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Interior File Listing Utility 11/26/89 Version 1.50 IFL Interior File Listing Utility Copyright 1989 by Martin Pollard. All rights reserved. This program may be freely copied and distributed, provided it is for personal, non-profit use only. I am asking for no monetary donations; thus, this program is truly Freeware. I only ask that, if distributed, the program and documentation not be altered in any way. Your cooperation with this simple request will be an incentive for newer and better versions of this program. Although I have tried to make this program as bug-free as possible, I will not be liable for any damages caused, either directly or indirectly, by the use of this program. This program is distributed without warranty, either expressed or implied. NOTE: Throughout this documentation, the term "archive file" is used to describe any file that contains multiple files. Likewise, the term "archiving program" is used to describe any program that creates and/or maintains an archive file. If you encounter any problems while using the program, or if you have any suggestions to improve the operation of IFL, you may contact me at any of these bulletin board systems (leave messages to "Silicon Wizard", my handle): The Pointe BBS Warp Speed BBS 313-885-1779 313-544-0405 300/1200/2400 baud 300/1200/2400 baud 24 hours 8pm to 8am nightly or drop me a line through the mail to 27825 Hoover, Apt. 4, Warren, MI, 48093. Please include a self-addressed stamped envelope to ensure a speedy reply. Letters that do not include an SASE will not necessarily be ignored; they just won't be replied to as quickly! -- 1 -- Interior File Listing Utility 11/26/89 Version 1.50 A SHORT HISTORY OF ARCHIVING PROGRAMS What exactly is an archiving program? It is a program that takes a group of files and stores them into one single file, called an archive file. Such an archiving program may or may not compress the files before storing them in the archive file. (Compression means to read the file, perform mathematical and probability calculations on the data -- which can be either text or binary data -- and write a new file containing the compressed information.) The first of these kinds of programs originated under the CP/M operating system. They were LU, SQ and USQ, which stood for Library Utility, Squeeze, and Unsqueeze. LU was a very primitive archiving program: It simply took files and placed them into an archive file (LU called them "library" files), with no compression performed on the data at all. The SQ program was usually used to compress files before they were stored by LU. (SQ used a method call Huffman encoding to compress the information. USQ, as you may have guessed, simply reversed the process.) LU-created files can usually be identified by the ".LBR" extension (although this was not required; the .LBR extension was usually used to maintain consistency) or the ".LQR" extension (if the library file was squeezed AFTER files were stored in it). For years, the combination of LU, SQ and USQ -- and its derivatives -- were the best thing since sliced bread. When the IBM PC appeared, these programs were, naturally, ported over to the MS-DOS operating system. However, users quickly felt the limitations of LU, SQ and USQ. These programs were originally written for slow 8-bit 8080- and Z80-based systems with a maximum of 64K of memory; the 16-bit 8088-based IBM PC was faster by comparison, and could access up to 640K of memory. Users figured there HAD to be a better way. System Enhancement Associates (SEA) came up with the better mousetrap with ARC, which essentially combined the functions of LU, SQ, and USQ by compressing files before storing them in the archive file. Even here, ARC took a different approach, replacing LU's fixed directory (which was at the beginning of each library file) with a "distributive" directory (files stored in the archive are preceded by a "header" describing the file in detail). Over the years, ARC has been improved with more user options and more advanced compression methods (like Dynamic Lempel-Zev- Welch, or "Crunching"), and has been ported to other operating systems (such as UNIX and VAX). Unfortunately, ARC had the big problem that plagued the early CP/M programs: It was very slow, especially on 8088-based systems. To solve this, Phil Katz of PKWARE created PKARC, an ARC "clone" that was so fast that it began to surpass ARC in popularity. Later enhancements to PKARC also included a Dynamic LZW variant called "Squashing". The combination of all these features catapulted PKARC right to the "top of the