1*13885a66Sdarrenr /* $NetBSD: count4bits.c,v 1.2 2012/07/22 14:27:36 darrenr Exp $ */ 2bc4097aaSchristos 3bc4097aaSchristos /* 4c9d5dc6cSdarrenr * Copyright (C) 2012 by Darren Reed. 5bc4097aaSchristos * 6bc4097aaSchristos * See the IPFILTER.LICENCE file for details on licencing. 7bc4097aaSchristos * 8*13885a66Sdarrenr * Id: count4bits.c,v 1.1.1.2 2012/07/22 13:44:38 darrenr Exp $ 9bc4097aaSchristos */ 10bc4097aaSchristos 11bc4097aaSchristos #include "ipf.h" 12bc4097aaSchristos 13bc4097aaSchristos 14bc4097aaSchristos /* 15bc4097aaSchristos * count consecutive 1's in bit mask. If the mask generated by counting 16bc4097aaSchristos * consecutive 1's is different to that passed, return -1, else return # 17bc4097aaSchristos * of bits. 18bc4097aaSchristos */ count4bits(ip)19bc4097aaSchristosint count4bits(ip) 20bc4097aaSchristos u_int ip; 21bc4097aaSchristos { 22bc4097aaSchristos int cnt = 0, i, j; 23bc4097aaSchristos u_int ipn; 24bc4097aaSchristos 25bc4097aaSchristos ip = ipn = ntohl(ip); 26bc4097aaSchristos for (i = 32; i; i--, ipn *= 2) 27bc4097aaSchristos if (ipn & 0x80000000) 28bc4097aaSchristos cnt++; 29bc4097aaSchristos else 30bc4097aaSchristos break; 31bc4097aaSchristos ipn = 0; 32bc4097aaSchristos for (i = 32, j = cnt; i; i--, j--) { 33bc4097aaSchristos ipn *= 2; 34bc4097aaSchristos if (j > 0) 35bc4097aaSchristos ipn++; 36bc4097aaSchristos } 37bc4097aaSchristos if (ipn == ip) 38bc4097aaSchristos return cnt; 39bc4097aaSchristos return -1; 40bc4097aaSchristos } 41