oarcdv.format

; ARCHIVE FORMAT


; FIRST BLOCK LOOKS ALMOST EXACTLY LIKE A DISK DIRECTORY EXCEPT FOR
; THE FIRST FOUR WORDS:

;	WORD 0 - ALWAYS -1 TO DISTINGUISH FROM OLD ARCHIVES
;	WORD 1 - "UDNAMP" RELATIVE POINTER WITHIN DIRECTORY TO
;		START OF FIRST NAME AREA BLOCK
;	WORD 2 - "UDESCP" BYTE NUMBER OF NEXT AVAILABLE BYTE IN
;		DESCRIPTOR AREA
;	WORD 3 - GC TAG - SYSTEM PACKED DATE/TIME OF LAST REARRANGEMENT
;		OF DIRECTORY (E.G. DELETION, INSERTION, GARBAGE COLLECTION)

; ONLY OTHER DIFFERENCE FROM STANDARD DISK DIRECTORY IS IN 5TH WORD
; OF EACH NAME BLOCK.  DISK USES LEFT HALF FOR REFERENCE DATE, DOESN'T
; USE RIGHT HALF.  ARC USES LEFT HALF FOR REFERENCE DATE, USES RIGHT HALF
; FOR COUNT OF NUMBER OF OPENS FOR READING.

; SECOND BLOCK:

;	WORD 2000 - ACCESS POINTER TO FIRST BLOCK IN FREE BLOCK CHAIN
;			(0=>CHAIN IS EMPTY)
;	WORD 2001 - NUMBER OF FREE WORDS IN ENTIRE ARCHIVE
;	WORD 2002 - NUMBER OF FREE BLOCKS IN ENTIRE ARCHIVE
;	WORD 2003 - NUMBER OF WORDS IN USE IN ENTIRE ARCHIVE
;	WORD 2004 - NUMBER OF BLOCKS IN USE IN ENTIRE ARCHIVE
;	WORD 2005 - RELATIVE POINTER (RELATIVE TO 2005) TO NEXT AVAILABLE
;			FBAT ENTRY  (0=>FBAT IS FULL)
;	WORDS 2006-<2005+200.> - THE FBAT - EACH ENTRY POINTS TO
;			THE FIRST DATA BLOCK IN A FILE.
;	WORDS <2005+200.>-EOF - DATA BLOCKS

; A DATA BLOCK:

;	HEADER - 4.9 BIT - 1=>BLOCK IS FREE
;		 4.8 BIT - 1=>LAST BLOCK IN FILE CHAIN
;		 4.9,4.8 BITS BOTH 1 => SINGLE WORD OF GARBAGE
;		 4.7 BIT - UNUSED
;		 4.6-3.6 - LENGTH-1 OF DATA AREA (NOT INCLUDING HEADER AND TRAILER)
;		 3.4-1.1 - DISK ADDRESS OF NEXT DATA BLOCK IN THE CHAIN

;	TRAILER - IDENTICAL TO HEADER EXCEPT
;		 3.4-1.1 - DISK ADDRESS OF PREVIOUS DATA BLOCK IN THE CHAIN