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annotate libraries/json/json.c @ 150:35fb4f92a887

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Limit maximum depth for JSON parser to 500
author jbe
date Wed Jul 30 23:11:38 2014 +0200 (2014-07-30)
parents 5229687c7601
children 6d2bb696f736
rev   line source
jbe@121 1 #include <lua.h>
jbe@121 2 #include <lauxlib.h>
jbe@122 3 #include <stdlib.h>
jbe@121 4 #include <string.h>
jbe@121 5
jbe@144 6 // maximum number of nested JSON values (objects and arrays):
jbe@150 7 // NOTE: The Lua reference states that the stack may typically contain at least
jbe@150 8 // "a few thousand elements". Since every nested level consumes
jbe@150 9 // 3 elements on the Lua stack (the object/array, its shadow table,
jbe@150 10 // a string key or a placeholder), we limit the number of nested levels
jbe@150 11 // to 500. If a stack overflow would still happen in the import function,
jbe@150 12 // this is detected nevertheless and an error is thrown (instead of
jbe@150 13 // returning nil and an error string).
jbe@150 14 #define JSON_MAXDEPTH 500
jbe@142 15
jbe@144 16 // macros for usage of Lua registry:
jbe@144 17 #define JSON_REGENT char
jbe@145 18 #define JSON_REGPOINTER void *
jbe@145 19 #define json_pushlightref(L, x) (lua_pushlightuserdata((L), &json_reference.x))
jbe@145 20 #define json_regpointer(x) (&json_registry.x)
jbe@145 21 #define json_regfetchpointer(L, x) (lua_pushlightuserdata((L), (x)), lua_rawget((L), LUA_REGISTRYINDEX))
jbe@145 22 #define json_regfetch(L, x) (json_regfetchpointer(L, json_regpointer(x)))
jbe@145 23 #define json_regstore(L, x) (lua_pushlightuserdata(L, json_regpointer(x)), lua_pushvalue(L, -2), lua_rawset(L, LUA_REGISTRYINDEX));
jbe@145 24
jbe@146 25 // generate dummy memory addresses that represent non-modifiable lightuserdata (dummy) objects:
jbe@145 26 static struct {
jbe@146 27 JSON_REGENT nullmark; // magic value to indicate JSON null value in shadow table
jbe@145 28 } json_reference;
jbe@145 29
jbe@138 30
jbe@144 31 // generate dummy memory addresses that represent Lua objects
jbe@145 32 // via lightuserdata keys and LUA_REGISTRYINDEX:
jbe@144 33 static struct {
jbe@145 34 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
jbe@145 35 JSON_REGENT unknownmt; // metatable for tables that may be either JSON objects or JSON arrays
jbe@145 36 JSON_REGENT objectmt; // metatable for JSON objects
jbe@145 37 JSON_REGENT arraymt; // metatable for JSON arrays
jbe@144 38 } json_registry;
jbe@138 39
jbe@145 40 // marks a Lua table as JSON object or JSON array:
jbe@136 41 // (returns its modified argument or a new table if argument is nil)
jbe@145 42 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
jbe@145 43 // check if argument is nil
jbe@136 44 if (lua_isnoneornil(L, 1)) {
jbe@145 45 // create new table at stack position 1:
jbe@136 46 lua_settop(L, 0);
jbe@136 47 lua_newtable(L);
jbe@145 48 // create shadow table (leaving previously created table on stack position 1):
jbe@144 49 json_regfetch(L, shadowtbl);
jbe@136 50 lua_pushvalue(L, 1);
jbe@136 51 lua_newtable(L);
jbe@143 52 lua_rawset(L, -3);
jbe@143 53 } else {
jbe@145 54 // push shadow table on top of stack:
jbe@144 55 json_regfetch(L, shadowtbl);
jbe@143 56 lua_pushvalue(L, 1);
jbe@143 57 lua_rawget(L, -2);
jbe@145 58 // if shadow table does not exist:
jbe@143 59 if (lua_isnil(L, -1)) {
jbe@145 60 // create shadow table and leave it on top of stack:
jbe@143 61 lua_newtable(L);
jbe@143 62 lua_pushvalue(L, 1);
jbe@143 63 lua_pushvalue(L, -2);
jbe@143 64 lua_rawset(L, -5);
jbe@143 65 }
jbe@145 66 // move elements from original table to shadow table (that's expected on top of stack):
jbe@143 67 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@143 68 lua_pushvalue(L, -2);
jbe@143 69 lua_pushnil(L);
jbe@143 70 lua_rawset(L, 1);
jbe@143 71 lua_pushvalue(L, -2);
jbe@143 72 lua_pushvalue(L, -2);
jbe@143 73 lua_rawset(L, -5);
jbe@143 74 }
jbe@136 75 }
jbe@138 76 // discard everything but table to return:
jbe@138 77 lua_settop(L, 1);
jbe@136 78 // set metatable:
jbe@145 79 json_regfetchpointer(L, mt);
jbe@136 80 lua_setmetatable(L, 1);
jbe@138 81 // return table:
jbe@136 82 return 1;
jbe@136 83 }
jbe@136 84
jbe@136 85 // marks a table as JSON object:
jbe@136 86 // (returns its modified argument or a new table if argument is nil)
jbe@136 87 static int json_object(lua_State *L) {
jbe@145 88 return json_mark(L, json_regpointer(objectmt));
