Return to 32 Bit CRC File Calculation
// CRCfileDlg.cpp : implementation file
//
// Copyright © 2000 - 2008 Richard A. Ellingson
// http://www.createwindow.com
// mailto:CreateWindow.com@comcast.net
#include "stdafx.h"
#include "CRCfile.h"
#include "CRCfileDlg.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App About
class CAboutDlg : public CDialog
{
public:
CAboutDlg();
// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL
// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};
CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}
void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
/////////////////////////////////////////////////////////////////////////////
// CCRCfileDlg dialog
CCRCfileDlg::CCRCfileDlg(CWnd* pParent /*=NULL*/)
: CDialog(CCRCfileDlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CCRCfileDlg)
m_csCRCtext = _T("");
m_csFileName = _T("");
m_csURL = _T("");
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}
void CCRCfileDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CCRCfileDlg)
DDX_Text(pDX, IDC_CRCTEXT, m_csCRCtext);
DDX_Text(pDX, IDC_FILENAME, m_csFileName);
DDX_Text(pDX, IDC_URL, m_csURL);
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CCRCfileDlg, CDialog)
//{{AFX_MSG_MAP(CCRCfileDlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_BN_CLICKED(IDC_OPEN, OnOpen)
ON_WM_DROPFILES()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
/////////////////////////////////////////////////////////////////////////////
// CCRCfileDlg message handlers
BOOL CCRCfileDlg::OnInitDialog()
{
CDialog::OnInitDialog();
// Add "About..." menu item to system menu.
// IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);
CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
// ******* Begin custom code *******
// We have a Minimize box on the dialog, but we don't want
// the Size and Maximize options on the system menu so disable them.
pSysMenu->EnableMenuItem(SC_SIZE, MF_GRAYED);
pSysMenu->EnableMenuItem(SC_MAXIMIZE, MF_GRAYED);
// ******* End custom code *******
}
}
// Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon
// TODO: Add extra initialization here
// ******* Begin custom code *******
// Don't forget to create the lookup table first
Init_CRC32_Table();
// Set the default text for the dialog box
m_csFileName = "no file selected";
m_csCRCtext = "0";
m_csURL = "http://www.createwindow.com";
UpdateData(FALSE);
// For convenience, we'll add file Drag and Drop support
DragAcceptFiles(TRUE);
// ******* End custom code *******
return TRUE; // return TRUE unless you set the focus to a control
}
void CCRCfileDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}
// If you add a minimize button to your dialog, you will need the code below
// to draw the icon. For MFC applications using the document/view model,
// this is automatically done for you by the framework.
void CCRCfileDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting
SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);
// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;
// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}
// The system calls this to obtain the cursor to display while the user drags
// the minimized window.
HCURSOR CCRCfileDlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}
// Everything above this line is AppWizard generated code
// except for a few lines in OnInitDialog()
// ******* Begin custom code *******
// Call this function only once to initialize the CRC table.
void CCRCfileDlg::Init_CRC32_Table()
{// Called by OnInitDialog()
// This is the official polynomial used by CRC-32
// in PKZip, WinZip and Ethernet.
ULONG ulPolynomial = 0x04c11db7;
// 256 values representing ASCII character codes.
for(int i = 0; i <= 0xFF; i++)
{
crc32_table[i]=Reflect(i, 8) << 24;
for (int j = 0; j < 8; j++)
crc32_table[i] = (crc32_table[i] << 1) ^ (crc32_table[i] & (1 << 31) ? ulPolynomial : 0);
crc32_table[i] = Reflect(crc32_table[i], 32);
}
}
// Reflection is a requirement for the official CRC-32 standard.
// You can create CRCs without it, but they won't conform to the standard.
ULONG CCRCfileDlg::Reflect(ULONG ref, char ch)
{// Used only by Init_CRC32_Table()
ULONG value(0);
// Swap bit 0 for bit 7
// bit 1 for bit 6, etc.
for(int i = 1; i < (ch + 1); i++)
{
if(ref & 1)
value |= 1 << (ch - i);
ref >>= 1;
}
return value;
}
// Handler for the "Select a file" button.
void CCRCfileDlg::OnOpen()
{
CFileDialog dlg(TRUE, NULL, "(all files)", OFN_HIDEREADONLY,
"All Files (*.*)|*.*||", this);
if(IDOK != dlg.DoModal())
return;
m_csFileName = dlg.GetPathName();
// Open the file and read it.
