base64.lua 1.2 KB

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  1. -- Lua 5.1+ base64 v3.0 (c) 2009 by Alex Kloss <alexthkloss@web.de>
  2. -- licensed under the terms of the LGPL2
  3. local moduleName = ...
  4. local M = {}
  5. _G[moduleName] = M
  6. -- character table string
  7. local b='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
  8. -- encoding
  9. function M.enc(data)
  10. return ((data:gsub('.', function(x)
  11. local r,b='',x:byte()
  12. for i=8,1,-1 do r=r..(b%2^i-b%2^(i-1)>0 and '1' or '0') end
  13. return r;
  14. end)..'0000'):gsub('%d%d%d?%d?%d?%d?', function(x)
  15. if (#x < 6) then return '' end
  16. local c=0
  17. for i=1,6 do c=c+(x:sub(i,i)=='1' and 2^(6-i) or 0) end
  18. return b:sub(c+1,c+1)
  19. end)..({ '', '==', '=' })[#data%3+1])
  20. end
  21. -- decoding
  22. function M.dec(data)
  23. data = string.gsub(data, '[^'..b..'=]', '')
  24. return (data:gsub('.', function(x)
  25. if (x == '=') then return '' end
  26. local r,f='',(b:find(x)-1)
  27. for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end
  28. return r;
  29. end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x)
  30. if (#x ~= 8) then return '' end
  31. local c=0
  32. for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(7-i) or 0) end
  33. return string.char(c)
  34. end))
  35. end
  36. return M