/*nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn
* PROGRAMMER: Roger W. Ehrich
* DATE: October 23, 2001
* 
* CALL: status = pos_number (string, number)
*
* PURPOSE: Parse a line containing a non-negative integer or *.  If *, return
*          32767, and if the string is empty, return 1.  The parser uses a
*          deterministic finite state machine (DFA).
*
* PARAMETERS: string  char *, a string containing the input number
*             number  int *, returns a positive number from the parse
*
* RETURNS:    status  int, 0 upon a successful parse or the index of the first
*                          character in error (first position is 1)
*
* NOTES: State 0: Skipping leading blanks or control characters
*        State 1: Found a sequence of consecutive numerals
*        State 2: Found a *
*        State 3: Skip trailing blanks or control characters
*        State 4: A trap state that indicates an error has occurred
*
*        class (char) classifies a character into one of 8 categories
uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu*/

	int pos_number (char *string, int *number) {

	  char next_state[4][8] =	// State transition matrix
	  {
	    {0, 0, 4, 2, 4, 4, 1, 4},
	    {3, 3, 4, 4, 4, 4, 1, 4},
	    {3, 3, 4, 4, 4, 4, 4, 4},
	    {3, 3, 4, 4, 4, 4, 4, 4}
	  };
	  char action[4][8] =		// Action matrix
	  {
	    {1, 1, 5, 2, 5, 5, 3, 5},
	    {1, 1, 5, 5, 5, 5, 4, 5},
	    {1, 1, 5, 5, 5, 5, 5, 5},
	    {1, 1, 5, 5, 5, 5, 5, 5}
	  };

	  char state = 1;		// The initial state
	  char act;			// The action to be taken
	  char star = 0;		// Haven't found a * yet when 0
	  int  status = 0;		// Good parse when 0
	  int  nlength = 0;		// The number of digits found
	  int  sum = 0;			// The partial sum of weighted digits
	  int  input;			// The class of the input character
	  int  j, ptr;			// Character offsets

// Return a 1 on an empty string

	  if (string[0] == '\0') {
	    *number = 1;
	    return status;
	    }

// Parse the string using the DFA

	  for (j = 0 ; string[j] != '\0' ; j++) {
	    input = class (string[j]);
	    act = action[state][input];
	    state = next_state[state][input];

// Decide what action to take, given present state and input character

	    switch (act) {
	      case 1: break;			// Act 1 - No action
	      case 2: star = string[j];		// Act 2 - Record a *
	              break;
	      case 3: ptr = j;			// Act 3 - Initialize a number
	              nlength = 1;
	              break;
	      case 4: nlength++;		// Act 4 - Append a digit
	              break;
	      case 5: status = j + 1;		// Act 5 - Return an error
	              *number = 0;
	              return status;
	      }
	    }

// Decode the number and check the bounds (maximum = 32767)

	  if (star != 0)
	    *number = 32767;
	  else
	    if (nlength == 0)
	      *number = 1;
	    else {
	      for (j = 0 ; j < nlength ; j++) {
	        sum += sum * 10 + string[ptr+j] - 48;
	        if (sum > 32767) sum = 32767;
	        }
	      *number = sum;
	      }

	  return status;
	  }