87 lines
3.2 KiB
Lua
87 lines
3.2 KiB
Lua
-- working lua base64 codec (c) 2006-2008 by Alex Kloss
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-- compatible with lua 5.0
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-- http://www.it-rfc.de
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-- licensed under the terms of the LGPL2
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-- bitshift functions (<<, >> equivalent)
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-- shift left
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local function lsh(value,shift)
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return math.mod((value*(2^shift)), 256)
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end
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-- shift right
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local function rsh(value,shift)
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return math.mod(math.floor(value/2^shift), 256)
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end
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-- return single bit (for OR)
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local function bit(x,b)
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return (math.mod(x, 2^b) - math.mod(x, 2^(b-1)) > 0)
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end
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-- logic OR for number values
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local function lor(x,y)
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result = 0
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for p=1,8 do result = result + (((bit(x,p) or bit(y,p)) == true) and 2^(p-1) or 0) end
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return result
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end
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-- encryption table
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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]='_'}
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-- function encode
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-- encodes input string to base64.
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function enc(data)
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local bytes = {}
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local result = ""
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for spos=0,string.len(data)-1,3 do
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for byte=1,3 do bytes[byte] = string.byte(string.sub(data,(spos+byte))) or 0 end
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result = string.format('%s%s%s%s%s',
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result,
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base64chars[rsh(bytes[1],2)],
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base64chars[lor(lsh((math.mod(bytes[1], 4)),4), rsh(bytes[2],4))] or "=",
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((string.len(data)-spos) > 1) and base64chars[lor(lsh(
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math.mod(bytes[2], 16)
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,2), rsh(bytes[3],6))] or "=",
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((string.len(data)-spos) > 2) and base64chars[(math.mod(bytes[3], 64))] or "="
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)
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end
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return result
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end
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-- decryption table
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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}
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local function is_b64_char(c)
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return base64bytes[c] ~= nil
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end
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function is_base64(text)
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for c in text:gmatch(".") do
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if not is_b64_char(c) then
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return false
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end
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end
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return true
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end
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-- function decode
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-- decode base64 input to string
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function dec(data)
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local chars = {}
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local result=""
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for dpos=0,string.len(data)-1,4 do
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for char=1,4 do chars[char] = base64bytes[(string.sub(data,(dpos+char),(dpos+char)) or "=")] end
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result = string.format('%s%s%s%s',
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result,
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string.char(lor(lsh(chars[1],2), rsh(chars[2],4))),
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(chars[3] ~= nil) and string.char(lor(lsh(chars[2],4), rsh(chars[3],2))) or "",
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(chars[4] ~= nil) and string.char(lor(math.mod(lsh(chars[3],6), 192), (chars[4]))) or ""
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)
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end
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return result
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end
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module('base64',package.seeall)
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