1 function encode.mime.atom_token(str)

2 local charset = "UTF-8" -- TODO: support other charsets via locale system

3 if

4 string.find(str, "^[0-9A-Za-z!#%$%%&'%*%+%-/=%?%^_`{|}~]+$")

5 then

6 return str

7 elseif

8 string.find(str, "^[\t 0-9A-Za-z!#%$%%&'%*%+%-/=%?%^_`{|}~]+$")

9 then

10 return '"' .. str .. '"'

11 elseif

12 string.find(str, "^[\t -~]*$")

13 then

14 local parts = { '"' }

15 for char in string.gmatch(str, ".") do

16 if char == '"' or char == "\\" then

17 parts[#parts+1] = "\\"

18 end

19 parts[#parts+1] = char

20 end

21 parts[#parts+1] = '"'

22 return table.concat(parts)

23 else

24 local parts = { "=?", charset, "?Q?" }

25 for char in string.gmatch(str, ".") do

26 local byte = string.byte(char)

27 if string.find(char, "^[0-9A-Za-z%.%-]$") then

28 parts[#parts+1] = char

29 else

30 local byte = string.byte(char)

31 if byte == 32 then

32 parts[#parts+1] = "_"

33 else

34 parts[#parts+1] = string.format("=%02X", byte)

35 end

36 end

37 end

38 parts[#parts+1] = "?="

39 return table.concat(parts)

40 end

41 end