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 0 (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 0 (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 0 (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 disksthat 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.

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 cannot exceed 2 TB per MBR disk. For example, a disk of type MBR can have a single 2-TB partition, two 1-TB partitions, or any combination that does not total more than 2 TB. If more space is required, a disk formatted as type GUID partition table (GPT) should be used. If third-party partitioning tools are used to work around this limitation on disks of type MBR larger than 2 TB, configuration operations via the disk partitioning IOCTL control codes will be limited.

Requirements

See Also

DeviceIoControl

Disk Management Control Codes

File System Recognition

IOCTL_DISK_SET_PARTITION_INFO_EX

PARTITION_INFORMATION_EX

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Build date: 10/22/2009