mirror of https://github.com/20kdc/OC-KittenOS.git
77 lines
1.8 KiB
Lua
77 lines
1.8 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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-- a: temporary
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-- touched by q,L
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-- b: sector accumulator
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-- c: bdivide accumulator
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-- d: temporary
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-- touched by q,L
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-- t: preproc accumulator
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-- q: function to submit to preproc
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-- s: temporary
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-- touched by L
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-- w: bdivide window
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-- L: function to submit to bdivide
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b,t,c,w="","","",("\x00"):rep(2^16)
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-- High-level breakdown:
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-- q 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 t (input buffer) and p (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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-- L is the actual decompressor. It has the same quirk as q, wanting two more bytes.
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-- It stores to c (compressed), and w (window).
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-- It outputs that which goes to the window to q 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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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((x - x % 5) / 5 + 1)), 2
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end
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function q(w)
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t = t .. w
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while #t > 1 do
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d, a = p(t:byte(), t:byte(2))
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b = b .. d
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t = t:sub(a)
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if #b > 511 then
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M(b:sub(1, 512))
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b = b:sub(513)
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end
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end
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end
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function L(d)
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c = c .. d
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while #c > 2 do
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s = c:byte()
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if s < 128 then
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s, c = c:sub(1, 1), c:sub(2)
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else
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a = c:byte(2) * 256 + c:byte(3) + 1
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s, c = w:sub(a, a + s - 125), c:sub(4)
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end
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q(s)
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w = (w .. s):sub(-2^16)
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end
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end
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