void * dkbtalloc(size_t n){
/*
* The memory we search for has to include the memory control header, but
* the user of malloc doesn't need to know this, so we'll just add it in
* for them.
*/
n=n+sizeof(node_t);
node_t *p= AVAIL->nlink; /* from the free list head */
node_t * q=NULL; /* to store the block after spliting */
while(p!=NULL){
if (p->size==n){ /* exaclly the same size */
block_remove(p); /* remove p from dll */
set_block_used(p); /* mark p as allocated */
set_prev_used(get_block_pnxt(p));/* set p's next physical block */
return (void*) p; /* return block p */
}
if (p->size>n){ /* suitable block is bigger than n */
q=block_split(p,n); /* splict p, q is the new block(right part) */
set_block_free(q); /* set new left block as free */
set_prev_used(q); /* the previous of q is used */
set_block_used(p);
block_remove(p);
return (void*)p;
}
p=p->nlink; /* move step further */
}
return NULL;
}
int get_free_block(jfs_t *jfs)
{
int groups, i;
if (jfs->d_img->size % (BLOCKSIZE * BLOCKS_PER_GROUP) == 0) {
groups = jfs->d_img->size / (BLOCKSIZE * BLOCKS_PER_GROUP);
} else {
groups = 1 + jfs->d_img->size / (BLOCKSIZE * BLOCKS_PER_GROUP);
}
for (i = 0; i < groups; i++) {
struct blockgroup *grp;
char block[BLOCKSIZE];
int freeblock;
/* read the blockgroup header */
jfs_read_block(jfs, block, i * BLOCKS_PER_GROUP);
grp = (struct blockgroup *)block;
freeblock = -1;
freeblock = find_free_block(grp->block_bitmap);
if (freeblock >= 0) {
set_block_used(grp->block_bitmap, freeblock);
jfs_write_block(jfs, block, i * BLOCKS_PER_GROUP);
/* if there's a free block in this group, then return it */
freeblock += i * BLOCKS_PER_GROUP;
/* printf("allocating free block: %d\n", freeblock);*/
return freeblock;
}
}
return -1;
}