jbe@136 89 }
jbe@136 90
jbe@136 91 // marks a table as JSON array:
jbe@136 92 // (returns its modified argument or a new table if argument is nil)
jbe@136 93 static int json_array(lua_State *L) {
jbe@145 94 return json_mark(L, json_regpointer(arraymt));
jbe@136 95 }
jbe@136 96
jbe@145 97 // internal states of JSON parser:
jbe@124 98 #define JSON_STATE_VALUE 0
jbe@124 99 #define JSON_STATE_OBJECT_KEY 1
jbe@124 100 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
jbe@124 101 #define JSON_STATE_OBJECT_VALUE 3
jbe@124 102 #define JSON_STATE_OBJECT_SEPARATOR 4
jbe@124 103 #define JSON_STATE_ARRAY_VALUE 5
jbe@124 104 #define JSON_STATE_ARRAY_SEPARATOR 6
jbe@124 105 #define JSON_STATE_END 7
jbe@121 106
jbe@145 107 // special Lua stack indicies for json_import function:
jbe@138 108 #define json_import_objectmt_idx 2
jbe@138 109 #define json_import_arraymt_idx 3
jbe@138 110 #define json_import_shadowtbl_idx 4
jbe@138 111 #define json_import_nullmark_idx 5
jbe@138 112
jbe@136 113 // decodes a JSON document:
jbe@121 114 static int json_import(lua_State *L) {
jbe@136 115 const char *str; // string to parse
jbe@136 116 size_t total; // total length of string to parse
jbe@136 117 size_t pos = 0; // current position in string to parse
jbe@136 118 size_t level = 0; // nested levels of objects/arrays currently being processed
jbe@145 119 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
jbe@136 120 char c; // variable to store a single character to be processed
jbe@145 121 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
jbe@145 122 char *cbuf; // C buffer to decode JSON string values
jbe@136 123 size_t writepos; // write position of decoded strings in C buffer
jbe@147 124 // stack shall contain one function argument:
jbe@138 125 lua_settop(L, 1);
jbe@147 126 // push objectmt onto stack position 2:
jbe@144 127 json_regfetch(L, objectmt);
jbe@147 128 // push arraymt onto stack position 3:
jbe@144 129 json_regfetch(L, arraymt);
jbe@147 130 // push shadowtbl onto stack position 4:
jbe@144 131 json_regfetch(L, shadowtbl);
jbe@147 132 // push nullmark onto stack position 5:
jbe@145 133 json_pushlightref(L, nullmark);
jbe@136 134 // require string as first argument:
jbe@136 135 str = luaL_checklstring(L, 1, &total);
jbe@136 136 // if string contains a NULL byte, this is a syntax error
jbe@136 137 if (strlen(str) != total) goto json_import_syntax_error;
jbe@136 138 // main loop of parser:
jbe@136 139 json_import_loop:
jbe@136 140 // skip whitespace and store next character in variable 'c':
jbe@146 141 while (c = str[pos],
jbe@146 142 c == ' ' ||
jbe@146 143 c == '\f' ||
jbe@146 144 c == '\n' ||
jbe@146 145 c == '\r' ||
jbe@146 146 c == '\t' ||
jbe@146 147 c == '\v'
jbe@146 148 ) pos++;
jbe@136 149 // switch statement to handle certain (single) characters:
jbe@121 150 switch (c) {
jbe@136 151 // handle end of JSON document:
jbe@121 152 case 0:
jbe@136 153 // if end of JSON document was expected, then return top element of stack as result:
jbe@124 154 if (mode == JSON_STATE_END) return 1;
jbe@136 155 // otherwise, the JSON document was malformed:
jbe@121 156 json_import_unexpected_eof:
jbe@121 157 lua_pushnil(L);
jbe@121 158 if (level == 0) lua_pushliteral(L, "Empty string");
jbe@121 159 else lua_pushliteral(L, "Unexpected end of JSON document");
jbe@121 160 return 2;
jbe@136 161 // new JSON object:
jbe@121 162 case '{':
jbe@136 163 // if a JSON object is not expected here, then return an error:
jbe@146 164 if (
jbe@146 165 mode != JSON_STATE_VALUE &&
jbe@146 166 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 167 mode != JSON_STATE_ARRAY_VALUE
jbe@146 168 ) goto json_import_syntax_error;
jbe@136 169 // create JSON object on stack:
jbe@136 170 lua_newtable(L);
jbe@136 171 // set metatable of JSON object:
jbe@138 172 lua_pushvalue(L, json_import_objectmt_idx);
jbe@125 173 lua_setmetatable(L, -2);
jbe@136 174 // create internal shadow table on stack:
jbe@136 175 lua_newtable(L);
jbe@146 176 // register internal shadow table:
jbe@123 177 lua_pushvalue(L, -2);
jbe@123 178 lua_pushvalue(L, -2);
jbe@138 179 lua_rawset(L, json_import_shadowtbl_idx);
jbe@146 180 // expect object key (or end of object) to follow:
jbe@136 181 mode = JSON_STATE_OBJECT_KEY;
jbe@146 182 // jump to common code for opening JSON object and JSON array:
jbe@142 183 goto json_import_open;
jbe@136 184 // new JSON array:
jbe@121 185 case '[':
