/* Fibonacci .c */

/* Shows how a (doubly) recursive program can be directly
 * translated from the MIPS code given in Pervin's book.
 * Of course it is a very, very inefficient way to do the
 * calculations but it shows that this can be done.
 */

#include <p32xxxx.h>
#include "db_utils.h"
#include "registers.h" /* Now can use usual names */
#include <stdlib.h>

int fib(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 > 30) {DBPRINTF("\nTakes too long!!\n"); continue;}

	   DBPRINTF("Fibonacci(%d) = %d\n", i, fib(i));
	};    /* end while */	

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

	return 0;
}

int fib(int n) /* Modified fibonacci.s from page 82 of PGA */
{	asm("   1: 	addiu	$sp, $sp, -12	;\
			sw	$ra, 0($sp)	;\
			sw	$a0, 4($sp)	;\
			sw	$s0, 8($sp)	;\
			li	$s0, 1		;\
			ble	$a0, $s0, 2f	;\
			addiu	$a0, $a0, -1	;\
			jal	1b		;\
			move	$s0, $v0	;\
			addiu	$a0, $a0, -1	;\
			jal	1b		;\
			add	$v0, $v0, $s0	;\
			j	3f		;\
		 2: 	move	$v0, $a0	;\
		 3:	lw	$s0, 8($sp)	;\
			lw	$a0, 4($sp)	;\
			lw	$ra, 0($sp)	;\
			addiu	$sp, $sp, 12	;\
			jr	$ra		;\
		" );
}