charts," as it were. (PKARC was later renamed to PKPAK.) SEA filed a lawsuit against PKWARE in 1988, charging unlawful use of ARC's source code and unfair business practices. (The details of the -- 2 -- Interior File Listing Utility 11/26/89 Version 1.50 lawsuit have been discussed elsewhere, so I will not go into them here.) The out-of-court settlement between Phil Katz and SEA ended production of PKARC; unfortunately, it also alienated many users and bulletin board system (BBS) operators. (The feeling was that SEA was trying to "win in the courtroom" because it was losing to PKARC in the marketplace.) That action, plus the rapidly-growing shift to PKZIP and LHARC, has probably spelled the end of the ARC format, despite SEA's release of an improved version of ARC. In the midst of the scuffle between SEA and PKWARE, NoGate Consulting released its own ARC-compatible program called PAK. PAK uses an even more advanced Dynamic LZW variant dubbed "Crushing" (later versions introduced another compression method, "Distilling", which gives PKZIP and LHARC a run for their money). PAK has created a sizable following of users, but has not caught on for two reasons: It is slower than PKARC, and the new compression methods, plus the various "enhancements" to the ARC format, make it incompatible with programs that process ARC files. After the lawsuit that ended production of PKARC, PKWARE introduced a totally new compression program, PKZIP. PKZIP, with its enhanced file format (including a second directory to assist in recovery of corrupt archives) and enhanced compression methods (tighter than almost all current archiving programs), has gained a large following. Animosity towards SEA, and the widespread popularity of PKARC, have also helped tremendously. Along with the main contenders, three other archiving programs exist that have each gained their own following of users: DWC by Dean W. Cooper, LHARC by Haruyasu Yoshizaki, and ZOO by Rahul Dhesi. DWC was introduced around the time of ARC's period of popularity, but due to an incompatible file format, it was never accepted into the mainstream. LHARC is an "import" from Japan (introduced shortly after PKZIP) which uses a high-performance compression method that occasionally beats out PKZIP for compression size. ZOO originated on UNIX and VAX systems, and has been ported to other non-MS-DOS environments as well. It is the program of choice for users who need to move files between these various environments. It can become highly confusing, to say the least, to work with all these different formats. This can be especially nerve-wracking to BBS users and operators, since BBSes may contain files in any (or ALL!) of these formats. What is needed is a single program to read them all. That's where IFL comes in. IFL TO THE RESCUE! IFL stands for Interior File List, and that's exactly what it does: It produces a listing of the contents of an archive file. The syntax for using IFL is very straightforward: IFL [options] filename -- 3 -- Interior File Listing Utility 11/26/89 Version 1.50 where "filename" is the name of the archive file you wish to view. If you do not specify an extension with the filename, IFL will automatically cycle through all the extensions it supports (appending them one at a time to the filename) until it finds the file. At this time, supported extensions include ARC, DWC, LZH, PAK, ZIP and ZOO. The filename may be preceded by a drive and/or a pathname. If no filename is specified, a help screen is displayed. You may specify various options on the command line to alter the operation of IFL. These options include: -B Normal output from IFL is a color display using direct screen writes (accessing the video memory directly). This method works on 100% IBM compatible systems only. If you are using a system that is not 100% IBM compatible (such as early Sanyo PCs or the Tandy 2000), use this option to force IFL to output text using the BIOS, which ensures total compatibility but is slower than direct screen writes. -P When a full screen of text has been displayed, IFL pauses and waits for the user to press a key to continue. Use this option to override this feature and provide a continuous listing. -R This option can be used to force IFL to output text to the standard output device. Using this option, the output can be rerouted to another device or a file using the ">" redirection symbol (refer to your MS-DOS manual if you are unfamiliar with redirection). In this mode, color is suppressed and the listing is continuous (no pause after a full screen). This mode is excellent for implementing IFL in a BBS environment. The output