Platform SDK: Hardware

FSCTL_GET_RETRIEVAL_POINTERS

Using the FSCTL_GET_RETRIEVAL_POINTERS control code retrieves a data structure that describes the allocation and location on disk of a specific file.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,             // handle to volume
  FSCTL_GET_RETRIEVAL_POINTERS, // dwIoControlCode operation
  (LPVOID) lpInBuffer,          // input buffer
  (DWORD) nInBufferSize,        // size of input buffer
  (LPVOID) lpOutBuffer,         // output buffer
  (DWORD) nOutBufferSize,       // size of output buffer
  (LPDWORD) lpBytesReturned,    // number of bytes returned
  (LPOVERLAPPED) lpOverlapped   // OVERLAPPED structure
);

Parameters

hDevice

[in] Handle to the alternate stream, file or directory for which file mapping is to be retrieved. To obtain a device handle, call the CreateFile function.

Encrypted files must be opened with FILE_READ_DATA, FILE_WRITE_DATA, FILE_APPEND_DATA, or FILE_EXECUTE access. Other files need only be opened with FILE_READ_ATTRIBUTES access. For more information, see File and Directory Security.

dwIoControlCode

[in] Control code for the operation. This value identifies the specific operation to be performed and the type of device on which to perform it. Use FSCTL_GET_RETRIEVAL_POINTERS for this operation.

lpInBuffer

[in] Pointer to the input buffer, a STARTING_VCN_INPUT_BUFFER structure.

nInBufferSize

[in] Size, in bytes, of the input buffer.

lpOutBuffer

[out] Pointer to the output buffer, a RETRIEVAL_POINTERS_BUFFER variably sized structure.

nOutBufferSize

[in] Size, in bytes, of the output buffer.

lpBytesReturned

[out] Pointer to a DWORD variable that receives the size, in bytes, of the data stored in the buffer pointed to by lpOutBuffer.

If the output buffer is too small to return any data, then the call fails, GetLastError returns the error code ERROR_INSUFFICIENT_BUFFER, and the returned byte count is zero.

If the output buffer is too small to hold all of the data but can hold some entries, then the operating system returns as much as fits, the call fails, GetLastError returns the error code ERROR_MORE_DATA, and lpBytesReturned indicates the amount of data returned. Your application should call DeviceIoControl again with the same operation, specifying a new starting point.

If lpOverlapped is NULL (nonoverlapped I/O), lpBytesReturned cannot be NULL.

If lpOverlapped is not NULL (overlapped I/O), lpBytesReturned can be NULL. If this is an overlapped operation, you can retrieve the number of bytes returned by calling the GetOverlappedResult function. If hDevice is associated with an I/O completion port, you can get the number of bytes returned by calling the GetQueuedCompletionStatus function.

lpOverlapped

[in] Pointer to an OVERLAPPED structure.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, lpOverlapped must point to a valid OVERLAPPED structure. In this case, DeviceIoControl is performed as an overlapped (asynchronous) operation. If the device was opened with the FILE_FLAG_OVERLAPPED flag and lpOverlapped is NULL, the function fails in unpredictable ways.

If hDevice was opened without specifying the FILE_FLAG_OVERLAPPED flag, lpOverlapped is ignored and DeviceIoControl does not return until the operation has been completed or an error occurs.

Return Values

If the operation succeeds, DeviceIoControl returns a nonzero value.

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

Possible return values include:

Last Error	Possible interpretation
ERROR_INVALID_PARAMETER	One or more of the following: The handle used is neither a file, a directory nor a view index (such as $Quota). The size of the input buffer is smaller than sizeof(STARTING_VCN_INPUT_BUFFER) starting VCN is less than 0. Other invalid parameter.
ERROR_INSUFFICIENT_BUFFER	The size of the output buffer is smaller than sizeof( RETRIEVAL_POINTERS_BUFFER )
ERROR_NOT_READY	The volume is NTFS and is unmounted.
ERROR_INVALID_USER_BUFFER	One or both of the buffers passed in were not within a valid address range.
ERROR_HANDLE_EOF	The volume is NTFS and the requested starting VCN is past the end of the file.
NO_ERROR	The output buffer contains the full list of VCN-to-LCN mappings from the starting VCN through to the end of the file/stream.
ERROR_MORE_DATA	The output buffer contains a partial list of VCN-to-LCN mappings for the file. More entries exist beyond this list, but the buffer was too small to include them. The caller should call again with either a larger buffer, a higher starting VCN, or both. The first member of the return structure contains a count of extents actually returned.

Remarks

The FSCTL_GET_RETRIEVAL_POINTERS operation retrieves a variably sized data structure that describes the allocation and location on disk of a specific file. The structure describes the mapping between virtual cluster numbers (VCN, offsets within the file/stream space) and logical cluster numbers (LCN, offsets within the volume space).

For the implications of overlapped I/O on this operation, see the Remarks section of the DeviceIoControl topic.

Requirements

  Windows NT/2000: Requires Windows 2000.
  Windows 95/98: Unsupported.
  Header: Declared in Winioctl.h.

FSCTL_GET_RETRIEVAL_POINTERS

Parameters

Return Values

Remarks

Requirements

See Also