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annotate libraries/json/json.c @ 152:7b5c13fdc2ec

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Reject arrays that exceed INT_MAX elements in JSON library
author jbe
date Thu Jul 31 01:02:46 2014 +0200 (2014-07-31)
parents 6d2bb696f736
children c8c91216255f
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@151 19 #define json_pushlightref(L, x) lua_pushlightuserdata((L), &json_reference.x)
jbe@145 20 #define json_regpointer(x) (&json_registry.x)
jbe@151 21 #define json_regfetchpointer(L, x) lua_rawgetp((L), LUA_REGISTRYINDEX, (x))
jbe@151 22 #define json_regfetch(L, x) json_regfetchpointer(L, json_regpointer(x))
jbe@151 23 #define json_regstore(L, x) lua_rawsetp(L, LUA_REGISTRYINDEX, json_regpointer(x))
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@152 124 size_t arraylen; // variable to temporarily store the array length
jbe@147 125 // stack shall contain one function argument:
jbe@138 126 lua_settop(L, 1);
jbe@147 127 // push objectmt onto stack position 2:
jbe@144 128 json_regfetch(L, objectmt);
jbe@147 129 // push arraymt onto stack position 3:
jbe@144 130 json_regfetch(L, arraymt);
jbe@147 131 // push shadowtbl onto stack position 4:
jbe@144 132 json_regfetch(L, shadowtbl);
jbe@147 133 // push nullmark onto stack position 5:
jbe@145 134 json_pushlightref(L, nullmark);
jbe@136 135 // require string as first argument:
jbe@136 136 str = luaL_checklstring(L, 1, &total);
jbe@136 137 // if string contains a NULL byte, this is a syntax error
jbe@136 138 if (strlen(str) != total) goto json_import_syntax_error;
jbe@136 139 // main loop of parser:
jbe@136 140 json_import_loop:
jbe@136 141 // skip whitespace and store next character in variable 'c':
jbe@146 142 while (c = str[pos],
jbe@146 143 c == ' ' ||
jbe@146 144 c == '\f' ||
jbe@146 145 c == '\n' ||
jbe@146 146 c == '\r' ||
jbe@146 147 c == '\t' ||
jbe@146 148 c == '\v'
jbe@146 149 ) pos++;
jbe@136 150 // switch statement to handle certain (single) characters:
jbe@121 151 switch (c) {
jbe@136 152 // handle end of JSON document:
jbe@121 153 case 0:
jbe@136 154 // if end of JSON document was expected, then return top element of stack as result:
jbe@124 155 if (mode == JSON_STATE_END) return 1;
jbe@136 156 // otherwise, the JSON document was malformed:
jbe@121 157 json_import_unexpected_eof:
jbe@121 158 lua_pushnil(L);
jbe@121 159 if (level == 0) lua_pushliteral(L, "Empty string");
jbe@121 160 else lua_pushliteral(L, "Unexpected end of JSON document");
jbe@121 161 return 2;
jbe@136 162 // new JSON object:
jbe@121 163 case '{':
jbe@136 164 // if a JSON object is not expected here, then return an error:
jbe@146 165 if (
jbe@146 166 mode != JSON_STATE_VALUE &&
jbe@146 167 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 168 mode != JSON_STATE_ARRAY_VALUE
jbe@146 169 ) goto json_import_syntax_error;
jbe@136 170 // create JSON object on stack:
jbe@136 171 lua_newtable(L);
jbe@136 172 // set metatable of JSON object:
jbe@138 173 lua_pushvalue(L, json_import_objectmt_idx);
jbe@125 174 lua_setmetatable(L, -2);
jbe@136 175 // create internal shadow table on stack:
jbe@136 176 lua_newtable(L);
jbe@146 177 // register internal shadow table:
jbe@123 178 lua_pushvalue(L, -2);
jbe@123 179 lua_pushvalue(L, -2);
jbe@138 180 lua_rawset(L, json_import_shadowtbl_idx);
jbe@146 181 // expect object key (or end of object) to follow:
jbe@136 182 mode = JSON_STATE_OBJECT_KEY;
jbe@146 183 // jump to common code for opening JSON object and JSON array:
jbe@142 184 goto json_import_open;
jbe@136 185 // new JSON array:
jbe@121 186 case '[':
jbe@136 187 // if a JSON array is not expected here, then return an error:
jbe@146 188 if (
jbe@146 189 mode != JSON_STATE_VALUE &&
jbe@146 190 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 191 mode != JSON_STATE_ARRAY_VALUE
jbe@146 192 ) goto json_import_syntax_error;
jbe@136 193 // create JSON array on stack:
jbe@136 194 lua_newtable(L);
jbe@136 195 // set metatable of JSON array:
jbe@138 196 lua_pushvalue(L, json_import_arraymt_idx);
jbe@125 197 lua_setmetatable(L, -2);
jbe@136 198 // create internal shadow table on stack:
jbe@136 199 lua_newtable(L);
jbe@146 200 // register internal shadow table:
jbe@123 201 lua_pushvalue(L, -2);
jbe@123 202 lua_pushvalue(L, -2);
jbe@138 203 lua_rawset(L, json_import_shadowtbl_idx);
jbe@140 204 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
jbe@140 205 lua_pushnil(L);
