crc529.h

//  (C) Copyright 2009-2011 Vit Kasal
//
//  Distributed under the Boost Software License, Version 1.0.
//  (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

#pragma once

#include <boost/type_traits.hpp>
#include <boost/cstdint.hpp>

namespace si
{
	//   unsigned int crc(unsigned int uiCount,unsigned char *pucDat);

	BOOST_STATIC_CONSTANT( boost::uint16_t, POLYNOM=0x8005);


	template<typename iterator>  boost::uint16_t crc(std::size_t uiCount,iterator it)
	{
		short int iTmp;
		unsigned short int uiTmp,uiTmp1,uiVal;
		iterator pucTmpDat;

		if (uiCount < 2) return(0);        // response value is "0" for none or one data boost::uint8_t
		pucTmpDat = it;

		uiTmp1 = *pucTmpDat++;
		uiTmp1 = (uiTmp1<<8) + *pucTmpDat++;

		if (uiCount == 2) return(uiTmp1);   // response value is CRC for two data boost::uint8_ts
		for (iTmp=(int)(uiCount>>1);iTmp>0;iTmp--)
		{

			if (iTmp>1)
			{
				uiVal = *pucTmpDat++;
				uiVal= (uiVal<<8) + *pucTmpDat++;
			}
			else
			{
				if (uiCount&1)               // odd number of data boost::uint8_ts, complete with "0"
				{
					uiVal = *pucTmpDat;
					uiVal= (uiVal<<8);
				}
				else
				{
					uiVal=0; //letzte Werte mit 0
				}
			}

			for (uiTmp=0;uiTmp<16;uiTmp++)
			{
				if (uiTmp1 & 0x8000)
				{
					uiTmp1  <<= 1;
					if (uiVal & 0x8000)uiTmp1++;
					uiTmp1 ^= POLYNOM;
				}
				else
				{
					uiTmp1  <<= 1;
					if (uiVal & 0x8000)uiTmp1++;
				}
				uiVal <<= 1;
			}
		}
		return(uiTmp1);
	}

}//namespace si