Function findindex

lib/lua/src/ltable.c:331–346

** returns the index of a 'key' for table traversals. First goes all ** elements in the array part, then elements in the hash part. The ** beginning of a traversal is signaled by 0. */

** beginning of a traversal is signaled by 0.
*/
static unsigned int findindex (lua_State *L, Table *t, TValue *key,
                               unsigned int asize) {
  unsigned int i;
  if (ttisnil(key)) return 0;  /* first iteration */
  i = ttisinteger(key) ? arrayindex(ivalue(key)) : 0;
  if (i - 1u < asize)  /* is 'key' inside array part? */
    return i;  /* yes; that's the index */
  else {
    const TValue *n = getgeneric(t, key, 1);
    if (l_unlikely(isabstkey(n)))
      luaG_runerror(L, "invalid key to 'next'");  /* key not found */
    i = cast_int(nodefromval(n) - gnode(t, 0));  /* key index in hash table */
    /* hash elements are numbered after array ones */
    return (i + 1) + asize;
  }
}


int luaH_next (lua_State *L, Table *t, StkId key) {