Squash (RISC OS)

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'''Squash''' files ([[RISC OS filetype|file type]] FCA, Squash) contain compressed data for single files on RISC OS systems.
== Overview ==
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Squash files (file type FCA, Squash) contain compressed data for single files on RISC OS systems.
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The [[file command]] calls this format "squished".
 
The [[file command]] calls this format "squished".
  
== Format ==
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== 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."
 
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."
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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 file type and date stamp of the original file.
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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.
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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:
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  dd if=input_file skip=20 bs=1 | gunzip -c - > output_file
  
The remaining data in the file (from offset 20 to the end) can be decompressed using gunzip.
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== Software ==
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* [https://github.com/mjwoodcock/riscosarc/ RISC OS de-archiver]
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* {{Deark}}
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* Or see the [[#Format details]] section above, for a way to convert to [[compress]] format.
  
 
== Sample files ==
 
== Sample files ==
* http://arcade.demon.co.uk/filepages/file77.htm → [ftp://arcade.demon.co.uk/data/077500/078950/078954 Time1], [ftp://arcade.demon.co.uk/data/072500/073900/073941 WATERFALL]
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* http://www.arcade-bbs.net/filepages/file77.htm → [ftp://www.arcade-bbs.net/data/077500/078950/078954 Time1], [ftp://www.arcade-bbs.net/data/072500/073900/073941 WATERFALL]
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* https://telparia.com/fileFormatSamples/archive/squash/
  
 
== References ==
 
== References ==
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* [http://acorn.riscos.com/riscos3/35/35DiscImage/Apps/!Squash/!Help Help file] for the Squash application
 
* [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
 
* [http://acorn.riscos.com/riscos3/37/37DiscImage/Manuals/Manual/BOOK2AB/E_18.HTM Manual page] in the RISC OS 3.7 user guide
* [http://mdfs.net/Docs/Comp/Acorn/Filetypes The Unofficial Acorn Filetypes List]
 
  
 
[[Category:RISC OS]]
 
[[Category:RISC OS]]

Revision as of 00:14, 3 October 2021

File Format
Name Squash (RISC OS)
Ontology

Squash files (file type FCA, Squash) contain compressed data for single files on RISC OS systems.

The file command calls this format "squished".

Contents

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:

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 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

Sample files

References

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