#!/usr/bin/env lua

-- Lua 5.1+ base64 v3.0 (c) 2009 by Alex Kloss <alexthkloss@web.de>

-- licensed under the terms of the LGPL2

-- http://lua-users.org/wiki/BaseSixtyFour

-- character table string

local b='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

-- encoding

local function enc(data)

	return ((data:gsub('.', function(x) 

		local r,b='',x:byte()

		for i=8,1,-1 do r=r..(b%2^i-b%2^(i-1)>0 and '1' or '0') end

		return r;

	end)..'0000'):gsub('%d%d%d?%d?%d?%d?', function(x)

		if (#x < 6) then return '' end

		local c=0

		for i=1,6 do c=c+(x:sub(i,i)=='1' and 2^(6-i) or 0) end

		return b:sub(c+1,c+1)

	end)..({ '', '==', '=' })[#data%3+1])

end

-- decoding

local function dec(data)

	data = string.gsub(data, '[^'..b..'=]', '')

	return (data:gsub('.', function(x)

		if (x == '=') then return '' end

		local r,f='',(b:find(x)-1)

		for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end

		return r;

	end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x)

		if (#x ~= 8) then return '' end

		local c=0

		for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(8-i) or 0) end

		return string.char(c)

	end))

end

return {

		encode = enc,

		decode = dec,

	}

-- the end vim: se ts=4 sw=4: