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Wayne Warthen 003481410f Update UNARC to Universal UNARC from Lars Nelson 
- Credit and thanks to Lars Nelson for providing an enhanced version of UNARC.
2023-10-30 12:07:26 -07:00

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UNARCU
Universal Archive File Extraction Utility
Version 1.0
Modified for Universal use by Lars Nelson
September 17, 2023
Modified for ZCPR3 by Gene Pizzetta
December 9, 1990
Original CP/M 2.2 version is
Copyright (C) 1986, 1987 by Robert A. Freed
All Rights Reserved
UNARCU allows the listing, typeout, printing, checking, and extraction of
member files contained in ARK and ARC archive files. These are commonly
used for compressed file storage on remote access bulletin boards. This is
a universal version and runs on the following CP/M compatible systems:
CP/M 2.2 with DRI CCP or ZCPRD&J
ZSDOS 1.2 and 2.0 with DRI CCP, ZCPRD&J or Zsystem
CP/M 3 with DRI CCP or Z3Plus
ZPM3 with DRI CCP or ZCCP
DU file specification is supported on all systems. If Zsystem is active
then named directories can be used and the bad directories flag is
automatically checked.
If datestamping is available then extracted files will recieve the ARK file's
stored date stamp. The program handles DateStamper, NZTIME and CP.M Plus
date stamping methods.
UNARCU requires at least 32K of free memory (TPA) for full support of all
archive file formats, but smaller systems may be able to use some of the
program's capabilities.
USAGE:
UNARCU {DU: or dir:}arcfile{.typ} {DU: or dir:}{afn.aft} {{/}options}
If a DIR or DU specification is not given for the archive file, the current
drive/user is assumed. The second filename, which can be ambiguous,
refers to a member file or files in the archive. DIR: file specification
only available when Zsystem is active. DU: specification always available.
If a DU or DIR specification is provided for the member filespec, it will be
extracted to that directory. To extract to the current directory, only a
colon is required. If a directory specification is given without a filename,
all files ("*.*") is assumed.
If no DU or DIR specification is given, UNARCU acts differently depending
on whether the member name is ambiguous or not. If the member name is
unambiguous, and the filetype is not restricted, the file will be typed to
the screen. If the member name is ambiguous, or if no member name is
given at all, a directory of the ARK will be displayed.
If no filetype is given for the archive file, UNARCU first tries ARK and then
ARC.
An on-line help message will be displayed if UNARCU is called with no
command tail or if the command tail is "//".
OPTIONS: Options may or may not be preceded by a slash, but the slash is
required if the options are not the third token (element) on the command
line.
C Check the validity of the archive and the given member
files. If a member filespec is not given, all files
("*.*") is assumed.
E Toggle erasing of existing files without asking on and
off. UNARCU may be configured to automatically erase,
during member file extraction, existing files in the
target directory that have the same name. Or it can
be configured to ask first. This option will turn off
user query before erasure, if it is on by default, and
vice versa.
N Toggle console paging on or off. UNARCU may be
configured to default to console paging or not. This
option will turn paging off, if the the default is on,
and vice-versa. Paging effects both archive directory
display and member file type-out. During member file
extraction, console paging is always off.
P Sends a member file to the printer (LST device). The
member name cannot be ambiguous. The file will be
printed continuously, with no formatting or paging.
UNARCU can be aborted at any time with ^C or ^K.
If screen paging is enabled, UNARCU pauses after the screen fills. The
listing may be resumed by typing any key other than ^S, ^C, or ^K. The
space bar displays one more line of output (overwriting the "[more]"
message) and the program will again pause. For hard copy terminals, line
feed may be used to prevent overprinting of the "[more]" line. If paging
is disabled, the display can be paused with ^S.
LISTING AN ARCHIVE DIRECTORY: UNARC always produces a detailed
console listing of all the member files of an archive, or of those members
which match the second file specification, if one is given. If no member
name is given, or if the member name is ambiguous, then UNARCU only lists
the directory, without doing anything else. (That is, unless the C option is
included.)
