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archangel07555

json.lua

Oct 4th, 2022
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  1. --
  2. -- json.lua
  3. --
  4. -- Copyright (c) 2020 rxi
  5. --
  6. -- Permission is hereby granted, free of charge, to any person obtaining a copy of
  7. -- this software and associated documentation files (the "Software"), to deal in
  8. -- the Software without restriction, including without limitation the rights to
  9. -- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  10. -- of the Software, and to permit persons to whom the Software is furnished to do
  11. -- so, subject to the following conditions:
  12. --
  13. -- The above copyright notice and this permission notice shall be included in all
  14. -- copies or substantial portions of the Software.
  15. --
  16. -- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17. -- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18. -- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19. -- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20. -- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21. -- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22. -- SOFTWARE.
  23. --
  24.  
  25. local json = { _version = "0.1.2" }
  26.  
  27. -------------------------------------------------------------------------------
  28. -- Encode
  29. -------------------------------------------------------------------------------
  30.  
  31. local encode
  32.  
  33. local escape_char_map = {
  34.   [ "\\" ] = "\\",
  35.   [ "\"" ] = "\"",
  36.   [ "\b" ] = "b",
  37.   [ "\f" ] = "f",
  38.   [ "\n" ] = "n",
  39.   [ "\r" ] = "r",
  40.   [ "\t" ] = "t",
  41. }
  42.  
  43. local escape_char_map_inv = { [ "/" ] = "/" }
  44. for k, v in pairs(escape_char_map) do
  45.   escape_char_map_inv[v] = k
  46. end
  47.  
  48.  
  49. local function escape_char(c)
  50.   return "\\" .. (escape_char_map[c] or string.format("u%04x", c:byte()))
  51. end
  52.  
  53.  
  54. local function encode_nil(val)
  55.   return "null"
  56. end
  57.  
  58.  
  59. local function encode_table(val, stack)
  60.   local res = {}
  61.   stack = stack or {}
  62.  
  63.   -- Circular reference?
  64.   if stack[val] then error("circular reference") end
  65.  
  66.   stack[val] = true
  67.  
  68.   if rawget(val, 1) ~= nil or next(val) == nil then
  69.     -- Treat as array -- check keys are valid and it is not sparse
  70.     local n = 0
  71.     for k in pairs(val) do
  72.       if type(k) ~= "number" then
  73.         error("invalid table: mixed or invalid key types")
  74.       end
  75.       n = n + 1
  76.     end
  77.     if n ~= #val then
  78.       error("invalid table: sparse array")
  79.     end
  80.     -- Encode
  81.     for i, v in ipairs(val) do
  82.       table.insert(res, encode(v, stack))
  83.     end
  84.     stack[val] = nil
  85.     return "[" .. table.concat(res, ",") .. "]"
  86.  
  87.   else
  88.     -- Treat as an object
  89.     for k, v in pairs(val) do
  90.       if type(k) ~= "string" then
  91.         error("invalid table: mixed or invalid key types")
  92.       end
  93.       table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
  94.     end
  95.     stack[val] = nil
  96.     return "{" .. table.concat(res, ",") .. "}"
  97.   end
  98. end
  99.  
  100.  
  101. local function encode_string(val)
  102.   return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
  103. end
  104.  
  105.  
  106. local function encode_number(val)
  107.   -- Check for NaN, -inf and inf
  108.   if val ~= val or val <= -math.huge or val >= math.huge then
  109.     error("unexpected number value '" .. tostring(val) .. "'")
  110.   end
  111.   return string.format("%.14g", val)
  112. end
  113.  
  114.  
  115. local type_func_map = {
  116.   [ "nil"     ] = encode_nil,
  117.   [ "table"   ] = encode_table,
  118.   [ "string"  ] = encode_string,
  119.   [ "number"  ] = encode_number,
  120.   [ "boolean" ] = tostring,
  121.   [ "function"] = function(f) return "\"" .. tostring(f) .. "\"" end,
  122. }
  123.  
  124.  
  125. encode = function(val, stack)
  126.   local t = type(val)
  127.   local f = type_func_map[t]
  128.   if f then
  129.     return f(val, stack)
  130.   end
  131.   error("unexpected type '" .. t .. "'")
  132. end
  133.  
