typedef struct FILE_POSITION_INFORMATION {
LARGE_INTEGER CurrentByteOffset;
} FILE_POSITION_INFORMATION, *PFILE_POSITION_INFORMATION;
FILE_READ_DATA or FILE_WRITE_DATA access to the file is required to change this information about the file, and the file must be opened for synchronous I/O.
If the file was opened or created with the FILE_NO_INTERMEDIATE_BUFFERING option, the value of CurrentByteOffset must be an integral multiple of the sector size of the underlying device.