Managing Memory for Game Developers - Learn C++ for Game Development - page 218

from this block. In this example, the fragmentation is redundant because we have not implemented
any way of tracking our free blocks of memory. One option would be to use a list to store all of
the free blocks rather than storing them in the memory allocation headers themselves. Writing a
full-featured memory allocator is a complicated task that could fill an entire book.
Note You can see that we have a valid case for using reinterpret_cast in our new and delete
operators. There aren't many valid cases for this type of cast. In this case we want to represent the same
memory address using a different type and therefore the reinterpret_cast is the correct option.
Listing 22-9 contains the last memory function for this section and it is used to print out the contents
of all active MemoryAllocationHeader objects in our heap.
Listing 22-9. The PrintAllocations Function
void PrintAllocations()
{
MemoryAllocationHeader* pHeader =
reinterpret_cast<MemoryAllocationHeader*>(pMemoryHeap);
while (pHeader != nullptr)
{
std::cout << pHeader << std::endl;
std::cout << pHeader->pStart << std::endl;
std::cout << pHeader->pNextFree << std::endl;
std::cout << pHeader->size << std::endl;
pHeader = reinterpret_cast<MemoryAllocationHeader*>(pHeader->pNextFree);
std::cout << std::endl << std::endl;
}
}
This function loops over all of the valid MemoryAllocationHeader pointers in our head and prints
their pStart , pNextFree , and size variables. Listing 22-10 shows an example main function that uses
these functions.
Listing 22-10. Using the Memory Heap
int _tmain(int argc, _TCHAR* argv[])
{
memset(pMemoryHeap, 0, SIZE_OF_MEMORY_HEADER);
PrintAllocations();
Simple* pSimple1 = new Simple();