jbe@136 186 // if a JSON array is not expected here, then return an error:
jbe@146 187 if (
jbe@146 188 mode != JSON_STATE_VALUE &&
jbe@146 189 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 190 mode != JSON_STATE_ARRAY_VALUE
jbe@146 191 ) goto json_import_syntax_error;
jbe@136 192 // create JSON array on stack:
jbe@136 193 lua_newtable(L);
jbe@136 194 // set metatable of JSON array:
jbe@138 195 lua_pushvalue(L, json_import_arraymt_idx);
jbe@125 196 lua_setmetatable(L, -2);
jbe@136 197 // create internal shadow table on stack:
jbe@136 198 lua_newtable(L);
jbe@146 199 // register internal shadow table:
jbe@123 200 lua_pushvalue(L, -2);
jbe@123 201 lua_pushvalue(L, -2);
jbe@138 202 lua_rawset(L, json_import_shadowtbl_idx);
jbe@140 203 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
jbe@140 204 lua_pushnil(L);
jbe@146 205 // expect array value (or end of array) to follow:
jbe@142 206 mode = JSON_STATE_ARRAY_VALUE;
jbe@142 207 // continue with common code for opening JSON object and JSON array:
jbe@146 208 // common code for opening JSON object or JSON array:
jbe@142 209 json_import_open:
jbe@142 210 // limit nested levels:
jbe@142 211 if (level >= JSON_MAXDEPTH) {
jbe@142 212 lua_pushnil(L);
jbe@142 213 lua_pushliteral(L, "Too many nested JSON levels");
jbe@142 214 return 2;
jbe@142 215 }
jbe@142 216 // additional buffer overflow protection:
jbe@142 217 if (!lua_checkstack(L, LUA_MINSTACK))
jbe@142 218 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
jbe@136 219 // increment level:
jbe@121 220 level++;
jbe@142 221 // consume input character:
jbe@142 222 pos++;
jbe@121 223 goto json_import_loop;
jbe@136 224 // end of JSON object:
jbe@121 225 case '}':
jbe@136 226 // if end of JSON object is not expected here, then return an error:
jbe@146 227 if (
jbe@146 228 mode != JSON_STATE_OBJECT_KEY &&
jbe@146 229 mode != JSON_STATE_OBJECT_SEPARATOR
jbe@146 230 ) goto json_import_syntax_error;
jbe@136 231 // jump to common code for end of JSON object and JSON array:
jbe@121 232 goto json_import_close;
jbe@136 233 // end of JSON array:
jbe@121 234 case ']':
jbe@136 235 // if end of JSON array is not expected here, then return an error:
jbe@146 236 if (
jbe@146 237 mode != JSON_STATE_ARRAY_VALUE &&
jbe@146 238 mode != JSON_STATE_ARRAY_SEPARATOR
jbe@146 239 ) goto json_import_syntax_error;
jbe@146 240 // pop nil key/magic (that was needed to keep stack balance):
jbe@140 241 lua_pop(L, 1);
jbe@136 242 // continue with common code for end of JSON object and JSON array:
jbe@136 243 // common code for end of JSON object or JSON array:
jbe@121 244 json_import_close:
jbe@136 245 // consume input character:
jbe@121 246 pos++;
jbe@136 247 // pop shadow table:
jbe@136 248 lua_pop(L, 1);
jbe@136 249 // check if nested:
jbe@121 250 if (--level) {
jbe@146 251 // if nested,
jbe@146 252 // check if outer(!) structure is an array or object:
jbe@140 253 if (lua_isnil(L, -2)) {
jbe@136 254 // select array value processing:
jbe@124 255 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 256 } else {
jbe@136 257 // select object value processing:
jbe@124 258 mode = JSON_STATE_OBJECT_VALUE;
jbe@121 259 }
jbe@136 260 // store value in outer structure:
jbe@121 261 goto json_import_process_value;
jbe@121 262 }
jbe@136 263 // if not nested, then expect end of JSON document and continue with loop:
jbe@136 264 mode = JSON_STATE_END;
jbe@121 265 goto json_import_loop;
jbe@136 266 // key terminator:
jbe@121 267 case ':':
jbe@136 268 // if key terminator is not expected here, then return an error:
jbe@124 269 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
jbe@121 270 goto json_import_syntax_error;
jbe@136 271 // consume input character:
jbe@121 272 pos++;
jbe@146 273 // expect object value to follow:
jbe@124 274 mode = JSON_STATE_OBJECT_VALUE;
jbe@146 275 // continue with loop:
jbe@121 276 goto json_import_loop;
jbe@136 277 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
jbe@121 278 case ',':
jbe@146 279 // branch according to parser state:
jbe@124 280 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
jbe@146 281 // expect an object key to follow:
jbe@124 282 mode = JSON_STATE_OBJECT_KEY;
jbe@124 283 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
jbe@146 284 // expect an array value to follow:
jbe@124 285 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 286 } else {
jbe@136 287 // if value terminator is not expected here, then return an error:
