Function str_find_aux

extlibs/lua/src/lstrlib.c:770–813

static int str_find_aux (lua_State *L, int find) {
  size_t ls, lp;
  const char *s = luaL_checklstring(L, 1, &ls);
  const char *p = luaL_checklstring(L, 2, &lp);
  size_t init = posrelatI(luaL_optinteger(L, 3, 1), ls) - 1;
  if (init > ls) {  /* start after string's end? */
    luaL_pushfail(L);  /* cannot find anything */
    return 1;
  }
  /* explicit request or no special characters? */
  if (find && (lua_toboolean(L, 4) || nospecials(p, lp))) {
    /* do a plain search */
    const char *s2 = lmemfind(s + init, ls - init, p, lp);
    if (s2) {
      lua_pushinteger(L, (s2 - s) + 1);
      lua_pushinteger(L, (s2 - s) + lp);
      return 2;
    }
  }
  else {
    MatchState ms;
    const char *s1 = s + init;
    int anchor = (*p == '^');
    if (anchor) {
      p++; lp--;  /* skip anchor character */
    }
    prepstate(&ms, L, s, ls, p, lp);
    do {
      const char *res;
      reprepstate(&ms);
      if ((res=match(&ms, s1, p)) != NULL) {
        if (find) {
          lua_pushinteger(L, (s1 - s) + 1);  /* start */
          lua_pushinteger(L, res - s);   /* end */
          return push_captures(&ms, NULL, 0) + 2;
        }
        else
          return push_captures(&ms, s1, res);
      }
    } while (s1++ < ms.src_end && !anchor);
  }
  luaL_pushfail(L);  /* not found */
  return 1;
}


static int str_find (lua_State *L) {