1 /*
2  * Exercise 3-6. Write a version of itoa that accepts three arguments instead
3  * of two. The third argument is a minimum field width; the converted number
4  * must be padded with blanks on the left if necessary to make it wide enough.
5  */
6 
7 #include <stdio.h>
8 #include <stdlib.h>
9 #include <limits.h>
10 #include <string.h>
11 
12 void reverse(char s[]) {
13 	int c, i, j;
14 	for (i = 0, j = strlen(s) - 1; i < j; i++, j--) {
15 		c = s[i];
16 		s[i] = s[j];
17 		s[j] = c;
18 	}
19 }
20 
21 void itoa(int n, char s[], int width) {
22 	int i, sign;
23 	if ((sign = n) < 0)
24 		n = -n;
25 	i = 0;
26 	do {
27 		s[i++] = n % 10 + '0';
28 	} while ((n /= 10) > 0);
29 	if (sign < 0)
30 		s[i++] = '-';
31 	while (i < width) {
32 		s[i++] = ' ';
33 	}
34 	s[i] = '\0';
35 	reverse(s);
36 }
37 
38 int assert(char *expect, char *actual) {
39 	printf("Expect: %s\n", expect);
40 	printf("Actual: %s\n", actual);
41 	return strcmp(expect, actual);
42 }
43 int main() {
44 	char s[100];
45 	char *t;
46 	itoa(231523, s, 10);
47 	assert("    231523", s);
48 	itoa(-131523, s, 10);
49 	assert("   -131523", s);
50 	itoa(34, s, 0);
51 	assert("34", s);
52 	itoa(-21, s, 0);
53 	assert("-21", s);
54 	itoa(0, s, 0);
55 	assert("0", s);
56 	itoa(0, s, 5);
57 	assert("    0", s);
58 }