OS/2 Shareware BBS: 9 Archive

home *** CD-ROM | disk | FTP | other *** search

/ OS/2 Shareware BBS: 9 Archive / 09-Archive.zip / PXOS221A.LZH / POLYXPLN.DOC < prev

Wrap

Text File | 1991-04-05 | 21KB | 490 lines

PolyXarc Configuration File Explanation Public Domain by Jeffrey J. Nonken 31 March, 1991 In this document I pick apart the configuration file that I distribute with PolyXarc, and explain some details about different archivers. I figured this would enhance my explanations in POLYXARC.DOC, which aren't as clear as I'd like them to be. Note that while I tried to be reasonably accurate, the version numbers and some other niggling details should not be considered completely reliable. Relax; this isn't a history test, it's just an overview of how PolyXarc interacts with various archivers. ARC === ARC files use different compression methods, depending on what program you're using and what it decides is the best method to use. These compression methods are represented in the .ARC files with what I call "levels", and what SEA calls "header types". Levels up to 9 are: Level Common name Compression method ---- ----------- ------------------ 1 stored No compression (short header) 2 Stored No compression (standard header) 3 Packed Repeated Character Compression 4 Squeezed RCC followed by Huffman 5 crunched 12 bit Lempel-Ziv 6 crunched RCC followed by 12 bit Lempel-Ziv 7 crunched RCC followed by 12 bit Lempel-Ziv, alternate hash function 8 Crunched RCC followed by variable 12 bit Lempel-Ziv with dynamic reset 9 Squashed variable 13 bit Lempel-Ziv with dynamic or Deviant reset PKware and Nogate Consulting call level 9 "Squashed"; SEA calls level 9 "Deviant". However, it is the same format. Level 10 is used differently by two different programs: PAK, which calls it "Crushed", and ARC+PLUS (also known as ARC 7.0). These two programs use different compression algorithms, and therefore archives with files compressed at level 10 are not compatible between the two. Level 11 is as of this writing only used by PAK 2.51 and is called "Distilled". 1 Who Can Decompress What | 1 2 3 4 5 6 7 8 9 10 11 ----------+------------------------------------------------------ ARC 4.5 | x x x x x x x ARC 5.0 | x x x x x x x x ARC 6.0 | x x x x x x x x x ARC 7.0 | x x x x x x x x x 1 PKUNPAK | x x x x x x x x x PAK 1.0 | x x x x x x x x x 2 PAK 2.5 | x x x x x x x x x 2 x x = can decompress 1 = ARC+PLUS version of level 10 2 = PAK version of level 10 ARCE is equivalent to ARC 5.0. XARC is equivalent to ARC 7.0 (ARC+PLUS). PKUNPAK is the same thing as PKXARC 3.60. As if that weren't confusing enough: as of ARC version 6.0, SEA came out with an extended format. Header types 1-19 are reserved for compression methods (what I call compression levels); header types 20 and up are reserved for extended information. This may include extended name and path information; extended date information; icon bit maps; and so on. This is called a "version 6" format ARC file, presumably because it was introduced with ARC version 6. So far only ARC versions 6 and 7 can dearchive a version 6 file. So we have to deal with both ARC levels and ARC versions. Fortunately for our sanity, only ARC+PLUS can create an ARC+PLUS- type level 10 header, and it can only do it in a version 6 ARC file, which according to Thom Henderson will always contain version 6 headers (type 20 and up). This means we can tell the difference between PAK level 10 and ARC+PLUS level 10 compression by checking the file for version 6 headers: if it's got version 6 headers and level 10 compression, it's ARC+PLUS; if it's only got version 5 headers and level 10 compression, it's PAK. This is exactly how PolyXarc tells the difference. In fact, when PolyXarc goes through the ARC file, it looks for both version and highest level. If it finds the archive is a version 6 file, it simply ignores all the version 5 dearchivers when it looks for the proper one to use. The following paragraphs describe the ARC description lines in POLYXARC.CFG. The examples I give assume you are attempting to decompress a file called TEST.ARC. Since the filenames are usually optional, I will put "[*.*]" where the filenames go. ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC 8 w "" arc e%2 %3 %4 This defines an ARC 5.x template. ARC 5 will extract up to level 8. Normal syntax is "arc e TEST.ARC [*.*]"; overwrite mode will use "arc ew TEST.ARC [*.*]". 2 ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC 8 /r "" arce %3 %4 %2 This defines a template for ARCE, which is a fast ARC extractor written in assembly. It is the equivalent of ARC version 5. Normal syntax is "arce TEST.ARC [*.*]"; overwrite mode will use "arce TEST.ARC [*.*] /r". ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC 9 /r "" pkxarc %2 %3 %4 This template is for PKXARC, which can extract up to level 9 compression. Normal syntax is "pkxarc TEST.ARC [*.*]"; overwrite mode will use "pkxarc /r TEST.ARC [*.*]". ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC 9 /r "" pkunpak %2 %3 %4 This template is for PKUNPAK, which can extract up to level 9 compression. PKUNPAK is version 3.61 of PKXARC; there are no real differences between them. Normal syntax is "pkunpak TEST.ARC [*.