jbe@146 206 // expect array value (or end of array) to follow:
jbe@142 207 mode = JSON_STATE_ARRAY_VALUE;
jbe@142 208 // continue with common code for opening JSON object and JSON array:
jbe@146 209 // common code for opening JSON object or JSON array:
jbe@142 210 json_import_open:
jbe@142 211 // limit nested levels:
jbe@142 212 if (level >= JSON_MAXDEPTH) {
jbe@142 213 lua_pushnil(L);
jbe@142 214 lua_pushliteral(L, "Too many nested JSON levels");
jbe@142 215 return 2;
jbe@142 216 }
jbe@142 217 // additional buffer overflow protection:
jbe@142 218 if (!lua_checkstack(L, LUA_MINSTACK))
jbe@142 219 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
jbe@136 220 // increment level:
jbe@121 221 level++;
jbe@142 222 // consume input character:
jbe@142 223 pos++;
jbe@121 224 goto json_import_loop;
jbe@136 225 // end of JSON object:
jbe@121 226 case '}':
jbe@136 227 // if end of JSON object is not expected here, then return an error:
jbe@146 228 if (
jbe@146 229 mode != JSON_STATE_OBJECT_KEY &&
jbe@146 230 mode != JSON_STATE_OBJECT_SEPARATOR
jbe@146 231 ) goto json_import_syntax_error;
jbe@136 232 // jump to common code for end of JSON object and JSON array:
jbe@121 233 goto json_import_close;
jbe@136 234 // end of JSON array:
jbe@121 235 case ']':
jbe@136 236 // if end of JSON array is not expected here, then return an error:
jbe@146 237 if (
jbe@146 238 mode != JSON_STATE_ARRAY_VALUE &&
jbe@146 239 mode != JSON_STATE_ARRAY_SEPARATOR
jbe@146 240 ) goto json_import_syntax_error;
jbe@146 241 // pop nil key/magic (that was needed to keep stack balance):
jbe@140 242 lua_pop(L, 1);
jbe@136 243 // continue with common code for end of JSON object and JSON array:
jbe@136 244 // common code for end of JSON object or JSON array:
jbe@121 245 json_import_close:
jbe@136 246 // consume input character:
jbe@121 247 pos++;
jbe@136 248 // pop shadow table:
jbe@136 249 lua_pop(L, 1);
jbe@136 250 // check if nested:
jbe@121 251 if (--level) {
jbe@146 252 // if nested,
jbe@146 253 // check if outer(!) structure is an array or object:
jbe@140 254 if (lua_isnil(L, -2)) {
jbe@136 255 // select array value processing:
jbe@124 256 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 257 } else {
jbe@136 258 // select object value processing:
jbe@124 259 mode = JSON_STATE_OBJECT_VALUE;
jbe@121 260 }
jbe@136 261 // store value in outer structure:
jbe@121 262 goto json_import_process_value;
jbe@121 263 }
jbe@136 264 // if not nested, then expect end of JSON document and continue with loop:
jbe@136 265 mode = JSON_STATE_END;
jbe@121 266 goto json_import_loop;
jbe@136 267 // key terminator:
jbe@121 268 case ':':
jbe@136 269 // if key terminator is not expected here, then return an error:
jbe@124 270 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
jbe@121 271 goto json_import_syntax_error;
jbe@136 272 // consume input character:
jbe@121 273 pos++;
jbe@146 274 // expect object value to follow:
jbe@124 275 mode = JSON_STATE_OBJECT_VALUE;
jbe@146 276 // continue with loop:
jbe@121 277 goto json_import_loop;
jbe@136 278 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
jbe@121 279 case ',':
jbe@146 280 // branch according to parser state:
jbe@124 281 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
jbe@146 282 // expect an object key to follow:
jbe@124 283 mode = JSON_STATE_OBJECT_KEY;
jbe@124 284 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
jbe@146 285 // expect an array value to follow:
jbe@124 286 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 287 } else {
jbe@136 288 // if value terminator is not expected here, then return an error:
jbe@136 289 goto json_import_syntax_error;
jbe@121 290 }
jbe@136 291 // consume input character:
jbe@121 292 pos++;
jbe@136 293 // continue with loop:
jbe@121 294 goto json_import_loop;
jbe@136 295 // string literal:
jbe@121 296 case '"':
jbe@146 297 // consume quote character:
jbe@146 298 pos++;
jbe@136 299 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
jbe@121 300 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
jbe@121 301 writepos = 0;
jbe@146 302 // loop through the characters until encountering end quote:
jbe@121 303 while ((c = str[pos++]) != '"') {
jbe@121 304 if (c == 0) {
jbe@146 305 // handle unexpected end of JSON document:
jbe@121 306 goto json_import_unexpected_eof;
jbe@121 307 } else if (c < 32 || c == 127) {
jbe@136 308 // do not allow ASCII control characters:
