DWC

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.

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 ASCII "". There is no header or signature at the beginning of the file.

The known versions of DWC always seem to produce files having bytes beginning 27 bytes from the end of the file. However, the software does not require this, and old versions still need to be evaluated.

Specifications

 * Archive format info, including DWC
 * DWC format info, from Corion.net and FileFormat.Info

Software

 * DWC (DOS binaries)
 * (1988-03-15)
 * (1988-05-31)
 * Ver. A5.10 (1990-03-07)