- /*
- * Mask out the bits smaller than pos in the current unit.
- * We are only interested in bits set higher than pos.
- */
- unsigned long curr_unit = bs->data[unit_number] & ~in_unit_mask;
-
- /* Find the next bit set in the unit. */
- unsigned long next_in_this_unit
- = _bitset_inside_ntz_value(set ? curr_unit : ~curr_unit);
-
- /* If there is a bit set in the current unit, exit. */
- if(next_in_this_unit < BS_UNIT_SIZE_BITS)
- return next_in_this_unit + unit_number * BS_UNIT_SIZE_BITS;
-
- /* Else search for set bits in the next units. */
- else {
- unsigned long i;
- for(i = unit_number + 1; i < bs->units; ++i) {
- unsigned long data = bs->data[i];
- unsigned long first_set = _bitset_inside_ntz_value(set ? data : ~data);
- if(first_set < BS_UNIT_SIZE_BITS)
- return first_set + i * BS_UNIT_SIZE_BITS;
+ if(unit_number >= bs->units)
+ return -1;
+
+ {
+ unsigned long bit_in_unit = pos & BS_UNIT_MASK;
+ unsigned long in_unit_mask = (1 << bit_in_unit) - 1;
+
+ /*
+ * Mask out the bits smaller than pos in the current unit.
+ * We are only interested in bits set higher than pos.
+ */
+ unsigned long curr_unit = bs->data[unit_number] & ~in_unit_mask;
+
+ /* Find the next bit set in the unit. */
+ unsigned long next_in_this_unit
+ = _bitset_inside_ntz_value(set ? curr_unit : ~curr_unit);
+
+ /* If there is a bit set in the current unit, exit. */
+ if(next_in_this_unit < BS_UNIT_SIZE_BITS)
+ return next_in_this_unit + unit_number * BS_UNIT_SIZE_BITS;
+
+ /* Else search for set bits in the next units. */
+ else {
+ unsigned long i;
+ for(i = unit_number + 1; i < bs->units; ++i) {
+ unsigned long data = bs->data[i];
+ unsigned long first_set = _bitset_inside_ntz_value(set ? data : ~data);
+ if(first_set < BS_UNIT_SIZE_BITS)
+ return first_set + i * BS_UNIT_SIZE_BITS;
+ }