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[Return]                   Backup Tape Capacity                   [Return]

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          The tape backup API is not really difficult...it's more or
  less like reading and writing to a file in sequential order, but it
  took more effort than I thought was really needed because of the
  surreal documentation. The function below is for my own good as much
  as anyone else's. The function, called by a dialog box in my little
  example, opens a tape, prepares the tape and waits for it to
  stabilize, then obtains the full and remaining capacity of the tape
  along with a couple other values of interest and displays the whole
  thing in a listbox. In the event of an error, the error code is also
  displayed in the listbox and the function ends. The main thing to note
  is the PrepareTape() function. Practically nothing can be done without
  calling it, and that's what burned me for a few hours.

 // === Obtain capacity and remaining space on a tape ==========================

 BOOL DoTapeSize( HWND hWnd )
 {
    HANDLE hFile;
    DWORD dwSize, dwStatus;
    TAPE_GET_MEDIA_PARAMETERS tgmp;
    char szOutput[ 64 ];

    hFile = CreateFile( "\\\\.\\TAPE0",                  //  Open the tape drive
                        GENERIC_READ | GENERIC_WRITE,   //  This defaults to the
                        0, 0, OPEN_EXISTING, 0, NULL );     //  first tape drive
    if( hFile == INVALID_HANDLE_VALUE )
       return( FALSE );                                  //  Exit if open failed
                      //  This is important...nothing really works if not called
    dwStatus = PrepareTape( hFile, TAPE_LOCK, FALSE );
    if( dwStatus != NO_ERROR &&
        dwStatus != ERROR_MEDIA_CHANGED )  //  Media change is apparently common
    {                                      //  so don't fail if that's the error
       wsprintf( szOutput, "Error %d with PrepareTape()", dwStatus );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       CloseHandle( hFile );
       return( FALSE );
    }

    dwStatus = GetTapeStatus( hFile );         //  Wait for the tape to be ready
    if( dwStatus != NO_ERROR )        //  Which it should be after PrepareTape()
    {
       wsprintf( szOutput, "Error %d with GetTapeStatus()", dwStatus );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       CloseHandle( hFile );
       return( FALSE );
    }

    memset( &tgmp, 0, sizeof(TAPE_GET_MEDIA_PARAMETERS) );
    dwSize = sizeof(TAPE_GET_MEDIA_PARAMETERS);          //  Get tape parameters
    dwStatus = GetTapeParameters( hFile, GET_TAPE_MEDIA_INFORMATION,
                                  &dwSize, &tgmp );

    if( dwStatus == NO_ERROR )             //  If no error, show tape parameters
    {
       wsprintf( szOutput, "Block Size: %d", tgmp.BlockSize );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       wsprintf( szOutput, "Partition Count: %d", tgmp.PartitionCount );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       wsprintf( szOutput, "Write Protected: %d", tgmp.WriteProtected );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       wsprintf( szOutput, "Capacity (lowpart): %d", tgmp.Capacity.LowPart );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       wsprintf( szOutput, "Remaining (lowpart): %d", tgmp.Remaining.LowPart );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
    }
    else
    {
       wsprintf( szOutput, "Error %d with GetTapeParameters()", dwStatus );
       SendDlgItemMessage( hWnd, 100, LB_ADDSTRING, 0, (LPARAM)szOutput );
       CloseHandle( hFile );
       return( FALSE );
    }
    CloseHandle( hFile );          //  Don't forget to close the handle and exit
    return( TRUE );
 }

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