The FSCTL_QUERY_ALLOCATED_RANGES request message requests that the server scan a file or alternate stream looking for byte ranges that may contain nonzero data, and then return information on those ranges. Only sparse files can have zeroed ranges known to the operating system. For other files, the server will return only a single range that contains the starting point and the length requested. The message contains a FILE_ALLOCATED_RANGE_BUFFER data element. The FILE_ALLOCATED_RANGE_BUFFER data element is as follows.
