util/json.lua

   1
   2 local type = type;
   3 local t_insert, t_concat, t_remove, t_sort = table.insert, table.concat, table.remove, table.sort;
   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                 if buffer.ordered then
  83                         local keys = {};
  84                         for k in pairs(hash) do
  85                                 t_insert(keys, k);
  86                         end
  87                         t_sort(keys);
  88                         for _,k in ipairs(keys) do
  89                                 stringsave(k, buffer);
  90                                 t_insert(buffer, ":");
  91                                 simplesave(hash[k], buffer);
  92                                 t_insert(buffer, ",");
  93                         end
  94                 else
  95                         for k,v in pairs(hash) do
  96                                 stringsave(k, buffer);
  97                                 t_insert(buffer, ":");
  98                                 simplesave(v, buffer);
  99                                 t_insert(buffer, ",");
 100                         end
 101                 end
 102                 if next(__hash) ~= nil then
 103                         t_insert(buffer, "\"__hash\":[");
 104                         for k,v in pairs(__hash) do
 105                                 simplesave(k, buffer);
 106                                 t_insert(buffer, ",");
 107                                 simplesave(v, buffer);
 108                                 t_insert(buffer, ",");
 109                         end
 110                         t_remove(buffer);
 111                         t_insert(buffer, "]");
 112                         t_insert(buffer, ",");
 113                 end
 114                 if next(__array) then
 115                         t_insert(buffer, "\"__array\":");
 116                         arraysave(__array, buffer);
 117                         t_insert(buffer, ",");
 118                 end
 119                 if mark ~= #buffer then t_remove(buffer); end
 120                 t_insert(buffer, "}");
 121         else
 122                 arraysave(__array, buffer);
 123         end
 124 end
 125
 126 function simplesave(o, buffer)
 127         local t = type(o);
 128         if t == "number" then
 129                 t_insert(buffer, tostring(o));
 130         elseif t == "string" then
 131                 stringsave(o, buffer);
 132         elseif t == "table" then
 133                 tablesave(o, buffer);
 134         elseif t == "boolean" then
 135                 t_insert(buffer, (o and "true" or "false"));
 136         else
 137                 t_insert(buffer, "null");
 138         end
 139 end
 140
 141 function json.encode(obj)
 142         local t = {};
 143         simplesave(obj, t);
 144         return t_concat(t);
 145 end
 146 function json.encode_ordered(obj)
 147         local t = { ordered = true };
 148         simplesave(obj, t);
 149         return t_concat(t);
 150 end
 151 function json.encode_array(obj)
 152         local t = {};
 153         arraysave(obj, t);
 154         return t_concat(t);
 155 end
 156
 157 -----------------------------------
 158
 159
 160 function json.decode(json)
 161         json = json.." "; -- appending a space ensures valid json wouldn't touch EOF
 162         local pos = 1;
 163         local current = {};
 164         local stack = {};
 165         local ch, peek;
 166         local function next()
 167                 ch = json:sub(pos, pos);
 168                 if ch == "" then error("Unexpected EOF"); end
 169                 pos = pos+1;
 170                 peek = json:sub(pos, pos);
 171                 return ch;
 172         end
 173
 174         local function skipwhitespace()
 175                 while ch and (ch == "\r" or ch == "\n" or ch == "\t" or ch == " ") do
 176                         next();
 177                 end
 178         end
 179         local function skiplinecomment()
 180                 repeat next(); until not(ch) or ch == "\r" or ch == "\n";
 181                 skipwhitespace();
 182         end
 183         local function skipstarcomment()
 184                 next(); next(); -- skip '/', '*'
 185                 while peek and ch ~= "*" and peek ~= "/" do next(); end
 186                 if not peek then error("eof in star comment") end
 187                 next(); next(); -- skip '*', '/'
 188                 skipwhitespace();
 189         end
 190         local function skipstuff()
 191                 while true do
 192                         skipwhitespace();
 193                         if ch == "/" and peek == "*" then
 194                                 skipstarcomment();
 195                         elseif ch == "/" and peek == "/" then
 196                                 skiplinecomment();
 197                         else
 198                                 return;
 199                         end
 200                 end
 201         end
 202
 203         local readvalue;
 204         local function readarray()
 205                 local t = {};
 206                 next(); -- skip '['
 207                 skipstuff();
 208                 if ch == "]" then next(); return t; end
 209                 t_insert(t, readvalue());
 210                 while true do
 211                         skipstuff();
 212                         if ch == "]" then next(); return t; end
 213                         if not ch then error("eof while reading array");
 214                         elseif ch == "," then next();
 215                         elseif ch then error("unexpected character in array, comma expected"); end
 216                         if not ch then error("eof while reading array"); end
 217                         t_insert(t, readvalue());
 218                 end
 219         end
 220
 221         local function checkandskip(c)
 222                 local x = ch or "eof";
 223                 if x ~= c then error("unexpected "..x..", '"..c.."' expected"); end
 224                 next();
 225         end
 226         local function readliteral(lit, val)
 227                 for c in lit:gmatch(".") do
 228                         checkandskip(c);
 229                 end
 230                 return val;
 231         end
 232         local function readstring()
 233                 local s = "";
 234                 checkandskip("\"");
 235                 while ch do
 236                         while ch and ch ~= "\\" and ch ~= "\"" do
 237                                 s = s..ch; next();
 238                         end
 239                         if ch == "\\" then
 240                                 next();
 241                                 if unescapes[ch] then
