util/json.lua

   1
   2 local type = type;
   3 local t_insert, t_concat, t_remove = table.insert, table.concat, table.remove;
   4 local s_char = string.char;
   5 local tostring, tonumber = tostring, tonumber;
   6 local pairs, ipairs = pairs, ipairs;
   7 local next = next;
   8 local error = error;
   9 local newproxy, getmetatable = newproxy, getmetatable;
  10 local print = print;
  11
  12 --module("json")
  13 local json = {};
  14
  15 local null = newproxy and newproxy(true) or {};
  16 if getmetatable and getmetatable(null) then
  17         getmetatable(null).__tostring = function() return "null"; end;
  18 end
  19 json.null = null;
  20
  21 local escapes = {
  22         ["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b",
  23         ["\f"] = "\\f", ["\n"] = "\\n", ["\r"] = "\\r", ["\t"] = "\\t"};
  24 local unescapes = {
  25         ["\""] = "\"", ["\\"] = "\\", ["/"] = "/",
  26         b = "\b", f = "\f", n = "\n", r = "\r", t = "\t"};
  27 for i=0,31 do
  28         local ch = s_char(i);
  29         if not escapes[ch] then escapes[ch] = ("\\u%.4X"):format(i); end
  30 end
  31
  32 local valid_types = {
  33         number  = true,
  34         string  = true,
  35         table   = true,
  36         boolean = true
  37 };
  38 local special_keys = {
  39         __array = true;
  40         __hash  = true;
  41 };
  42
  43 local simplesave, tablesave, arraysave, stringsave;
  44
  45 function stringsave(o, buffer)
  46         -- FIXME do proper utf-8 and binary data detection
  47         t_insert(buffer, "\""..(o:gsub(".", escapes)).."\"");
  48 end
  49
  50 function arraysave(o, buffer)
  51         t_insert(buffer, "[");
  52         if next(o) then
  53                 for i,v in ipairs(o) do
  54                         simplesave(v, buffer);
  55                         t_insert(buffer, ",");
  56                 end
  57                 t_remove(buffer);
  58         end
  59         t_insert(buffer, "]");
  60 end
  61
  62 function tablesave(o, buffer)
  63         local __array = {};
  64         local __hash = {};
  65         local hash = {};
  66         for i,v in ipairs(o) do
  67                 __array[i] = v;
  68         end
  69         for k,v in pairs(o) do
  70                 local ktype, vtype = type(k), type(v);
  71                 if valid_types[vtype] or v == null then
  72                         if ktype == "string" and not special_keys[k] then
  73                                 hash[k] = v;
  74                         elseif (valid_types[ktype] or k == null) and __array[k] == nil then
  75                                 __hash[k] = v;
  76                         end
  77                 end
  78         end
  79         if next(__hash) ~= nil or next(hash) ~= nil or next(__array) == nil then
  80                 t_insert(buffer, "{");
  81                 local mark = #buffer;
  82                 for k,v in pairs(hash) do
  83                         stringsave(k, buffer);
  84                         t_insert(buffer, ":");
  85                         simplesave(v, buffer);
  86                         t_insert(buffer, ",");
  87                 end
  88                 if next(__hash) ~= nil then
  89                         t_insert(buffer, "\"__hash\":[");
  90                         for k,v in pairs(__hash) do
  91                                 simplesave(k, buffer);
  92                                 t_insert(buffer, ",");
  93                                 simplesave(v, buffer);
  94                                 t_insert(buffer, ",");
  95                         end
  96                         t_remove(buffer);
  97                         t_insert(buffer, "]");
  98                         t_insert(buffer, ",");
  99                 end
 100                 if next(__array) then
 101                         t_insert(buffer, "\"__array\":");
 102                         arraysave(__array, buffer);
 103                         t_insert(buffer, ",");
 104                 end
 105                 if mark ~= #buffer then t_remove(buffer); end
 106                 t_insert(buffer, "}");
 107         else
 108                 arraysave(__array, buffer);
 109         end
 110 end
 111
 112 function simplesave(o, buffer)
 113         local t = type(o);
 114         if t == "number" then
 115                 t_insert(buffer, tostring(o));
 116         elseif t == "string" then
 117                 stringsave(o, buffer);
 118         elseif t == "table" then
 119                 tablesave(o, buffer);
 120         elseif t == "boolean" then
 121                 t_insert(buffer, (o and "true" or "false"));
 122         else
 123                 t_insert(buffer, "null");
 124         end
 125 end
 126
 127 function json.encode(obj)
 128         local t = {};
 129         simplesave(obj, t);
 130         return t_concat(t);
 131 end
 132
 133 -----------------------------------
 134
 135
 136 function json.decode(json)
 137         local pos = 1;
 138         local current = {};