Open_File();
}
// This function uses the crc32_table lookup table
// to generate a CRC for csData
int CCRCfileDlg::Get_CRC(CString &csData, DWORD dwSize)
{
// Be sure to use unsigned variables,
// because negative values introduce high bits
// where zero bits are required.
ULONG crc(0xffffffff);
int len;
unsigned char* buffer;
len = dwSize;
// Save the text in the buffer.
buffer = (unsigned char*)(LPCTSTR)csData;
// Perform the algorithm on each character
// in the string, using the lookup table values.
while(len--)
crc = (crc >> 8) ^ crc32_table[(crc & 0xFF) ^ *buffer++];
// Exclusive OR the result with the beginning value.
return crc^0xffffffff;
}
// Handler for Close program messages
void CCRCfileDlg::OnCancel()
{
// TODO: Add extra cleanup here
// I like to override this function so the dialog
// doesn't close when the Escape key is pressed.
if(GetKeyState(VK_ESCAPE) & 128)
return;
CDialog::OnCancel();
}
// This function adds file Drag and Drop support.
// It isn't needed to calculate the CRC.
void CCRCfileDlg::OnDropFiles(HDROP hDropInfo)
{
char lpszFile[MAX_PATH];
CFileFind file;
DragQueryFile(hDropInfo, 0, lpszFile, MAX_PATH);
BOOL trufal = file.FindFile(lpszFile);
if(trufal)
{
file.FindNextFile();
if(!file.IsDirectory())
{
m_csFileName = lpszFile;
//Open the file and read it.
Open_File();
}
}
// Let CDialog release the memory used in hDropInfo
CDialog::OnDropFiles(hDropInfo);
}
// Open the file, read it, and obtain the CRC from Get_CRC()
void CCRCfileDlg::Open_File()
{
HANDLE hFile = {NULL};
DWORD dwSize, bytes_read;
// Open the file and get ready to read it.
// Don't be confused by the CreateFile() function,
// we're only opening an existing file.
hFile = CreateFile(m_csFileName, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
NULL, OPEN_EXISTING,
FILE_FLAG_SEQUENTIAL_SCAN, NULL);
if(hFile == INVALID_HANDLE_VALUE)
{
MessageBox("Failed to open the file.\n\n" + m_csFileName, "Error - CRC File Demo");
return;
}
// Get the file size so we know how long to make our buffer.
dwSize = GetFileSize(hFile, NULL);
// Create a CString buffer of the proper length
// and fill it with spaces.
CString csData(' ', dwSize);
// Read the file into the buffer
ReadFile(hFile, csData.GetBuffer(dwSize), dwSize, &bytes_read, NULL);
// We're done with the file handle so close it.
CloseHandle(hFile);
// Always release the buffer after writing to it.
csData.ReleaseBuffer();
// Check to be sure we read the whole file.
if(dwSize != bytes_read)
{
MessageBox("Failed to read the file.\n\n" + m_csFileName, "Error - CRC File Demo");
return;
}
// Note: At this point, we can't use normal string functions
// on csData because it might contain NULL characters.
// In other words, GetLength() will only return the count
// up to the first NULL. Always include dwSize when passing
// the string so we know the full length.
int nCRC = Get_CRC(csData, dwSize);
// Convert the returned integer into a character string.
char ch[20];
itoa(nCRC, ch, 16); // Note that the integer is a 16 bit hex
// Send the CRC string to the dialog.
m_csCRCtext = ch;
// If the file path is likely to be too long to display shorten it.
int nMax = 60;
if(m_csFileName.GetLength() > nMax)
m_csFileName = m_csFileName.Left(3) + "..." + m_csFileName.Right(nMax -6);
UpdateData(FALSE);
}
// ******* End custom code *******