/*
 * Copyright (C) 1993-2001 by Darren Reed.
 *
 * See the IPFILTER.LICENCE file for details on licencing.
 *
 * $Id: count4bits.c,v 1.1 2002/06/15 04:46:39 darrenr Exp $
 */

#include "ipf.h"


/*
 * count consecutive 1's in bit mask.  If the mask generated by counting
 * consecutive 1's is different to that passed, return -1, else return #
 * of bits.
 */
int     count4bits(ip)
u_int   ip;
{
        int cnt = 0, i, j;
        u_int ipn;

        ip = ipn = ntohl(ip);
        for (i = 32; i; i--, ipn *= 2)
                if (ipn & 0x80000000)
                        cnt++;
                else
                        break;
        ipn = 0;
        for (i = 32, j = cnt; i; i--, j--) {
                ipn *= 2;
                if (j > 0)
                        ipn++;
        }
        if (ipn == ip)
                return cnt;
        return -1;
}