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         json = json.." "; -- appending a space ensures valid json wouldn't touch EOF
 138         local pos = 1;
 139         local current = {};
 140         local stack = {};
 141         local ch, peek;
 142         local function next()
 143                 ch = json:sub(pos, pos);
 144                 if ch == "" then error("Unexpected EOF"); end
 145                 pos = pos+1;
 146                 peek = json:sub(pos, pos);
 147                 return ch;
 148         end
 149
 150         local function skipwhitespace()
 151                 while ch and (ch == "\r" or ch == "\n" or ch == "\t" or ch == " ") do
 152                         next();
 153                 end
 154         end
 155         local function skiplinecomment()
 156                 repeat next(); until not(ch) or ch == "\r" or ch == "\n";
 157                 skipwhitespace();
 158         end
 159         local function skipstarcomment()
 160                 next(); next(); -- skip '/', '*'
 161                 while peek and ch ~= "*" and peek ~= "/" do next(); end
 162                 if not peek then error("eof in star comment") end
 163                 next(); next(); -- skip '*', '/'
 164                 skipwhitespace();
 165         end
 166         local function skipstuff()
 167                 while true do
 168                         skipwhitespace();
 169                         if ch == "/" and peek == "*" then
 170                                 skipstarcomment();
 171                         elseif ch == "/" and peek == "*" then
 172                                 skiplinecomment();
 173                         else
 174                                 return;
 175                         end
 176                 end
 177         end
 178
 179         local readvalue;
 180         local function readarray()
 181                 local t = {};
 182                 next(); -- skip '['
 183                 skipstuff();
 184                 if ch == "]" then next(); return t; end
 185                 t_insert(t, readvalue());
 186                 while true do
 187                         skipstuff();
 188                         if ch == "]" then next(); return t; end
 189                         if not ch then error("eof while reading array");
 190                         elseif ch == "," then next();
 191                         elseif ch then error("unexpected character in array, comma expected"); end
 192                         if not ch then error("eof while reading array"); end
 193                         t_insert(t, readvalue());
 194                 end
 195         end
 196
 197         local function checkandskip(c)
 198                 local x = ch or "eof";
 199                 if x ~= c then error("unexpected "..x..", '"..c.."' expected"); end
 200                 next();
 201         end
 202         local function readliteral(lit, val)
 203                 for c in lit:gmatch(".") do
 204                         checkandskip(c);
 205                 end
 206                 return val;
 207         end
 208         local function readstring()
 209                 local s = "";
 210                 checkandskip("\"");
 211                 while ch do
 212                         while ch and ch ~= "\\" and ch ~= "\"" do
 213                                 s = s..ch; next();
 214                         end
 215                         if ch == "\\" then
 216                                 next();
 217                                 if unescapes[ch] then
 218                                         s = s..unescapes[ch];
 219                                         next();
 220                                 elseif ch == "u" then
 221                                         local seq = "";
 222                                         for i=1,4 do
 223                                                 next();
 224                                                 if not ch then error("unexpected eof in string"); end
 225                                                 if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end
 226                                                 seq = seq..ch;
 227                                         end
 228                                         s = s..s.char(tonumber(seq, 16)); -- FIXME do proper utf-8
 229                                         next();
 230                                 else error("invalid escape sequence in string"); end
 231                         end
 232                         if ch == "\"" then
 233                                 next();
 234                                 return s;
 235                         end
 236                 end
 237                 error("eof while reading string");
 238         end
 239         local function readnumber()
 240                 local s = "";
 241                 if ch == "-" then
 242                         s = s..ch; next();
 243                         if not ch:match("[0-9]") then error("number format error"); end
 244                 end
 245                 if ch == "0" then
 246                         s = s..ch; next();
 247                         if ch:match("[0-9]") then error("number format error"); end
 248                 else
 249                         while ch and ch:match("[0-9]") do
 250                                 s = s..ch; next();
 251                         end
 252                 end
 253                 if ch == "." then
 254                         s = s..ch; next();
 255                         if not ch:match("[0-9]") then error("number format error"); end
 256                         while ch and ch:match("[0-9]") do
 257                                 s = s..ch; next();
 258                         end
 259                         if ch == "e" or ch == "E" then
 260                                 s = s..ch; next();
 261                                 if ch == "+" or ch == "-" then
 262                                         s = s..ch; next();
 263                                         if not ch:match("[0-9]") then error("number format error"); end
 264                                         while ch and ch:match("[0-9]") do
 265                                                 s = s..ch; next();
 266                                         end
 267                                 end
 268                         end
 269                 end
 270                 return tonumber(s);
 271         end
 272         local function readmember(t)
 273                 skipstuff();
 274                 local k = readstring();
 275                 skipstuff();
 276                 checkandskip(":");
 277                 t[k] = readvalue();
 278         end
 279         local function fixobject(obj)
 280                 local __array = obj.__array;
 281                 if __array then
 282                         obj.__array = nil;
 283                         for i,v in ipairs(__array) do
 284                                 t_insert(obj, v);
 285                         end
 286                 end
 287                 local __hash = obj.__hash;
 288                 if __hash then
 289                         obj.__hash = nil;
 290                         local k;
 291                         for i,v in ipairs(__hash) do
 292                                 if k ~= nil then
 293                                         obj[k] = v; k = nil;
 294                                 else
 295                                         k = v;
 296                                 end
 297                         end
 298                 end
 299                 return obj;
 300         end
 301         local function readobject()
 302                 local t = {};
 303                 next(); -- skip '{'
 304                 skipstuff();
 305                 if ch == "}" then next(); return t; end
 306                 if not ch then error("eof while reading object"); end
 307                 readmember(t);
 308                 while true do
 309                         skipstuff();
 310                         if ch == "}" then next(); return fixobject(t); end
 311                         if not ch then error("eof while reading object");
 312                         elseif ch == "," then next();
 313                         elseif ch then error("unexpected character in object, comma expected"); end
 314                         if not ch then error("eof while reading object"); end
 315                         readmember(t);
 316                 end
 317         end
 318
 319         function readvalue()
 320                 skipstuff();
 321                 while ch do
 322                         if ch == "{" then
 323                                 return readobject();
 324                         elseif ch == "[" then
 325                                 return readarray();
 326                         elseif ch == "\"" then
 327                                 return readstring();
 328                         elseif ch:match("[%-0-9%.]") then
 329                                 return readnumber();
 330                         elseif ch == "n" then
 331                                 return readliteral("null", null);
 332                         elseif ch == "t" then
 333                                 return readliteral("true", true);
 334                         elseif ch == "f" then
 335                                 return readliteral("false", false);
 336                         else
 337                                 error("invalid character at value start: "..ch);
 338                         end
 339                 end
 340                 error("eof while reading value");
 341         end
 342         next();
 343         return readvalue();
 344 end
 345
 346 function json.test(object)
 347         local encoded = json.encode(object);
 348         local decoded = json.decode(encoded);
 349         local recoded = json.encode(decoded);
 350         if encoded ~= recoded then
 351                 print("FAILED");
 352                 print("encoded:", encoded);
 353                 print("recoded:", recoded);
 354         else
 355                 print(encoded);
 356         end
 357         return encoded == recoded;
 358 end
 359
 360 return json;