util.json: Initial commit.
authorWaqas Hussain <waqas20@gmail.com>
Mon, 27 Dec 2010 14:37:04 +0000 (19:37 +0500)
committerWaqas Hussain <waqas20@gmail.com>
Mon, 27 Dec 2010 14:37:04 +0000 (19:37 +0500)
util/json.lua [new file with mode: 0644]

diff --git a/util/json.lua b/util/json.lua
new file mode 100644 (file)
index 0000000..40939bb
--- /dev/null
@@ -0,0 +1,356 @@
+
+local type = type;
+local t_insert, t_concat, t_remove = table.insert, table.concat, table.remove;
+local s_char = string.char;
+local tostring, tonumber = tostring, tonumber;
+local pairs, ipairs = pairs, ipairs;
+local next = next;
+local error = error;
+local newproxy, getmetatable = newproxy, getmetatable;
+local print = print;
+
+--module("json")
+local json = {};
+
+local null = newproxy and newproxy(true) or {};
+if getmetatable and getmetatable(null) then
+       getmetatable(null).__tostring = function() return "null"; end;
+end
+json.null = null;
+
+local escapes = {
+       ["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b",
+       ["\f"] = "\\f", ["\n"] = "\\n", ["\r"] = "\\r", ["\t"] = "\\t"};
+local unescapes = {
+       ["\""] = "\"", ["\\"] = "\\", ["/"] = "/",
+       b = "\b", f = "\f", n = "\n", r = "\r", t = "\t"};
+for i=0,31 do
+       local ch = s_char(i);
+       if not escapes[ch] then escapes[ch] = ("\\u%.4X"):format(i); end
+end
+
+local valid_types = {
+       number  = true,
+       string  = true,
+       table   = true,
+       boolean = true
+};
+local special_keys = {
+       __array = true;
+       __hash  = true;
+};
+
+local simplesave, tablesave, arraysave, stringsave;
+
+function stringsave(o, buffer)
+       -- FIXME do proper utf-8 and binary data detection
+       t_insert(buffer, "\""..(o:gsub(".", escapes)).."\"");
+end
+
+function arraysave(o, buffer)
+       t_insert(buffer, "[");
+       if next(o) then
+               for i,v in ipairs(o) do
+                       simplesave(v, buffer);
+                       t_insert(buffer, ",");
+               end
+               t_remove(buffer);
+       end
+       t_insert(buffer, "]");
+end
+
+function tablesave(o, buffer)
+       local __array = {};
+       local __hash = {};
+       local hash = {};
+       for i,v in ipairs(o) do
+               __array[i] = v;
+       end
+       for k,v in pairs(o) do
+               local ktype, vtype = type(k), type(v);
+               if valid_types[vtype] or v == null then
+                       if ktype == "string" and not special_keys[k] then
+                               hash[k] = v;
+                       elseif (valid_types[ktype] or k == null) and __array[k] == nil then
+                               __hash[k] = v;
+                       end
+               end
+       end
+       if next(__hash) ~= nil or next(hash) ~= nil or next(__array) == nil then
+               t_insert(buffer, "{");
+               local mark = #buffer;
+               for k,v in pairs(hash) do
+                       stringsave(k, buffer);
+                       t_insert(buffer, ":");
+                       simplesave(v, buffer);
+                       t_insert(buffer, ",");
+               end
+               if next(__hash) ~= nil then
+                       t_insert(buffer, "\"__hash\":[");
+                       for k,v in pairs(__hash) do
+                               simplesave(k, buffer);
+                               t_insert(buffer, ",");
+                               simplesave(v, buffer);
+                               t_insert(buffer, ",");
+                       end
+                       t_remove(buffer);
+                       t_insert(buffer, "]");
+                       t_insert(buffer, ",");
+               end
+               if next(__array) then
+                       t_insert(buffer, "\"__array\":");
+                       arraysave(__array, buffer);
+                       t_insert(buffer, ",");
+               end
+               if mark ~= #buffer then t_remove(buffer); end
+               t_insert(buffer, "}");
+       else
+               arraysave(__array, buffer);
+       end
+end
+
+function simplesave(o, buffer)
+       local t = type(o);
+       if t == "number" then
+               t_insert(buffer, tostring(o));
+       elseif t == "string" then
+               stringsave(o, buffer);
+       elseif t == "table" then
+               tablesave(o, buffer);
+       elseif t == "boolean" then
+               t_insert(buffer, (o and "true" or "false"));
+       else
+               t_insert(buffer, "null");
+       end
+end
+
+function json.encode(obj)
+       local t = {};
+       simplesave(obj, t);
+       return t_concat(t);
+end
+
+-----------------------------------
+
+
+function json.decode(json)
+       local pos = 1;
+       local current = {};
+       local stack = {};
+       local ch, peek;
+       local function next()
+               ch = json:sub(pos, pos);
+               pos = pos+1;
+               peek = json:sub(pos, pos);
+               return ch;
+       end
+       
+       local function skipwhitespace()
+               while ch and (ch == "\r" or ch == "\n" or ch == "\t" or ch == " ") do
+                       next();
+               end
+       end
+       local function skiplinecomment()
+               repeat next(); until not(ch) or ch == "\r" or ch == "\n";
+               skipwhitespace();
+       end
+       local function skipstarcomment()
+               next(); next(); -- skip '/', '*'
+               while peek and ch ~= "*" and peek ~= "/" do next(); end
+               if not peek then error("eof in star comment") end
+               next(); next(); -- skip '*', '/'
+               skipwhitespace();
+       end
+       local function skipstuff()
+               while true do
+                       skipwhitespace();
+                       if ch == "/" and peek == "*" then
+                               skipstarcomment();
+                       elseif ch == "/" and peek == "*" then
+                               skiplinecomment();
+                       else
+                               return;
+                       end
+               end
+       end
+       
+       local readvalue;
+       local function readarray()
+               local t = {};
+               next(); -- skip '['
+               skipstuff();
+               if ch == "]" then next(); return t; end
+               t_insert(t, readvalue());
+               while true do
+                       skipstuff();
+                       if ch == "]" then next(); return t; end
+                       if not ch then error("eof while reading array");
+                       elseif ch == "," then next();
+                       elseif ch then error("unexpected character in array, comma expected"); end
+                       if not ch then error("eof while reading array"); end
+                       t_insert(t, readvalue());