A sample directory listing:
A0>UNARCU CODES
Archive File = A0:CODES.ARK
Name Length Disk Method Ver Stored Saved Date Time CRC
============ ======= ==== ======== === ======= ===== ========= ====== ====
ABLE .DOC 24320 24k Crunched 8 11777 52% 30 Apr 86 10:50a 42C0
BRAVO .COM 17152 17k Squeezed 4 14750 14% 2 May 86 4:11p 8CBD
CHARLIE .TXT 234 1k Packed 3 99 58% 2 May 86 4:11p 8927
==== ======= ==== ======= === ====
Total 3 41706 42k 26626 36% 58A4
The listing is equivalent to the "verbose" listing of the MS-DOS ARC
program, with the addition of the "Disk" and "Ver" fields, which are unique
to UNARCU and previous UNARC versions. The listing requires 78-columns
of terminal width.
"Name" is the filename which will be generated if the file is extracted by
UNARCU. This is not necessarily the same as the name recorded in the
archive file. Although CP/M and MS-DOS file naming conventions are
identical, two conversions are made to guarantee filename validity: Lower-
case letters are converted to upper-case and non-printing characters are
converted to dollar signs ("$"). Archive entries are usually maintained and
listed in alphabetical order.
"Length" is the uncompressed file length, i.e., the number of bytes the file
will occupy if extracted to disk, exclusive of any additional length imposed
by the file system. MS-DOS permits files of arbitrary lengths, but CP/M
restricts files to multiples of 128 bytes.
"Disk" is the actual amount of space required to extract the file to a CP/M
disk, expressed as a multiple of 1K (1024) bytes. The number is dependent
on the output drive's allocation block size, which can range from 1K to 16K
bytes. Typically, 1K is used for single-density floppy disks, 2K for
double-density floppies, and 4K for hard disks. In the absence of an
explicit output drive, UNARCU uses the block size of the currently logged
drive, or a configured default size.
"Method" is the compression method used: "Unpacked", "Packed",
"Squeezed", "Crunched", "Squashed", or "Unknown!". If the method
"Unknown!" appears, it likely indicates a faulty archive file or a newer
compression method not yet supported by UNARCU.
"Ver" is the version of compression method used. UNARC supports versions
1-9: unpacked files, versions 1 or 2; packed files, version 3; squeezed
files, version 4; crunched files, versions 5 and squashed files, version 9.
"Stored" is the compressed file length, that is, the number of bytes
occupied by the file in the archive, not including the directory information
overhead, which adds an additional 29 bytes to each member file.
"Saved" indicates the percentage of the original file length which was saved
by compression. Higher values indicate better compression. The MS-DOS
ARC documentation refers to this as the "stowage factor". The value shown
in the totals applies to the archive as a whole, excluding directory
overhead.
"Date" and "Time" are the file modification stamp at the time it was added
to the archive.
"CRC" is an internal 16-bit cyclic redundancy check value computed when a
file is added to an archive, expressed in hexadecimal. UNARCU checks file
validity by recomputing this value when it extracts a file. The value is
calculated by a different method than that used by either of the two
popular public domain programs, CRCK and CHEK, but it is a quite valid and
reliable error-detection mechanism. The value is given for completeness
only. The total in the last line is the 16-bit sum of the displayed CRC
values and is useful for comparing entire archives. Since the CRC values
are computed before compression, the total should be the same for all
archives created from the same set of input files, without regard for
variations in file order or compression methods.
The "Total" line is displayed only if more than one file appears in the
listing.
EXTRACTING FILES FROM AN ARCHIVE: If the second command line
parameter contains a DU or DIR specification UNARCU will extract the
selected member file or files to to the indicated disk directory. If the
directory specification is given without a filename, all member files will be
extracted to the indicated directory. If only a colon is given, the current
drive/user will be assumed.
