Module:JSON

- -- Uploaded by User:Ori.livneh. -- Commit c8e9378f1c of git://github.com/craigmj/json4lua.git -- With very light modifications: --  -- Changed 'see LICENSE.txt' to full text of license. --  -- Dropped "module('json')"; return a table instead. - -- JSON4Lua: JSON encoding / decoding support for the Lua language. -- json Module. -- Author: Craig Mason-Jones -- Homepage: http://json.luaforge.net/ -- Version: 0.9.50 -- 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: --  encode(o) --    Returns the table / string / boolean / number / nil / json.null value as a JSON-encoded string. --  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 --    0.9.50 Radical performance improvement on decode from Eike Decker. Many thanks! --	 0.9.40 Changed licence to MIT License (MIT) --  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. --         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") local tostring = tostring

local base = _G

- -- Module declaration -

-- 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 encode (v) -- Handle nil values if v==nil then return "null" end local vtype = base.type(v)

-- Handle strings if vtype=='string' then return '"' .. encodeString(v) .. '"'	   -- Need to handle encoding in string end -- Handle booleans if vtype=='number' or vtype=='boolean' then return base.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, encode(v[i])) end else	-- An object, not an array for i,j in base.pairs(v) do       if isEncodable(i) and isEncodable(j) then table.insert(rval, '"' .. encodeString(i) .. '":' .. 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 base.assert(false,'encode attempt to encode unsupported type ' .. vtype .. ':' .. base.tostring(v)) end

--- Decodes a JSON string and returns the decoded value as a Lua data structure / value. -- @param s The string to scan. -- @return Lua objectthat was scanned, as a Lua table / string / number / boolean or nil. function decode(s) -- Function is re-defined below after token and other items are created. -- Just defined here for code neatness. return null 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. -

--- 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 qrep = {["\\"]="\\\\", ['"']='\\"',['\r']='\\r',['\n']='\\n',['\t']='\\t'} function encodeString(s) return tostring(s):gsub('["\\\r\n\t]',qrep) 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 base.pairs(t) do   if (base.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 = base.type(o) return (t=='string' or t=='boolean' or t=='number' or t=='nil' or t=='table') or (t=='function' and o==null) end

-- Radical performance improvement for decode from Eike Decker! do local type = base.type local error = base.error local assert = base.assert local print = base.print local tonumber = base.tonumber -- initialize some values to be used in decoding function -- initializes a table to contain a byte=>table mapping -- the table contains tokens (byte values) as keys and maps them on other -- token tables (mostly, the boolean value 'true' is used to indicate termination	-- of a token sequence) -- the token table's purpose is, that it allows scanning a sequence of bytes -- until something interesting has been found (e.g. a token that is not expected) -- name is a descriptor for the table to be printed in error messages local function init_token_table (tt) local struct = {} local value function struct:link(other_tt) value = other_tt return struct end function struct:to(chars) for i=1,#chars do 				tt[chars:byte(i)] = value end return struct end return function (name) tt.name = name return struct end end -- keep "named" byte values at hands local c_esc, c_e, c_l, c_r, c_u, c_f, c_a, c_s, c_slash = ("\\elrufas/"):byte(1,9) -- token tables - tt_doublequote_string = strDoubleQuot, tt_singlequote_string = strSingleQuot local tt_object_key, tt_object_colon, tt_object_value, tt_doublequote_string, tt_singlequote_string, tt_array_value, tt_array_seperator, tt_numeric, tt_boolean, tt_null, tt_comment_start, tt_comment_middle, tt_ignore --< tt_ignore is special - marked tokens will be tt_ignored = {},{},{},{},{},{},{},{},{},{},{},{},{}	-- strings to be used in certain token tables local strchars = "" -- all valid string characters (all except newlines) local allchars = "" -- all characters that are valid in comments --local escapechar = {} for i=0,0xff do 		local c = string.char(i) if c~="\n" and c~="\r" then strchars = strchars .. c end allchars = allchars .. c --escapechar[i] = "\\" .. string.char(i) end --		charstounescape = "\"\'\\bfnrt/";	unescapechars = "\"'\\\b\f\n\r\t\/";	for i=1,--