+               end
+       end
+       
+       local function checkandskip(c)
+               local x = ch or "eof";
+               if x ~= c then error("unexpected "..x..", '"..c.."' expected"); end
+               next();
+       end
+       local function readliteral(lit, val)
+               for c in lit:gmatch(".") do
+                       checkandskip(c);
+               end
+               return val;
+       end
+       local function readstring()
+               local s = "";
+               checkandskip("\"");
+               while ch do
+                       while ch and ch ~= "\\" and ch ~= "\"" do
+                               s = s..ch; next();
+                       end
+                       if ch == "\\" then
+                               next();
+                               if unescapes[ch] then
+                                       s = s..unescapes[ch];
+                                       next();
+                               elseif ch == "u" then
+                                       local seq = "";
+                                       for i=1,4 do
+                                               next();
+                                               if not ch then error("unexpected eof in string"); end
+                                               if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end
+                                               seq = seq..ch;
+                                       end
+                                       s = s..s.char(tonumber(seq, 16)); -- FIXME do proper utf-8
+                                       next();
+                               else error("invalid escape sequence in string"); end
+                       end
+                       if ch == "\"" then
+                               next();
+                               return s;
+                       end
+               end
+               error("eof while reading string");
+       end
+       local function readnumber()
+               local s = "";
+               if ch == "-" then
+                       s = s..ch; next();
+                       if not ch:match("[0-9]") then error("number format error"); end
+               end
+               if ch == "0" then
+                       s = s..ch; next();
+                       if ch:match("[0-9]") then error("number format error"); end
+               else
+                       while ch and ch:match("[0-9]") do
+                               s = s..ch; next();
+                       end
+               end
+               if ch == "." then
+                       s = s..ch; next();
+                       if not ch:match("[0-9]") then error("number format error"); end
+                       while ch and ch:match("[0-9]") do
+                               s = s..ch; next();
+                       end
+                       if ch == "e" or ch == "E" then
+                               s = s..ch; next();
+                               if ch == "+" or ch == "-" then
+                                       s = s..ch; next();
+                                       if not ch:match("[0-9]") then error("number format error"); end
+                                       while ch and ch:match("[0-9]") do
+                                               s = s..ch; next();
+                                       end
+                               end
+                       end
+               end
+               return tonumber(s);
+       end
+       local function readmember(t)
+               local k = readstring();
+               checkandskip(":");
+               t[k] = readvalue();
+       end
+       local function fixobject(obj)
+               local __array = obj.__array;
+               if __array then
+                       obj.__array = nil;
+                       for i,v in ipairs(__array) do
+                               t_insert(obj, v);
+                       end
+               end
+               local __hash = obj.__hash;
+               if __hash then
+                       obj.__hash = nil;
+                       local k;
+                       for i,v in ipairs(__hash) do
+                               if k ~= nil then
+                                       obj[k] = v; k = nil;
+                               else
+                                       k = v;
+                               end
+                       end
+               end
+               return obj;
+       end
+       local function readobject()
+               local t = {};
+               next(); -- skip '{'
+               skipstuff();
+               if ch == "}" then next(); return t; end
+               if not ch then error("eof while reading object"); end
+               readmember(t);
+               while true do
+                       skipstuff();
+                       if ch == "}" then next(); return fixobject(t); end
+                       if not ch then error("eof while reading object");
+                       elseif ch == "," then next();
+                       elseif ch then error("unexpected character in object, comma expected"); end
+                       if not ch then error("eof while reading object"); end
+                       readmember(t);
+               end
+       end
+       
+       function readvalue()
+               skipstuff();
+               while ch do
+                       if ch == "{" then
+                               return readobject();
+                       elseif ch == "[" then
+                               return readarray();
+                       elseif ch == "\"" then
+                               return readstring();
+                       elseif ch:match("[%-0-9%.]") then
+                               return readnumber();
+                       elseif ch == "n" then
+                               return readliteral("null", null);
+                       elseif ch == "t" then
+                               return readliteral("true", true);
+                       elseif ch == "f" then
+                               return readliteral("false", false);
+                       else
+                               error("invalid character at value start: "..ch);
+                       end
+               end
+               error("eof while reading value");
+       end
+       next();
+       return readvalue();
+end
+
+function json.test(object)
+       local encoded = json.encode(object);
+       local decoded = json.decode(encoded);
+       local recoded = json.encode(decoded);
+       if encoded ~= recoded then
+               print("FAILED");
+               print("encoded:", encoded);
+               print("recoded:", recoded);
+       else
+               print(encoded);
+       end
+       return encoded == recoded;
+end
+
+return json;