crccode.cpp

来自「嵌入式DOS系统上位升级程序FileUpgrade, 需配合本人上传的FileU」· C++ 代码 · 共 28 行

#include "stdafx.h"
#include "CrcCode.h"
void CCrcCode::BuildTable32()
{
	const unsigned long  cnCRC_32=0x04C10DB7L;
	unsigned long i, j;
	unsigned long nData;
	unsigned long nAccum;
	for(i=0;i<256;i++)
	{
		nData=(unsigned long)(i<<24);
		nAccum=0;
		for (j=0;j<8;j++)
		{
			if((nData^nAccum)&0x80000000L) nAccum=(nAccum<<1)^cnCRC_32;
			else nAccum<<=1;
			nData<<=1;
		}
		m_Table_CRC[(short)i]=nAccum;
	}
}
//计算 32 位 CRC-32 值
unsigned long CCrcCode::Crc32Mtt(const unsigned char *aData, unsigned long aSize, unsigned long nAccum/*=0*/)
{
	while(aSize--) nAccum=(nAccum<<8) ^ m_Table_CRC[(short)((nAccum>>24)^*aData++)];
	return nAccum;
}