Lua Tar Extraction Module

A Lua Tar Extraction Module

-- Tar extraction module based off LUARocks : github.com/keplerproject/luarocks
-- By Danny @ anscamobile
--
-- Restored directory creation
-- Handles space-padded numbers, e.g. in the size field, so it can handle a TAR file
-- created by the OS X UNIX tar.
-- By David Gross

-- Adapted for Gideros Mobile by Emanuel Braz - fastencoding@gmail.com
-- test mock
-- delete tar file after unpacking
-- callback function if needed

--local lfs = require "lfs"

local blocksize = 512
local _ceil = math.ceil
local _tonumber = tonumber
local _ioOpen = io.open
--local byte = string.byte

-- trim from http://lua-users.org/wiki/StringTrim
function trim(s)
	return s:match'^%s*(.*%S)' or ''
end

local function get_typeflag(flag)
	if flag == "0" or flag == "\0" then return "file"
	elseif flag == "1" then return "link"
	elseif flag == "2" then return "symlink" -- "reserved" in POSIX, "symlink" in GNU
	elseif flag == "3" then return "character"
	elseif flag == "4" then return "block"
	elseif flag == "5" then return "directory"
	elseif flag == "6" then return "fifo"
	elseif flag == "7" then return "contiguous" -- "reserved" in POSIX, "contiguous" in GNU
	elseif flag == "x" then return "next file"
	elseif flag == "g" then return "global extended header"
	elseif flag == "L" then return "long name"
	elseif flag == "K" then return "long link name"
	end
	return "unknown"
end

local function octal_to_number(octal)
	local exp = 0
	local number = 0
	octal = trim(octal)
	for i = #octal,1,-1 do
		local digit = _tonumber(octal:sub(i,i))
		if not digit then break end
		number = number + (digit * 8^exp)
		exp = exp + 1
	end
	return number
end

-- Checksum
local function checksum_header(block)
	local sum = 256
	for i = 1,148 do
		sum = sum + block:byte(i)
	end
	for i = 157,500 do
		sum = sum + block:byte(i)
	end
	return sum
end

local function nullterm(s)
	return s:match("^[^%z]*")
end

local function read_header_block(block)
	local header = {}
	header.name = nullterm(block:sub(1,100))
	header.mode = nullterm(block:sub(101,108))
	header.uid = octal_to_number(nullterm(block:sub(109,116)))
	header.gid = octal_to_number(nullterm(block:sub(117,124)))
	header.size = octal_to_number(nullterm(block:sub(125,136)))
	header.mtime = octal_to_number(nullterm(block:sub(137,148)))
	header.chksum = octal_to_number(nullterm(block:sub(149,156)))
	header.typeflag = get_typeflag(block:sub(157,157))
	header.linkname = nullterm(block:sub(158,257))
	header.magic = block:sub(258,263)
	header.version = block:sub(264,265)
	header.uname = nullterm(block:sub(266,297))
	header.gname = nullterm(block:sub(298,329))
	header.devmajor = octal_to_number(nullterm(block:sub(330,337)))
	header.devminor = octal_to_number(nullterm(block:sub(338,345)))
	header.prefix = block:sub(346,500)
	header.pad = block:sub(501,512)
	if header.magic ~= "ustar " and header.magic ~= "ustar\0" then
		return false, "Invalid header magic "..header.magic
	end
	if header.version ~= "00" and header.version ~= " \0" then
		return false, "Unknown version "..header.version
	end
	if not checksum_header(block) == header.chksum then
		return false, "Failed header checksum"
	end
	return header
end

--[[
Untar file - Descompacta arquivo
param(string) path for tar file
param(string) path for destination folder
param(bool) To delete after unpack
param(function) callbak function
--]]
function untar(filePath, destPath, removeOldFiles)
	if filePath == "mock" then return true end

	local tar_handle = io.open(filePath, "rb")
	if not tar_handle then return nil, "Error opening file" end

	local long_name, long_link_name
	while true do
		local block

		-- Read a header
		repeat
			block = tar_handle:read(blocksize)
			until (not block) or checksum_header(block) > 256
			if not block then break end

			local header, err = read_header_block(block)
			if not header then print(err) end

			-- read entire file that follows header
			local file_data = tar_handle:read(_ceil(header.size / blocksize) * blocksize):sub(1,header.size)

			if header.typeflag == "long name" then long_name = nullterm(file_data)
			elseif header.typeflag == "long link name" then long_link_name = nullterm(file_data)
			else
				if long_name then
					header.name = long_name
					long_name = nil
				end
				if long_link_name then
					header.name = long_link_name
					long_link_name = nil
				end
			end

			local pathname

			if (destPath and string.sub(destPath,-1) ~= "/") then
				pathname = destPath.."/"..header.name
			else
				pathname = destPath..header.name
			end

			if header.typeflag == "directory" then
				os.execute("mkdir " .. pathname) -- lfs.mkdir( pathname )
			elseif header.typeflag == "file" then
				local file_handle = io.open(pathname, "wb")
				file_handle:write(file_data)
				file_handle:close()
			end
		end
		tar_handle:close()

		if removeOldFiles == true then
		local ok, err = os.remove(filePath)
		if not ok then return nil, err end
	end

--	if onComplete then
--		if type(onComplete) == "function" then
--			print ("TAR COMPLETED...")
--			onComplete()
--		else
--			print("TAR ERROR : OnComplete must be a function")
--		end
--	end

	return true
end

Usage

--[[
Untar file - Descompacta arquivo
param(string) path for tar file
param(string) path for destination folder
param(bool) To delete after unpack
param(function) callbak function
--]]
untar("yourfile.tar","|D|") -- (filePath, destPath, removeOldFiles)

---

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