OC-KittenOS/inst/deflate/instdeco.lua

-- Copyright (C) 2018-2021 by KittenOS NEO contributors
--
-- Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted.
--
-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
-- THIS SOFTWARE.

-- THIS NEXT LINE IS CLEARLY AWFUL
$bdBDWindow = nil

-- THE DEFLATE DECOMPRESSOR OF MADNESS --

-- Core I/O --

-- $dfAlignToByteRemaining is
--  set to 8 in the outer engine

${
function $dfGetIntField($L|lLen, $L|lVal)
 $lVal = 0
 for $L|lI = 0, $lLen - 1 do
  if coroutine.yield() then
   $lVal = $lVal + 2^$lI
  end
 end
 return $lVal
end
$}

-- Huffman Core --
-- The approach here is based around 1-prefixed integers.
-- These are stored in a flat table.
-- So 0b1000 is the pattern 000.

${
function $dfReadHuffmanSymbol($L|lTree, $L|lVal)
 $lVal = 1
 while not $lTree[$lVal] do
  $lVal = ($lVal * 2) + $dfGetIntField(1)
 end
 return $lTree[$lVal]
end
$}

${
function $dfGenHuffmanTree($L|lCodeLens)
 -- $L|lI (used everywhere; defining inside creates a bug because it gets globalized)
 $L|lNextCode = {}
 ${
 -- To explain:
 -- lNextCode is needed all the way to the end.
 -- But lBLCount isn't needed after it's used to
 --  generate lNextCode.
 -- And lCode is very, very temporary.
 -- Hence this massive block.
 $L|lBLCount = {}
 -- Note the 0
 for $lI = 0, 15 do
  $lBLCount[$lI] = 0
 end
 for $lI = 0, #$lCodeLens do
  ${
  $L|lCodeLen = $lCodeLens[$lI]
  if $lCodeLen ~= 0 then
   $lBLCount[$lCodeLen] = $lBLCount[$lCodeLen] + 1
  end
  $}
 end

 $L|lCode = 0
 for $lI = 1, 15 do
  $lCode = ($lCode + $lBLCount[$lI - 1]) * 2
  $lNextCode[$lI] = $lCode
 end
 $}

 $L|lTree = {}
 for $lI = 0, #$lCodeLens do
  ${
  $L|lCodeLen = $lCodeLens[$lI]
  if $lCodeLen ~= 0 then
   $L|lPow = math.floor(2 ^ $lCodeLen)
   assert($lNextCode[$lCodeLen] < $lPow, "Tl" .. $lCodeLen)
   $L|lK = $lNextCode[$lCodeLen] + $lPow
   assert(not $lTree[$lK], "conflict @ " .. $lK)
   $lTree[$lK] = $lI
   $lNextCode[$lCodeLen] = $lNextCode[$lCodeLen] + 1
  end
  $}
 end
 return $lTree
end
$}

-- DEFLATE fixed trees --
${
$L|dfFixedTL = {}
for $L|lI = 0, 143 do $dfFixedTL[$lI] = 8 end
for $lI = 144, 255 do $dfFixedTL[$lI] = 9 end
for $lI = 256, 279 do $dfFixedTL[$lI] = 7 end
for $lI = 280, 287 do $dfFixedTL[$lI] = 8 end
$dfFixedLit = $dfGenHuffmanTree($dfFixedTL)
-- last line possibly destroyed dfFixedTL, but that's alright
$dfFixedTL = {}
for $lI = 0, 31 do $dfFixedTL[$lI] = 5 end
$dfFixedDst = $dfGenHuffmanTree($dfFixedTL)
$}

-- DEFLATE LZ Core --

$dfWindow = ("\x00"):rep(2^15)
$dfPushBuf = ""
${
function $dfOutput($L|lData)
 $dfWindow = ($dfWindow .. $lData):sub(-2^15)
 $dfPushBuf = $dfPushBuf .. $lData
end
$}

$dfBittblLength = {
 0, 0, 0, 0, 0, 0, 0, 0,
 1, 1, 1, 1, 2, 2, 2, 2,
 3, 3, 3, 3, 4, 4, 4, 4,
 5, 5, 5, 5, 0
}
$dfBasetblLength = {
 3, 4, 5, 6, 7, 8, 9, 10,
 11, 13, 15, 17, 19, 23, 27, 31,
 35, 43, 51, 59, 67, 83, 99, 115,
 131, 163, 195, 227, 258
}
$dfBittblDist = {
 0, 0, 0, 0, 1, 1, 2, 2,
 3, 3, 4, 4, 5, 5, 6, 6,
 7, 7, 8, 8, 9, 9, 10, 10,
 11, 11, 12, 12, 13, 13
}
$dfBasetblDist = {
 1, 2, 3, 4, 5, 7, 9, 13,
 17, 25, 33, 49, 65, 97, 129, 193,
 257, 385, 513, 769, 1025, 1537, 2049, 3073,
 4097, 6145, 8193, 12289, 16385, 24577
}

${
function $dfReadBlockBody($L|lLit, $L|lDst, $L|lLitSym, $L|lLen, $L|lDCode, $L|lPtr)
 while true do
  $lLitSym = $dfReadHuffmanSymbol($lLit)
  if $lLitSym <= 255 then
   $dfOutput(string.char($lLitSym))
  elseif $lLitSym == 256 then
   return
  elseif $lLitSym <= 285 then
   $lLen = $dfBasetblLength[$lLitSym - 256] + $dfGetIntField($dfBittblLength[$lLitSym - 256])
   $lDCode = $dfReadHuffmanSymbol($lDst)
   $lPtr = 32769 - ($dfBasetblDist[$lDCode + 1] + $dfGetIntField($dfBittblDist[$lDCode + 1]))
   for $L|lI = 1, $lLen do
    $dfOutput($dfWindow:sub($lPtr, $lPtr))
   end
  else
   error("nt" .. v)
  end
 end
end
$}

-- Huffman Dynamics --

${
function $dfReadHuffmanDynamicSubcodes($L|lDistLens, $L|lCount, $L|lMetatree, $L|lCode)
 -- used a lot: $L|lI
 $lCode = 0
 $lDistLens[-1] = 0
 while $lCode < $lCount do
  -- use a tmpglb since it's just for the chain
  $L|lInstr = $dfReadHuffmanSymbol($lMetatree)
  if $lInstr < 16 then
   $lDistLens[$lCode] = $lInstr
   $lCode = $lCode + 1
  elseif $lInstr == 16 then
   for $lI = 1, 3 + $dfGetIntField(2) do
    $lDistLens[$lCode] = $lDistLens[$lCode - 1]
    $lCode = $lCode + 1
    assert($lCode <= $lCount, "sc.over")
   end
  elseif $lInstr == 17 then
   for $lI = 1, 3 + $dfGetIntField(3) do
    $lDistLens[$lCode] = 0
    $lCode = $lCode + 1
    assert($lCode <= $lCount, "sc.over")
   end
  elseif $lInstr == 18 then
   for $lI = 1, 11 + $dfGetIntField(7) do
    $lDistLens[$lCode] = 0
    $lCode = $lCode + 1
    assert($lCode <= $lCount, "sc.over")
   end
  else
   -- is this even possible?
   error("sc.unki")
  end
 end
 $lDistLens[-1] = nil
 return $lDistLens
end
$}

$dfDynamicMetalensScramble = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15}

${
function $dfReadHuffmanDynamic($L|lState, $L|lLiteralSize, $L|lDistanceSize, $L|lDistanceLens)
 -- $L|lI loop variable, used all over
 -- to save on locals, this is reused
 -- as metalens
 $lState = {}
 for $lI = 0, 18 do $lState[$lI] = 0 end
 $lLiteralSize = $dfGetIntField(5) + 257
 $lDistanceSize = $dfGetIntField(5) + 1
 for $lI = 1, $dfGetIntField(4) + 4 do
  $lState[$dfDynamicMetalensScramble[$lI]] = $dfGetIntField(3)
 end
 -- as metatree
 $lState = $dfGenHuffmanTree($lState)
 -- as concatenated subcodes
 $lState = $dfReadHuffmanDynamicSubcodes({}, $lLiteralSize + $lDistanceSize, $lState)
 -- The distance lengths are removed from lState,
 --  while being added to lDistanceLens
 -- The result is completion
 $lDistanceLens = {}
 for $lI = 0, $lDistanceSize - 1 do
  $lDistanceLens[$lI] = $lState[$lLiteralSize + $lI]
  $lState[$lLiteralSize + $lI] = nil
 end
 return $dfGenHuffmanTree($lState), $dfGenHuffmanTree($lDistanceLens)
end
$}

-- Main Thread --

${
$dfThread = coroutine.create(function ($L|lFinal, $L|lLitLen)
 while true do
  $lFinal = coroutine.yield()
  $L|lBlockType = $dfGetIntField(2)
  if $lBlockType == 0 then
   -- literal
   $dfGetIntField($dfAlignToByteRemaining)
   $lLitLen = $dfGetIntField(16)
   -- this is weird, ignore it
   $dfGetIntField(16)
   for $L|lI = 1, $lLitLen do
    $dfOutput(string.char($dfGetIntField(8)))
   end
  elseif $lBlockType == 1 then
   -- fixed Huffman
   $dfReadBlockBody($dfFixedLit, $dfFixedDst)
  elseif $lBlockType == 2 then
   -- dynamic Huffman
   $dfReadBlockBody($dfReadHuffmanDynamic())
  else
   error("b3")
  end
  while $lFinal do
   coroutine.yield()
  end
 end
end)
$}

-- The Outer Engine --

coroutine.resume($dfThread)
${
function $engineInput($L|lData, $L|lByte)
 for $L|lI = 1, #$lData do
  $lByte = $lData:byte($lI)
  $dfAlignToByteRemaining = 8
  while $dfAlignToByteRemaining > 0 do
   -- If we're providing the first bit (v = 8), then there are 7 bits remaining.
   -- So this hits 0 when the *next* 8 yields will provide an as-is byte.
   $dfAlignToByteRemaining = $dfAlignToByteRemaining - 1
   assert(coroutine.resume($dfThread, $lByte % 2 == 1))
   $lByte = math.floor($lByte / 2)
  end
 end
 -- flush prepared buffer
 $engineOutput($dfPushBuf)
 $dfPushBuf = ""
end
$}