-- obj key reader, expects the end of the object or a quoted string as key init_token_table (tt_object_key) "object (' or \" or } or, expected)" 		:link(tt_singlequote_string) :to "'"		:link(tt_doublequote_string) :to '"' :link(true)                 :to "}" :link(tt_object_key)        :to "," :link(tt_comment_start)     :to "/" :link(tt_ignore)            :to " \t\r\n" -- after the key, a colon is expected (or comment) init_token_table (tt_object_colon) "object (: expected)" :link(tt_object_value)      :to ":" :link(tt_comment_start)     :to "/" :link(tt_ignore)            :to" \t\r\n" -- as values, anything is possible, numbers, arrays, objects, boolean, null, strings init_token_table (tt_object_value) "object ({ or [ or ' or \" or number or boolean or null expected)"		:link(tt_object_key)        :to "{" 		:link(tt_array_seperator)    :to "[" 		:link(tt_singlequote_string) :to "'" 		:link(tt_doublequote_string) :to '"' :link(tt_numeric)           :to "0123456789.-" :link(tt_boolean)           :to "tf" :link(tt_null)              :to "n" :link(tt_comment_start)     :to "/" :link(tt_ignore)            :to " \t\r\n" -- token tables for reading strings init_token_table (tt_doublequote_string) "double quoted string" :link(tt_ignore)            :to (strchars) :link(c_esc)                :to "\\" :link(true)                 :to '"'	init_token_table (tt_singlequote_string) "single quoted string"		:link(tt_ignore)             :to (strchars)		:link(c_esc)                 :to "\\" 		:link(true)                  :to "'"	-- array reader that expects termination of the array or a comma that indicates the next value	init_token_table (tt_array_value) "array (, or ] expected)"		:link(tt_array_seperator)    :to "," 		:link(true)                  :to "]"		:link(tt_comment_start)      :to "/" 		:link(tt_ignore)             :to " \t\r\n"	-- a value, pretty similar to tt_object_value	init_token_table (tt_array_seperator) "array ({ or [ or ' or \" or number or boolean or null expected)" :link(tt_object_key)        :to "{" :link(tt_array_seperator)   :to "[" :link(tt_singlequote_string) :to "'" :link(tt_doublequote_string) :to '"' 		:link(tt_comment_start)      :to "/" 		:link(tt_numeric)            :to "0123456789.-" 		:link(tt_boolean)            :to "tf" 		:link(tt_null)               :to "n" 		:link(tt_ignore)             :to " \t\r\n"	-- valid number tokens	init_token_table (tt_numeric) "number"		:link(tt_ignore)             :to "0123456789.-Ee"	-- once a comment has been started with /, a * is expected	init_token_table (tt_comment_start) "comment start (* expected)"		:link(tt_comment_middle)     :to "*"	-- now everything is allowed, watch out for * though. The next char is then checked manually	init_token_table (tt_comment_middle) "comment end"		:link(tt_ignore)             :to (allchars)		:link(true)                  :to "*"	function decode (js_string)		local pos = 1 -- position in the string		-- read the next byte value		local function next_byte  pos = pos + 1 return js_string:byte(pos-1) end -- in case of error, report the location using line numbers local function location local n = ("\n"):byte local line,lpos = 1,0 for i=1,pos do 				if js_string:byte(i) == n then line,lpos = line + 1,1 else lpos = lpos + 1 end end return "Line "..line.." character "..lpos end -- debug func --local function status (str) --	print(str.." ("..s:sub(math.max(1,p-10),p+10)..")") --end -- read the next token, according to the passed token table local function next_token (tok) while pos <= #js_string do				local b = js_string:byte(pos) local t = tok[b] if not t then error("Unexpected character at "..location..": "..						string.char(b).." ("..b..") when reading "..tok.name.."\nContext: \n"..						js_string:sub(math.max(1,pos-30),pos+30).."\n"..(" "):rep(pos+math.min(-1,30-pos)).."^") end pos = pos + 1 if t~=tt_ignore then return t end end error("unexpected termination of JSON while looking for "..tok.name) end -- read a string, double and single quoted ones local function read_string (tok) local start = pos --local returnString = {} repeat local t = next_token(tok) if t == c_esc then --table.insert(returnString, js_string:sub(start, pos-2)) --table.insert(returnString, escapechar[ js_string:byte(pos) ]) pos = pos + 1 --start = pos end -- jump over escaped chars, no matter what until t == true -- return (base.loadstring("return " .. js_string:sub(start-1, pos-1) ) ) return js_string:sub(start,pos-2)