Below is a directory listing as might be generated during file extraction,
along with some possible warning messages:
A0>UNARCU CODES B1:
Archive File = A0:CODES.ARK
Output Directory = B1:
Name Length Disk Method Ver Stored Saved Date Time CRC
============ ======= ==== ======== === ======= ===== ========= ====== ====
ABLE .DOC 24320 24k Crunched 8 11777 52% 30 Apr 86 10:50a 42C0
Replace existing output file (y/n)? Y
BRAVO .COM 17152 18k Squeezed 4 14740 14% 2 May 86 4:11p 8CBD
Warning: Extracted file has incorrect CRC
Warning: Extracted file has incorrect length
Warning: Bad archive file header, bytes skipped = 10
CHARLIE .TXT 234 2k Packed 3 99 58% 2 May 86 4:11p 8927
==== ======= ==== ======= === ====
Total 3 41706 44k 26616 36% 58A4
"Replace existing output file (y/n)?" appears if a file of the same name
exists in the output directory, requiring a "Y" or "N" response. Any
response other than "Y" will be consided to be the same as "N". If UNARCU
has been configured to erase without query, this message will not appear.
The first two of the "Warning:" messages above indicate that either the
cyclic redundancy check (CRC) value or the extracted file length does not
match the value recorded in the archive header when the original file was
added. The third warning message is displayed if the proper format for
the beginning of a new member is not detected, but UNARCU recovered by
skipping a certain number of bytes in the archive file. If a recovery
attempt fails, UNARC aborts and issues a different message, "Invalid archive
file format". The appearance of any of these messages probably means the
file data has been corrupted in some way.
If the original MS-DOS file length was not an exact multiple of 128 bytes,
the final record of the extracted file will be padded with 1Ah characters
(ASCII ^Z).
Disk space in the listing will be correct for the specified output directory.
In the two examples above, drive A has 1K allocation blocks while drive B
has a 2K blocks, which accounts for the differences in the two listings. To
determine the exact disk space requirements before extracting files, log
into the desired output drive and take an UNARCU directory listing of the
ARK file.
If a file extraction is aborted with ^C, any partial output file will have to
be deleted manually.
TYPING MEMBER FILES: Typing the contents of a member file in an archive
to the console may be requested by giving a non-ambiguous filename and no
output disk directory as the second command line parameter. For example:
A0>UNARCU CODES ABLE.DOC
Archive File = A0:CODES.ARK
Name Length Disk Method Ver Stored Saved Date Time CRC
============ ======= ==== ======== === ======= ===== ========= ====== ====
ABLE .DOC 24320 24k Crunched 8 11777 52% 30 Apr 86 10:50a 42C0
-------------------------------------------------------------------------------
This is file ABLE.DOC, contained within the archive CODES.ARK. Typeout will
proceed until the end of this file, so you'd better be patient. For somebody
who has nothing to say, I've written an awfully big file here. If you don't
want to read all 24K of it, you can type ^C ....
The specified file is assumed to contain valid ASCII text data. All bytes
are masked to seven bits and all control characters are ignored except
horizontal tabs, which are expanded to blanks with stops at every eighth
column), and line feeds, vertical tabs, and form feeds, all of which generate
a new line. SUB (^Z) is interpreted as the end of the file. Backspaces and
carriage returns are ignored, so text will not be obscured.
UNARCU will refuse to type files whose filetype indicates are not ASCII text
files, including COM, CMD, EXE, OBJ, OVL, REL, PRL, CRL, IRL, INI, SYS,
BAD, ARK, ARC, LBR, ?Q?, ?Y? and ?Z?. If one of these or other restricted
types is given, directory information only is listed.
CRC and file length checking are not performed when a file is typed to the
screen.
