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FSCTL_CREATE_OR_GET_OBJECT_ID control code

Retrieves the object identifier for the specified file or directory. If no object identifier exists, using FSCTL_CREATE_OR_GET_OBJECT_ID creates one.

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



BOOL DeviceIoControl(
  (HANDLE) hDevice,              // handle to device
  FSCTL_CREATE_OR_GET_OBJECT_ID, // 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 file or directory. To retrieve a handle, call the CreateFile function.

dwIoControlCode

The control code for the operation. Use FSCTL_CREATE_OR_GET_OBJECT_ID 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 the output buffer, a FILE_OBJECTID_BUFFER structure. The object identifier associated with the hDevice parameter is returned in this buffer.

nOutBufferSize

The size of the output buffer, in bytes. The buffer must be large enough to contain a FILE_OBJECTID_BUFFER structure.

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 returns no 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 has completed. 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 was opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.

If hDevice was 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 has been completed. Otherwise, the function does not return until the operation has been completed 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

Object identifiers are used to track files and directories. They are invisible to most applications and should never be modified by applications. Modifying an object identifier can result in the loss of data from portions of a file, up to and including entire volumes of data.

This operation creates an object identifier if the object does not already have one. To test for the presence of an object identifier, and retrieve it if it exists, use the FSCTL_GET_OBJECT_ID operation. To create an object identifier without first testing for the presence of one, use the FSCTL_SET_OBJECT_ID operation.

In Windows Server 2012, this function is supported by the following technologies.

TechnologySupported

Server Message Block (SMB) 3.0 protocol

Yes

SMB 3.0 Transparent Failover (TFO)

Yes

SMB 3.0 with Scale-out File Shares (SO)

Yes

Cluster Shared Volume File System (CsvFS)

Yes

Resilient File System (ReFS)

No

 

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
FILE_OBJECTID_BUFFER
FSCTL_DELETE_OBJECT_ID
FSCTL_GET_OBJECT_ID
FSCTL_SET_OBJECT_ID
FSCTL_SET_OBJECT_ID_EXTENDED
Object Identifiers

 

 

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