/**
* Measure how well the hash function performs
* (1.0 is perfect - no stepping needed).
*
* Smaller is better!
*/
double BLI_smallhash_calc_quality(SmallHash *sh)
{
uint64_t sum = 0;
unsigned int i;
if (sh->nentries == 0)
return -1.0;
for (i = 0; i < sh->nbuckets; i++) {
if (sh->buckets[i].key != SMHASH_KEY_UNUSED) {
uint64_t count = 0;
SmallHashEntry *e, *e_final = &sh->buckets[i];
unsigned int h = smallhash_key(e_final->key);
unsigned int hoff = 1;
for (e = &sh->buckets[h % sh->nbuckets];
e != e_final;
h = SMHASH_NEXT(h, hoff), e = &sh->buckets[h % sh->nbuckets])
{
count += 1;
}
sum += count;
}
}
return ((double)(sh->nentries + sum) / (double)sh->nentries);
}
BLI_INLINE SmallHashEntry *smallhash_lookup_first_free(SmallHash *sh, const uintptr_t key)
{
SmallHashEntry *e;
unsigned int h = (unsigned int)key;
unsigned int hoff = 1;
for (e = &sh->buckets[h % sh->nbuckets];
smallhash_val_is_used(e->val);
h = SMHASH_NEXT(h, hoff), e = &sh->buckets[h % sh->nbuckets])
{
/* pass */
}
return e;
}
BLI_INLINE SmallHashEntry *smallhash_lookup(SmallHash *sh, const uintptr_t key)
{
SmallHashEntry *e;
unsigned int h = (unsigned int)key;
unsigned int hoff = 1;
BLI_assert(key != SMHASH_KEY_UNUSED);
/* note: there are always more buckets then entries,
* so we know there will always be a free bucket if the key isn't found. */
for (e = &sh->buckets[h % sh->nbuckets];
e->val != SMHASH_CELL_FREE;
h = SMHASH_NEXT(h, hoff), e = &sh->buckets[h % sh->nbuckets])
{
if (e->key == key) {
/* should never happen because unused keys are zero'd */
BLI_assert(e->val != SMHASH_CELL_UNUSED);
return e;
}
}
return NULL;
}
