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作者:青岛郎锐 来源:天极网 2007年10月17日
关键字:
BYTE CCRCDlg::CheckOut(BYTE *byteData, UINT nCount) { …… static BYTE CheckTable[256]= { 0x00,0x07,0x0e,0x09,0x1c,0x1b,0x12,0x15,0x38,0x3f, 0x36,0x31,0x24,0x23,0x2a,0x2d,0x70,0x77,0x7e,0x79, 0x6c,0x6b,0x62,0x65,0x48,0x4f,0x46,0x41,0x54,0x53, 0x5a,0x5d,0xe0,0xe7,0xee,0xe9,0xfc,0xfb,0xf2,0xf5, 0xd8,0xdf,0xd6,0xd1,0xc4,0xc3,0xca,0xcd,0x90,0x97, 0x9e,0x99,0x8c,0x8b,0x82,0x85,0xa8,0xaf,0xa6,0xa1, 0xb4,0xb3,0xba,0xbd,0xc7,0xc0,0xc9,0xce,0xdb,0xdc, 0xd5,0xd2,0xff,0xf8,0xf1,0xf6,0xe3,0xe4,0xed,0xea, 0xb7,0xb0,0xb9,0xbe,0xab,0xac,0xa5,0xa2,0x8f,0x88, 0x81,0x86,0x93,0x94,0x9d,0x9a,0x27,0x20,0x29,0x2e, 0x3b,0x3c,0x35,0x32,0x1f,0x18,0x11,0x16,0x03,0x04, 0x0d,0x0a,0x57,0x50,0x59,0x5e,0x4b,0x4c,0x45,0x42, 0x6f,0x68,0x61,0x66,0x73,0x74,0x7d,0x7a,0x89,0x8e, 0x87,0x80,0x95,0x92,0x9b,0x9c,0xb1,0xb6,0xbf,0xb8, 0xad,0xaa,0xa3,0xa4,0xf9,0xfe,0xf7,0xf0,0xe5,0xe2, 0xeb,0xec,0xc1,0xc6,0xcf,0xc8,0xdd,0xda,0xd3,0xd4, 0x69,0x6e,0x67,0x60,0x75,0x72,0x7b,0x7c,0x51,0x56, 0x5f,0x58,0x4d,0x4a,0x43,0x44,0x19,0x1e,0x17,0x10, 0x05,0x02,0x0b,0x0c,0x21,0x26,0x2f,0x28,0x3d,0x3a, 0x33,0x34,0x4e,0x49,0x40,0x47,0x52,0x55,0x5c,0x5b, 0x76,0x71,0x78,0x7f,0x6a,0x6d,0x64,0x63,0x3e,0x39, 0x30,0x37,0x22,0x25,0x2c,0x2b,0x06,0x01,0x08,0x0f, 0x1a,0x1d,0x14,0x13,0xae,0xa9,0xa0,0xa7,0xb2,0xb5, 0xbc,0xbb,0x96,0x91,0x98,0x9f,0x8a,0x8d,0x84,0x83, 0xde,0xd9,0xd0,0xd7,0xc2,0xc5,0xcc,0xcb,0xe6,0xe1, 0xe8,0xef,0xfa,0xfd,0xf4,0xf3 }; …… BYTE Result = CheckTable[*byteData]; for(UINT i=1;i<nCount;i++)//对数据流进行CRC校验和计算 { Result = Result^(*(byteData+i)); Result = CheckTable[Result]; } …… return Result;//返回计算出来的CRC校验和。 } |
…… //首先读取文件到缓存中去,并得到文件的长度 file.Open(FileName,CFile::modeReadWrite); int FileLen=file.GetLength(); //为缓存动态分配内存空间 BYTE* buf; buf=new BYTE [FileLen]; file.SeekToBegin(); file.Read(buf,FileLen); //调用CheckOut函数计算BMP位图的位图阵列部分(38字节以后部分)的CRC校验码 BYTE crc=CheckOut(buf+38,FileLen-38); //在前面提到过模2减法,在以2为模的加、减法中,都是和异或运算相同的。 //把经过模2减法的计算结果保存到BMP位图的保留空间中 buf[6]=0^crc; file.Seek(6,CFile::begin); file.Write(buf+6,1); //释放申请过的内存空间、关闭打开的文件 delete[] buf; file.Close(); …… |
…… file.Open(FileName,CFile::modeReadWrite); int FileLen=file.GetLength(); …… //读取文件到缓存 BYTE* buf; buf=new BYTE [FileLen+1]; file.SeekToBegin(); file.Read(buf,FileLen); file.Close(); //将印鉴恢复到数据序列的末尾 buf[FileLen]=buf[6]; //计算带有校验码(印鉴)的序列被G(x)标准多项式整除的余数 BYTE crc=CheckOut(buf+38,FileLen-37); //判断crc(余数)是否为0(即能否整除),来判定文件的原始性。 if(crc!=0) AfxMessageBox("警告!文件被改动过了!"); //CRC校验错误!印鉴有损。 else AfxMessageBox("文件没有发生过改动!"); //CRC校验正确,印鉴完好。 delete[] buf; …… |
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