void *heap_malloc(struct Heap* heap, size_t size);
void *heap_calloc(struct Heap* heap, size_t size);
void heap_free(struct Heap* heap, void * mem);
void *heap_malloc(struct Heap* heap, size_t size);
void *heap_calloc(struct Heap* heap, size_t size);
void heap_free(struct Heap* heap, void * mem);