Function luaH_getn

Source/Misc/lua/src/lua.c:9800–9816

** 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 (t->node == dummynode)  /* hash part is empty? */
return j;  /* that is easy... */
else return unbound_search(t, j);
}