Returns the sector offset to the first logical cluster number (LCN) of the file system relative to the start of the volume.

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

BOOL DeviceIoControl(
  (HANDLE) hDevice,                    // handle to volume
  (LPVOID) NULL,                       // input buffer
  (DWORD) 0,                           // size of input buffer
  (LPVOID) lpOutBuffer,                // output buffer
  (DWORD) nOutBufferSize,              // size of output buffer
  (LPDWORD) lpBytesReturned,           // number of bytes returned
  (LPOVERLAPPED) lpOverlapped          // OVERLAPPED structure


Adding the value retrieved by FSCTL_GET_RETRIEVAL_POINTER_BASE to the value retrieved by the FSCTL_GET_RETRIEVAL_POINTERS control code results in a volume-relative file extent offset.

In Windows 8 and Windows Server 2012, this code is supported by the following technologies.

Technology Supported
Server Message Block (SMB) 3.0 protocol No
SMB 3.0 Transparent Failover (TFO) No
SMB 3.0 with Scale-out File Shares (SO) No
Cluster Shared Volume File System (CsvFS) Yes


Minimum supported client Windows 7 [desktop apps only]
Minimum supported server Windows Server 2008 R2 [desktop apps only]
Header winioctl.h (include Windows.h)

See also