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/*  crc.cpp 
 
    CRC error checking */ 
 
/* 
 *  @(#) crc.cc 1.5, last edit: 6/15/94 16:55:30 
 *  @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de) 
 *  @(#) Berlin University of Technology 
 * 
 *  This program is free software; you can redistribute it and/or modify 
 *  it under the terms of the GNU General Public License as published by 
 *  the Free Software Foundation; either version 2 of the License, or 
 *  (at your option) any later version. 
 * 
 *  This program is distributed in the hope that it will be useful, 
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of 
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 *  GNU General Public License for more details. 
 * 
 *  You should have received a copy of the GNU General Public License 
 *  along with this program; if not, write to the Free Software 
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
 */ 
 
#include "all.h" 
#include "crc.h" 
 
// polynomial generator 
const uint16 Crc16::polynomial = 0x8005; 
 
void Crc16::add_bits (uint32 bitstring, uint32 length) 
{ 
  uint32 bitmask = 1 << (length - 1); 
  do 
	 if (!(crc & 0x8000) ^ !(bitstring & bitmask)) 
	 { 
		crc <<= 1; 
		crc ^= polynomial; 
	 } 
	 else 
		crc <<= 1; 
  while (bitmask >>= 1); 
}