mirror of https://github.com/20kdc/OC-KittenOS.git
62 lines
1.4 KiB
Lua
62 lines
1.4 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
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-- format:
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-- 0-127 for constants
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-- <block + 128>, <(len - 3) * 2, + lowest bit is upper bit of position>, <position - 1>
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io.write("\x00") -- initiation character
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local blockCache = {}
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local window = 0
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local blockUse = 128
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for i = 128, 128 + blockUse - 1 do
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blockCache[i] = ("\x00"):rep(512)
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end
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local function runBlock(blk)
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-- firstly, get current block index
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local blockIndex = window + 128
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window = (window + 1) % blockUse
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blockCache[blockIndex] = ""
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-- ok, now work on the problem
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local i = 1
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while i <= #blk do
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local bestData = blk:sub(i, i)
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local bestRes = bestData
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local bestScore = 1
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for bid = 128, 128 + blockUse - 1 do
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for lm = 0, 127 do
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local al = lm + 3
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local pfx = blk:sub(i, i + al - 1)
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if #pfx ~= al then
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break
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end
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local p = blockCache[bid]:find(pfx, 1, true)
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if not p then
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break
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end
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local score = al / 3
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if score > bestScore then
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bestData = string.char(bid) .. string.char((lm * 2) + math.floor((p - 1) / 256)) .. string.char((p - 1) % 256)
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bestRes = pfx
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bestScore = score
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end
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end
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end
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-- ok, encode!
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io.write(bestData)
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blockCache[blockIndex] = blockCache[blockIndex] .. bestRes
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i = i + #bestRes
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end
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end
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while 1 do
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local blkd = io.read(512)
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runBlock(blkd)
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if #blkd < 512 then
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return
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end
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end
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