Module:Json

-- - -- Minor modification by User:Nanaki: --  -- Using tonumber instead of evaluating with loadstring in decode_scanNumber - -- JSON4Lua: JSON encoding / decoding support for the Lua language. -- json Module. -- Author: Craig Mason-Jones -- Homepage: http://github.com/craigmj/json4lua/ -- Version: 1.0.0 -- This module is released under the MIT License (MIT). -- -- Copyright (c) 2009 Craig Mason-Jones -- -- Permission is hereby granted, free of charge, to any person obtaining a copy -- of this software and associated documentation files (the "Software"), to deal -- in the Software without restriction, including without limitation the rights -- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell -- copies of the Software, and to permit persons to whom the Software is -- furnished to do so, subject to the following conditions: -- -- The above copyright notice and this permission notice shall be included in -- all copies or substantial portions of the Software. -- -- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR -- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, -- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE -- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER -- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, -- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN -- THE SOFTWARE. -- -- USAGE: -- This module exposes two functions: --  json.encode(o) --    Returns the table / string / boolean / number / nil / json.null value as a JSON-encoded string. --  json.decode(json_string) --    Returns a Lua object populated with the data encoded in the JSON string json_string. -- -- REQUIREMENTS: --  compat-5.1 if using Lua 5.0 -- -- CHANGELOG --  0.9.20 Introduction of local Lua functions for private functions (removed _ function prefix). --         Fixed Lua 5.1 compatibility issues. --  		Introduced json.null to have null values in associative arrays. --         json.encode performance improvement (more than 50%) through table.concat rather than .. --         Introduced decode ability to ignore /**/ comments in the JSON string. --  0.9.10 Fix to array encoding / decoding to correctly manage nil/null values in arrays. - - -- Imports and dependencies - local math = require('math') local string = require("string") local table = require("table") - -- Module declaration - local json = {}            -- Public namespace local json_private = {}    -- Private namespace -- Public functions -- Private functions local decode_scanArray local decode_scanComment local decode_scanConstant local decode_scanNumber local decode_scanObject local decode_scanString local decode_scanWhitespace local encodeString local isArray local isEncodable - -- PUBLIC FUNCTIONS - --- Encodes an arbitrary Lua object / variable. -- @param v The Lua object / variable to be JSON encoded. -- @return String containing the JSON encoding in internal Lua string format (i.e. not unicode) function json.encode (v) -- Handle nil values if v==nil then return "null" end local vtype = type(v) -- Handle strings if vtype=='string' then return '"' .. json_private.encodeString(v) .. '"'	   -- Need to handle encoding in string end -- Handle booleans if vtype=='number' or vtype=='boolean' then return tostring(v) end -- Handle tables if vtype=='table' then local rval = {} -- Consider arrays separately local bArray, maxCount = isArray(v) if bArray then for i = 1,maxCount do       table.insert(rval, json.encode(v[i])) end else	-- An object, not an array for i,j in pairs(v) do       if isEncodable(i) and isEncodable(j) then table.insert(rval, '"' .. json_private.encodeString(i) .. '":' .. json.encode(j)) end end end if bArray then return '[' .. table.concat(rval,',') ..']' else return '{' .. table.concat(rval,',') .. '}'   end end -- Handle null values if vtype=='function' and v==null then return 'null' end assert(false,'encode attempt to encode unsupported type ' .. vtype .. ':' .. tostring(v)) end --- Decodes a JSON string and returns the decoded value as a Lua data structure / value. -- @param s The string to scan. -- @param [startPos] Optional starting position where the JSON string is located. Defaults to 1. -- @param Lua object, number The object that was scanned, as a Lua table / string / number / boolean or nil, -- and the position of the first character after -- the scanned JSON object. function json.decode(s, startPos) startPos = startPos and startPos or 1 startPos = decode_scanWhitespace(s,startPos) assert(startPos<=string.len(s), 'Unterminated JSON encoded object found at position in [' .. s .. ']') local curChar = string.sub(s,startPos,startPos) -- Object if curChar=='{' then return decode_scanObject(s,startPos) end -- Array if curChar=='[' then return decode_scanArray(s,startPos) end -- Number if string.find("+-0123456789.e", curChar, 1, true) then return decode_scanNumber(s,startPos) end -- String if curChar==" or curChar==' then   return decode_scanString(s,startPos)  end  if string.sub(s,startPos,startPos+1)=='/*' then    return json.decode(s, decode_scanComment(s,startPos))  end  -- Otherwise, it must be a constant  return decode_scanConstant(s,startPos) end --- The null function allows one to specify a null value in an associative array (which is otherwise -- discarded if you set the value with 'nil' in Lua. Simply set