ei_hash *ei_hash_newtab(int tabsize)
{
ei_hash *tab=NULL;
int bucketpos=sizeof(*tab);
/* make sure size is odd, then increase until prime */
tabsize |= 0x1;
while (!ei_isprime(tabsize)) tabsize +=2;
/* we will only do one malloc, so "sizeof(*tab)"
* must be adjusted to align tab->tab properly
*/
ei_align(bucketpos);
/* single malloc, then fill in all fields */
if ((tab = malloc(bucketpos + (tabsize * (sizeof(*(tab->tab))))))) {
tab->tab = (ei_bucket **)((char *)tab + bucketpos);
memset(tab->tab,0,tabsize*sizeof(*(tab->tab)));
tab->hash = ei_dohash;
tab->size = tabsize;
tab->npos = 0;
tab->nelem = 0;
tab->freelist = NULL;
}
return tab;
}
/* move the elements from oldtab to a new table newsize. The old table
* is freed and the caller should discard the pointer. On failure
* (i.e. if malloc fails) return the old table and do nothing.
*/
ei_hash *ei_hash_resize(ei_hash *oldtab, int newsize)
{
ei_hash *newtab=NULL;
ei_bucket *b, *next;
int i,h;
/* make sure size is odd, then increase until prime */
newsize |= 0x1;
while (!ei_isprime(newsize)) newsize +=2;
if (newsize == oldtab->size) return oldtab;
/* make a new table */
if (!(newtab = ei_hash_newtab(newsize))) return oldtab;
newtab->hash = oldtab->hash;
/* move the buckets, rehashing */
/* note that this will reverse the order of any chains */
for (i=0; i<oldtab->size; i++) {
b=oldtab->tab[i];
while (b) {
next = b->next;
h = b->rawhash % newtab->size;
b->next=newtab->tab[h];
if (!newtab->tab[h]) newtab->npos++;
newtab->tab[h]=b;
b = next;
}
}
/* the new table has the same number of elements as the old one */
newtab->nelem = oldtab->nelem;
/* the new table takes over the freelist from the old one */
newtab->freelist = oldtab->freelist;
/* now it's safe to remove the old table */
free(oldtab);
return newtab;
}
