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From: sag2@ur-tut.UUCP (Dent Arthur Dent)
Newsgroups: net.sources.d
Subject: ARC for UNIX
Message-ID: 
Date: Sun, 14-Sep-86 16:47:41 EDT
Article-I.D.: ur-tut.688
Posted: Sun Sep 14 16:47:41 1986
Date-Received: Sun, 14-Sep-86 20:24:32 EDT
Reply-To: sag2@ur-tut.UUCP (Dent Arthur Dent)
Organization: Univ. of Rochester Computing Center
Lines: 37

A while ago I downloaded from the net a program that created archives 
compatible with ARC for the IBMPC.  I compiled it on a Pyramid but the
program either hung or core-dumped when run.  I then transferred it to
my account an a Vax 11-750 running Ultrix 1.2.  The program eventually
ran and created an archive readable by ARC on the IBMPC.  The only problem
I have found thus far is that when checking the CRC value, the program
on the Vax sometimes gives an 8-digit hex as opposed to a 4-digit hex
value.  Could this be from something left in the code that only works
correctly on MS-DOS like the "b" in the fopen() type parameter.

Note that the archive unarcs fine on both the Vax and the PC.  One segment
of code I am suspicious of is the bit operations used in arcadd():

   return ((crc>>8)&0x00ff) ^ crctab[(crc^c)&0x00ff];

where crc is an int an c is an unsigned char.  Since my memory of bit
operations is a bit unclear, what exactly is this supposed to do and
is there a way in which it can produce, for example a CRC of fffa301
on a Vax and a CRC for the same archive, same file of a301.  It appears
as though all errors are caused by the four high-order bits being
ffff on the Vax whereas on the PC there are no bits except the four bits
(by bits I really mean hexadecimal digits).

Please let me know via email what is going on here and when and if there
is going to be another post of an improved arc for UNIX.

-- Steven Grotten
uucp:	{seismo, allegra, decvax, cmcl2, topaz, harvard}!rochester!ur-tut!sag2
BITNET: sag2@UORVM
Physical:43 01' 40'' N, 77 37' 49'' W

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