DWC

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The documentation says that in 1988 the compressor/decompressor source code rights were sold to a company called DS Technologies.
 
The documentation says that in 1988 the compressor/decompressor source code rights were sold to a company called DS Technologies.
 +
 +
== File structure ==
 +
 +
DWC archive format overview
 +
 +
  This documentation contains educated guesswork derived from
 +
  observing the behavior of DWC (mainly v5.10). It extends and
 +
  corrects some earlier descriptions of the format.
 +
 +
  - Byte order is little-endian.
 +
  - CRC algorithm is [[CRC-16#CRC-16/ARC|CRC-16/ARC]].
 +
  - Sizes and offsets are in bytes, unless otherwise noted.
 +
 +
Archive Trailer segment
 +
 +
  Let EOF = the DWC file size.
 +
 +
  Offset  Size Label    Description
 +
  ------  ---- -----    -----------
 +
  EOF-27  2    tsize    Size of trailer (usually 27, larger OK)
 +
  EOF-25  1    fhsize    Size of each member file header (usually 34,
 +
                          larger OK, slightly smaller maybe OK)
 +
  EOF-24  13            Name of header file ("h" command), NUL-
 +
                          terminated
 +
  EOF-11  4              Archive timestamp ([[Unix time]])
 +
  EOF-7    4    nmembers  Number of member files
 +
  EOF-3    3              "DWC" signature
 +
 +
Member File Headers segment
 +
 +
  Sequence of nmembers headers, each fhsize bytes, starts at
 +
  EOF-tsize-(fhsize×nmembers).
 +
 +
Member File Header
 +
 +
  Offset  Size Label    Description
 +
  ------  ---- -----    -----------
 +
  +0      13            Base filename, NUL terminated
 +
  +13      4              Original size
 +
  +17      4              Timestamp ([[Unix time]])
 +
  +21      4    csize    Compressed size
 +
  +25      4    fdpos    Offset (from start of file) of File Data segment
 +
  +29      1              Low 4 bits: Compression method (1=Crunched,
 +
                          2=not compressed).
 +
                          0x40 bit: Set if file is encrypted.
 +
  +30      1    cmtsize  Size of comment field
 +
  +31      1    pathsize  Size of path field
 +
  +32      2              CRC of *compressed* (and potentially encrypted)
 +
                          data
 +
 +
File Data
 +
 +
  One segment per member file. Starts at fdpos.
 +
 +
  Offset          Size      Description
 +
  ------          ----      -----------
 +
  +0              csize    Compressed data
 +
  +csize          pathsize  Path, NUL-terminated
 +
  +csize+pathsize  cmtsize  File comment, NUL-terminated
  
 
== Identification ==
 
== Identification ==

Revision as of 20:45, 12 November 2021

File Format
Name DWC
Ontology
Extension(s) .dwc
Wikidata ID Q28600485
Released 1986

DWC is a compressed archive utility and file format that was patterned after ARC, but is not compatible with that format. It was designed to be faster and more compact than ARC, but have similar functionality. Its compression scheme is based on LZW.

It includes a utility to make self-extracting archives.

Contents

Discussion

DWC was created by Dean W. Cooper in 1986 as a higher performance alternative to the ARC (both ARC & PKARC) and Zoo file archiving tools. The file COMPARE.DOC (in e.g. version A5.01) reports both compression and time improvements over DWC's competitors.

Source code for some versions prior to A5.01 was apparently made public, but we have not located any copies.

The documentation says that in 1988 the compressor/decompressor source code rights were sold to a company called DS Technologies.

File structure 

DWC archive format overview

 This documentation contains educated guesswork derived from
  observing the behavior of DWC (mainly v5.10). It extends and
  corrects some earlier descriptions of the format.

 - Byte order is little-endian.
 - CRC algorithm is CRC-16/ARC.
 - Sizes and offsets are in bytes, unless otherwise noted.

Archive Trailer segment

 Let EOF = the DWC file size.

 Offset   Size Label     Description
 ------   ---- -----     -----------
 EOF-27   2    tsize     Size of trailer (usually 27, larger OK)
 EOF-25   1    fhsize    Size of each member file header (usually 34,
                          larger OK, slightly smaller maybe OK)
 EOF-24   13             Name of header file ("h" command), NUL-
                          terminated
 EOF-11   4              Archive timestamp (Unix time)
 EOF-7    4    nmembers  Number of member files
 EOF-3    3              "DWC" signature

Member File Headers segment

 Sequence of nmembers headers, each fhsize bytes, starts at
 EOF-tsize-(fhsize×nmembers).

Member File Header

 Offset   Size Label     Description
 ------   ---- -----     -----------
 +0       13             Base filename, NUL terminated
 +13      4              Original size
 +17      4              Timestamp (Unix time)
 +21      4    csize     Compressed size
 +25      4    fdpos     Offset (from start of file) of File Data segment
 +29      1              Low 4 bits: Compression method (1=Crunched,
                          2=not compressed).
                         0x40 bit: Set if file is encrypted.
 +30      1    cmtsize   Size of comment field
 +31      1    pathsize  Size of path field
 +32      2              CRC of *compressed* (and potentially encrypted)
                          data

File Data

 One segment per member file. Starts at fdpos.

 Offset           Size      Description
 ------           ----      -----------
 +0               csize     Compressed data
 +csize           pathsize  Path, NUL-terminated
 +csize+pathsize  cmtsize   File comment, NUL-terminated

Identification

Files end with a 27-byte trailer that starts with bytes 1b 00 (the trailer size) and ends with ASCII "DWC". There is no header or signature at the beginning of the file.

Specifications

Software

Further reading

Retrieved from "http://fileformats.archiveteam.org/index.php?title=DWC&oldid=41127"
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