  134.  
  135. function json.encode(val)
  136.   return ( encode(val) )
  137. end
  138.  
  139.  
  140. -------------------------------------------------------------------------------
  141. -- Decode
  142. -------------------------------------------------------------------------------
  143.  
  144. local parse
  145.  
  146. local function create_set(...)
  147.   local res = {}
  148.   for i = 1, select("#", ...) do
  149.     res[ select(i, ...) ] = true
  150.   end
  151.   return res
  152. end
  153.  
  154. local space_chars   = create_set(" ", "\t", "\r", "\n")
  155. local delim_chars   = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
  156. local escape_chars  = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
  157. local literals      = create_set("true", "false", "null")
  158.  
  159. local literal_map = {
  160.   [ "true"  ] = true,
  161.   [ "false" ] = false,
  162.   [ "null"  ] = nil,
  163. }
  164.  
  165.  
  166. local function next_char(str, idx, set, negate)
  167.   for i = idx, #str do
  168.     if set[str:sub(i, i)] ~= negate then
  169.       return i
  170.     end
  171.   end
  172.   return #str + 1
  173. end
  174.  
  175.  
  176. local function decode_error(str, idx, msg)
  177.   local line_count = 1
  178.   local col_count = 1
  179.   for i = 1, idx - 1 do
  180.     col_count = col_count + 1
  181.     if str:sub(i, i) == "\n" then
  182.       line_count = line_count + 1
  183.       col_count = 1
  184.     end
  185.   end
  186.   error( string.format("%s at line %d col %d", msg, line_count, col_count) )
  187. end
  188.  
  189.  
  190. local function codepoint_to_utf8(n)
  191.   -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
  192.   local f = math.floor
  193.   if n <= 0x7f then
  194.     return string.char(n)
  195.   elseif n <= 0x7ff then
  196.     return string.char(f(n / 64) + 192, n % 64 + 128)
  197.   elseif n <= 0xffff then
  198.     return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
  199.   elseif n <= 0x10ffff then
  200.     return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
  201.                        f(n % 4096 / 64) + 128, n % 64 + 128)
  202.   end
  203.   error( string.format("invalid unicode codepoint '%x'", n) )
  204. end
  205.  
  206.  
  207. local function parse_unicode_escape(s)
  208.   local n1 = tonumber( s:sub(1, 4),  16 )
  209.   local n2 = tonumber( s:sub(7, 10), 16 )
  210.    -- Surrogate pair?
  211.   if n2 then
  212.     return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
  213.   else
  214.     return codepoint_to_utf8(n1)
  215.   end
  216. end
  217.  
  218.  
  219. local function parse_string(str, i)
  220.   local res = ""
  221.   local j = i + 1
  222.   local k = j
  223.  
  224.   while j <= #str do
  225.     local x = str:byte(j)
  226.  
  227.     if x < 32 then
  228.       decode_error(str, j, "control character in string")
  229.  
  230.     elseif x == 92 then -- `\`: Escape
  231.       res = res .. str:sub(k, j - 1)
  232.       j = j + 1
  233.       local c = str:sub(j, j)
  234.       if c == "u" then
  235.         local hex = str:match("^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1)
  236.                  or str:match("^%x%x%x%x", j + 1)
  237.                  or decode_error(str, j - 1, "invalid unicode escape in string")
  238.         res = res .. parse_unicode_escape(hex)
  239.         j = j + #hex
  240.       else
  241.         if not escape_chars[c] then
  242.           decode_error(str, j - 1, "invalid escape char '" .. c .. "' in string")
  243.         end
  244.         res = res .. escape_char_map_inv[c]
  245.       end
  246.       k = j + 1
  247.  
  248.     elseif x == 34 then -- `"`: End of string
  249.       res = res .. str:sub(k, j - 1)
  250.       return res, j + 1
  251.     end
  252.  
  253.     j = j + 1
  254.   end
  255.  
  256.   decode_error(str, i, "expected closing quote for string")
  257. end
  258.  
  259.  
  260. local function parse_number(str, i)
  261.   local x = next_char(str, i, delim_chars)
  262.   local s = str:sub(i, x - 1)
  263.   local n = tonumber(s)
  264.   if not n then
  265.     decode_error(str, i, "invalid number '" .. s .. "'")
  266.   end
  267.   return n, x
  268. end
  269.  