*]"; overwrite mode will use "pkunpak /r TEST.ARC [*.*]". ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC 11 /WA "" pak /e %2 %3 %4 This template is for PAK, which can extract up to level 11. However, PAK will not extract level 10 files if the archive was made by ARC+PLUS, but only if it was made by PAK. Normal syntax is "PAK /e TEST.ARC [*.*]"; overwrite mode will use "PAK /e /WA TEST.ARC [*.*]". ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC 11 /WA /WO pak /e %1%2 %3 %4 This is an alternate syntax for PAK 2.51. If you use this line, if PAK encounters a file already on disk that it is trying to extract from the archive, if the archive file is newer, PAK will replace the older file. Normally without the /WO parameter PAK will stop and ask whether you want to overwrite. In this case syntax for extraction will be "pak /e /WO TEST.ARC [*.*]", and for overwrite will be "pak /e /WA TEST.ARC [*.*]". 3 ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC6 9 w "" arc e%2 %3 %4 This defines an ARC 6.0 template. ARC 6 will extract up to level 9. In addition, it can extract from version 6 ARC files up to level 9. Normal syntax is "arc e TEST.ARC [*.*]"; overwrite mode will use "arc ew TEST.ARC [*.*]". ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC6 10 /o ! xarc %2 %3 %4 This defines a template for XARC. XARC is a free-distribution unarchiver for ARC 7.0, also called ARC+PLUS. XARC will extract up to level 9, and will also extract version 6 ARC files up to level 10. Note that XARC will not extract PAK level 10 files, but only ARC+PLUS level 10 files. Normal syntax is "xarc TEST.ARC [*.*]"; overwrite mode will use "xarc /o TEST.ARC [*.*]". ARC level overwrite extract command_template ---- ----- --------- ------- ---------------- ARC6 10 o ! arc e%2 %3 %4 This defines a template for ARC 7.0 (ARC+PLUS). ARC+PLUS will extract up to level 9, and will also extract version 6 ARC files up to level 10. Note that ARC+PLUS will not extract PAK level 10 files, but only ARC+PLUS level 10 files. Normal syntax is "arc e TEST.ARC [*.*]"; overwrite mode will use "arc eo TEST.ARC [*.*]". OTHER ARCHIVERS =============== There is a plethora of formats other than ARC. Every year or so sees a new archiver, usually with a new format, and each time it seems that improvements have been made on the speed or amount of compression or both. And each format is incompatible with all the others. The strength of PolyXarc is in the fact that you can program it to recognize new formats simply by adding a line in the configuration file. Most archivers leave a "signature"; some constant set of values or characters imbedded in the archive file for distinguishing one type of archive from another. PolyXarc can be configured to read that signature and determine which dearchiver to use to access the files in the archive. Thus come the Signature lines in the configuration file. Each one shows not only the command template, but also the signature and where to find it. For these examples I will use TEST.ext, where ext is the archiver's native extension. 4 DWC --- First we'll tackle DWC. DWC stands for David W. Cooper, the author of the program. Originally DWC source was available, but Mr. Cooper sold his program to a commercial interest; versions written since then have not had source available. In fact, I have only seen one version at all since then. DWC also requires that all its archives have ".DWC" as an extension. It also is unusual because it has its signature at the end of the file, rather than at or near the beginning of the file as most archivers do. That can cause problems for recognition after an XMODEM-type download, because the end of a file transferred via XMODEM is padded with extra characters, and the signature is no longer at a fixed location from the end of the file. Since DWC isn't particularly fast and doesn't make particularly small archives, all this makes it of rather limited use. You'll notice that the signature, "DWC", is shown to be at -3. That means that PolyXarc should count backwards from the end of the file by three characters. That count actually starts from just past the end of the file; the last character in the file would be at -1. So "DWC" is actually the last three characters of the file. SIGNATURE offset signature overwrite extract command_template --------- ------ --------- --------- ------- ---------------- SIGNATURE -3 DWC w "" dwc e%2 %3 %4 Normal syntax is "dwc e TEST.ARC [*.*]"; overwrite mode will use "dwc ew TEST.ARC [*.*]". LHARC ----- LHARC, written by a Japanese gentleman named Haruyasu Yoshizaki, came out around 1990. It stopped at version 1.13 for a while, but in 1991 Yoshi came out with version 2.05. LHARC creates some of the smallest archives of all, but unfortunatly is very, very slow. However, verion 2.0x is a great improvement over 1.1x; it not only has a new, smaller compression algorithm, but is much faster (though still slow), and can even create backwards- compatible files that are slightly smaller than the original program made. It is now called LHA. LHARC's signature is actually the compression method flag for the first file. Fortunatly that flag is always in the same place. Flags seen so far are "-lh0-" through "-lh5-", so we just look for the first three characters, "-lh"; as long as Yoshi doesn't change the way the archiver works, that should be able to handle LHARC files forever. 