 139         local stack = {};
 140         local ch, peek;
 141         local function next()
 142                 ch = json:sub(pos, pos);
 143                 pos = pos+1;
 144                 peek = json:sub(pos, pos);
 145                 return ch;
 146         end
 147
 148         local function skipwhitespace()
 149                 while ch and (ch == "\r" or ch == "\n" or ch == "\t" or ch == " ") do
 150                         next();
 151                 end
 152         end
 153         local function skiplinecomment()
 154                 repeat next(); until not(ch) or ch == "\r" or ch == "\n";
 155                 skipwhitespace();
 156         end
 157         local function skipstarcomment()
 158                 next(); next(); -- skip '/', '*'
 159                 while peek and ch ~= "*" and peek ~= "/" do next(); end
 160                 if not peek then error("eof in star comment") end
 161                 next(); next(); -- skip '*', '/'
 162                 skipwhitespace();
 163         end
 164         local function skipstuff()
 165                 while true do
 166                         skipwhitespace();
 167                         if ch == "/" and peek == "*" then
 168                                 skipstarcomment();
 169                         elseif ch == "/" and peek == "*" then
 170                                 skiplinecomment();
 171                         else
 172                                 return;
 173                         end
 174                 end
 175         end
 176
 177         local readvalue;
 178         local function readarray()
 179                 local t = {};
 180                 next(); -- skip '['
 181                 skipstuff();
 182                 if ch == "]" then next(); return t; end
 183                 t_insert(t, readvalue());
 184                 while true do
 185                         skipstuff();
 186                         if ch == "]" then next(); return t; end
 187                         if not ch then error("eof while reading array");
 188                         elseif ch == "," then next();
 189                         elseif ch then error("unexpected character in array, comma expected"); end
 190                         if not ch then error("eof while reading array"); end
 191                         t_insert(t, readvalue());
 192                 end
 193         end
 194
 195         local function checkandskip(c)
 196                 local x = ch or "eof";
 197                 if x ~= c then error("unexpected "..x..", '"..c.."' expected"); end
 198                 next();
 199         end
 200         local function readliteral(lit, val)
 201                 for c in lit:gmatch(".") do
 202                         checkandskip(c);
 203                 end
 204                 return val;
 205         end
 206         local function readstring()
 207                 local s = "";
 208                 checkandskip("\"");
 209                 while ch do
 210                         while ch and ch ~= "\\" and ch ~= "\"" do
 211                                 s = s..ch; next();
 212                         end
 213                         if ch == "\\" then
 214                                 next();
 215                                 if unescapes[ch] then
 216                                         s = s..unescapes[ch];
 217                                         next();
 218                                 elseif ch == "u" then
 219                                         local seq = "";
 220                                         for i=1,4 do
 221                                                 next();
 222                                                 if not ch then error("unexpected eof in string"); end
 223                                                 if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end
 224                                                 seq = seq..ch;
 225                                         end
 226                                         s = s..s.char(tonumber(seq, 16)); -- FIXME do proper utf-8
 227                                         next();
 228                                 else error("invalid escape sequence in string"); end
 229                         end
 230                         if ch == "\"" then
 231                                 next();
 232                                 return s;
 233                         end
 234                 end
 235                 error("eof while reading string");
 236         end
 237         local function readnumber()
 238                 local s = "";
 239                 if ch == "-" then
 240                         s = s..ch; next();
 241                         if not ch:match("[0-9]") then error("number format error"); end
 242                 end
 243                 if ch == "0" then
 244                         s = s..ch; next();
 245                         if ch:match("[0-9]") then error("number format error"); end
 246                 else
