| Current Path : /usr/src/contrib/ipfilter/lib/ |
FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
| Current File : //usr/src/contrib/ipfilter/lib/count4bits.c |
/* $FreeBSD: release/9.1.0/contrib/ipfilter/lib/count4bits.c 170268 2007-06-04 02:54:36Z darrenr $ */
/*
* Copyright (C) 2002 by Darren Reed.
*
* See the IPFILTER.LICENCE file for details on licencing.
*
* $Id: count4bits.c,v 1.1.4.1 2006/06/16 17:20:57 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;
}