from IFL is in the form of a columnar table. The following information is displayed: Length The length of the file when uncompressed, in bytes. Size Now The length of the compressed file, in bytes. This is the number of bytes the file actually take up inside the archive file. % The percentage of space saved by compression. Method The compression method used to store the file. Valid methods are listed elsewhere in this manual. Date and The date and time of the last modification of the file. Time This is usually not the date and time in which the file was stored. -- 4 -- Interior File Listing Utility 11/26/89 Version 1.50 Filename The name of the stored file. Note that files in LZH, ZIP and ZOO archives may contain a pathname (indicated by forward slashes "/"). Below the main listing will be displayed total values for all the files displayed. Shown are totals for length, size now, ratio (overall), and number of files. Note that these totals do NOT take into account the overhead for file headers, the central directory of ZIP archives, or the extra information found in "extended" ARC-format archives (such as those created by the latest versions of ARC, PKPAK and PAK). UNSUPPORTED FEATURES * Self-extracting archives. * Extra information stored in the ARC format. This includes directories in ARC 6.0 archives, pathnames and comments in PAK archives, and comments in PKARC archives. The ARC format was never designed for this extended information, and since each of the above programs uses a different method of storing its information, it becomes a real pain to try to support all of it. Therefore, IFL supports *NONE* of it. * Comments stored in PKZIP archives. The ability to display the main ZIP comment may be added in the future. COMPRESSION METHODS Below is a list of all the known compression methods that IFL supports, along with the archive formats that use them. A detailed explanation of each compression method is beyond the scope of this manual. Unknown! An unknown compression method was encountered. (ARC, DWC, LZH, PAK, ZIP, ZOO) --- The file is not compressed. (ARC, DWC, LZH, PAK, ZIP, ZOO) crunched The file is compressed using LZW compression (fixed 12- bit). (ARC) Crunched The file is compressed using Dynamic LZW compression (code size from 9 to 12 bits) with repeat-byte compression and adaptive reset. (ARC, DWC, PAK, ZOO) Crushed The file is compressed using Dynamic LZW compression (code size from 2 to 13 bits) with partial adaptive reset. (PAK) -- 5 -- Interior File Listing Utility 11/26/89 Version 1.50 Directory This is not a compression method, but an indicator of a subdirectory stored in an ARC 6.0 archive (which is no longer supported by IFL). (ARC) Distilled The file is compressed using Huffman/sliding window compression. (PAK) Frozen The file is compressed using a hybrid of Dynamic LZW and Huffman compression. (LZH) Imploded The file is compressed using Shannon-Fano tree compression. (ZIP) Packed The file is compressed using repeat-byte compression. (ARC, PAK) Reduced # The file is compressed using probabilistic and repeat- byte compression. The "#" indicates the compression level (1-4). (ZIP) Shrunk The file is compressed using Dynamic LZW compression (code size of 9 to 13 bits) with partial adaptive reset. (ZIP) Squashed The file is compressed using Dynamic LZW compression (code size of 9 to 13 bits) with adaptive reset. (ARC, PAK) Squeezed The file is compressed using Huffman encoding. (ARC, PAK) ERROR MESSAGES Listed below are all the error messages produced by IFL. If you receive an error while using IFL, check this list for the probable cause. "Archive format not supported" The specified file is not in a format that IFL can process. Either the file was created with an unsupported archiving program, or the file is a self-extracting archive (which IFL does not support). "Can't access file 'filename'" IFL could not, for some reason, access the specified file. The file may not exist on the disk, or some other error may be preventing IFL from accessing the file. "Can't read archive file" IFL encountered an error while reading the archive file. (Pretty straightforward, eh?!) -- 6 -- Interior File Listing Utility 11/26/89 Version 1.50 "Invalid ARC header ID" "Invalid LZH header ID" "Invalid ZIP header ID" "Invalid ZOO header ID" Each entry in an archive file is preceded by a header that identifies the file, and includes such information as the filename, the compressed and uncompressed length, the date and time, etc. If this header is not in the place that IFL expects it, or if the header contains invalid information, this error message is displayed. -- 7 --