luaTar.lua

--[[

	ABJ4403's LuaTar
	(C) 2022-2024 ABJ4403

	Licensed under GNU GPL v3 License

]]
local tar = {
	VERSION = 4
}
function tar.add(tarPath,fileName,content)
	local tarFile,err = io.open(tarPath,"ab")
	if not tarFile then return err or false end
	content = content or ""
	local isFolder = content == "" and fileName:sub(#fileName,#fileName) == "/"
	-- note: %07o = octal
	local header =
		fileName..("\0"):rep(100 - #fileName)..	-- Name
		'0000666\0'..														-- Mode
		("%07o"):format(0)..'\0'..							-- UID
		("%07o"):format(0)..'\0'..							-- GID
		("%011o"):format(#content)..'\0'..			-- Size
		("%011o"):format(0)..'\0'..							-- Last modified
		("\0"):rep(7)..' '..										-- Checksum
		(isFolder and "5" or "0")..							-- Type (0/1/2:file/hardlink/symlink)
		("\0"):rep(100)..												-- linked file name (we dont want those symlinks and stuf so aint using one
		("\0"):rep(88)..												-- UnixStandardTar header (6b) + version (2b), user + group (64b), device major + minor number (16b)
		("\0"):rep(167)					 								-- UStar Filename prefix
	-- Checksum
	local sum = 224
	for i=1,512 do
		sum = sum + header:byte(i)
	end
	header =
		header:sub(1,148)..
		("%06o"):format(sum)..
		header:sub(155)
	tarFile:write(
		header..
		content..
		("\0"):rep((512 - #content) % 512) -- Tar file has 512 bytes block size
	)
	tarFile:close()
	return true
end
function tar.extract(tarPath,fileName)
	local file = io.open(tarPath,"rb")
	if not file then return end
	while true do
		local block = file:read(512) -- read every block
		if not block then break end
		local fileSize = tonumber(block:sub(125,135),8) -- get the file size
		if not fileSize then print("Found a block with likely empty file size bytes, break.")break end
		if block:sub(1,math.min(100,#fileName)) == fileName then -- if a block starts with filename
			local data = file:read(fileSize) -- read the whole thing
			file:close()
			return data
		end
		local skipBlk = math.ceil((fileSize-.00000000000000001) / 512) -- extra zeroes to fix Lua floating point integer bug
		file:seek("cur",skipBlk * 512)
	end
	file:close()
end
function tar.remove(tarPath,fileName)
	local file = io.open(tarPath,"rb")
	if not file then return end
	local removedFiles = 0
	local output = io.open(tarPath..".tmp","wb")
	while true do
		local block = file:read(512)
		if not block then break end
		if block:sub(1,math.min(100,#fileName)) == fileName then -- ignores the block with the file that is going to be removed
			local fileSize = tonumber(block:sub(125,135),8)
			if not fileSize then print("Found a block with likely empty file size bytes, break.")break end
			local skipBlk = math.ceil((fileSize-.00000000000000001) / 512) -- extra zeroes to fix Lua floating point integer bug
			file:seek("cur",skipBlk * 512)
			removedFiles = removedFiles + 1
		else
			output:write(block) -- write the rest of the block to temporary file
		end
	end
	file:close()
	output:close()
	os.remove(tarPath)
	os.rename(tarPath..".tmp",tarPath)
	return removedFiles
end
function tar.parseHeader(tarPath)
	local ret = {}
	local file = io.open(tarPath,"rb")
	if not file then return end
	while true do
	--read
		local block = file:read(512)
		if not block then break end
		local fileName = block:sub(1,100):gsub("\0+$","")
		if fileName == "" then print("Found a block with empty filename, likely empty header, break.")break end
	--checksum verify
		local sum = 224
		local checksum = tonumber(block:sub(149,154),8)
		block = block:sub(1,148).."\0\0\0\0\0\0"..block:sub(155) -- original was bunch of NULs
		for i=1,#block do
			sum = sum + block:byte(i)
		end
		local checksumValid =
			checksum and
			sum - checksum == 0
	--result
		local header = {
			isValid = checksumValid,
			--headerBytes = block,
			mode = block:sub(101,107),
			uid = tonumber(block:sub(109,115),8),
			gid = tonumber(block:sub(117,123),8),
			size = tonumber(block:sub(125,135),8),
			lastModified = tonumber(block:sub(137,147),8),
			["checksum"] = checksum,
			["type"] = tonumber(block:sub(156,156)),
			linkedName = block:sub(157,257),
			ustar = {
				--headerBytes = block:sub(158,501),
				ustarHeader = block:sub(258,263),
				version = block:sub(264,265),
				user = block:sub(266,297),
				group = block:sub(298,329),
				devMajor = block:sub(330,337),
				devMinor = block:sub(338,345),
				filenamePrefix = block:sub(346,501),
			}
		}
		ret[fileName] = header
	--seek block
		if not header.size then print("FILE SIZE BUG DETECTED! CANNOT CONTINUE!!")break end
		local skipBlk =
			math.ceil((header.size-.00000000000000001) / 512) -- extra zeroes to fix Lua floating point integer bug
		file:seek("cur",skipBlk * 512)
	end
	file:close()
	return ret
end
function tar.queryFile(tarPath)
	local fileList = {}
	for k in pairs(tar.parseHeader(tarPath)) do
		if k:sub(#k,#k) ~= "/" then
			table.insert(fileList,k)
		end
	end
	return fileList
end
function tar.queryFolder(tarPath)
	local fileList = {}
	for k in pairs(tar.parseHeader(tarPath)) do
		if k:sub(#k,#k) == "/" then
			table.insert(fileList,k)
		end
	end
	return fileList
end
return tar