t = { first=json.null } function null  return null -- so json.null will also return null ;-) end - -- Internal, PRIVATE functions. -- Following a Python-like convention, I have prefixed all these 'PRIVATE' -- functions with an underscore. - --- Scans an array from JSON into a Lua object -- startPos begins at the start of the array. -- Returns the array and the next starting position -- @param s The string being scanned. -- @param startPos The starting position for the scan. -- @return table, int The scanned array as a table, and the position of the next character to scan. function decode_scanArray(s,startPos) local array = {}	-- The return value local stringLen = string.len(s) assert(string.sub(s,startPos,startPos)=='[','decode_scanArray called but array does not start at position ' .. startPos .. ' in string:\n'..s ) startPos = startPos + 1 -- Infinite loop for array elements repeat startPos = decode_scanWhitespace(s,startPos) assert(startPos<=stringLen,'JSON String ended unexpectedly scanning array.') local curChar = string.sub(s,startPos,startPos) if (curChar==']') then return array, startPos+1 end if (curChar==',') then startPos = decode_scanWhitespace(s,startPos+1) end assert(startPos<=stringLen, 'JSON String ended unexpectedly scanning array.') object, startPos = json.decode(s,startPos) table.insert(array,object) until false end --- Scans a comment and discards the comment. -- Returns the position of the next character following the comment. -- @param string s The JSON string to scan. -- @param int startPos The starting position of the comment function decode_scanComment(s, startPos) assert( string.sub(s,startPos,startPos+1)=='/*', "decode_scanComment called but comment does not start at position " .. startPos) local endPos = string.find(s,'*/',startPos+2) assert(endPos~=nil, "Unterminated comment in string at " .. startPos) return endPos+2 end --- Scans for given constants: true, false or null -- Returns the appropriate Lua type, and the position of the next character to read. -- @param s The string being scanned. -- @param startPos The position in the string at which to start scanning. -- @return object, int The object (true, false or nil) and the position at which the next character should be -- scanned. function decode_scanConstant(s, startPos) local consts = { ["true"] = true, ["false"] = false, ["null"] = nil } local constNames = {"true","false","null"} for i,k in pairs(constNames) do   if string.sub(s,startPos, startPos + string.len(k) -1 )==k then return consts[k], startPos + string.len(k) end end assert(nil, 'Failed to scan constant from string ' .. s .. ' at starting position ' .. startPos) end --- Scans a number from the JSON encoded string. -- Returns the number, and the position of the next character -- after the number. -- @param s The string being scanned. -- @param startPos The position at which to start scanning. -- @return number, int The extracted number and the position of the next character to scan. function decode_scanNumber(s,startPos) local endPos = startPos+1 local stringLen = string.len(s) local acceptableChars = "+-0123456789.e" while (string.find(acceptableChars, string.sub(s,endPos,endPos), 1, true)	and endPos<=stringLen	) do    endPos = endPos + 1 end local stringValue = string.sub(s,startPos, endPos-1) local stringEval = tonumber(stringValue) assert(stringEval, 'Failed to scan number [ ' .. stringValue .. '] in JSON string at position ' .. startPos .. ' : ' .. endPos) return stringEval, endPos end --- Scans a JSON object into a Lua object. -- startPos begins at the start of the object. -- Returns the object and the next starting position. -- @param s The string being scanned. -- @param startPos The starting position of the scan. -- @return table, int The scanned object as a table and the position of the next character to scan. function decode_scanObject(s,startPos) local object = {} local stringLen = string.len(s) local key, value assert(string.sub(s,startPos,startPos)=='{','decode_scanObject called but object does not start at position ' .. startPos .. ' in string:\n' .. s) startPos = startPos + 1 repeat startPos = decode_scanWhitespace(s,startPos) assert(startPos<=stringLen, 'JSON string ended unexpectedly while scanning object.') local curChar = string.sub(s,startPos,startPos) if (curChar=='}') then return object,startPos+1 end if (curChar==',') then startPos = decode_scanWhitespace(s,startPos+1) end assert(startPos<=stringLen, 'JSON string ended unexpectedly scanning object.') -- Scan the key key, startPos = json.decode(s,startPos) assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key) startPos = decode_scanWhitespace(s,startPos) assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key) assert(string.sub(s,startPos,startPos)==':','JSON object key-value assignment mal-formed at ' .. startPos) startPos = decode_scanWhitespace(s,startPos+1) assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key) value, startPos = json.decode(s,startPos) object[key]=value until false	-- infinite loop while key-value pairs are found end -- START SoniEx2 -- Initialize some things used by decode_scanString -- You know, for efficiency local escapeSequences = { ["\\t"] = "\t", ["\\f"] = "\f", ["\\r"] = "\r", ["\\n"] = "\n", ["\\b"] = "\b" } setmetatable(escapeSequences, {__index = function(t,k) -- skip "\" aka strip escape  return string.sub(k,2) end}) -- END SoniEx2 --- Scans a JSON string from the opening inverted comma or single quote to the -- end of the string. -- Returns the string extracted as a Lua string, -- and the position of the next non-string character -- (after the closing inverted comma or single quote). -- @param s The string being scanned. -- @param startPos The starting position of the scan. -- @return string, int The extracted string as a Lua string, and the next character to parse. function decode_scanString(s,startPos) assert(startPos, 'decode_scanString(..) called without start position') local startChar = string.sub(s,startPos,startPos) -- START SoniEx2 -- PS: I don't think single quotes are valid JSON assert(startChar == " or startChar == ','decode_scanString called for a non-string') --assert(startPos, "String decoding failed: missing closing " .. startChar .. " for string at position " .. oldStart)  local t = {}  local i,j = startPos,startPos  while string.find(s, startChar, j+1) ~= j+1 do    local oldj = j    i,j = string.find(s, "\\.", j+1)    local x,y = string.find(s, startChar, oldj+1)    if not i or x < i then      i,j = x,y-1    end    table.insert(t, string.sub(s, oldj+1, i-1))    if string.sub(s, i, j) == "\\u" then      local a = string.sub(s,j+1,j+4)      j = j + 4      local n = tonumber(a, 16)      assert(n, "String decoding failed: bad Unicode escape " .. a .. " at position " .. i .. " : " .. j)      -- math.floor(x/2^y) == lazy right shift      -- a % 2^b == bitwise_and(a, (2^b)-1)      -- 64 = 2^6      -- 4096 = 2^12 (or 2^6 * 2^6)      local x      if n < 0x80 then x = string.char(n % 0x80) elseif n < 0x800 then -- [110x xxxx] [10xx xxxx] x = string.char(0xC0 + (math.floor(n/64) % 0x20), 0x80 + (n % 0x40)) else -- [1110 xxxx] [10xx xxxx] [10xx xxxx] x = string.char(0xE0 + (math.floor(n/4096) % 0x10), 0x80 + (math.floor(n/64) % 0x40), 0x80 + (n % 0x40)) end table.insert(t, x)   else table.insert(t, escapeSequences[string.sub(s, i, j)]) end end table.insert(t,string.sub(j, j+1)) assert(string.find(s, startChar, j+1), "String decoding failed: missing closing " .. startChar .. " at position " .. j .. "(for string at position " .. startPos .. ")") return table.concat(t,""), j+2 -- END SoniEx2 end --- Scans a JSON string skipping all whitespace from the current start position. -- Returns the position of the first non-whitespace character, or nil if the whole end of string is reached. -- @param s The string being scanned -- @param startPos The starting position where we should begin removing whitespace. -- @return int The first position where non-whitespace was encountered, or string.len(s)+1 if the end of string -- was reached. function decode_scanWhitespace(s,startPos) local whitespace=" \n\r\t" local stringLen = string.len(s) while ( string.find(whitespace, string.sub(s,startPos,startPos), 1, true) and startPos <= stringLen) do    startPos = startPos + 1 end return startPos end --- Encodes a string to be JSON-compatible. -- This just involves back-quoting inverted commas, back-quotes and newlines, I think ;-) -- @param s The string to return as a JSON encoded (i.e. backquoted string) -- @return The string appropriately escaped. local escapeList = {   ['"']  = '\\"',    ['\\'] = '\\\\',    ['/']  = '\\/',     ['\b'] = '\\b',    ['\f'] = '\\f',    ['\n'] = '\\n',    ['\r'] = '\\r',    ['\t'] = '\\t' } function json_private.encodeString(s) local s = tostring(s) return s:gsub(".", function(c) return escapeList[c] end) -- SoniEx2: 5.0 compat end -- Determines whether the given Lua type is an array or a table / dictionary. -- We consider any table an array if it has indexes 1..n for its n items, and no -- other data in the table. -- I think this method is currently a little 'flaky', but can't think of a good way around it yet... -- @param t The table to evaluate as an array -- @return boolean, number True if the table can be represented as an array, false otherwise. If true, -- the second returned value is the maximum -- number of indexed elements in the array. function isArray(t) -- Next we count all the elements, ensuring that any non-indexed elements are not-encodable -- (with the possible exception of 'n') local maxIndex = 0 for k,v in pairs(t) do   if (type(k)=='number' and math.floor(k)==k and 1<=k) then	-- k,v is an indexed pair if (not isEncodable(v)) then return false end	-- All array elements must be encodable maxIndex = math.max(maxIndex,k) else if (k=='n') then if v ~= table.getn(t) then return false end -- False if n does not hold the number of elements else -- Else of (k=='n') if isEncodable(v) then return false end end -- End of (k~='n') end -- End of k,v not an indexed pair end -- End of loop across all pairs return true, maxIndex end --- Determines whether the given Lua object / table / variable can be JSON encoded. The only -- types that are JSON encodable are: string, boolean, number, nil, table and json.null. -- In this implementation, all other types are ignored. -- @param o The object to examine. -- @return boolean True if the object should be JSON encoded, false if it should be ignored. function isEncodable(o) local t = type(o) return (t=='string' or t=='boolean' or t=='number' or t=='nil' or t=='table') or (t=='function' and o==null) end return json --