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Path: utzoo!mnetor!seismo!caip!clyde!burl!ulysses!mhuxr!mhuxt!houxm!ihnp4!icom!andy
From: andy@icom.UUCP (Andrew H. Marrinson)
Newsgroups: net.bugs.4bsd,net.unix-wizards
Subject: cpio -S -b flags
Message-ID: <685@icom.UUCP>
Date: Sat, 6-Sep-86 13:24:25 EDT
Article-I.D.: icom.685
Posted: Sat Sep  6 13:24:25 1986
Date-Received: Sun, 7-Sep-86 09:58:54 EDT
References: <761@smeagol.UUCP>
Organization: ICOM Sys., Arlington Hts, IL
Lines: 39
Keywords: cpio  byteswap  header
Xref: mnetor net.bugs.4bsd:918 net.unix-wizards:7801

> 	There are two undocumented options, `-S' and `-b', that are supposed
> to be for "swap half words" and "swap both words".  I'm not sure under what
> circumstance these switches would be used (swap halfwords only when 
> 1/2 word != byte?  Swap both when in `pass' mode?).  Any explanation?
> -- 
> 	Greg Earle		UUCP: sdcrdcf!smeagol!earle; attmail!earle
> 	JPL			ARPA: elroy!smeagol!earle@csvax.caltech.edu

Assuming these are the same as in sysV, I believe halfwords refers
(ambiguously) to 16-bit quantites.  The -b option does both byte-swapping
and halfword (word) swapping.  To summarize then:

byte:		0	1	2	3	4	5	6	7
contents:	A	B	C	D	E	F	G	H
-s:		B	A	D	C	F	E	H	G
-S:		C	D	A	B	G	H	E	F
-b:		D	C	B	A	H	G	F	E

I seem to recall that when DEC introduced the VAX, longwords (32-bit) were
stored "word-swapped" from the order implied by the multiply/divide
instructions on the PDP-11, or at least from the order used in the PDP-11 C
compiler, thus requiring the -S flag.

I wonder if vn adds the .signature?  Just to be safe here it is, possibly
twice:

	andy@icom.UUCP
	Or for those of		Andrew H. Marrinson
	you who wish to		ICOM Systems, Inc.
	play it the hard	Arlington Heights, IL 60005
	way: ihnp4!icom!andy

-- 

	andy@icom.UUCP
	Or for those of		Andrew H. Marrinson
	you who wish to		ICOM Systems, Inc.
	play it the hard	Arlington Heights, IL 60005
	way: ihnp4!icom!andy