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41 lines
729 B
C
41 lines
729 B
C
/* $NetBSD: count4bits.c,v 1.2 2012/07/22 14:27:36 darrenr Exp $ */
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/*
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* Copyright (C) 2012 by Darren Reed.
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*
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* See the IPFILTER.LICENCE file for details on licencing.
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*
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* Id: count4bits.c,v 1.1.1.2 2012/07/22 13:44:38 darrenr Exp $
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*/
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#include "ipf.h"
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/*
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* count consecutive 1's in bit mask. If the mask generated by counting
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* consecutive 1's is different to that passed, return -1, else return #
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* of bits.
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*/
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int count4bits(ip)
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u_int ip;
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{
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int cnt = 0, i, j;
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u_int ipn;
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ip = ipn = ntohl(ip);
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for (i = 32; i; i--, ipn *= 2)
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if (ipn & 0x80000000)
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cnt++;
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else
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break;
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ipn = 0;
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for (i = 32, j = cnt; i; i--, j--) {
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ipn *= 2;
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if (j > 0)
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ipn++;
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}
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if (ipn == ip)
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return cnt;
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return -1;
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}
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