Exercise 3.05

Page 64

Write the function itob(n,s,b) that converts the integer n into a base b character representation in the string s. In particular, itob(n,s,16) formats n as a hexadecimal integer in s.

#include <stdbool.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

#define LEN 1000

void itob(int n, char s[], int b);
void reverse(char s[]);

int main()
{
	char s[LEN];

	itob(254, s, 16);

	printf("%s", s);
}

void itob(int n, char s[], int b)
{
	int i, val, sign;

	if ((sign = n) < 0)
		n = -n;
	i = 0;
	do {
		val = n % b;
		s[i++] = val <= 9 ? (val + '0') : (val - 10 + 'a');
	} while ((n /= b) > 0);
	if (sign < 0)
		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;
	}
}