Function checkformat

lib/lua/src/lstrlib.c:1225–1238

** Check whether a conversion specification is valid. When called, ** first character in 'form' must be '%' and last character must ** be a valid conversion specifier. 'flags' are the accepted flags; ** 'precision' signals whether to accept a precision. */

** 'precision' signals whether to accept a precision.
*/
static void checkformat (lua_State *L, const char *form, const char *flags,
                                       int precision) {
  const char *spec = form + 1;  /* skip '%' */
  spec += strspn(spec, flags);  /* skip flags */
  if (*spec != '0') {  /* a width cannot start with '0' */
    spec = get2digits(spec);  /* skip width */
    if (*spec == '.' && precision) {
      spec++;
      spec = get2digits(spec);  /* skip precision */
    }
  }
  if (!isalpha(uchar(*spec)))  /* did not go to the end? */
    luaL_error(L, "invalid conversion specification: '%s'", form);
}


/*