 242                                         s = s..unescapes[ch];
 243                                         next();
 244                                 elseif ch == "u" then
 245                                         local seq = "";
 246                                         for i=1,4 do
 247                                                 next();
 248                                                 if not ch then error("unexpected eof in string"); end
 249                                                 if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end
 250                                                 seq = seq..ch;
 251                                         end
 252                                         s = s..s.char(tonumber(seq, 16)); -- FIXME do proper utf-8
 253                                         next();
 254                                 else error("invalid escape sequence in string"); end
 255                         end
 256                         if ch == "\"" then
 257                                 next();
 258                                 return s;
 259                         end
 260                 end
 261                 error("eof while reading string");
 262         end
 263         local function readnumber()
 264                 local s = "";
 265                 if ch == "-" then
 266                         s = s..ch; next();
 267                         if not ch:match("[0-9]") then error("number format error"); end
 268                 end
 269                 if ch == "0" then
 270                         s = s..ch; next();
 271                         if ch:match("[0-9]") then error("number format error"); end
 272                 else
 273                         while ch and ch:match("[0-9]") do
 274                                 s = s..ch; next();
 275                         end
 276                 end
 277                 if ch == "." then
 278                         s = s..ch; next();
 279                         if not ch:match("[0-9]") then error("number format error"); end
 280                         while ch and ch:match("[0-9]") do
 281                                 s = s..ch; next();
 282                         end
 283                         if ch == "e" or ch == "E" then
 284                                 s = s..ch; next();
 285                                 if ch == "+" or ch == "-" then
 286                                         s = s..ch; next();
 287                                         if not ch:match("[0-9]") then error("number format error"); end
 288                                         while ch and ch:match("[0-9]") do
 289                                                 s = s..ch; next();
 290                                         end
 291                                 end
 292                         end
 293                 end
 294                 return tonumber(s);
 295         end
 296         local function readmember(t)
 297                 skipstuff();
 298                 local k = readstring();
 299                 skipstuff();
 300                 checkandskip(":");
 301                 t[k] = readvalue();
 302         end
 303         local function fixobject(obj)
 304                 local __array = obj.__array;
 305                 if __array then
 306                         obj.__array = nil;
 307                         for i,v in ipairs(__array) do
 308                                 t_insert(obj, v);
 309                         end
 310                 end
 311                 local __hash = obj.__hash;
 312                 if __hash then
 313                         obj.__hash = nil;
 314                         local k;
 315                         for i,v in ipairs(__hash) do
 316                                 if k ~= nil then
 317                                         obj[k] = v; k = nil;
 318                                 else
 319                                         k = v;
 320                                 end
 321                         end
 322                 end
 323                 return obj;
 324         end
 325         local function readobject()
 326                 local t = {};
 327                 next(); -- skip '{'
 328                 skipstuff();
 329                 if ch == "}" then next(); return t; end
 330                 if not ch then error("eof while reading object"); end
 331                 readmember(t);
 332                 while true do
 333                         skipstuff();
 334                         if ch == "}" then next(); return fixobject(t); end
 335                         if not ch then error("eof while reading object");
 336                         elseif ch == "," then next();
 337                         elseif ch then error("unexpected character in object, comma expected"); end
 338                         if not ch then error("eof while reading object"); end
 339                         readmember(t);
 340                 end
 341         end
 342
 343         function readvalue()
 344                 skipstuff();
 345                 while ch do
 346                         if ch == "{" then
 347                                 return readobject();
 348                         elseif ch == "[" then
 349                                 return readarray();
 350                         elseif ch == "\"" then
 351                                 return readstring();
 352                         elseif ch:match("[%-0-9%.]") then
 353                                 return readnumber();
 354                         elseif ch == "n" then
 355                                 return readliteral("null", null);
 356                         elseif ch == "t" then
 357                                 return readliteral("true", true);
 358                         elseif ch == "f" then
 359                                 return readliteral("false", false);
 360                         else
 361                                 error("invalid character at value start: "..ch);
 362                         end
 363                 end
 364                 error("eof while reading value");
 365         end
 366         next();
 367         return readvalue();
 368 end
 369
 370 function json.test(object)
 371         local encoded = json.encode(object);
 372         local decoded = json.decode(encoded);
 373         local recoded = json.encode(decoded);
 374         if encoded ~= recoded then
 375                 print("FAILED");
 376                 print("encoded:", encoded);
 377                 print("recoded:", recoded);
 378         else
 379                 print(encoded);
 380         end
 381         return encoded == recoded;
 382 end
 383
 384 return json;