Compare two files are exactly the same

Usually our computers are attacked by viruses or other spyware website.

I don't know whether they modified files in our computer,especially execute files, or maybe HTML files.

Now, make a program to compare two files if they are exactly the same. I'd like use it to compare suspected file withe backup file.

Just wrote the code as below:

void CFileCompareDlg::OnBrowse()
{
// TODO: Add your control notification handler code here
CFileDialog filedlg(TRUE, NULL, NULL);
if(filedlg.DoModal() == IDOK)
{
m_fileName1 = filedlg.GetPathName();
}

UpdateData(FALSE);

}

void CFileCompareDlg::OnBrowse2()
{
// TODO: Add your control notification handler code here
CFileDialog filedlg(TRUE, NULL, NULL);
if(filedlg.DoModal() == IDOK)
{
m_fileName2 = filedlg.GetPathName();
}

UpdateData(FALSE);

}

void CFileCompareDlg::OnCompare()
{
// TODO: Add your control notification handler code here
UpdateData(TRUE);
if(m_fileName1.Compare("")>0 && m_fileName2.Compare("")>0)
{
LPTSTR lpszFileName1 = new TCHAR[m_fileName1.GetLength()+1];
_tcscpy(lpszFileName1, m_fileName1);
CFile file1(lpszFileName1, CFile::modeRead|CFile::typeBinary|CFile::shareDenyNone);
ASSERT(file1);

LPTSTR lpszFileName2 = new TCHAR[m_fileName2.GetLength()+1];
_tcscpy(lpszFileName2, m_fileName2);
CFile file2(lpszFileName2, CFile::modeRead|CFile::typeBinary|CFile::shareDenyNone);
ASSERT(file2);

ULONGLONG ullFileLength1, ullFileLength2;
if((ullFileLength1=file1.GetLength()) != (ullFileLength2=file2.GetLength()))
{
MessageBox("The two files are not same length!");
return;
}

BYTE byte1, byte2;
ULONGLONG ullPos = 0;
while(ullFileLength1!=0)
{
file1.Read(&byte1, 1);
file2.Read(&byte2, 1);
ullPos ++;
if(byte1 != byte2)
{
char ch_Message[100];
sprintf(ch_Message, "The two files are not same at %d!", ullPos);
MessageBox(ch_Message);
return;
}
--ullFileLength1;
}
delete []lpszFileName1;
delete []lpszFileName2;

MessageBox("The two files are exactly the same!");
return;
}
else
{
MessageBox("Pls enter two files to be compared!");
return;
}

}

void CFileCompareDlg::OnExit()
{
// TODO: Add your control notification handler code here
CDialog::OnOK();
}