Question

I have this implementation in C#.

If I am not wrong, it is used to: offsetting the memory location indicated by allocatedObject by size number of bytes and converting the memory pointer to an Int64

short size = getSize();

IntPtr allocatedObject;

long posInMemory = allocatedObject.Offset(size).ToInt64();

How can I achieve this in C++: the position in memory of the IntPtr (void *allocatedObject;) and convert the memory pointer to an Int64.

Answer 1

Assuming you have an int64_t type that represents a 64bits integer, you would first cast the pointer to a pointer to char (that by definition has sizeof = 1), then offset it by the size, then cast it again to a pointer to int64_t.

static_cast< int64_t* >( static_cast< char* >( allocatedObject ) + size )

That’s because you cannot do pointer arithmetics with a void pointer, as it has no size. Alternatively, you could reinterpret_cast the pointer to a std::intptr_t (an integer big enough to contain any pointer), increase it by size and then cast to pointer to int64_t.