Ar (Haruhiko Okumura) - Revision history

Taritta at 12:52, 1 November 2023

2023-11-01T12:52:57Z

Taritta at 12:25, 1 November 2023

2023-11-01T12:25:32Z

Jsummers: /* Related formats */

2021-09-17T17:07:13Z

‎Related formats

Jsummers at 16:50, 17 September 2021

2021-09-17T16:50:45Z

Jsummers at 14:45, 14 August 2021

2021-08-14T14:45:12Z

Jsummers: /* Software */

2021-08-12T17:09:25Z

‎Software

Jsummers: Created page with "{{FormatInfo |name=ar (Haruhiko Okumura) |formattype=electronic |subcat=Archiving |released=1990 }} {{DISPLAYTITLE:ar (Haruhiko Okumura)}}'''ar''' is a compressed archive util..."

2021-08-11T17:56:30Z

Created page with "{{FormatInfo |name=ar (Haruhiko Okumura) |formattype=electronic |subcat=Archiving |released=1990 }} {{DISPLAYTITLE:ar (Haruhiko Okumura)}}'''ar''' is a compressed archive util..."

New page

{{FormatInfo
|name=ar (Haruhiko Okumura)
|formattype=electronic
|subcat=Archiving
|released=1990
}}
{{DISPLAYTITLE:ar (Haruhiko Okumura)}}'''ar''' is a compressed archive utility developed by Haruhiko Okumura. It is not related to the [[AR|Unix ar archiver]].

== Discussion ==
ar was essentially a preview of the influential family of compression methods used by [[LHA]] version 2.x: the "<code>lh5</code>" method and related methods.

There seem to have been two main versions of ar. Neither has a clear version number, but based on the distribution filenames, and other information from Okumura, we may call them '''ar001''' (or "ar v0.01"), and '''ar002''' (or "ar v0.02").

ar was distributed mainly as source code, though most distributions of ar002 include a DOS binary.

ar001 uses its own file format, not known to be compatible with anything else. ar002 uses [[LHA]] file format.

== Format details ==
ar's compression is based on [[LZ77 with Huffman coding|LZ77 with static Huffman coding]]. ar001 by default uses a 4K history buffer, like LHA's "<code>lh4</code>" method. ar002 by default uses an 8K history buffer, like "<code>lh5</code>". It's unclear whether the ar compression methods are 100% compatible with the standard LHA methods, but they're at least very close.

The [[CRC-16]] algorithm used by ar001 is not the same as the one used by ar002 and LHA. It seems to be the one called "CRC-16/IBM-SDLC" by [https://reveng.sourceforge.io/crc-catalogue/16.htm CRC RevEng].

== Identifiers ==
Neither version has a default or recommended filename extension.

== Identification ==
ar001 files have no signature. Robust identification would probably have to involve verifying the header CRC.

For ar002, refer to [[LHA#Identification]].

== Specifications ==
For the header formats, see the comments near the beginning of the ar.c file in the corresponding distribution.

See also [[LHA#Specifications]].

== Software ==
ar001:
* {{CdTextfiles|swexplorer/disk1/A065/AR001.ZIP|AR001.ZIP}} - Source code
* [https://www.pcorner.com/list/UTILITY/AR_EXE.ZIP/INFO/ AR_EXE.ZIP] - Unofficial DOS binary (untested)

ar002:
* {{CdTextfiles|sourcecode/msdos/arc_lbr/ar002.zip|AR002.ZIP}} - Source code + DOS binary
* https://oku.edu.mie-u.ac.jp/~okumura/compression/ar002/

== Links ==
* [https://oku.edu.mie-u.ac.jp/~okumura/compression/history.html History of Data Compression in Japan]

@@ Line 58: / Line 58: @@
 * https://oku.edu.mie-u.ac.jp/~okumura/compression/ar002/
 * [{{SACFTPURL|pack|ar_110.zip}} "AR v1.1"] - ar002 with modifications by Terran Melconian (DOS binary + source code)
 * See also [[LHA#Software]].

@@ Line 59: / Line 59: @@
 * [{{SACFTPURL|pack|ar_110.zip}} "AR v1.1"] - ar002 with modifications by Terran Melconian (DOS binary + source code)
 * See also [[LHA#Software]].
 == Links ==
 * [https://oku.edu.mie-u.ac.jp/~okumura/compression/history.html History of Data Compression in Japan]

@@ Line 39: / Line 39: @@
 Formats derived from ar's compression scheme, directly or indirectly, include:
 * [[LHA]] "lh5" compression
-* [[Zoo]]
+* [[Zoo]] "LZH" compression
 * [[ARJ]]
 * [[SCO compress LZH]]

@@ Line 3: / Line 3: @@
 |formattype=electronic
 |subcat=Archiving
 |released=1990
 }}
@@ Line 22: / Line 23: @@
 == Identifiers ==
-Neither version has a default or recommended filename extension.
+Neither version of ar has a default or recommended filename extension.
 == Identification ==
@@ Line 28: / Line 31: @@
 For ar002, refer to [[LHA#Identification]].
 == Specifications ==
@@ Line 42: / Line 57: @@
 * {{CdTextfiles|sourcecode/msdos/arc_lbr/ar002.zip|AR002.ZIP}} - Source code + DOS binary
 * https://oku.edu.mie-u.ac.jp/~okumura/compression/ar002/
 * See also [[LHA#Software]].
 == Links ==
 * [https://oku.edu.mie-u.ac.jp/~okumura/compression/history.html History of Data Compression in Japan]

@@ Line 19: / Line 19: @@
 ar's compression is based on [[LZ77 with Huffman coding|LZ77 with static Huffman coding]]. ar001 by default uses a 4K history buffer, like LHA's "<code>lh4</code>" method. ar002 by default uses an 8K history buffer, like "<code>lh5</code>". It's unclear whether the ar compression methods are 100% compatible with the standard LHA methods, but they're at least very close.
-The [[CRC-16]] algorithm used by ar001 is not the same as the one used by ar002 and LHA. It seems to be the one called "CRC-16/IBM-SDLC" by [https://reveng.sourceforge.io/crc-catalogue/16.htm CRC RevEng].
+The [[CRC-16]] algorithm used by ar001 is different from the one used by ar002 and LHA. It seems to be equivalent to the one called "CRC-16/IBM-SDLC" by [https://reveng.sourceforge.io/crc-catalogue/16.htm CRC RevEng].
 == Identifiers ==
@@ Line 32: / Line 32: @@
 For the header formats, see the comments near the beginning of the ar.c file in the corresponding distribution.
-See also [[LHA#Specifications]].
+See also [[LHA#Format documentation]].
 == Software ==