菜鸟求部分代码解析(C++ MFC)10进制转16进制、CRC-16校验
求高手帮我解读下一些代码,看了几遍也有的地方没明白。不知之处以用红字标志,请各位帮我讲的仔细点!谢谢高手!
void CCRCProgramDlg::OnButtonGetcrc()
{
// TODO: Add your control notification handler code here
UpdateData(TRUE);
char data[512];
int len=Str2Hex(m_strEditRawdata,data);
unsigned char *ptemp=(unsigned char*)((LPCTSTR)data);
unsigned short cc=CreateCRC(ptemp,len);
1 下面两句求解析
unsigned short hightbit=cc/256;
unsigned short lowbit = cc-hightbit*256;
if (hightbit == 0 && hightbit == 0 && m_strEditRawdata.GetLength() == 0 )
{
m_strEditCRCResult.Empty();
}
CString strHighBit;
strHighBit.Format("%02x",hightbit);
CString strLowBit;
strLowBit.Format("%02x",lowbit);
m_strEditCRCResult = strLowBit + ' ' + strHighBit;
if ((hightbit == 0 &&lowbit == 0 )|| m_strEditRawdata.GetLength() == 0 )
{
m_strEditCRCResult.Empty();
}
UpdateData(false);
}
//---------------------下面为校验码处理函数-----------------------
#define CRC16_GEN_POL 0x8005
#define MKSHORT(a,b) ((unsigned short) (a) | ((unsigned short)(b) << 8))
/* ::---------------------------------------------------------------------
:: FN: CreateCRC; CRC in ANSI - C
:: Synopsis: static void CreateCRC(BYTE *CommData,WORD uLen)
:: Function: formation of the CRC16 checksum.
------------------------------------------------------------------------*/
unsigned short CCRCProgramDlg::CreateCRC(unsigned char *CommData, unsigned int uLen )
{
unsigned short uCrc16;
unsigned char abData[2];
uCrc16 = 0;
abData[0] = 0;
if(uLen==0)
return(uCrc16);
else
{
while (uLen-- )
{
abData[1] = abData[0];
abData[0] = *CommData++;
if(uCrc16 & 0x8000) //2条件语句为什么是这样
{
uCrc16 = (uCrc16 & 0x7fff) << 1;
uCrc16 ^= CRC16_GEN_POL;
}
else
{
uCrc16 <<= 1;
}
3 下面一句求解析,MKSHORT是什么函数啊,网上没找到
uCrc16 ^= MKSHORT (abData[0] , abData[1]);
}
// uCrc16 = 0;
return(uCrc16);
}
}
int CCRCProgramDlg::Str2Hex(CString str, char* data)
{
int t,t1;
int rlen=0,len=str.GetLength();
//data.SetSize(len/2);
for(int i=0;i<len;)
{
char l,h=str[i];
if(h==' ')
{
i++;
continue;
}
i++;
if(i>=len)
break;
l=str[i];
t=HexChar(h);
t1=HexChar(l);
if((t==16)||(t1==16))
break;
else
t=t*16+t1;
i++;
data[rlen]=(char)t;
rlen++;
}
return rlen;
}
4 下面求一句句注释
char CCRCProgramDlg::HexChar(char c)//转换成16进制
{
if((c>='0')&&(c<='9'))//进位
return c-0x30;//0x30等于0??为什么
else if((c>='A')&&(c<='F'))
return c-'A'+10;
else if((c>='a')&&(c<='f'))
return c-'a'+10;
else
return 0x10;
}