5 SIGNATURE offset signature overwrite extract command_template --------- ------ --------- --------- ------- ---------------- SIGNATURE 2 -lh /mc "" lharc e %2 %3 %4 SIGNATURE 2 -lh /mc "" lha e %2 %3 %4 Normal syntax is "lharc e TEST.LZH [*.*]" or "lha e TEST.LZH [*.*]". Overwrite syntax is "lharc e /mc TEST.LZH [*.*]" or "lha e /mc TEST.LZH [*.*]" XARCMAC ------- There is an ARC-like program available for the MacIntosh computer. An extractor is available for the IBM family, called "XARCMAC". The run-time help claims the files are ARC compatible, but none of the ARC programs I have will extract files from it. Fortunatly it has a unique signature; instead of storing a hex 1A as the first byte of the file, which ARC does, this format has a 1B. XARCMAC -- at least, the version given to me -- will only extract and list files, and has no overwrite mode. It is really only useful for extracting files created on a MacIntosh by the one particular program. SIGNATURE offset signature overwrite extract command_template --------- ------ --------- --------- ------- ---------------- SIGNATURE 0 <1B> "" "" xarcmac e %3 %4 Notice that this signature has angle-brackets <> around the signature. That means it gets treated as a hex value, rather than text. The only syntax PolyXarc will create with this is "xarcmac e TEST.MAC [*.*]". ZOO --- Though relatively slow and cumbersome, Rahul Dhesi's program ZOO has been ported onto a number of platforms and is quite popular in some circles. This one is awfully straightforward; the signature is "ZOO" and is at the very beginning of the file. SIGNATURE offset signature overwrite extract command_template --------- ------ --------- --------- ------- ---------------- SIGNATURE 0 ZOO o "" zoo x%2 %3 %4 Normal syntax is "zoo x TEST.ZOO [*.*]"; overwrite mode is "zoo xo TEST.ZOO [*.*]". Note that the overwrite command is the letter O, not the number 0. There is an extract-only program available on most platforms, called "BOOZ". I do not presently have a copy of it, but I'm sure the syntax would be quite simple to add to PolyXarc. 6 ARJ --- This is a new archiver; version 1.00 was released early in 1991. It creates very small archives quickly. The author also claims to be working on a program called ARJX that is supposed to make even smaller files even more quickly. As it stands, ARJ is one of the best archivers for speed and size. SIGNATURE offset signature overwrite extract command_template --------- ------ --------- --------- ------- ---------------- SIGNATURE 0 <60EA> -y "" arj e %2 %3 %4 Normal syntax is "arj e TEST.ARJ [*.*]"; overwrite syntax is "arj e -y TEST.ARJ [*.*]". ZIP --- PKZIP is the latest offering from Phil Katz. PKZIP is generally recognized as creating the smallest archives, and being the fastest archiver for the compression ratio, though some of the other new programs and new versions of old programs have been giving it a run for its money. LHARC also sometimes makes smaller files, though nobody has been able to positively demonstrate a clear edge of one over the other. PAK 2.51 now also includes ZIP capability. This allows a lot of versatility in one program. However, PKZIP is still faster and still usually produces smaller archives. SIGNATURE offset signature overwrite extract command_template --------- ------ --------- --------- ------- ---------------- SIGNATURE 0 PK -o "" pkunzip %2 %3 %4 SIGNATURE 0 PK /WA "" pak e /z %2 %3 %4 SIGNATURE 0 PK /WA /WO pak e /z %1%2 %3 %4 See the ARC section for notes on PAK's overwrite modes. Normal syntax is: "pkunzip TEST.ZIP [*.*]" or "pak e /z TEST.ZIP [*.*]" or "pak e /z /WO TEST.ZIP [*.*]". Overwrite syntax is "pkunzip -o TEST.ZIP [*.*]" or "pak e /z /WA TEST.ZIP [*.*]". Note that the /z is not necessary; once PAK determines the file type, it will correctly treat it as a .ZIP file. - - - Well, that concludes our little lecture. If you have any questions about the options I've chosen, or the syntaxes for the different archivers, I recommend you look at the documentation that came with the archiver. If you're still confused, try using the examples in POLYXARC.CFG. Make sure the archiver is in your execution path someplace. 7 If you have an archiver I haven't covered here, please let me know. Especially, if it isn't a commercial product, send me a copy of the archiver; I'm always interested in adding new ones, and it's easiest to support and test if I have a copy available to run. Jeffrey J. Nonken 1706 Cherrie Circle Blue Bell, Pa. 19422-3412 BBS: (215)279-9799 HST/v.32 Fidonet: 1:273/715 Internet: Jeffrey.Nonken@f715.n273.z1.fidonet.org Note: the above Snailmail address and phone number may change in the next few months. Please use my Fidonet or Internet address, or check the latest Nodelist for the current information. 8