jbe@136 288 goto json_import_syntax_error;
jbe@121 289 }
jbe@136 290 // consume input character:
jbe@121 291 pos++;
jbe@136 292 // continue with loop:
jbe@121 293 goto json_import_loop;
jbe@136 294 // string literal:
jbe@121 295 case '"':
jbe@146 296 // consume quote character:
jbe@146 297 pos++;
jbe@136 298 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
jbe@121 299 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
jbe@121 300 writepos = 0;
jbe@146 301 // loop through the characters until encountering end quote:
jbe@121 302 while ((c = str[pos++]) != '"') {
jbe@121 303 if (c == 0) {
jbe@146 304 // handle unexpected end of JSON document:
jbe@121 305 goto json_import_unexpected_eof;
jbe@121 306 } else if (c < 32 || c == 127) {
jbe@136 307 // do not allow ASCII control characters:
jbe@136 308 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
jbe@136 309 // by this parser to allow different encodings than Unicode
jbe@121 310 lua_pushnil(L);
jbe@121 311 lua_pushliteral(L, "Unexpected control character in JSON string");
jbe@121 312 return 2;
jbe@121 313 } else if (c == '\\') {
jbe@136 314 // read next char after backslash escape:
jbe@121 315 c = str[pos++];
jbe@121 316 switch (c) {
jbe@136 317 // unexpected end-of-string:
jbe@121 318 case 0:
jbe@121 319 goto json_import_unexpected_eof;
jbe@136 320 // unescaping of quotation mark, slash, and backslash:
jbe@121 321 case '"':
jbe@121 322 case '/':
jbe@121 323 case '\\':
jbe@121 324 cbuf[writepos++] = c;
jbe@121 325 break;
jbe@136 326 // unescaping of backspace:
jbe@146 327 case 'b': cbuf[writepos++] = '\b'; break;
jbe@136 328 // unescaping of form-feed:
jbe@146 329 case 'f': cbuf[writepos++] = '\f'; break;
jbe@136 330 // unescaping of new-line:
jbe@146 331 case 'n': cbuf[writepos++] = '\n'; break;
jbe@136 332 // unescaping of carriage-return:
jbe@146 333 case 'r': cbuf[writepos++] = '\r'; break;
jbe@136 334 // unescaping of tabulator:
jbe@146 335 case 't': cbuf[writepos++] = '\t'; break;
jbe@136 336 // unescaping of UTF-16 characters
jbe@121 337 case 'u':
jbe@121 338 lua_pushnil(L);
jbe@121 339 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
jbe@121 340 return 2;
jbe@136 341 // unexpected escape sequence:
jbe@121 342 default:
jbe@121 343 lua_pushnil(L);
jbe@121 344 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
jbe@121 345 return 2;
jbe@121 346 }
jbe@121 347 } else {
jbe@136 348 // normal character:
jbe@121 349 cbuf[writepos++] = c;
jbe@121 350 }
jbe@121 351 }
jbe@136 352 // process buffer to Lua string:
jbe@121 353 luaL_pushresultsize(&luabuf, writepos);
jbe@136 354 // continue with processing of decoded string:
jbe@121 355 goto json_import_process_value;
jbe@121 356 }
jbe@136 357 // process values whose type is is not deducible from a single character:
jbe@136 358 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
jbe@146 359 // for numbers,
jbe@146 360 // use strtod() call to parse a (double precision) floating point number:
jbe@122 361 char *endptr;
jbe@122 362 double numval;
jbe@122 363 numval = strtod(str+pos, &endptr);
jbe@146 364 // catch parsing errors:
jbe@122 365 if (endptr == str+pos) goto json_import_syntax_error;
jbe@146 366 // consume characters that were parsed:
jbe@122 367 pos += endptr - (str+pos);
jbe@146 368 // push parsed (double precision) floating point number on Lua stack:
jbe@122 369 lua_pushnumber(L, numval);
jbe@122 370 } else if (!strncmp(str+pos, "true", 4)) {
jbe@136 371 // consume 4 input characters for "true":
jbe@121 372 pos += 4;
jbe@147 373 // put Lua true value onto stack:
jbe@136 374 lua_pushboolean(L, 1);
jbe@121 375 } else if (!strncmp(str+pos, "false", 5)) {
jbe@136 376 // consume 5 input characters for "false":
jbe@121 377 pos += 5;
jbe@147 378 // put Lua false value onto stack:
jbe@136 379 lua_pushboolean(L, 0);
jbe@121 380 } else if (!strncmp(str+pos, "null", 4)) {
jbe@136 381 // consume 4 input characters for "null":
jbe@136 382 pos += 4;
jbe@147 383 // put special null-marker onto stack:
jbe@138 384 lua_pushvalue(L, json_import_nullmark_idx);
jbe@121 385 } else {
jbe@136 386 // all other cases are a syntax error:
jbe@121 387 goto json_import_syntax_error;
jbe@121 388 }
jbe@136 389 // process a decoded value or key value pair (expected on top of Lua stack):
jbe@136 390 json_import_process_value:
jbe@121 391 switch (mode) {
jbe@136 392 // an object key has been read:
jbe@124 393 case JSON_STATE_OBJECT_KEY:
