Function hllDenseSet

app/redis-6.2.6/src/hyperloglog.c:493–503

Low level function to set the dense HLL register at 'index' to the * specified value if the current value is smaller than 'count'. * * 'registers' is expected to have room for HLL_REGISTERS plus an * additional byte on the right. This requirement is met by sds strings * automatically since they are implicitly null terminated. * * The function always succeed, however if as a result of the op

 * the approximated cardinality changed, 1 is returned. Otherwise 0
 * is returned. */
int hllDenseSet(uint8_t *registers, long index, uint8_t count) {
    uint8_t oldcount;

    HLL_DENSE_GET_REGISTER(oldcount,registers,index);
    if (count > oldcount) {
        HLL_DENSE_SET_REGISTER(registers,index,count);
        return 1;
    } else {
        return 0;
    }
}

/* "Add" the element in the dense hyperloglog data structure.
 * Actually nothing is added, but the max 0 pattern counter of the subset