 247                         while ch and ch:match("[0-9]") do
 248                                 s = s..ch; next();
 249                         end
 250                 end
 251                 if ch == "." then
 252                         s = s..ch; next();
 253                         if not ch:match("[0-9]") then error("number format error"); end
 254                         while ch and ch:match("[0-9]") do
 255                                 s = s..ch; next();
 256                         end
 257                         if ch == "e" or ch == "E" then
 258                                 s = s..ch; next();
 259                                 if ch == "+" or ch == "-" then
 260                                         s = s..ch; next();
 261                                         if not ch:match("[0-9]") then error("number format error"); end
 262                                         while ch and ch:match("[0-9]") do
 263                                                 s = s..ch; next();
 264                                         end
 265                                 end
 266                         end
 267                 end
 268                 return tonumber(s);
 269         end
 270         local function readmember(t)
 271                 skipstuff();
 272                 local k = readstring();
 273                 skipstuff();
 274                 checkandskip(":");
 275                 t[k] = readvalue();
 276         end
 277         local function fixobject(obj)
 278                 local __array = obj.__array;
 279                 if __array then
 280                         obj.__array = nil;
 281                         for i,v in ipairs(__array) do
 282                                 t_insert(obj, v);
 283                         end
 284                 end
 285                 local __hash = obj.__hash;
 286                 if __hash then
 287                         obj.__hash = nil;
 288                         local k;
 289                         for i,v in ipairs(__hash) do
 290                                 if k ~= nil then
 291                                         obj[k] = v; k = nil;
 292                                 else
 293                                         k = v;
 294                                 end
 295                         end
 296                 end
 297                 return obj;
 298         end
 299         local function readobject()
 300                 local t = {};
 301                 next(); -- skip '{'
 302                 skipstuff();
 303                 if ch == "}" then next(); return t; end
 304                 if not ch then error("eof while reading object"); end
 305                 readmember(t);
 306                 while true do
 307                         skipstuff();
 308                         if ch == "}" then next(); return fixobject(t); end
 309                         if not ch then error("eof while reading object");
 310                         elseif ch == "," then next();
 311                         elseif ch then error("unexpected character in object, comma expected"); end
 312                         if not ch then error("eof while reading object"); end
 313                         readmember(t);
 314                 end
 315         end
 316
 317         function readvalue()
 318                 skipstuff();
 319                 while ch do
 320                         if ch == "{" then
 321                                 return readobject();
 322                         elseif ch == "[" then
 323                                 return readarray();
 324                         elseif ch == "\"" then
 325                                 return readstring();
 326                         elseif ch:match("[%-0-9%.]") then
 327                                 return readnumber();
 328                         elseif ch == "n" then
 329                                 return readliteral("null", null);
 330                         elseif ch == "t" then
 331                                 return readliteral("true", true);
 332                         elseif ch == "f" then
 333                                 return readliteral("false", false);
 334                         else
 335                                 error("invalid character at value start: "..ch);
 336                         end
 337                 end
 338                 error("eof while reading value");
 339         end
 340         next();
 341         return readvalue();
 342 end
 343
 344 function json.test(object)
 345         local encoded = json.encode(object);
 346         local decoded = json.decode(encoded);
 347         local recoded = json.encode(decoded);
 348         if encoded ~= recoded then
 349                 print("FAILED");
 350                 print("encoded:", encoded);
 351                 print("recoded:", recoded);
 352         else
 353                 print(encoded);
 354         end
 355         return encoded == recoded;
 356 end
 357
 358 return json;