jutils.lua

--[[
    This is a util code for Computercraft
    download:
    pastebin get zLQD13rf jutils

    then load it with
    os.loadAPI("jutils")

    usage example:
    jutils.Decrypt("VmZ0ZlZmBGtwAQVjVmDlAvZmAQRwAQN5VmDkAPZ0ZQxwZmDkVmDkAPZ0ZwHwZmDlVmZ0Zj==","thekey")

--]]

Jutils = {}

-- string stuff
function split(text, delimiter)
  if text.find(text, delimiter) == nil then
    return { text }
  end

  local splited_texts = {}
  local last_position

  for splited_text, position in text:gmatch("(.-)"..delimiter.."()") do
    table.insert(splited_texts, splited_text)
    last_position = position
  end
  table.insert(splited_texts, string.sub(text, last_position))
  return splited_texts
end

function split_lines(text)
  local lines = {}
  local function splitter(line)
    table.insert(lines, line)
    return ""
  end
  text:gsub("(.-\r?\n)", splitter)
  return lines
end

-- Returns the ASCII bytecode of either 'a' or 'A'
function ascii_base(s)
  return s:lower() == s and ('a'):byte() or ('A'):byte()
end

-- ROT13 is based on Caesar ciphering algorithm, using 13 as a key
function caesar_cipher(str, key)
  return (str:gsub('%a', function(s)
    local base = ascii_base(s)
    return string.char(((s:byte() - base + key) % 26) + base)
  end))
end

-- str     : a string to be ciphered
-- returns : the ciphered string
function rot13(str)
  return caesar_cipher(str, 13)
end

-- str     : a string to be deciphered
-- returns : the deciphered string
function derot13(str)
  return caesar_cipher(str, -13)
end


function _keyToInt(str)
    local z=0;
    for i = 1, #str do
        z= z+string.byte(i)
    end
    return z
end
-- number stuff
function round(num, n)
  local mult = 10^(n or 0)
  return math.floor(num * mult + 0.5) / mult
end


-- table stuff
function dump(table)
  for key, value in pairs(table) do
    print("["..key.."] ", value)
  end
end

function equal(table1, table2)
  local result = true

  for i=1, #table1 do
    if table1[i] ~= table2[i] then
      result = false
      break
    end
  end

  return result
end

-- other stuff

-- 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)
    local bit = bit
    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 = ""
    local rsh = rsh
    local lsh = lsh
    local lor = lor
    local strformat = string.format
    local strchar = string.char
    local base64chars = base64chars

    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 = strformat('%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

-- 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=""
    local rsh = rsh
    local lsh = lsh
    local lor = lor
    local strformat = string.format
    local strchar = string.char
    local base64chars = base64chars

    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
        result = strformat('%s%s%s%s',result,strchar(lor(lsh(chars[1],2), rsh(chars[2],4))),(chars[3] ~= nil) and strchar(lor(lsh(chars[2],4), rsh(chars[3],2))) or "",(chars[4] ~= nil) and strchar(lor(lsh(chars[3],6) % 192, (chars[4]))) or "")
    end
    return result
end

-- some type of encryption here
function Encrypt(str,encryptionKey)
    local str = textutils.serialize( str )
    local encrypted = ''
    for i = 1, #str do
        encrypted = encrypted .. '#' .. string.byte(str:sub(i, i)) + _keyToInt(encryptionKey)
    end
    return rot13( enc( derot13(encrypted)) )
end
function Decrypt(str,encryptionKey)
    local decrypted = ''
    local   str = derot13(str)
            str = dec(str)
            str = rot13(str)
    for x in str:gmatch('#(%d+)') do
        decrypted = decrypted .. string.char(x - _keyToInt(encryptionKey))
    end
    return textutils.unserialize(decrypted)
end