jbe@136 394 // if an object key is not a string, then this is a syntax error:
jbe@121 395 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
jbe@146 396 // expect key terminator to follow:
jbe@124 397 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
jbe@146 398 // continue with loop:
jbe@121 399 goto json_import_loop;
jbe@136 400 // a key value pair has been read:
jbe@124 401 case JSON_STATE_OBJECT_VALUE:
jbe@136 402 // store key value pair in outer shadow table:
jbe@130 403 lua_rawset(L, -3);
jbe@146 404 // expect value terminator (or end of object) to follow:
jbe@124 405 mode = JSON_STATE_OBJECT_SEPARATOR;
jbe@146 406 // continue with loop:
jbe@121 407 goto json_import_loop;
jbe@136 408 // an array value has been read:
jbe@124 409 case JSON_STATE_ARRAY_VALUE:
jbe@136 410 // store value in outer shadow table:
jbe@140 411 lua_rawseti(L, -3, lua_rawlen(L, -3) + 1);
jbe@146 412 // expect value terminator (or end of object) to follow:
jbe@124 413 mode = JSON_STATE_ARRAY_SEPARATOR;
jbe@146 414 // continue with loop
jbe@121 415 goto json_import_loop;
jbe@136 416 // a single value has been read:
jbe@124 417 case JSON_STATE_VALUE:
jbe@136 418 // leave value on top of stack, expect end of JSON document, and continue with loop:
jbe@124 419 mode = JSON_STATE_END;
jbe@121 420 goto json_import_loop;
jbe@121 421 }
jbe@146 422 // syntax error handling (reachable by goto statement):
jbe@136 423 json_import_syntax_error:
jbe@121 424 lua_pushnil(L);
jbe@121 425 lua_pushliteral(L, "Syntax error in JSON document");
jbe@121 426 return 2;
jbe@121 427 }
jbe@121 428
jbe@146 429 // special Lua stack indicies for json_path function:
jbe@138 430 #define json_path_shadowtbl_idx 1
jbe@138 431 #define json_path_nullmark_idx 2
jbe@146 432
jbe@146 433 // stack offset of arguments to json_path function:
jbe@138 434 #define json_path_idxshift 2
jbe@138 435
jbe@146 436 // gets a value or its type from a JSON document (passed as first argument)
jbe@147 437 // using a path (passed as variable number of keys after first argument):
jbe@137 438 static int json_path(lua_State *L, int type_mode) {
jbe@146 439 int stacktop; // stack index of top of stack (after shifting)
jbe@146 440 int idx = 2 + json_path_idxshift; // stack index of current argument to process
jbe@148 441 // insert shadowtbl into stack at position 1 (shifting the arguments):
jbe@144 442 json_regfetch(L, shadowtbl);
jbe@138 443 lua_insert(L, 1);
jbe@148 444 // insert nullmark into stack at position 2 (shifting the arguments):
jbe@145 445 json_pushlightref(L, nullmark);
jbe@138 446 lua_insert(L, 2);
jbe@146 447 // store stack index of top of stack:
jbe@138 448 stacktop = lua_gettop(L);
jbe@146 449 // use first argument as "current value" (stored on top of stack):
jbe@138 450 lua_pushvalue(L, 1 + json_path_idxshift);
jbe@146 451 // process each "path key" (2nd argument and following arguments):
jbe@138 452 while (idx <= stacktop) {
jbe@146 453 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
jbe@137 454 if (lua_isnil(L, -1)) return 1;
jbe@137 455 // try to get shadow table of "current value":
jbe@130 456 lua_pushvalue(L, -1);
jbe@138 457 lua_rawget(L, json_path_shadowtbl_idx);
jbe@126 458 if (lua_isnil(L, -1)) {
jbe@137 459 // if no shadow table is found,
jbe@130 460 if (lua_type(L, -1) == LUA_TTABLE) {
jbe@146 461 // and if "current value" is a table,
jbe@146 462 // drop nil from stack:
jbe@146 463 lua_pop(L, 1);
jbe@137 464 // get "next value" using the "path key":
jbe@130 465 lua_pushvalue(L, idx++);
jbe@130 466 lua_gettable(L, -2);
jbe@130 467 } else {
jbe@137 468 // if "current value" is not a table,
jbe@146 469 // then the path cannot be walked and nil (already on top of stack) is returned:
jbe@137 470 return 1;
jbe@130 471 }
jbe@130 472 } else {
jbe@137 473 // if a shadow table is found,
jbe@137 474 // set "current value" to its shadow table:
jbe@130 475 lua_replace(L, -2);
jbe@137 476 // get "next value" using the "path key":
jbe@130 477 lua_pushvalue(L, idx++);
jbe@130 478 lua_rawget(L, -2);
jbe@126 479 }
jbe@137 480 // the "next value" replaces the "current value":
jbe@130 481 lua_replace(L, -2);
jbe@126 482 }
jbe@137 483 if (!type_mode) {
jbe@137 484 // if a value (and not its type) was requested,
jbe@137 485 // check if value is the null-marker, and store nil on top of Lua stack in that case:
jbe@138 486 if (lua_rawequal(L, -1, json_path_nullmark_idx)) lua_pushnil(L);
jbe@137 487 } else {
