#------------------------------------------------------------------------------
# $File: acorn,v 1.8 2021/04/26 15:56:00 christos Exp $
# acorn: file(1) magic for files found on Acorn systems
#
# RISC OS Chunk File Format
# From RISC OS Programmer's Reference Manual, Appendix D
# We guess the file type from the type of the first chunk.
0 lelong 0xc3cbc6c5 RISC OS Chunk data
>12 string OBJ_ \b, AOF object
>12 string LIB_ \b, ALF library
# RISC OS AIF, contains "SWI OS_Exit" at offset 16.
16 lelong 0xef000011 RISC OS AIF executable
# RISC OS Draw files
# From RISC OS Programmer's Reference Manual, Appendix E
0 string Draw RISC OS Draw file data
# RISC OS new format font files
# From RISC OS Programmer's Reference Manual, Appendix E
0 string FONT\0 RISC OS outline font data,
>5 byte x version %d
0 string FONT\1 RISC OS 1bpp font data,
>5 byte x version %d
0 string FONT\4 RISC OS 4bpp font data
>5 byte x version %d
# RISC OS Music files
# From RISC OS Programmer's Reference Manual, Appendix E
0 string Maestro\r RISC OS music file
>8 byte x version %d
>8 byte x type %d
# Digital Symphony data files
# From: Bernard Jungen (bern8817@euphonynet.be)
0 string \x02\x01\x13\x13\x13\x01\x0d\x10 Digital Symphony sound sample (RISC OS),
>8 byte x version %d,
>9 pstring x named "%s",
>(9.b+19) byte =0 8-bit logarithmic
>(9.b+19) byte =1 LZW-compressed linear
>(9.b+19) byte =2 8-bit linear signed
>(9.b+19) byte =3 16-bit linear signed
>(9.b+19) byte =4 SigmaDelta-compressed linear
>(9.b+19) byte =5 SigmaDelta-compressed logarithmic
>(9.b+19) byte >5 unknown format
0 string \x02\x01\x13\x13\x14\x12\x01\x0b Digital Symphony song (RISC OS),
>8 byte x version %d,
>9 byte =1 1 voice,
>9 byte !1 %d voices,
>10 leshort =1 1 track,
>10 leshort !1 %d tracks,
>12 leshort =1 1 pattern
>12 leshort !1 %d patterns
0 string \x02\x01\x13\x13\x10\x14\x12\x0e
>9 byte =0 Digital Symphony sequence (RISC OS),
>>8 byte x version %d,
>>10 byte =1 1 line,
>>10 byte !1 %d lines,
>>11 leshort =1 1 position
>>11 leshort !1 %d positions
>9 byte =1 Digital Symphony pattern data (RISC OS),
>>8 byte x version %d,
>>10 leshort =1 1 pattern
>>10 leshort !1 %d patterns
# From: Joerg Jenderek
# URL: https://www.kyzer.me.uk/pack/xad/#PackDir
# reference: https://www.kyzer.me.uk/pack/xad/xad_PackDir.lha/PackDir.c
# GRR: line below is too general as it matches also "Git pack" in ./revision
0 string PACK\0
# check for valid compression method 0-4
>5 ulelong <5
# https://www.riscosopen.org/wiki/documentation/show/Introduction%20To%20Filing%20Systems
# To skip "Git pack" version 0 test for root directory object like
# ADFS::RPC.$.websitezip.FONTFIX
>>9 string >ADFS\ PackDir archive (RISC OS)
# TrID labels above as "Acorn PackDir compressed Archive"
# compression mode y (0 - 4) for GIF LZW with a maximum n bits
# (y~n,0~12,1~13,2~14,3~15,4~16)
>>>5 ulelong+12 x \b, LZW %u-bits compression
# https://www.filebase.org.uk/filetypes
# !Packdir compressed archive has three hexadecimal digits code 68E
!:mime application/x-acorn-68E
!:ext pkd/bin
# null terminated root directory object like IDEFS::IDE-4.$.Apps.GRAPHICS.!XFMPdemo
>>>9 string x \b, root "%s"
# load address 0xFFFtttdd, ttt is the object filetype and dddddddddd is time
>>>>&1 ulelong x \b, load address %#x
# execution address 0xdddddddd dddddddddd is 40 bit unsigned centiseconds since 1.1.1900 UTC
>>>>&5 ulelong x \b, exec address %#x
# attributes (bits: 0~owner read,1~owner write,3~no delete,4~public read,5~public write)
>>>>&9 ulelong x \b, attributes %#x
# number of entries in this directory. for root dir 0
#>>>&13 ulelong x \b, entries %#x
# the entries start here with object name
>>>>&17 string x \b, 1st object "%s"
