void *check_add_elem_and_sbrk(void *ptr_to_ret, size_t size)
{
if (add_elem_in_list(g_str->nb_of_elems) == -1)
return (NULL);
if ((ptr_to_ret = my_sbrk(size)) == (void*)-1)
return (NULL);
return (ptr_to_ret);
}
/*~~~~~~~~~~~~~HELPER FUNCTIONS~~~~~~~~~~~~~*/
static void setupHeap() {
freelist[7] = my_sbrk(SBRK_SIZE);
// if there is no space on the heap
if ((int)freelist[7] == -1) {
// set error code
ERRNO = OUT_OF_MEMORY;
}
freelist[7]->in_use = 0;
freelist[7]->size = SBRK_SIZE;
freelist[7]->next = NULL;
freelist[7]->prev = NULL;
heap = freelist[7];
}
void* my_malloc(size_t size)
{
//Checking for correct parameter
int checkSize = size;
if (checkSize <= 0)
{
return NULL;
}
int currentSize = 16;
//We start with the smallest size and move up until we find the first block size that
//fits our requirement
int index = 0;
//Also keep track of an index which tells us which index of the free list corresponds to our block size
int adjustedSize = size + sizeof(metadata_t);
//We need to add the size of the metadata to the size required by the user to account for the overhead
//Checking for error conditions
if (size <= 0)
{
return NULL;
}
if (adjustedSize > SBRK_SIZE)
{
ERRNO = SINGLE_REQUEST_TOO_LARGE;
return NULL;
}
while (currentSize < adjustedSize)
{
currentSize = currentSize*2;
index++;
//keeping doubling the size of the block until I find the first fit and also increment the
//index to keep it consistent with the free list
}
//if we don't have the block of the required size to give then, start from the index we are at
//then we keep going down to bigger block sizes until we get a block which is available to be used
if (freelist[index] == NULL)
{
int n = index;
while (n < FREELIST_SIZE && freelist[n] == NULL)
{
n++;
}
if (n >= FREELIST_SIZE)
{
metadata_t* brkPtr = my_sbrk(SBRK_SIZE);
if (brkPtr == NULL)
{
//If the call to my_sbrk returns NULL then we have reached the out of memory condition
ERRNO = OUT_OF_MEMORY;
return NULL;
}
if (heap == NULL)
{
heap = brkPtr;
//Setting the heap pointer to point to the beginning of the current heap space
//NOTE THAT ONLY THE FIRST CALL TO MALLOC RETURNS THE BEGINNING OF THE HEAP
}
freelist[7] = brkPtr;
freelist[7]->size = SBRK_SIZE;
freelist[7]->in_use = 0;
freelist[7]->next = NULL;
freelist[7]->prev = NULL;
}
else
{
split_memBlock(freelist[n], n);
//We found the block of smallest size that can be used so we split it
//and we send the split blocks to the index which is one less
}
return my_malloc(size);
}
else
{
//get the first available block from the freelist to give to the user
metadata_t* give_to_user = freelist[index];
remove_freelist_top(give_to_user, index);
give_to_user->in_use = 1;
give_to_user->next = NULL;
give_to_user->prev = NULL;
give_to_user++;
//skip over the metadata and get that pointer to the free space
ERRNO = NO_ERROR;
//return the pointer that comes after skipping over the metadata portion of the block
return give_to_user;
}
}