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[hashset feature] Iterator bugfixes - handle empty hashset and change iteration order so rehashed buckets can be skipped #1147

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Oct 18, 2024
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[hashset feature] Iterator bugfixes - handle empty hashset and change iteration order so rehashed buckets can be skipped #1147

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57 changes: 31 additions & 26 deletions src/hashset.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1296,27 +1296,28 @@ size_t hashsetScan(hashset *t, size_t cursor, hashsetScanFunction fn, void *priv
/* Advance cursor. */
cursor = nextCursor(cursor, mask);
} else {
/* Let table0 be the the smaller table and table1 the bigger one. */
int table0, table1;
int table_small, table_large;
if (t->bucketExp[0] <= t->bucketExp[1]) {
table0 = 0;
table1 = 1;
table_small = 0;
table_large = 1;
} else {
table0 = 1;
table1 = 0;
table_small = 1;
table_large = 0;
}

size_t mask0 = expToMask(t->bucketExp[table0]);
size_t mask1 = expToMask(t->bucketExp[table1]);
size_t mask_small = expToMask(t->bucketExp[table_small]);
size_t mask_large = expToMask(t->bucketExp[table_large]);

/* Emit elements in the smaller table, if this bucket hasn't already
* been rehashed. */
if (table0 == 0 && !cursorIsLessThan(cursor, t->rehashIdx)) {
bucket *b = &t->tables[table0][cursor & mask0];
for (int pos = 0; pos < ELEMENTS_PER_BUCKET; pos++) {
if (b->presence & (1 << pos)) {
void *emit = emit_ref ? &b->elements[pos] : b->elements[pos];
fn(privdata, emit);
if (table_small == 0 && !cursorIsLessThan(cursor, t->rehashIdx)) {
bucket *b = &t->tables[table_small][cursor & mask_small];
if (b->presence) {
for (int pos = 0; pos < ELEMENTS_PER_BUCKET; pos++) {
if (b->presence & (1 << pos)) {
void *emit = emit_ref ? &b->elements[pos] : b->elements[pos];
fn(privdata, emit);
}
}
}
in_probe_sequence |= b->everfull;
Expand All @@ -1325,21 +1326,23 @@ size_t hashsetScan(hashset *t, size_t cursor, hashsetScanFunction fn, void *priv
/* Iterate over indices in larger table that are the expansion of
* the index pointed to by the cursor in the smaller table. */
do {
/* Emit elements in table 1. */
bucket *b = &t->tables[table1][cursor & mask1];
for (int pos = 0; pos < ELEMENTS_PER_BUCKET; pos++) {
if (b->presence & (1 << pos)) {
void *emit = emit_ref ? &b->elements[pos] : b->elements[pos];
fn(privdata, emit);
/* Emit elements in bigger table. */
bucket *b = &t->tables[table_large][cursor & mask_large];
if (b->presence) {
for (int pos = 0; pos < ELEMENTS_PER_BUCKET; pos++) {
if (b->presence & (1 << pos)) {
void *emit = emit_ref ? &b->elements[pos] : b->elements[pos];
fn(privdata, emit);
}
}
}
in_probe_sequence |= b->everfull;

/* Increment the reverse cursor not covered by the smaller mask.*/
cursor = nextCursor(cursor, mask1);
cursor = nextCursor(cursor, mask_large);

/* Continue while bits covered by mask difference is non-zero */
} while ((cursor & (mask0 ^ mask1)) && cursor != start_cursor);
} while (cursor & (mask_small ^ mask_large) && cursor != start_cursor);
}
if (cursor == 0) {
cursor_passed_zero = 1;
Expand Down Expand Up @@ -1431,8 +1434,11 @@ int hashsetNext(hashsetIterator *iter, void **elemptr) {
} else {
iter->fingerprint = hashsetFingerprint(iter->hashset);
}
if (iter->hashset->tables[0] == NULL) {
/* empty hashset, we're done */
break;
}
iter->index = 0;
/* skip the rehashed slots in table[0] */
if (hashsetIsRehashing(iter->hashset)) {
iter->index = iter->hashset->rehashIdx;
}
Expand All @@ -1442,9 +1448,8 @@ int hashsetNext(hashsetIterator *iter, void **elemptr) {
iter->posInBucket++;
if (iter->posInBucket >= ELEMENTS_PER_BUCKET) {
iter->posInBucket = 0;
iter->index++;
if (iter->index >= (long)numBuckets(iter->hashset->bucketExp[iter->table])) {
iter->index = 0;
iter->index = nextCursor(iter->index, expToMask(iter->hashset->bucketExp[iter->table]));
if (iter->index == 0) {
if (hashsetIsRehashing(iter->hashset) && iter->table == 0) {
iter->table++;
} else {
Expand Down
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