jbe@137 488 // if the type was requested,
jbe@137 489 // check if value is the null-marker:
jbe@138 490 if (lua_rawequal(L, -1, json_path_nullmark_idx)) {
jbe@137 491 // if yes, store string "null" on top of Lua stack:
jbe@130 492 lua_pushliteral(L, "null");
jbe@137 493 } else {
jbe@137 494 // otherwise,
jbe@138 495 // check if metatable indicates "object" or "array":
jbe@138 496 if (lua_getmetatable(L, -1)) {
jbe@144 497 json_regfetch(L, objectmt);
jbe@138 498 if (lua_rawequal(L, -2, -1)) {
jbe@146 499 // if value has metatable for JSON objects,
jbe@138 500 // return string "object":
jbe@138 501 lua_pushliteral(L, "object");
jbe@138 502 return 1;
jbe@138 503 }
jbe@144 504 json_regfetch(L, arraymt);
jbe@138 505 if (lua_rawequal(L, -3, -1)) {
jbe@146 506 // if value has metatable for JSON arrays,
jbe@146 507 // return string "object":
jbe@138 508 lua_pushliteral(L, "array");
jbe@138 509 return 1;
jbe@138 510 }
jbe@146 511 // remove 3 metatables (one of the value, two for comparison) from stack:
jbe@138 512 lua_pop(L, 3);
jbe@138 513 }
jbe@138 514 // otherwise, get the Lua type:
jbe@138 515 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
jbe@126 516 }
jbe@126 517 }
jbe@137 518 // return the top most value on the Lua stack:
jbe@137 519 return 1;
jbe@130 520 }
jbe@130 521
jbe@147 522 // gets a value from a JSON document (passed as first argument)
jbe@147 523 // using a path (passed as variable number of keys after first argument):
jbe@130 524 static int json_get(lua_State *L) {
jbe@137 525 return json_path(L, 0);
jbe@130 526 }
jbe@130 527
jbe@147 528 // gets a value's type from a JSON document (passed as first argument)
jbe@147 529 // using a path (variable number of keys after first argument):
jbe@130 530 static int json_type(lua_State *L) {
jbe@137 531 return json_path(L, 1);
jbe@130 532 }
jbe@130 533
jbe@147 534 // checks if a value in a JSON document (first argument) is
jbe@147 535 // explicitly set to null:
jbe@130 536 static int json_isnull(lua_State *L) {
jbe@137 537 const char *jsontype;
jbe@147 538 // call json_type function with variable arguments:
jbe@138 539 lua_pushcfunction(L, json_type);
jbe@137 540 lua_insert(L, 1);
jbe@137 541 lua_call(L, lua_gettop(L) - 1, 1);
jbe@147 542 // return true if result equals to string "null", otherwise return false:
jbe@137 543 jsontype = lua_tostring(L, -1);
jbe@137 544 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
jbe@137 545 else lua_pushboolean(L, 0);
jbe@137 546 return 1;
jbe@130 547 }
jbe@130 548
jbe@146 549 // special Lua stack indicies for json_setnull function:
jbe@138 550 #define json_setnull_unknownmt_idx 3
jbe@138 551 #define json_setnull_objectmt_idx 4
jbe@138 552 #define json_setnull_arraymt_idx 5
jbe@138 553 #define json_setnull_shadowtbl_idx 6
jbe@138 554
jbe@147 555 // sets a value in a JSON object or JSON array explicitly to null:
jbe@147 556 // NOTE: JSON null is different than absence of a key
jbe@131 557 static int json_setnull(lua_State *L) {
jbe@147 558 // stack shall contain two function arguments:
jbe@131 559 lua_settop(L, 2);
jbe@148 560 // push unknownmt onto stack position 3:
jbe@144 561 json_regfetch(L, unknownmt);
jbe@148 562 // push objectmt onto stack position 4:
jbe@144 563 json_regfetch(L, objectmt);
jbe@148 564 // push arraymt onto stack position 5:
jbe@144 565 json_regfetch(L, arraymt);
jbe@148 566 // push shadowtbl onto stack position 6:
jbe@144 567 json_regfetch(L, shadowtbl);
jbe@147 568 // set metatable if necessary (leaves unknown number of elements on stack):
jbe@138 569 if (
jbe@147 570 !lua_getmetatable(L, 1) || (
jbe@147 571 !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
jbe@147 572 !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
jbe@147 573 !lua_rawequal(L, -1, json_setnull_arraymt_idx)
jbe@147 574 )
jbe@138 575 ) {
jbe@138 576 lua_pushvalue(L, json_setnull_unknownmt_idx);
jbe@138 577 lua_setmetatable(L, 1);
jbe@138 578 }
jbe@147 579 // try to get shadow table:
jbe@131 580 lua_pushvalue(L, 1);
jbe@138 581 lua_rawget(L, json_setnull_shadowtbl_idx);
jbe@131 582 if (lua_isnil(L, -1)) {
jbe@147 583 // if no shadow table is found,
jbe@147 584 // create new shadow table (and leave it on top of stack):
jbe@131 585 lua_newtable(L);
jbe@147 586 // register shadow table:
jbe@131 587 lua_pushvalue(L, 1);
jbe@131 588 lua_pushvalue(L, -2);
jbe@138 589 lua_rawset(L, json_setnull_shadowtbl_idx);
jbe@131 590 }
jbe@147 591 // push key (second argument) and null-marker after shadow table onto stack:
