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.
Parameters
mask: number
a gulong containing flags
nth_bit: number
the index of the bit to start the search from
Returns number
the index of the first bit set which is higher than nth_bit, or -1 if no higher bits are set
Find the position of the first bit set in
mask, searching from (but not including)nth_bitupwards. Bits are numbered from 0 (least significant) to sizeof(gulong) * 8 - 1 (31 or 63, usually). To start searching from the 0th bit, setnth_bitto -1.