std::endl; }
};
template< typename V, typename L >
struct List
{
typedef V value_type;
static void Print()
{
std::cout << value_type::val << ", ";
L::Print();
}
};
template< class List > struct Next;
template< class V, class L >
struct Next< List< V, L > >
{
typedef L NextType;
};
template< unsigned n, int i = 0, int until = n + i, class G = NullItem >
class Generate
{
typedef List< Value< int, i >, G > NewList;
public:
typedef typename Generate< n, i + 1, until, NewList >::NextType NextType;
};
template< unsigned n, int until, class G >
class Generate<n, until, until, G>
{
public:
typedef G NextType;
};
// Linear class hierarchy
struct IBase
{
virtual ~IBase() {}
virtual void Print() = 0;
};
template< class TList >
struct CRTP : CRTP< typename Next< TList >::NextType >
{
virtual void Print()
{
cout << typeid( *this ).name() << " " << TList::value_type::val << endl;
}
};
template<>
struct CRTP< NullItem > : IBase
{
// IBase
virtual void Print()
{
cout << typeid( *this ).name() << endl;
}
};
void TestDownCast( IBase *b )
{
static const int NUM_CASTS = 10 * 1000;
struct timeval tvStart, tvEnd;
gettimeofday( &tvStart, NULL );
for( int i = 0; i < NUM_CASTS; ++i )
{
CRTP< NullItem > *pCRTP = dynamic_cast< CRTP< NullItem > * >( b );
/*if ( pCRTP )
{
cout << "downcasted successfully" << endl;
}*/
}
gettimeofday( &tvEnd, NULL );
int64_t elapsed = (int64_t)( tvEnd.tv_sec - tvStart.tv_sec ) * 1000000 +
( tvEnd.tv_usec - tvStart.tv_usec );
cout << NUM_CASTS << " casts : elapsed " << elapsed << " us" << endl;
}
int main()
{
static const int NUM_ITEMS = 500;
typedef Generate< NUM_ITEMS >::NextType GenList;
//GenList::Print();
CRTP< GenList > r;
//r.Print();
TestDownCast( &r );
return 0;
}
g++ dc.cpp -o dc
./dc
10000 casts : elapsed 97958 us
Не «ШОК!ФОТО!» ли это?
