Previous: Parsing a Template String, Up: Formatted Output   [Contents][Index]

12.12.11 Example of Parsing a Template String

Here is an example of decoding argument types for a format string. We assume this is part of an interpreter which contains arguments of type NUMBER, CHAR, STRING and STRUCTURE (and perhaps others which are not valid here). 

/* Test whether the nargs specified objects
   in the vector args are valid
   for the format string format:
   if so, return 1.
   If not, return 0 after printing an error message.  */

int
validate_args (char *format, int nargs, OBJECT *args)
{
  int *argtypes;
  int nwanted;

  /* Get the information about the arguments.
     Each conversion specification must be at least two characters
     long, so there cannot be more specifications than half the
     length of the string.  */

  argtypes = (int *) alloca (strlen (format) / 2 * sizeof (int));
  nwanted = parse_printf_format (string, nelts, argtypes);

  /* Check the number of arguments.  */
  if (nwanted > nargs)
    {
      error ("too few arguments (at least %d required)", nwanted);
      return 0;
    }

  /* Check the C type wanted for each argument
     and see if the object given is suitable.  */
  for (i = 0; i < nwanted; i++)
    {
      int wanted;

      if (argtypes[i] & PA_FLAG_PTR)
	wanted = STRUCTURE;
      else
	switch (argtypes[i] & ~PA_FLAG_MASK)
	  {
	  case PA_INT:
	  case PA_FLOAT:
	  case PA_DOUBLE:
	    wanted = NUMBER;
	    break;
	  case PA_CHAR:
	    wanted = CHAR;
	    break;
	  case PA_STRING:
	    wanted = STRING;
	    break;
	  case PA_POINTER:
	    wanted = STRUCTURE;
	    break;
	  }
      if (TYPE (args[i]) != wanted)
	{
	  error ("type mismatch for arg number %d", i);
	  return 0;
	}
    }
  return 1;
}