PRINTING MEMBER FILES: A single member file may be sent to the printer
(CP/M LST device) with the "P" option as the third parameter on the
command line with or without a preceding slash. In addition, the member
name must be non-ambiguous and must not be preceded by a drive or user
specification. For example:
A0>UNARCU CODES CHARLIE.TXT P
or
A0>UNARCU CODES CHARLIE.TXT /P
The contents of the specified file is passed directly to the printer without
alteration, additional formatting, or even paging. The user should make
sure it contains data suitable for printer output. This unfiltered operation
is particularly well-suited for the output of binary graphics images to
dot-matrix printers. These files can be extremely large, but compress quite
well, often to less than 5% of their original size. The same filetypes
excluded from typing are also excluded from printing. Printing may be
paused or aborted with ^S and ^C respectively.
CHECKING MEMBER FILES: With the "C" option UNARCU can be directed to
extract one or more member files from an archive, without actually storing
them as disk files. This operation performs file CRC and length checking,
so it is useful for verifying correct modem data transmission of an archive.
If the "C" is the second parameter on the command line, it must be
preceded by a slash. In that case all files in the archive will be checked.
If a member filename is given, it may be ambiguous, but it cannot be
preceded by a disk directory specification. For example:
A0>UNARCU CODES *.DOC C
or
A0>UNARCU CODES /C
FILE DATE STAMPING: ARK and ARC files contain only a member file's
modification date and time. When a member is extracted under ZSDOS or
CP/M 3 with date stamping, its modification date will be transferred to disk
as both the create and modification file date stamps. If the modification
date is not included in the archive, then the extracted file will be stamped
with the current date and time.
SECURITY: Z-Node security is handled automatically by UNARCU when
Zsystem is running. If the Wheel byte is off (reset), file extraction,
archive checking, and file printing are all disabled. In addition, UNARCU
can be configured to disable file type-out or to limit type-out to a maximum
number of lines.
Directory security depends on the file specification parsing of ZCPR 3.3 or
higher to indicate that the DU or DIR are illegal. Security should be
adequate, however, under other CPR's.
PROGRAM CONFIGURATION OPTIONS: Several configuration bytes are
available to tailor the program for specific requirements, particularly for
RCP/M systems. With the Wheel byte off, UNARCU can be used by remote
callers only for archive directory listing and, optionally, for member file
typeout.
Configuration bytes also determine the default conditions for the N and E
command line options and the filetypes excluded from type-out.
Other configuration points are provided for non-standard systems and need
not concern the majority of users running ZCPR3, NZ-COM, or Z3PLUS.
Patching is accomplished using ZCNFG and the configuration file,
UNARCUnn.CFG, where nn is the current version. The options are discussed
in detail in the CFG file help screens. ZCNFG will find the CFG file
automatically, even if you change the name of the program, as long as you
do not change the name of the CFG file.
For most users no configuration is necessary.
ABOUT ARC/ARK FILES: The files which UNARCU processes utilize a format
that was introduced by the ARC shareware utility program, which executes
on 16-bit computers running the MS-DOS (or PC-DOS) operating system.
This format has achieved widespread popularity since the ARC program
first appeared in March 1985, and it has become the de facto standard for
file storage on remote access systems catering to 16-bit computer users.
This file format also achieved popularity on RCP/Ms (Remote CP/M) systems.
While ARC files have given way to ZIP files in general, many ARC files are
available on the web containing CP/M software.
RCP/M system operators adopted the convention of naming CP/M archive
files with the filetype ARK. This differentiates these from MS-DOS archive
files, which use the filetype ARC. This is a naming convention only; there
is no difference in format, and UNARC will accept files of either type
interchangeably.
An archive is a group of files compressed and collected together into a
single file in such a way that the individual files may be recovered intact.
In this respect, archives are similar in function to libraries (LBR files),
which have been commonplace on CP/M systems since 1982, when the
original LU library utility program was introduced by Gary P. Novosielski.
