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-- Base64-encoding

-- Sourced from http://en.wikipedia.org/wiki/Base64

local base64 = {}

base64._VERSION = 'scm-1'

base64._AUTHOR = 'Daniel Lindsley'

base64._LICENSE = 'BSD'

local index_table = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'

function to_binary(integer)

local remaining = tonumber(integer)

local bin_bits = ''

for i = 7, 0, -1 do

local current_power = math.pow(2, i)

if remaining >= current_power then

bin_bits = bin_bits .. '1'

remaining = remaining - current_power

else

bin_bits = bin_bits .. '0'

end

end

return bin_bits

end

function from_binary(bin_bits)

return tonumber(bin_bits, 2)

end

function base64.encode(to_encode)

local bit_pattern = ''

local encoded = ''

local trailing = ''

for i = 1, string.len(to_encode) do

bit_pattern = bit_pattern .. to_binary(string.byte(string.sub(to_encode, i, i)))

end

-- Check the number of bytes. If it's not evenly divisible by three,

-- zero-pad the ending & append on the correct number of ``=``s.

if string.len(bit_pattern) % 3 == 2 then

trailing = '=='

bit_pattern = bit_pattern .. '0000000000000000'

elseif string.len(bit_pattern) % 3 == 1 then

trailing = '='

bit_pattern = bit_pattern .. '00000000'

end

for i = 1, string.len(bit_pattern), 6 do

local byte = string.sub(bit_pattern, i, i+5)

local offset = tonumber(from_binary(byte))

encoded = encoded .. string.sub(index_table, offset+1, offset+1)

end

return string.sub(encoded, 1, -1 - string.len(trailing)) .. trailing

end

function base64.decode(to_decode)

local padded = to_decode:gsub("%s", "")

local unpadded = padded:gsub("=", "")

local bit_pattern = ''

local decoded = ''

for i = 1, string.len(unpadded) do

local char = string.sub(to_decode, i, i)

local offset, _ = string.find(index_table, char)

if offset == nil then

error("Invalid character '" .. char .. "' found.")

end

bit_pattern = bit_pattern .. string.sub(to_binary(offset-1), 3)

end

for i = 1, string.len(bit_pattern), 8 do

local byte = string.sub(bit_pattern, i, i+7)

decoded = decoded .. string.char(from_binary(byte))

end

local padding_length = padded:len()-unpadded:len()

if (padding_length == 1 or padding_length == 2) then

decoded = decoded:sub(1,-2)

end

return decoded

end

return base64