mirror of
https://github.com/20kdc/OC-KittenOS.git
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86 lines
2.0 KiB
Lua
86 lines
2.0 KiB
Lua
-- This is released into the public domain.
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-- No warranty is provided, implied or otherwise.
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-- BDIVIDE (r5 edition) and PREPROC (r9 edition)
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-- decompression engine for installer
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-- cb: sector accumulator
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-- ct: preproc accumulator
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-- cc: bdivide accumulator
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-- cw: bdivide window
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-- cp: function to submit to preproc
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-- cd: function to submit to bdivide
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cb,ct,cc,cw="","","",("\x00"):rep(2^16)
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-- High-level breakdown:
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-- CP is unescaper & TAR-sector-breakup.
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-- It'll only begin to input if at least 3 bytes are available,
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-- so you'll want to throw in 2 extra zeroes at the end of stream as done here.
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-- It uses Ct (input buffer) and Cp (output buffer).
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-- Ignore its second argument, as that's a lie, it's just there for a local.
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-- CD is the actual decompressor. It has the same quirk as CP, wanting two more bytes.
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-- It stores to Cc (compressed), and Cw (window).
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-- It outputs that which goes to the window to CP also.
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-- And it also uses a fake local.
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-- SEE compress.lua FOR THIS FUNCTION
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function p(x, y)
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if x == 126 then
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if y >= 32 then
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return ({
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-- Before adding to this, check how installer size is changed.
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"\x7E", "\x7F"
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})[y - 31], 3
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end
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return string.char(y), 3
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elseif x == 127 then
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return string.char(128 + y), 3
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elseif x >= 32 then
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return string.char(x), 2
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elseif x == 31 then
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return "\n", 2
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elseif x == 30 then
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return "\x00", 2
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end
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return string.char(("enart"):byte(x % 5 + 1), ("ndtelh"):byte(math.floor(x / 5) + 1)), 2
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end
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function cp(d, b, a)
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ct = ct .. d
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while #ct > 1 do
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b, a = p(ct:byte(), ct:byte(2))
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cb = cb .. b
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ct = ct:sub(a)
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if #cb > 511 then
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M(cb:sub(1, 512))
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cb = cb:sub(513)
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end
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end
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end
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function cd(d, b, p)
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cc = cc .. d
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while #cc > 2 do
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b = cc:byte()
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if b < 128 then
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b, cc = cc:sub(1, 1), cc:sub(2)
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else
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p = cc:byte(2) * 256 + cc:byte(3) + 1
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b, cc = cw:sub(p, p + b - 125), cc:sub(4)
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end
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cp(b)
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cw = (cw .. b):sub(-65536)
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end
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end
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-- quick & dirty integration with the existing stuff
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function L(d)
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if not d then
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cd("\x00\x00")cp("\x00\x00")
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else
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cd(d)
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end
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end
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