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- #!/usr/local/bin/lua
- -- Based on http://lua-users.org/wiki/BaseSixtyFour by Alex Kloss
- -- compatible with lua 5.1
- -- http://www.it-rfc.de
- -- licensed under the terms of the LGPL2
- b64 = {}
- -- bitshift functions (<<, >> equivalent)
- -- shift left
- local function lsh(value,shift)
- return (value*(2^shift)) % 256
- end
- -- shift right
- local function rsh(value,shift)
- -- Lua builds with no floating point don't define math.
- if math then return math.floor(value/2^shift) % 256 end
- return (value/2^shift) % 256
- end
- -- return single bit (for OR)
- local function bit(x,b)
- return (x % 2^b - x % 2^(b-1) > 0)
- end
- -- logic OR for number values
- local 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
- -- Character decoding table
- 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 nil, "ERROR! Char is invalid for Base64 encoding: "..char end
- end
- -- function decode
- -- decode base64 input to string
- function b64.decode(data)
- local chars = {}
- local result=""
- for dpos=0,string.len(data)-1,4 do
- 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
- return b64
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