Function luaH_getn

src/Chain/libraries/glua/ltable.cpp:775–791

** Try to find a boundary in table 't'. A 'boundary' is an integer index ** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil). */

** such that t[i] is non-nil and t[i+1] is nil (and 0 if t[1] is nil).
*/
int luaH_getn(Table *t) {
    unsigned int j = t->sizearray;
    if (j > 0 && ttisnil(&t->array[j - 1])) {
        /* there is a boundary in the array part: (binary) search for it */
        unsigned int i = 0;
        while (j - i > 1) {
            unsigned int m = (i + j) / 2;
            if (ttisnil(&t->array[m - 1])) j = m;
            else i = m;
        }
        return i;
    }
    /* else must find a boundary in hash part */
    else if (isdummy(t->node))  /* hash part is empty? */
        return j;  /* that is easy... */
    else return unbound_search(t, j);
}