#include <p32xxxx.h>
#include "db_utils.h"
#include "registers.h"
#include <stdlib.h>

int fac(int);

int i; /* Global */

int main(void)
{
     char buffer[10];

     while(1)
     {
	DBPRINTF("\nPlease input an integer (negative to quit):\n");
	i  =  0;    /* buffer is not reinitialized */
	while (i++ <= 9) buffer[i] = '\0';

	DBGETS(buffer,10);
	i = atoi(buffer);
	if (i < 0) break;
	if (i > 12) {DBPRINTF("\nToo large!\n"); continue;}
	
	DBPRINTF("Factorial(%d) = %d\n", i, fac(i));
      }; /* end while */	

     DBPUTS("\nProgram terminated. \n");
     DBPUTS("Click HALT=F5 and then RESET=F6 to stop the microcontroller.\n");

     return 0;

} /* end main */

int fac(int n) /* Modified factorial.s from page 80 of PGA */
{	asm("	1: 	addiu	$sp, $sp, -12	;\
			sw	$ra, 0($sp)	;\
			sw	$a0, 4($sp)	;\
			sw	$s0, 8($sp)	;\
			beqz	$a0, 2f		;\
			addiu	$a0, $a0, -1	;\
			jal	1b		;\
			lw	$s0, 4($sp)	;\
			mult	$v0, $s0	;\
			mflo	$v0		;\
			j	3f		;\
		 2: 	addiu	$v0, $0, 1	;\
		 3:	lw	$s0, 8($sp)	;\
			lw	$a0, 4($sp)	;\
			lw	$ra, 0($sp)	;\
			addiu	$sp, $sp, 12	;\
			jr	$ra		;\
		" );
}