nodemcu-httpserver/b64.lua

#!/usr/local/bin/lua
-- http://lua-users.org/wiki/BaseSixtyFour
-- working lua base64 codec (c) 2006-2008 by Alex Kloss
-- compatible with lua 5.1
-- http://www.it-rfc.de
-- licensed under the terms of the LGPL2

-- bitshift functions (<<, >> equivalent)
-- shift left
function lsh(value,shift)
	return (value*(2^shift)) % 256
end

-- shift right
function rsh(value,shift)
	return math.floor(value/2^shift) % 256
end

-- return single bit (for OR)
function bit(x,b)
	return (x % 2^b - x % 2^(b-1) > 0)
end

-- logic OR for number values
function lor(x,y)
	result = 0
	for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end
	return result
end

-- encryption table
local base64chars = {
   [0]='A',
   [1]='B',
   [2]='C',
   [3]='D',
   [4]='E',
   [5]='F',
   [6]='G',
   [7]='H',
   [8]='I',
   [9]='J',
   [10]='K',
   [11]='L',
   [12]='M',
   [13]='N',
   [14]='O',
   [15]='P',
   [16]='Q',
   [17]='R',
   [18]='S',
   [19]='T',
   [20]='U',
   [21]='V',
   [22]='W',
   [23]='X',
   [24]='Y',
   [25]='Z',
   [26]='a',
   [27]='b',
   [28]='c',
   [29]='d',
   [30]='e',
   [31]='f',
   [32]='g',
   [33]='h',
   [34]='i',
   [35]='j',
   [36]='k',
   [37]='l',
   [38]='m',
   [39]='n',
   [40]='o',
   [41]='p',
   [42]='q',
   [43]='r',
   [44]='s',
   [45]='t',
   [46]='u',
   [47]='v',
   [48]='w',
   [49]='x',
   [50]='y',
   [51]='z',
   [52]='0',
   [53]='1',
   [54]='2',
   [55]='3',
   [56]='4',
   [57]='5',
   [58]='6',
   [59]='7',
   [60]='8',
   [61]='9',
   [62]='-',
   [63]='_'
}

-- function encode
-- encodes input string to base64.
function enc(data)
	local bytes = {}
	local result = ""
	for spos=0,string.len(data)-1,3 do
		for byte=1,3 do bytes[byte] = string.byte(string.sub(data,(spos+byte))) or 0 end
		result = string.format('%s%s%s%s%s',result,base64chars[rsh(bytes[1],2)],base64chars[lor(lsh((bytes[1] % 4),4), rsh(bytes[2],4))] or "=",((#data-spos) > 1) and base64chars[lor(lsh(bytes[2] % 16,2), rsh(bytes[3],6))] or "=",((#data-spos) > 2) and base64chars[(bytes[3] % 64)] or "=")
	end
	return result
end

local function toBase64Byte(char)
   ascii = string.byte(char, 1)
   if ascii >= string.byte('A', 1) and ascii <= string.byte('Z', 1) then
      return ascii - string.byte('A', 1)
   elseif ascii >= string.byte('a', 1) and ascii <= string.byte('z', 1) then
      return ascii - string.byte('a', 1) + 26
   elseif ascii >= string.byte('0', 1) and ascii <= string.byte('9', 1) then
      return ascii + 4
   elseif ascii == string.byte('-', 1) then
      return 62
   elseif ascii == string.byte('_', 1) then
      return 63
   elseif ascii == string.byte('=', 1) then
      return nil
   else
      return "ERROR! Char is invalid for Base64 encoding: "..char
   end
end

print(toBase64Byte('A'))
print(toBase64Byte('B'))
print(toBase64Byte('C'))
print(toBase64Byte('D'))
print(toBase64Byte('a'))
print(toBase64Byte('b'))
print(toBase64Byte('c'))
print(toBase64Byte('d'))

-- decryption table
local base64bytes = {
   ['A']=0,
   ['B']=1,
   ['C']=2,
   ['D']=3,
   ['E']=4,
   ['F']=5,
   ['G']=6,
   ['H']=7,
   ['I']=8,
   ['J']=9,
   ['K']=10,
   ['L']=11,
   ['M']=12,
   ['N']=13,
   ['O']=14,
   ['P']=15,
   ['Q']=16,
   ['R']=17,
   ['S']=18,
   ['T']=19,
   ['U']=20,
   ['V']=21,
   ['W']=22,
   ['X']=23,
   ['Y']=24,
   ['Z']=25,
   ['a']=26,
   ['b']=27,
   ['c']=28,
   ['d']=29,
   ['e']=30,
   ['f']=31,
   ['g']=32,
   ['h']=33,
   ['i']=34,
   ['j']=35,
   ['k']=36,
   ['l']=37,
   ['m']=38,
   ['n']=39,
   ['o']=40,
   ['p']=41,
   ['q']=42,
   ['r']=43,
   ['s']=44,
   ['t']=45,
   ['u']=46,
   ['v']=47,
   ['w']=48,
   ['x']=49,
   ['y']=50,
   ['z']=51,
   ['0']=52,
   ['1']=53,
   ['2']=54,
   ['3']=55,
   ['4']=56,
   ['5']=57,
   ['6']=58,
   ['7']=59,
   ['8']=60,
   ['9']=61,
   ['-']=62,
   ['_']=63,
   ['=']=nil
}

-- function decode
-- decode base64 input to string
function dec(data)
	local chars = {}
	local result=""
	for dpos=0,string.len(data)-1,4 do
--		for char=1,4 do chars[char] = base64bytes[(string.sub(data,(dpos+char),(dpos+char)) or "=")] end
		for char=1,4 do chars[char] = toBase64Byte((string.sub(data,(dpos+char),(dpos+char)) or "=")) end
			result = string.format(
		   '%s%s%s%s',
		   result,
		   string.char(lor(lsh(chars[1],2), rsh(chars[2],4))),
		   (chars[3] ~= nil) and string.char(lor(lsh(chars[2],4),
		   rsh(chars[3],2))) or "",
		   (chars[4] ~= nil) and string.char(lor(lsh(chars[3],6) % 192,
		   (chars[4]))) or ""
		)
	end
	return result
end

-- command line if not called as library
if (arg ~= nil) then
	local func = 'enc'
	for n,v in ipairs(arg) do
		if (n > 0) then
			if (v == "-h") then print "base64.lua [-e] [-d] text/data" break
			elseif (v == "-e") then func = 'enc'
			elseif (v == "-d") then func = 'dec'
			else print(_G[func](v)) end
		end
	end
else
	module('base64',package.seeall)
end