unpackpkg.moon

-- You are probably going to have a much, much better time using my Python implementation… 
-- https://gist.github.com/uyjulian/55475c98c631632ddfd5453469726439

file_util = require"file_util"
ffi = require"ffi"
bit = require"bit"
S = require"syscall"
struct = require"struct"

dir = arg[1] .. "_"
S.mkdir(dir, "RWXU")
f = io.open(arg[1], "rb")
indat = f\read("*a")
f\close()

___1, total, bl = struct.unpack("<I4I4", indat)
--the first uint32 is all zeros...
--print("filecount: " .. total)
trim = (s) ->
	return s\match'^%z*(.*%Z)' or ''

--get entries
filez = {}
num = total

ffi.cdef[[void * memmove(void *dst, const void *src, size_t len);]]

decompress = (v) ->
	des, bl = struct.unpack("<I4", indat, bl)
	if des ~= v.decsize
		des = (des > v.decsize) and des or v.decsize
	cms, bl = struct.unpack("<I4", indat, bl)
	if (cms ~= v.cmpsize) and ((v.cmpsize - cms) ~= 4)
		error("compression size in header and stream don't match")
	num3, bl = struct.unpack("<I4", indat, bl)
	fin = bl + cms - 13
	cd = ffi.new("unsigned char[?]", des)
	i = 0
	num4 = 0

	while bl <= fin
		i += 1
		b, bl = struct.unpack("<I1", indat, bl)
		if b == num3
			i += 1
			b2, bl = struct.unpack("<I1", indat, bl)
			if b2 ~= num3
				i += 1
				if b2 >= num3
					b2 -= 1
				b3, bl = struct.unpack("<I1", indat, bl)
				ffi.C.memmove(cd + (num4), cd + (num4 - b2), b3)
				num4 += b3
			else
				cd[num4] = b2
				num4 += 1
		else
			cd[num4] = b
			num4 += 1

	return ffi.string(cd, des)


while num ~= 0
	num -= 1
	filename, bl = struct.unpack("<c64", indat, bl)
	filename = trim(filename)
	decsize, cmpsize, offset, flags, bl = struct.unpack("<I4I4I4I4", indat, bl)
	compressed = bit.band(flags, 1) ~= 0
	skip4bytes = bit.band(flags, 2) ~= 0
	filez[total - num] = {:filename, :cmpsize, :decsize, :offset, :flags, :compressed, :skip4bytes}
	

--extract entries
for i, v in ipairs(filez)
	-- print("filename: " .. v.filename)
	-- print("compressed size: " .. v.cmpsize)
	-- print("decompressed size: " .. v.decsize)
	-- print("offset: " .. v.offset)
	-- print("extra flags: 0x" .. bit.tohex(v.flags))
	-- print("compressed: " .. (v.compressed and "true" or "false"))
	-- print("skip 4 bytes: " .. (v.skip4bytes and "true" or "false"))
	-- print("file number: " .. i)
	bl = v.offset + 1
	data = ""
	if v.skip4bytes
		bl += 4
	if v.compressed
		data = decompress(v)
	else
		if v.cmpsize ~= v.decsize
			error("compress size is not equal to decompress size")
		data = string.sub(indat, bl, bl + v.decsize)
	file_util.writefile(dir .. "/" .. v.filename, data)