Exercise 2.22 MIPS Coding and ASCII Strings その2

2.22 [20] <§§2.7, 2.8> Write a procedure, bcount, in MIPS assembly language. The bcount procedure takes a single argument, which is a pointer to a string in register $a0, and it returns a count of the total number of b characters in the string in register $v0 . You must use your bfind procedure in Exercise 2.36 in your implementation of bcount

文字列の長さを数える関数を書きなさい。

#include <stdio.h>
#include <assert.h>
#include <string.h>

int bcount(const char *s);

int bcount(const char *s)
{
	int cnt;
	const char *p;

	assert(s!=NULL);
	
	cnt = 0;
	for(p=s;*p!='\0';p++){
		cnt++;
	}
	assert(cnt >= 0);

	return cnt;
}

char *test_data[] = {"1", "02", "003", "abcdef", "", NULL};

int main(void)
{
	
	int i;
	int golden;
	int ans;
	int err;

	err = 0;

	for(i=0;test_data[i]!=NULL;i++){
		golden = strlen(test_data[i]);
		ans = bcount(test_data[i]);
		if(ans == golden) {
			printf("OK:%d\n", ans);
		} else {
			err++;
			printf("ERROR:data = %s, golden = %d, ans = %d\n", 
						 test_data[i], golden, ans);
		}
	}


	if(err!=0){
	 	printf("ERROR %d found\n", err);
 	} else {
		 printf("ALL DATA PASSED\n");
	 }
	return 0;
}

答え

bcount:
	lbu	$2,0($4)
	b	.L8
	move	$3,$0

.L10:
	addiu	$4,$4,1
	lbu	$2,0($4)
	addiu	$3,$3,1
.L8:
	bne	$2,$0,.L10
	move	$2,$3

	j	$31
	nop