The two file formats, however, are not compatible.)
The distinguishing characteristic of an ARC archive is that its component
files are automatically compressed when they are added to the archive, so
that the resulting file occupies a minimum amount of disk space. Of
course, file compression techniques have also been commonplace in the CP/M
world since 1981, when the public domain SQ and USQ "squeeze and
unsqueeze" programs were introduced by Richard Greenlaw.
The SQ/USQ programs and their numerous popular descendants utilize a
well-known general-purpose form of data compression (Huffman coding).
This technique, which is also utilized in ARC files, performs well for many
text files but often produces poor compression of binary files (e.g., object
program COM files). The ARC program also provides an advanced data
compression method, which it terms "crunching." This method (which is
based on the Lempel-Ziv-Welch or "LZW" algorithm) performs better than
squeezing in most cases, often achieving 50% or better compression of ASCII
text files, 15-40% compression of binary object files, and as much as 95%
compression of bit-mapped graphics image files.
Five different methods are actually employed for storing files in an
archive. The method chosen for a particular file is the one which results
in the best compression for that file:
1. No compression ("unpacked"). The file is stored in its
original form.
2. Run-length encoding ("packed"). Repeated sequences of 3-
255 identical bytes are compressed into a three-byte sequence.
3. Huffman coding ("squeezed"). Each 8-bit byte (after run-
length encoding) is encoded by a variable number of bits, with
bit length (approximately) inversely proportional to the
frequency of occurence of the corresponding byte.
4. LZW compression ("crunched"). Variable-length strings
of bytes (in theory, up to nearly 4000 bytes in length) are
represented by a single (maximum) 12-bit code (after run-length
encoding).
5. LZW compression ("squashed"). This is a variation of
crunching which uses (maximum) 13-bit codes (and no run-length
encoding).
Since one of the five methods involves no compression at all, the resulting
archive entry will never be larger than the original file.
The last release of the MS-DOS ARC program (version 5.20) has eliminated
squeezing as a compression technique. However, UNARC continues to
process squeezed files for compatibility with archives created by earlier
versions of ARC and by other MS-DOS archiving programs (notably PKARC).
The squashed compression method was introduced by the MS-DOS programs
PKARC and PKXARC. UNARC can process files which use this method,
although it is not universally accepted by other MS-DOS archive extraction
programs (including ARC).
During its lifetime, the ARC program has undergone numerous revisions
which have employed different variations on some of the above methods,
particularly LZW compression. In order to retain compatibility with
archives created by earlier program revisions, ARC stores a "version"
indicator with each file in an archive. Based on this indicator, the latest
release of the ARC program can always extract files created by older
releases (although it will only use the latest data compression versions when
adding new files to an archive).
The current release of UNARC supports archive file versions generated by
all releases of the following MS-DOS programs through (at least) the
indicated program versions:
ARC 5.20 (24 Oct 86), by System Enhancement Associates, Inc.
ARCA 1.22 (13 Sep 86), by Wayne Chin and Vernon Buerg
ARCH 5.38 (26 Jun 86), by Les Satenstein
PKARC 2.0 (15 Dec 86), by Phil Katz (PKWARE, Inc.)
UNARC does not recognize, but is unaffected by, the non-standard archive
and file commenting feature of PKARC.
Although the above discussion has emphasized the origin of archive files
for the MS-DOS operating system, their use did spread to many other
systems. Programs compatible with MS-DOS ARC have appeared for UNIX,
Atari 68000, VAX/VMS, and TOPS-20 systems. A CP/M utility for building
archive files is also available.
For additional information about archive files and the MS-DOS ARC utility,
refer to the documentation file, ARC.DOC, which is available on the web.
For additional information about the LZW algorithm (and data compression
methods in general), refer to the article "A Technique for High-Performance
Data Compression", by Terry A. Welch, in IEEE Computer magazine, Vol. 17,
No. 6, June 1984.

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