  270.  
  271. local function parse_literal(str, i)
  272.   local x = next_char(str, i, delim_chars)
  273.   local word = str:sub(i, x - 1)
  274.   if not literals[word] then
  275.     decode_error(str, i, "invalid literal '" .. word .. "'")
  276.   end
  277.   return literal_map[word], x
  278. end
  279.  
  280.  
  281. local function parse_array(str, i)
  282.   local res = {}
  283.   local n = 1
  284.   i = i + 1
  285.   while 1 do
  286.     local x
  287.     i = next_char(str, i, space_chars, true)
  288.     -- Empty / end of array?
  289.     if str:sub(i, i) == "]" then
  290.       i = i + 1
  291.       break
  292.     end
  293.     -- Read token
  294.     x, i = parse(str, i)
  295.     res[n] = x
  296.     n = n + 1
  297.     -- Next token
  298.     i = next_char(str, i, space_chars, true)
  299.     local chr = str:sub(i, i)
  300.     i = i + 1
  301.     if chr == "]" then break end
  302.     if chr ~= "," then decode_error(str, i, "expected ']' or ','") end
  303.   end
  304.   return res, i
  305. end
  306.  
  307.  
  308. local function parse_object(str, i)
  309.   local res = {}
  310.   i = i + 1
  311.   while 1 do
  312.     local key, val
  313.     i = next_char(str, i, space_chars, true)
  314.     -- Empty / end of object?
  315.     if str:sub(i, i) == "}" then
  316.       i = i + 1
  317.       break
  318.     end
  319.     -- Read key
  320.     if str:sub(i, i) ~= '"' then
  321.       decode_error(str, i, "expected string for key")
  322.     end
  323.     key, i = parse(str, i)
  324.     -- Read ':' delimiter
  325.     i = next_char(str, i, space_chars, true)
  326.     if str:sub(i, i) ~= ":" then
  327.       decode_error(str, i, "expected ':' after key")
  328.     end
  329.     i = next_char(str, i + 1, space_chars, true)
  330.     -- Read value
  331.     val, i = parse(str, i)
  332.     -- Set
  333.     res[key] = val
  334.     -- Next token
  335.     i = next_char(str, i, space_chars, true)
  336.     local chr = str:sub(i, i)
  337.     i = i + 1
  338.     if chr == "}" then break end
  339.     if chr ~= "," then decode_error(str, i, "expected '}' or ','") end
  340.   end
  341.   return res, i
  342. end
  343.  
  344.  
  345. local char_func_map = {
  346.   [ '"' ] = parse_string,
  347.   [ "0" ] = parse_number,
  348.   [ "1" ] = parse_number,
  349.   [ "2" ] = parse_number,
  350.   [ "3" ] = parse_number,
  351.   [ "4" ] = parse_number,
  352.   [ "5" ] = parse_number,
  353.   [ "6" ] = parse_number,
  354.   [ "7" ] = parse_number,
  355.   [ "8" ] = parse_number,
  356.   [ "9" ] = parse_number,
  357.   [ "-" ] = parse_number,
  358.   [ "t" ] = parse_literal,
  359.   [ "f" ] = parse_literal,
  360.   [ "n" ] = parse_literal,
  361.   [ "[" ] = parse_array,
  362.   [ "{" ] = parse_object,
  363. }
  364.  
  365.  
  366. parse = function(str, idx)
  367.   local chr = str:sub(idx, idx)
  368.   local f = char_func_map[chr]
  369.   if f then
  370.     return f(str, idx)
  371.   end
  372.   decode_error(str, idx, "unexpected character '" .. chr .. "'")
  373. end
  374.  
  375.  
  376. function json.decode(str)
  377.   if type(str) ~= "string" then
  378.     error("expected argument of type string, got " .. type(str))
  379.   end
  380.   local res, idx = parse(str, next_char(str, 1, space_chars, true))
  381.   idx = next_char(str, idx, space_chars, true)
  382.   if idx <= #str then
  383.     decode_error(str, idx, "trailing garbage")
  384.   end
  385.   return res
  386. end
  387.  
  388.  
  389. return json
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