Function codepoint

extlibs/lua/src/lutf8lib.c:122–148

** codepoint(s, [i, [j [, lax]]]) -> returns codepoints for all ** characters that start in the range [i,j] */

** characters that start in the range [i,j]
*/
static int codepoint (lua_State *L) {
  size_t len;
  const char *s = luaL_checklstring(L, 1, &len);
  lua_Integer posi = u_posrelat(luaL_optinteger(L, 2, 1), len);
  lua_Integer pose = u_posrelat(luaL_optinteger(L, 3, posi), len);
  int lax = lua_toboolean(L, 4);
  int n;
  const char *se;
  luaL_argcheck(L, posi >= 1, 2, "out of range");
  luaL_argcheck(L, pose <= (lua_Integer)len, 3, "out of range");
  if (posi > pose) return 0;  /* empty interval; return no values */
  if (pose - posi >= INT_MAX)  /* (lua_Integer -> int) overflow? */
    return luaL_error(L, "string slice too long");
  n = (int)(pose -  posi) + 1;  /* upper bound for number of returns */
  luaL_checkstack(L, n, "string slice too long");
  n = 0;  /* count the number of returns */
  se = s + pose;  /* string end */
  for (s += posi - 1; s < se;) {
    utfint code;
    s = utf8_decode(s, &code, !lax);
    if (s == NULL)
      return luaL_error(L, "invalid UTF-8 code");
    lua_pushinteger(L, code);
    n++;
  }
  return n;
}


static void pushutfchar (lua_State *L, int arg) {