1 --[[--

2 json_string = -- JavaScript code representing the given datum (with quotes, if needed)

3 encode.json(

4 obj -- true, false, nil or a number or string

5 )

6

7 This function encodes any native datatype or atom in JavaScript object notation (JSON).

8 TODO: can't distinguish unambiguously between empty object and empty list!

9

10 --]]--

11

12 -- TODO: check if numeric representations are JSON compatible

13

14 function encode.json(obj)

15 if obj == nil then

16 return "null";

17 elseif atom.has_type(obj, atom.boolean) then

18 return tostring(obj)

19 elseif atom.has_type(obj, atom.number) then

20 return tostring(obj)

21 elseif type(obj) == "table" then

22 local parts = {}

23 local first = true

24 if #obj > 0 then

25 parts[#parts+1] = "["

26 for idx, value in ipairs(obj) do

27 if first then

28 first = false

29 else

30 parts[#parts+1] = ","

31 end

32 parts[#parts+1] = tostring(value)

33 end

34 parts[#parts+1] = "]"

35 else

36 parts[#parts+1] = "{"

37 for key, value in pairs(obj) do

38 if first then

39 first = false

40 else

41 parts[#parts+1] = ","

42 end

43 parts[#parts+1] = encode.json(key)

44 parts[#parts+1] = ":"

45 parts[#parts+1] = encode.json(value)

46 end

47 parts[#parts+1] = "}"

48 end

49 return table.concat(parts)

50 else

51 return

52 '"' ..

53 string.gsub(atom.dump(obj), ".",

54 function (char)

55 if char == '\r' then return '\\r' end

56 if char == '\n' then return '\\n' end

57 if char == '\\' then return '\\\\' end

58 if char == '"' then return '\\"' end

59 if char == '/' then return '\\/' end -- allowed according to RFC4627, needed for </script>

60 local byte = string.byte(char)

61 if byte < 32 then return string.format("\\u%04x", byte) end

62 end

63 ) ..

64 '"'

65 end

66 end