Malloc pointer identification

Question

So, I have this purpose for implementing my own malloc and free in C. The problem is one of the requirements for the function memory_free(void *ptr). It should return 1 if the pointer is invalid, i.e. It has not been allocated, memory_alloc(unsigned int size)or otherwise returns 0. I simply cannot figure out how to do this without being completely ineffective.

So, my memory structure is this: I have a global pointer to the beginning of the array, which I get as a heap. Each memory block has a header intto report its size and free it.

This is my memory_free (void * ptr) function right now, TYPE typedef unsigned int:

int memory_free(void *ptr)
{
    void *head = ptr;
    if (head == NULL)
        return 1;
    head -= sizeof(TYPE);
    if (!((*(TYPE*) head) & 1 ))
        return 1;
    (*(TYPE*) head) &= ~0x1;
    return 0;
}

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Answer 1

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Answer 2

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