ReadFile() problem

retreive the error with GetLastError()

look at this:

http://www.microsoft.com/whdc/driver/tips/OverlappedIo.mspx

ike

Thanks,

Unfortunately, as i said I'm new to this. It all seems unnecessarily complicated to be honest; i was able to accomplish this with 7 lines of code in C, and yet, with WIN32, it requires non-intuitive functions with a ludicrous amount of parameters, all of which are microsoft proprietary datatypes. You cant just call GetLastError(), you need to parse the output using another function, FormatMessage. I thought APIs were supposed to make life easier as opposed to harder??

FYI:
>>#include <iostream.h>

iostream.h is not part of the C++ standard, and should not be used in any new code.  It's not portable, and will not compile on modern compilers like VC++ 7.x and 8.0.

You should use the extensionless version which is part of the C++ standard, and it is portable.
#include <iostream>
using namespace std;

Some STL *.h libraries have bugs in them, because these libraries are no longer being maintained by the compiler manufature.

Update: GetLastError() is returning error "the parameter is incorrect" - anybody know what could cause this

rgds
pushpop

Two things:

You have to specify LPDWORD bytesRead and you have to read at least the sector size (512 bytes for example)

This works for me:

...
if(ReadFile(hDevice, buffer, 512, &dwBytesRead, NULL)==FALSE)  /*read first 20 bytes of MBR*/
...

Dont forge to increase your buffer size.

Bernd

Bernd: Thanks for that! I tried reading data in sector-sized chunks, but it didn't work, but I didn't specify LPDWORD bytesRead, so i'll try that and let you know how I'm getting on. I'm using Visual C++ 6.0, if that makes a difference, thougl I wouldnt expect it to!

Thanks to everyone for your help so far :-)

rgds

pushpop

Ok, I got that working, but now I'm having another problem. The buffer is being prematurely truncated, and I think it's because there are 0-value bytes that the program is mistaking for null-terminators. Could anyone offer any help?

here is the code:

//filename: main.cpp
//function: draws the main program window
//author:  

#include <windows.h>
#include "Resource.h"
#include <cstring>                                                //header file which contains message values
#include <iostream>
#include <cstring>
using namespace std;
#include <string.h>

//---------------------------------------------------------------------------
HWND hWnd;
LRESULT CALLBACK DlgProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK AboutProc(HWND hWndDlg, UINT Msg, WPARAM wParam, LPARAM lParam);

char * drive ="\\\\.\\PhysicalDrive0";
char * temp;
BYTE buffer[513];
HWND hWndJump;
HWND hWndEdit;
HANDLE hfile;
LPVOID lpMsgBuf;
DWORD bytesRead;
HINSTANCE hInst;
//---------------------------------------------------------------------------
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                           LPSTR lpCmdLine, int nCmdShow)
{
      DialogBox(hInstance, MAKEINTRESOURCE(IDD_DLGFIRST),                              //make the dialog
                hWnd, reinterpret_cast<DLGPROC>(DlgProc));



      hInst = hInstance;
      return FALSE;

      
}
//---------------------------------------------------------------------------
LRESULT CALLBACK AboutProc(HWND hWndDlg, UINT Msg, WPARAM wParam, LPARAM lParam)
{
            HWND textBoxHandle = GetDlgItem(hWndDlg,IDD_ABOUTTEXT);
            char * aboutMsg =   "Copyright \251 2006 Eric Chubb\n\n"
            "THE SOFTWARE IS PROVIDED ""AS IS"", WITHOUT "
            "WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, "
            "INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF "
            "MERCHANTABILITY, FITNESS FOR A PARTICULAR "
            "PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE "
            "COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES "
            "OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, "
            "TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN "
            "CONNECTION WITH THE SOFTWARE OR THE USE OR "
            "OTHER DEALINGS IN THE SOFTWARE.\n\n"
            "Version history: 0.1 - Basic disk analysis implemented - "
            "Master boot record only";
      switch(Msg)
            {
                  case WM_INITDIALOG:      
                        
                        SetWindowText(textBoxHandle,aboutMsg);
                        return TRUE;
                  
                  case WM_COMMAND:
                        
                        switch(wParam)
                        {
                              case IDC_OKBUTT:      
                        
                              EndDialog(hWndDlg,0);
                              return TRUE;
                        }

                        
            }
            return FALSE;
                  
}



LRESULT CALLBACK DlgProc(HWND hWndDlg, UINT Msg, WPARAM wParam, LPARAM lParam)
{
      hWndEdit = GetDlgItem(hWndDlg,IDC_EDIT1);
      switch(Msg)
      {
            case WM_INITDIALOG:      
                              
                              //when the dialog box is instantiated..

                  return TRUE;
                  
            
                  
                  case WM_COMMAND:      // command received?
                  
                  
                        switch(wParam)
                        {
                              case IDD_ABOUTBUTTON:// about the program
                  
                            DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUT),
                              hWnd, (DLGPROC)AboutProc);
                                                
                                            return FALSE;
                              
                        case IDOK:       
                              hfile = CreateFile(drive,GENERIC_READ,                   //open drive
                     FILE_SHARE_READ|FILE_SHARE_WRITE,
                     NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL,
                     NULL);
      
      
                  if(hfile==INVALID_HANDLE_VALUE)                                          //if the device cant be mounted
                                                                                                      //print why
                  {
                  
                              FormatMessage(                                                      //woeful formatting prerequisite
                              FORMAT_MESSAGE_ALLOCATE_BUFFER |                        //converts the DWORD error value
                                                                                                      //returned by GetLastError()
                            FORMAT_MESSAGE_FROM_SYSTEM |                              //into a string and prints it
                              FORMAT_MESSAGE_IGNORE_INSERTS,
                              NULL,
                              GetLastError(),
                              0, // Default language
                              (LPTSTR) &lpMsgBuf,
                              0,
                              NULL );
                              MessageBox( NULL, (LPCTSTR)lpMsgBuf, "Error opening device", MB_OK | MB_ICONWARNING );

                  
                        return FALSE;
                        break;
                        
                        
                  }
   
            
                  hWndJump = GetDlgItem(hWndDlg,IDJUMPINSTR);                        //Get text box handle

                  if(ReadFile(hfile,buffer,512,&bytesRead,NULL)==FALSE)                        //read first 512 bytes of MBR or say whats wrong
                  {
                              FormatMessage(
                              FORMAT_MESSAGE_ALLOCATE_BUFFER |
                            FORMAT_MESSAGE_FROM_SYSTEM |
                              FORMAT_MESSAGE_IGNORE_INSERTS,
                              NULL,
                              GetLastError(),
                              0, // Default language
                              (LPTSTR) &lpMsgBuf,
                              0,
                              NULL );
                              MessageBox( NULL, (LPCSTR)lpMsgBuf, "Disk read error", MB_OK | MB_ICONWARNING );
                              SetWindowText(hWndJump,"device error");
                              return FALSE;
                        
                  }
      
      
                  //SetWindowText(hWndJump,buffer);
                  temp = reinterpret_cast<TCHAR *>(buffer);
                  SetWindowText(hWndEdit,temp);
                  return TRUE;
            
                  
            
                  case IDCANCEL:// i want out
                        EndDialog(hWndDlg, 0);
                        return TRUE;

                        break;
                        

                  
            }
      }
      return FALSE;

      
}


//---------------------------------------------------------------------------

Ok thanks I'll try it this evening and let you know how I got on

Thanks for your answer, it worked a treat!