106 lines
5.2 KiB
Plaintext
106 lines
5.2 KiB
Plaintext
Notes for ARC 5.21e October 31, 1991
|
|
|
|
ARC 5.21 for Unix is currently at patch level 6. The code provided
|
|
here has been used on 4.3 BSD based Unix systems and on the Atari ST. (The
|
|
GNU C compiler, version 1.40, was used to make the ST version. It should
|
|
still compile with Mark Williams C, but I haven't bothered to try it.) The
|
|
current version is over twice as fast as previous releases, for all file
|
|
compression and decompression operations. It also fixes longstanding bugs
|
|
in the squash code and in the tmclock DST code.
|
|
|
|
The Arcinfo file describes the ARC 5.xx directory format. The 6.xx
|
|
format contains additional information that is not supported here.
|
|
|
|
System V support in the shar file Sysvarcstuf was provided by Jon
|
|
Zeeff, Janet Walz, and Rich Salz. You will probably also need the dirent
|
|
directory library written by Doug Gwyn; this can be obtained from uunet or
|
|
many other comp.sources.unix archive sites.
|
|
|
|
The tmclock.c file was stolen from Jef Poskanzer's tws library,
|
|
as distributed in PHOON, PHase of the mOON, and slightly hacked by me.
|
|
|
|
The man page was originally from Leo Wilson, with updates by me.
|
|
|
|
/ Howard Chu
|
|
___ /_ , ,_. Jet Propulsion Laboratory
|
|
/ /(_/(__ hyc@hanauma.jpl.nasa.gov
|
|
/
|
|
|
|
Notes for ARC 5.21 June 6, 1988
|
|
|
|
This program is based on the MSDOS ARC program, version 5.21, plus
|
|
a few enhancements...
|
|
|
|
o ARC also performs Huffman Squeezing on data. The Huffman Squeeze
|
|
algorithm was removed from MSDOS ARC after version 5.12. It turns
|
|
out to be more efficient than Lempel-Ziv style compression when
|
|
compressing graphic images. Squeeze analysis is always done now,
|
|
and the best of packing, squeezing, or crunching is used.
|
|
|
|
o Compresses and extracts Squashed files. "Squashing" was created
|
|
by Phil Katz in his PKxxx series of ARC utility programs for
|
|
MSDOS. Dan Lanciani wrote the original modifications to ARC's
|
|
Crunch code to handle Squashing. I've made minor changes since
|
|
then, mostly to reduce the amount of memory required. The 'q'
|
|
option flag must be specified to Squash files. The Squashing
|
|
algorithm will be used instead of the usual Crunch algorithm,
|
|
and will be compared against packing and squeezing, as before.
|
|
|
|
System specific notes:
|
|
|
|
On MTS, an additional option flag, 'i' for "image mode," was
|
|
used. ARC assumes files are text, by default, and will translate
|
|
MTS files from EBCDIC to ASCII before storing in an archive, and
|
|
translates from ASCII to EBCDIC upon extraction. Specifying the
|
|
'i' flag will inhibit this translation. This would most commonly
|
|
be used when shipping binary images such as TeX DVI files, other
|
|
.ARC files stored within an archive, etc... The 'r' (run) command
|
|
is omitted. It just doesn't seem very useful. Also, ARC cannot
|
|
restore MTS files with their original time stamps. (Maybe in a
|
|
future release...)
|
|
|
|
On Unix(tm) systems, the 'i' flag is also present. Unix ARC
|
|
assumes a binary file, by default. Here the only translation
|
|
involved is in end-of-line processing. When storing text files, ARC will
|
|
change '\n' to '\r\n', and does the opposite when extracting files.
|
|
Carriage returns in any other location are preserved when extracting.
|
|
This translation only occurs if the 'i' flag is given.
|
|
|
|
On the Atari ST, the 'h' (for "hold screen") option is present,
|
|
which simply delays exiting the program. This is typically used when
|
|
executing ARC from the desktop, to allow reading all of ARC's output
|
|
before the screen is cleared and the desktop is redrawn. The program
|
|
will prompt and wait for a keypress before exiting. Note that since
|
|
there are no "options" for the MARC program, the "hold screen" option
|
|
is always active for MARC.
|
|
|
|
On both Unix and Atari systems, ARC & MARC will search for an
|
|
environment variable named "ARCTEMP" or "TMPDIR." If present, any
|
|
temporary files will be created in the specified directory. This is
|
|
probably insignificant for Unix users, but can be handy on the Atari,
|
|
in combination with a RAMdisk. Highly recommended for floppy users.
|
|
(Unfortunately, you can only take advantage of this when running some
|
|
form of command shell that allows setting environment variables. Thus,
|
|
you won't see any speed gains when running from the desktop.)
|
|
|
|
That about covers things. The enclosed documentation is taken directly
|
|
from the MSDOS distribution of ARC. Unless specified differently here,
|
|
the programs behave indentically. Note that ARC521.DOC is identical to
|
|
ARC520.DOC - the differences between the two versions are described in
|
|
the file CHANGES.521.
|
|
|
|
Oh yeah - this program may be distributed freely so long as you don't
|
|
modify it in any way. You may not charge for distributing it. (Don't
|
|
feel bad, I can't charge for it either. }-) It'd be nice if you kept
|
|
this and the other enclosed doc files with it when distributing, but
|
|
I'm not going to make a fuss about it. Most people are so familiar
|
|
with the program by now that it wouldn't matter much anyway. You
|
|
should keep this README file around, so bug reports & such will find
|
|
their way back to me. (Bugs? What bugs? Nah, there aren't any bugs...)
|
|
|
|
/ Howard Chu
|
|
___ /_ , ,_. University of Michigan
|
|
/ /(_/(__ hyc@umix.cc.umich.edu
|
|
/ umix!hyc
|
|
'
|