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IOCTL_DISK_GET_PARTITION_INFO_EX control code

Retrieves extended information about the type, size, and nature of a disk partition.

To perform this operation, call the DeviceIoControl function with the following parameters.



BOOL DeviceIoControl(
  (HANDLE) hDevice,                 // handle to a partition
  IOCTL_DISK_GET_PARTITION_INFO_EX, // dwIoControlCode
  NULL,                             // lpInBuffer
  0,                                // nInBufferSize
  (LPVOID) lpOutBuffer,             // output buffer
  (DWORD) nOutBufferSize,           // size of output buffer
  (LPDWORD) lpBytesReturned,        // number of bytes returned
  (LPOVERLAPPED) lpOverlapped       // OVERLAPPED structure
);

Parameters

hDevice

A handle to the disk device from which partition information is retrieved. To retrieve a device handle, call the CreateFile function.

dwIoControlCode

The control code for the operation. Use IOCTL_DISK_GET_PARTITION_INFO_EX for this operation.

lpInBuffer

Not used with this operation. Set to NULL.

nInBufferSize

Not used with this operation. Set to zero.

lpOutBuffer

A pointer to a buffer that receives the partition information. For more information, see PARTITION_INFORMATION_EX.

nOutBufferSize

The size of the output buffer, in bytes.

lpBytesReturned

A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

  • If the output buffer is too small, the call fails, GetLastError returns ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is zero.
  • If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation does not return output data and lpOutBuffer is NULL, DeviceIoControl makes use of lpBytesReturned. After such an operation, the value of lpBytesReturned is meaningless.
  • If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this parameter is not NULL and the operation returns data, lpBytesReturned is meaningless until the overlapped operation is complete. To retrieve the number of bytes returned, call GetOverlappedResult. If hDevice is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.
lpOverlapped

A pointer to an OVERLAPPED structure.

  • If hDevice is opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.
  • If hDevice is opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this case, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.
  • For overlapped operations, DeviceIoControl returns immediately, and the event object is signaled when the operation is complete. Otherwise, the function does not return until the operation is complete or an error occurs.

Return value

If the operation completes successfully, DeviceIoControl returns a nonzero value.

If the operation fails or is pending, DeviceIoControl returns zero. To get extended error information, call GetLastError.

Remarks

The IOCTL_DISK_GET_PARTITION_INFO_EX control code is supported on basic disks. It is only supported on dynamic disks that are boot or system disks, or have retained entries in the partition table. The DiskPart.exe command RETAIN can be used to do this for other dynamic simple partitions.

The disk support can be summarized as follows.

Disk typeIOCTL_DISK_GET_PARTITION_INFOIOCTL_DISK_GET_PARTITION_INFO_EX
Basic master boot record (MBR)YesYes
Basic GUID partition table (GPT)NoYes
Dynamic MBR boot/systemYesYes
Dynamic MBR dataYesNo
Dynamic GPT boot/systemNoYes
Dynamic GPT dataNoNo

 

Currently, GPT is supported only on 64-bit systems.

If the partition is on a disk formatted as type master boot record (MBR), partition size totals are limited. For more information, see the Remarks section of IOCTL_DISK_SET_DRIVE_LAYOUT.

Requirements

Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]

Header

WinIoCtl.h (include Windows.h)

See also

DeviceIoControl
Disk Management Control Codes
File System Recognition
IOCTL_DISK_SET_PARTITION_INFO_EX
PARTITION_INFORMATION_EX

 

 

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