jbe@131 592 lua_pushvalue(L, 2);
jbe@145 593 json_pushlightref(L, nullmark);
jbe@147 594 // store key and null-marker in shadow table:
jbe@131 595 lua_rawset(L, -3);
jbe@147 596 // return nothing:
jbe@131 597 return 0;
jbe@131 598 }
jbe@131 599
jbe@147 600 // returns the length of a JSON array (or zero for a table without numeric keys):
jbe@130 601 static int json_len(lua_State *L) {
jbe@147 602 // stack shall contain one function argument:
jbe@130 603 lua_settop(L, 1);
jbe@148 604 // try to get corresponding shadow table for first argument:
jbe@144 605 json_regfetch(L, shadowtbl);
jbe@130 606 lua_pushvalue(L, 1);
jbe@138 607 lua_rawget(L, -2);
jbe@147 608 // if shadow table does not exist, return length of argument, else length of shadow table:
jbe@147 609 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
jbe@123 610 return 1;
jbe@123 611 }
jbe@123 612
jbe@146 613 // special Lua stack indicies for json_index function:
jbe@141 614 #define json_index_nullmark_idx 3
jbe@141 615 #define json_index_shadowtbl_idx 4
jbe@141 616
jbe@130 617 static int json_index(lua_State *L) {
jbe@148 618 // stack shall contain two function arguments:
jbe@130 619 lua_settop(L, 2);
jbe@148 620 // push nullmark onto stack position 3:
jbe@148 621 json_pushlightref(L, nullmark);
jbe@148 622 // push shadowtbl onto stack position 4:
jbe@144 623 json_regfetch(L, shadowtbl);
jbe@148 624 // get corresponding shadow table for first argument:
jbe@130 625 lua_pushvalue(L, 1);
jbe@141 626 lua_rawget(L, json_index_shadowtbl_idx);
jbe@148 627 // throw error if no shadow table was found:
jbe@139 628 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 629 // use key passed as second argument to lookup value in shadow table:
jbe@130 630 lua_pushvalue(L, 2);
jbe@130 631 lua_rawget(L, -2);
jbe@148 632 // if value is null-marker, then push nil onto stack:
jbe@141 633 if (lua_rawequal(L, -1, json_index_nullmark_idx)) lua_pushnil(L);
jbe@148 634 // return either looked up value, or nil
jbe@127 635 return 1;
jbe@127 636 }
jbe@127 637
jbe@130 638 static int json_newindex(lua_State *L) {
jbe@148 639 // stack shall contain three function arguments:
jbe@130 640 lua_settop(L, 3);
jbe@148 641 // get corresponding shadow table for first argument:
jbe@144 642 json_regfetch(L, shadowtbl);
jbe@123 643 lua_pushvalue(L, 1);
jbe@143 644 lua_rawget(L, -2);
jbe@148 645 // throw error if no shadow table was found:
jbe@130 646 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 647 // replace first argument with shadow table:
jbe@130 648 lua_replace(L, 1);
jbe@148 649 // reset stack and use second and third argument to write to shadow table:
jbe@139 650 lua_settop(L, 3);
jbe@130 651 lua_rawset(L, 1);
jbe@148 652 // return nothing:
jbe@148 653 return 0;
jbe@121 654 }
jbe@121 655
jbe@146 656 // special Lua stack indicies for json_pairs_iterfunc function:
jbe@139 657 #define json_pairs_iterfunc_nullmark_idx 3
jbe@139 658 #define json_pairs_iterfunc_shadowtbl_idx 4
jbe@139 659
jbe@135 660 static int json_pairs_iterfunc(lua_State *L) {
jbe@149 661 // stack shall contain two function arguments:
jbe@135 662 lua_settop(L, 2);
jbe@149 663 // push nullmark onto stack position 3:
jbe@149 664 json_pushlightref(L, nullmark);
jbe@149 665 // push shadowtbl onto stack position 4:
jbe@144 666 json_regfetch(L, shadowtbl);
jbe@149 667 // get corresponding shadow table for first argument:
jbe@135 668 lua_pushvalue(L, 1);
jbe@139 669 lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
jbe@149 670 // throw error if no shadow table was found:
jbe@135 671 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 672 // get next key value pair from shadow table (using previous key from argument 2)
jbe@149 673 // and return nothing if there is no next pair:
jbe@135 674 lua_pushvalue(L, 2);
jbe@135 675 if (!lua_next(L, -2)) return 0;
jbe@149 676 // replace null-marker with nil:
jbe@139 677 if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
jbe@135 678 lua_pop(L, 1);
jbe@135 679 lua_pushnil(L);
jbe@135 680 }
jbe@149 681 // return key and value (or key and nil, if null-marker was found):
jbe@135 682 return 2;
jbe@135 683 }
jbe@135 684
jbe@149 685 // returns a triple such that 'for key, value in pairs(obj) do ... end'
jbe@149 686 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
jbe@135 687 static int json_pairs(lua_State *L) {
