CString 16进制字符串转为 BYTE[] 数组

static int HexToNum(CString str)
{

int dem=0;
for(int i=0;i<str.GetLength();i++)
{
result=dem*16;
if((str[i]<='9')&&(str[i]>='0'))        //0~9之间的字符
result+=str[i]-'0';
else if((str[i]<='F')&&(str[i]>='A'))   //A~F之间的字符
result+=str[i]-'A'+10;
else if((str[i]<='f')&&(str[i]>='a'))   //a~f之间的字符
result+=str[i]-'a'+10;
else
return -1;                          //出错时返回-1
}
return dem;
}

cmd [0] = HexToNum(str[0]);
cmd[1] = HexToNum(str[1]);
cmd [2] = HexToNum(str[2]);
cmd[13 = HexToNum(str[3]);