tcpl_ex-3-6.c

/*
 * Exercise 3-6. Write a version of itoa that accepts three arguments instead 
 * of two. The third argument is a minimum field width; the converted number 
 * must be padded with blanks on the left if necessary to make it wide enough. 
 */
#include <stdio.h>
#include <limits.h>
#define abs(x) ((x) > 0) ? (x) : -(x)

void itoa(int n, char s[], int width);
void reverse(char s[]);
 
int main(void) {
    char buffer[20];
    
    itoa(INT_MIN, buffer, 20);
    printf("Buffer:%s\n", buffer);
    
    return 0;
}
 
void itoa(int n, char s[], int width) {
    int i, sign;
    
    sign = n;
    i = 0;
    do {
        s[i++] = abs(n % 10) + '0';
    } while ((n /= 10) != 0);
    if (sign < 0)
        s[i++] = '-';
    
    while (i < width )    /*  Only addition to original function  */
        s[i++] = ' ';
    
    s[i] = '\0';
    reverse(s);
}
 
void reverse(char s[]) {
    int c, i, j;
    for ( i = 0, j = strlen(s)-1; i < j; i++, j--) {
        c = s[i];
        s[i] = s[j];
        s[j] = c;
    }
}