/* $NetBSD: count4bits.c,v 1.2 2012/07/22 14:27:36 darrenr Exp $ */ /* * Copyright (C) 2012 by Darren Reed. * * See the IPFILTER.LICENCE file for details on licencing. * * Id: count4bits.c,v 1.1.1.2 2012/07/22 13:44:38 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; }