//
// coalesce - boundary tag coalescing. Return ptr to coalesced block
//
static void *coalesce(void *bp)
{
FL_Pointer prev = PREV_BLKP(bp);
FL_Pointer next = NEXT_BLKP(bp);
size_t prev_alloc = GET_ALLOC(FTRP(prev));
size_t next_alloc = GET_ALLOC(HDRP(next));
size_t size = GET_SIZE(HDRP(bp));
//CASE 1 : Both neighbors are allocated
if (prev_alloc && next_alloc) {
// we need to add free list node here b/c we do not do it in mm_free
CL_append(&free_list, bp);
}
//CASE 2 : Only next free
else if (prev_alloc && !next_alloc) {
// unlink node thats next, b/c our current position will be beggining of new free node
CL_unlink(next);
CL_append(&free_list, bp);
size += GET_SIZE(HDRP(next));
PUT(HDRP(bp), PACK(size,0));
PUT(FTRP(bp), PACK(size,0));
}
//CASE 3 : Only prev free
else if (!prev_alloc && next_alloc){
size += GET_SIZE(HDRP(prev));
// no need to make new here b/c one exists at prev_node
PUT(FTRP(bp), PACK(size,0));
PUT(HDRP(prev), PACK(size,0));
bp = prev;
}
//CASE 4 : both neighbors unallocated
else {
size += GET_SIZE(HDRP(prev))
+ GET_SIZE(FTRP(next));
// unlink node that is above us, we can ignore the one below us because that
// will serve ad the head for this free block
CL_unlink(next);
PUT(HDRP(prev), PACK(size,0));
PUT(FTRP(next), PACK(size,0));
bp = prev;
}
return bp;
}
//
//
// Practice problem 9.9
//
// place - Place block of asize bytes at start of free block bp
// and split if remainder would be at least minimum block size
//
static void place(void *bp, size_t asize)
{
size_t csize = GET_SIZE(HDRP(bp));
if((csize - asize) >= (2 * DSIZE)) {
CL_unlink(bp);
PUT(HDRP(bp), PACK(asize, 1));
PUT(FTRP(bp), PACK(asize, 1));
bp = NEXT_BLKP(bp);
PUT(HDRP(bp), PACK(csize - asize, 0));
PUT(FTRP(bp), PACK(csize - asize, 0));
CL_tack(&free_list, bp);
}
else {
CL_unlink(bp);
PUT(HDRP(bp), PACK(csize, 1));
PUT(FTRP(bp), PACK(csize, 1));
}
}
//
// coalesce - boundary tag coalescing. Return ptr to coalesced block
//
static void *coalesce(void *bp)
{
FL_Pointer prev = PREV_BLKP(bp);
FL_Pointer next = NEXT_BLKP(bp);
size_t prev_alloc = GET_ALLOC(FTRP(prev));
size_t next_alloc = GET_ALLOC(HDRP(next));
size_t size = GET_SIZE(HDRP(bp));
if (prev_alloc && next_alloc) {
CL_tack(&free_list, bp); // case 1 neighbours = 1 add a return?
}
else if (prev_alloc && !next_alloc) { // case 2 next is free
CL_unlink(next);
CL_tack(&free_list, bp);
size += GET_SIZE(HDRP(next));
PUT(HDRP(bp), PACK(size, 0));
PUT(FTRP(bp), PACK(size, 0));
}
else if (!prev_alloc && next_alloc) { // case 3 prev is free
size += GET_SIZE(HDRP(prev));
PUT(FTRP(bp), PACK(size, 0));
PUT(HDRP(prev), PACK(size, 0));
bp = prev;
}
else { // both next and prev free
size += GET_SIZE(HDRP(prev)) + GET_SIZE(FTRP(next));
CL_unlink(next);
PUT(HDRP(prev), PACK(size, 0 ));
PUT(FTRP(next), PACK(size, 0));
bp = prev;
}
return bp;
}