jbe@149 688 // return triple of function json_pairs_iterfunc, first argument, and nil:
jbe@139 689 lua_pushcfunction(L, json_pairs_iterfunc);
jbe@135 690 lua_pushvalue(L, 1);
jbe@135 691 lua_pushnil(L);
jbe@135 692 return 3;
jbe@135 693 }
jbe@135 694
jbe@146 695 // special Lua stack indicies for json_ipairs_iterfunc function:
jbe@139 696 #define json_ipairs_iterfunc_nullmark_idx 3
jbe@139 697 #define json_ipairs_iterfunc_shadowtbl_idx 4
jbe@139 698
jbe@134 699 static int json_ipairs_iterfunc(lua_State *L) {
jbe@134 700 int idx;
jbe@149 701 // stack shall contain two function arguments:
jbe@134 702 lua_settop(L, 2);
jbe@149 703 // push nullmark onto stack position 3:
jbe@149 704 json_pushlightref(L, nullmark);
jbe@149 705 // push shadowtbl onto stack position 4:
jbe@144 706 json_regfetch(L, shadowtbl);
jbe@149 707 // calculate new index by incrementing second argument:
jbe@134 708 idx = lua_tointeger(L, 2) + 1;
jbe@149 709 // get corresponding shadow table for first argument:
jbe@134 710 lua_pushvalue(L, 1);
jbe@139 711 lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
jbe@149 712 // throw error if no shadow table was found:
jbe@134 713 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 714 // do integer lookup in shadow table:
jbe@134 715 lua_rawgeti(L, -1, idx);
jbe@149 716 // return nothing if there was no value:
jbe@134 717 if (lua_isnil(L, -1)) return 0;
jbe@149 718 // return new index and
jbe@149 719 // either the looked up value if it is not equal to the null-marker
jbe@149 720 // or nil instead of null-marker:
jbe@134 721 lua_pushinteger(L, idx);
jbe@139 722 if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
jbe@134 723 else lua_pushvalue(L, -2);
jbe@134 724 return 2;
jbe@134 725 }
jbe@134 726
jbe@149 727 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
jbe@149 728 // iterates through all values (including JSON null represented as Lua nil):
jbe@134 729 static int json_ipairs(lua_State *L) {
jbe@149 730 // return triple of function json_ipairs_iterfunc, first argument, and zero:
jbe@139 731 lua_pushcfunction(L, json_ipairs_iterfunc);
jbe@134 732 lua_pushvalue(L, 1);
jbe@134 733 lua_pushinteger(L, 0);
jbe@134 734 return 3;
jbe@134 735 }
jbe@134 736
jbe@149 737 // functions in library module:
jbe@121 738 static const struct luaL_Reg json_module_functions[] = {
jbe@133 739 {"object", json_object},
jbe@133 740 {"array", json_array},
jbe@121 741 {"import", json_import},
jbe@130 742 {"get", json_get},
jbe@127 743 {"type", json_type},
jbe@123 744 {"isnull", json_isnull},
jbe@131 745 {"setnull", json_setnull},
jbe@121 746 {NULL, NULL}
jbe@121 747 };
jbe@121 748
jbe@149 749 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
jbe@126 750 static const struct luaL_Reg json_metatable_functions[] = {
jbe@130 751 {"__len", json_len},
jbe@130 752 {"__index", json_index},
jbe@130 753 {"__newindex", json_newindex},
jbe@135 754 {"__pairs", json_pairs},
jbe@134 755 {"__ipairs", json_ipairs},
jbe@126 756 {NULL, NULL}
jbe@126 757 };
jbe@126 758
jbe@149 759 // initializes json library:
jbe@121 760 int luaopen_json(lua_State *L) {
jbe@149 761 // empty stack:
jbe@126 762 lua_settop(L, 0);
jbe@149 763 // push library module onto stack position 1:
jbe@149 764 lua_newtable(L);
jbe@149 765 // register library functions:
jbe@149 766 luaL_setfuncs(L, json_module_functions, 0);
jbe@149 767 // create and store unknownmt:
jbe@138 768 lua_newtable(L);
jbe@138 769 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 770 json_regstore(L, unknownmt);
jbe@149 771 // create and store objectmt:
jbe@138 772 lua_newtable(L);
jbe@138 773 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 774 json_regstore(L, objectmt);
jbe@149 775 // create and store arraymt:
jbe@138 776 lua_newtable(L);
jbe@138 777 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 778 json_regstore(L, arraymt);
jbe@149 779 // create and store ephemeron table to store shadow tables for each JSON object/array
jbe@149 780 // to allow NULL values returned as nil
jbe@149 781 lua_newtable(L);
jbe@138 782 lua_newtable(L); // metatable for ephemeron table
jbe@121 783 lua_pushliteral(L, "__mode");
jbe@121 784 lua_pushliteral(L, "k");
jbe@138 785 lua_rawset(L, -3);
jbe@138 786 lua_setmetatable(L, -2);
jbe@144 787 json_regstore(L, shadowtbl);
jbe@149 788 // return library module stored on lowest stack position:
jbe@138 789 lua_settop(L, 1);
jbe@121 790 return 1;
jbe@121 791 }

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