Find the position of the first bit set in mask, searching from (but not including) nth_bit upwards. Bits are numbered from 0 (least significant) to sizeof(gulong) * 8 - 1 (31 or 63, usually). To start searching from the 0th bit, set nth_bit to -1.
a gulong containing flags
the index of the bit to start the search from
the index of the first bit set which is higher than nth_bit
See Implementation
Find the position of the first bit set in mask, searching from (but not including) nth_bit upwards. Bits are numbered from 0 (least significant) to sizeof(gulong) * 8 - 1 (31 or 63, usually). To start searching from the 0th bit, set nth_bit to -1.