-- We consider the situation where no escaped chars were encountered separately, -- and use the fastest possible return in this case. --if 0 == #returnString then --	return js_string:sub(start,pos-2) --else --	table.insert(returnString, js_string:sub(start,pos-2)) --	return table.concat(returnString,""); --end --return js_string:sub(start,pos-2) end local function read_num local start = pos while pos <= #js_string do				local b = js_string:byte(pos) if not tt_numeric[b] then break end pos = pos + 1 end return tonumber(js_string:sub(start-1,pos-1)) end -- read_bool and read_null are both making an assumption that I have not tested: -- I would expect that the string extraction is more expensive than actually -- making manual comparision of the byte values local function read_bool pos = pos + 3 local a,b,c,d = js_string:byte(pos-3,pos) if a == c_r and b == c_u and c == c_e then return true end pos = pos + 1 if a ~= c_a or b ~= c_l or c ~= c_s or d ~= c_e then error("Invalid boolean: "..js_string:sub(math.max(1,pos-5),pos+5)) end return false end -- same as read_bool: only last local function read_null pos = pos + 3 local u,l1,l2 = js_string:byte(pos-3,pos-1) if u == c_u and l1 == c_l and l2 == c_l then return nil end error("Invalid value (expected null):"..js_string:sub(pos-4,pos-1)..				" ("..js_string:byte(pos-1).."="..js_string:sub(pos-1,pos-1).." / "..c_l..")") end local read_object_value,read_object_key,read_array,read_value,read_comment -- read a value depending on what token was returned, might require info what was used (in case of comments) function read_value (t,fromt) if t == tt_object_key        then return read_object_key({}) end if t == tt_array_seperator   then return read_array({}) end if t == tt_singlequote_string or 			  t == tt_doublequote_string then return read_string(t) end if t == tt_numeric           then return read_num end if t == tt_boolean           then return read_bool end if t == tt_null              then return read_null end if t == tt_comment_start     then return read_value(read_comment(fromt)) end error("unexpected termination - "..js_string:sub(math.max(1,pos-10),pos+10)) end -- read comments until something noncomment like surfaces, using the token reader which was -- used when stumbling over this comment function read_comment (fromt) while true do				next_token(tt_comment_start) while true do					local t = next_token(tt_comment_middle) if next_byte == c_slash then local t = next_token(fromt) if t~= tt_comment_start then return t end break end end end end -- read arrays, empty array expected as o arg function read_array (o,i) --if not i then status "arr open" end i = i or 1 -- loop until ... while true do				o[i] = read_value(next_token(tt_array_seperator),tt_array_seperator) local t = next_token(tt_array_value) if t == tt_comment_start then t = read_comment(tt_array_value) end if t == true then -- ... we found a terminator token --status "arr close" return o 				end i = i + 1 end end -- object value reading function read_object_value (o) local t = next_token(tt_object_value) return read_value(t,tt_object_value) end -- object key reading, might also terminate the object function read_object_key (o) while true do				local t = next_token(tt_object_key) if t == tt_comment_start then t = read_comment(tt_object_key) end if t == true then return o end if t == tt_object_key then return read_object_key(o) end local k = read_string(t) if next_token(tt_object_colon) == tt_comment_start then t = read_comment(tt_object_colon) end local v = read_object_value(o) o[k] = v			end end -- now let's read data from our string and pretend it's an object value local r = read_object_value if pos<=#js_string then -- not sure about what to do with dangling characters --error("Dangling characters in JSON code ("..location..")") end return r	end end

return { encode = encode, decode = decode }