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To determine a partition in which disks

winload (3)
This is my first article, hope to be useful. thanks everybody to support!


Windows Disk Management make we can know all partitions on a disk easily. For example, the disk1 includes C: and D:, the disk2 includes E: and F:. Now we can get a disk number of a specified partition by using drive letter.
The IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS control code is provided to retrieve the physical location and disk number of a specified partition on one or more disks.

A structure is declared as follows:
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typedef struct _VOLUME_DISK_EXTENTS
{
      DWORD NumberOfDiskExtents;
      DISK_EXTENT Extents[ANYSIZE_ARRAY];
} VOLUME_DISK_EXTENTS;


This structure hold a result which IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS is executed by DeviceIoControl. In which, NumberOfDiskExtents represents that this partition was inclued in the number of disk. Usually, if a partition exists in a basic disk, its value is 1. however, a partition exists in dynamic disk and it is a striped or spanned volume. In this case, and its value is greater than 1 to represent a available size of the array Extents.

The structure DISK_EXTENT declaring is the below:
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typedef struct _DISK_EXTENT
{
      DWORD DiskNumber;
      LARGE_INTEGER StartingOffset;
      LARGE_INTEGER ExtentLength;
} DISK_EXTENT;


In this structure DiskNumber is a disk number that the partition lies, so the DiskNumber is a member we desire the most. The member StartingOffset is a start physical location of this partition(in bytes), this is, the location of DBR.


Related example source code is as follows:

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//-----------------------------
#include <stdio.h>
#include <tchar.h>
#include <windows.h>
#include <winioctl.h>

 
typedef struct _DISK_EXTENT
{  
      DWORD DiskNumber;  
      LARGE_INTEGER StartingOffset;  
      LARGE_INTEGER ExtentLength;
} DISK_EXTENT,  *PDISK_EXTENT;

typedef struct _VOLUME_DISK_EXTENTS
{  
      DWORD NumberOfDiskExtents;  
      DISK_EXTENT Extents[ANYSIZE_ARRAY];
} VOLUME_DISK_EXTENTS,  *PVOLUME_DISK_EXTENTS;

 
#define IOCTL_VOLUME_BASE   ((DWORD) ‘V’)
#define IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS \
                  CTL_CODE(IOCTL_VOLUME_BASE, 0,  \
                  METHOD_BUFFERED, FILE_ANY_ACCESS)

 
int _tmain(int argc,  TCHAR* argv[])
{
      TCHAR szPath[MAX_PATH] = {0};
       _stprintf(szPath, _T("\\\\.\\%c:"), _T(’C'));
       HANDLE hHandle = CreateFile(szPath
               , GENERIC_READ|GENERIC_WRITE
               , FILE_SHARE_WRITE|FILE_SHARE_READ
               , NULL
               , OPEN_EXISTING
               , FILE_ATTRIBUTE_NORMAL
               , NULL);

       if (hHandle == INVALID_HANDLE_VALUE)
       {
              _tprintf(_T("Open %s failed\n"), szPath);
              return -1;
       }
 
       VOLUME_DISK_EXTENTS volumeDiskExtents;
       DWORD dwBytesReturned = 0;
       BOOL bResult = DeviceIoControl(hHandle
                    , IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS
                    , NULL
                    , 0
                    , &volumeDiskExtents
                    , sizeof(volumeDiskExtents)
                    , &dwBytesReturned
                    , NULL);
 
       CloseHandle(hHandle);
       if (!bResult)
       {
              _tprintf(_T("Failed to issue the control code!\n"));
              return -1;
       }

       _tprintf(_T("The below is a information about %s\n"), 
                     szPath);

       for (DWORD n = 0; 
                     n < volumeDiskExtents.NumberOfDiskExtents; 
                     ++n)
       {
              PDISK_EXTENT pDiskExtent = 
                                   &volumeDiskExtents.Extents[n];

              _tprintf(_T("Disk number: %d\n")
                                 , pDiskExtent->DiskNumber);
              _tprintf(_T("DBR start sector: %I64d\n")
                                 , pDiskExtent->StartingOffset.QuadPart
                                   /512);
       }

       return 0;
}


By the above example code, hope you can understand the usage of this control code. This section code can be compiled successfully on Visual C++6.0 environment.

Author by Wobin.Mei , on June 20th, 2009
My blog is wobinmei.blog.com


george135 (268)
This has been posted 15 years ago on Compuserve and Usenet ... (and see MSDN code)
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