View source for Squash (RISC OS)

{{FormatInfo
|formattype=electronic
|subcat=Compression
}}
'''Squash''' files ([[RISC OS filetype|file type]] FCA, Squash) contain compressed data for single files on RISC OS systems.

The [[file command]] calls this format "squished".

== Format details ==

According to the help text for the Squash application, "The Squash module currently compresses using a 12-bit LZW algorithm but no guarantee is made that this will be so in the future."

The compressed data is preceded by a header, with offsets measured in bytes and all values stored in little-endian byte order:

{| class="wikitable" width="50%"
! Offset || Description
|-
! 0
| "SQSH" (4 byte ID)
|-
! 4
| Length of the original, uncompressed file in bytes
|-
! 8
| Load address of the original file
|-
! 12
| Execution address of the original file
|-
! 16
| Reserved (should be 0)
|}

As with a number of data formats related to filing systems on RISC OS, the load and execution addresses are actually used to hold the [[RISC OS filetype|file type]] and date stamp of the original file.

The remaining data in the file (from offset 20 to the end) is in [[compress]] format, and can be decompressed using gunzip. One way to do this is to run the following in a bash shell:

  dd if=input_file skip=20 bs=1 | gunzip -c - > output_file

== Software ==
* [https://github.com/mjwoodcock/riscosarc/ RISC OS de-archiver]
* {{Deark}}
* Or see the [[#Format details]] section above, for a way to convert to [[compress]] format.

== Sample files ==
* http://www.arcade-bbs.net/filepages/file77.htm → {{ArcadeBBSLink|078954|Time1}}, {{ArcadeBBSLink|073941|WATERFALL}}
* {{DexvertSamples|archive/squash}}

== References ==

* [http://acorn.riscos.com/riscos3/35/35DiscImage/Apps/!Squash/!Help Help file] for the Squash application
* [http://acorn.riscos.com/riscos3/37/37DiscImage/Manuals/Manual/BOOK2AB/E_18.HTM Manual page] in the RISC OS 3.7 user guide

[[Category:RISC OS]]