A file range specification for RDC downloads.

 typedef struct _FRS_RDC_SOURCE_NEED {
   ULONGLONG needOffset;
   ULONGLONG needSize;
 } FRS_RDC_SOURCE_NEED;

needOffset: The offset in the marshaled source file.

needSize: The number of data (uncompressed), in bytes, to retrieve.

The client uses this structure to request source data from the server when downloading a file with RDC.