jbe@136 309 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
jbe@136 310 // by this parser to allow different encodings than Unicode
jbe@121 311 lua_pushnil(L);
jbe@121 312 lua_pushliteral(L, "Unexpected control character in JSON string");
jbe@121 313 return 2;
jbe@121 314 } else if (c == '\\') {
jbe@136 315 // read next char after backslash escape:
jbe@121 316 c = str[pos++];
jbe@121 317 switch (c) {
jbe@136 318 // unexpected end-of-string:
jbe@121 319 case 0:
jbe@121 320 goto json_import_unexpected_eof;
jbe@136 321 // unescaping of quotation mark, slash, and backslash:
jbe@121 322 case '"':
jbe@121 323 case '/':
jbe@121 324 case '\\':
jbe@121 325 cbuf[writepos++] = c;
jbe@121 326 break;
jbe@136 327 // unescaping of backspace:
jbe@146 328 case 'b': cbuf[writepos++] = '\b'; break;
jbe@136 329 // unescaping of form-feed:
jbe@146 330 case 'f': cbuf[writepos++] = '\f'; break;
jbe@136 331 // unescaping of new-line:
jbe@146 332 case 'n': cbuf[writepos++] = '\n'; break;
jbe@136 333 // unescaping of carriage-return:
jbe@146 334 case 'r': cbuf[writepos++] = '\r'; break;
jbe@136 335 // unescaping of tabulator:
jbe@146 336 case 't': cbuf[writepos++] = '\t'; break;
jbe@136 337 // unescaping of UTF-16 characters
jbe@121 338 case 'u':
jbe@121 339 lua_pushnil(L);
jbe@121 340 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
jbe@121 341 return 2;
jbe@136 342 // unexpected escape sequence:
jbe@121 343 default:
jbe@121 344 lua_pushnil(L);
jbe@121 345 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
jbe@121 346 return 2;
jbe@121 347 }
jbe@121 348 } else {
jbe@136 349 // normal character:
jbe@121 350 cbuf[writepos++] = c;
jbe@121 351 }
jbe@121 352 }
jbe@136 353 // process buffer to Lua string:
jbe@121 354 luaL_pushresultsize(&luabuf, writepos);
jbe@136 355 // continue with processing of decoded string:
jbe@121 356 goto json_import_process_value;
jbe@121 357 }
jbe@136 358 // process values whose type is is not deducible from a single character:
jbe@136 359 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
jbe@146 360 // for numbers,
jbe@146 361 // use strtod() call to parse a (double precision) floating point number:
jbe@122 362 char *endptr;
jbe@122 363 double numval;
jbe@122 364 numval = strtod(str+pos, &endptr);
jbe@146 365 // catch parsing errors:
jbe@122 366 if (endptr == str+pos) goto json_import_syntax_error;
jbe@146 367 // consume characters that were parsed:
jbe@122 368 pos += endptr - (str+pos);
jbe@146 369 // push parsed (double precision) floating point number on Lua stack:
jbe@122 370 lua_pushnumber(L, numval);
jbe@122 371 } else if (!strncmp(str+pos, "true", 4)) {
jbe@136 372 // consume 4 input characters for "true":
jbe@121 373 pos += 4;
jbe@147 374 // put Lua true value onto stack:
jbe@136 375 lua_pushboolean(L, 1);
jbe@121 376 } else if (!strncmp(str+pos, "false", 5)) {
jbe@136 377 // consume 5 input characters for "false":
jbe@121 378 pos += 5;
jbe@147 379 // put Lua false value onto stack:
jbe@136 380 lua_pushboolean(L, 0);
jbe@121 381 } else if (!strncmp(str+pos, "null", 4)) {
jbe@136 382 // consume 4 input characters for "null":
jbe@136 383 pos += 4;
jbe@147 384 // put special null-marker onto stack:
jbe@138 385 lua_pushvalue(L, json_import_nullmark_idx);
jbe@121 386 } else {
jbe@136 387 // all other cases are a syntax error:
jbe@121 388 goto json_import_syntax_error;
jbe@121 389 }
jbe@136 390 // process a decoded value or key value pair (expected on top of Lua stack):
jbe@136 391 json_import_process_value:
jbe@121 392 switch (mode) {
jbe@136 393 // an object key has been read:
jbe@124 394 case JSON_STATE_OBJECT_KEY:
jbe@136 395 // if an object key is not a string, then this is a syntax error:
jbe@121 396 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
jbe@146 397 // expect key terminator to follow:
jbe@124 398 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
jbe@146 399 // continue with loop:
jbe@121 400 goto json_import_loop;
jbe@136 401 // a key value pair has been read:
jbe@124 402 case JSON_STATE_OBJECT_VALUE:
jbe@136 403 // store key value pair in outer shadow table:
jbe@130 404 lua_rawset(L, -3);
jbe@146 405 // expect value terminator (or end of object) to follow:
jbe@124 406 mode = JSON_STATE_OBJECT_SEPARATOR;
jbe@146 407 // continue with loop:
jbe@121 408 goto json_import_loop;
jbe@136 409 // an array value has been read:
jbe@124 410 case JSON_STATE_ARRAY_VALUE:
jbe@152 411 // get current array length:
jbe@152 412 arraylen = lua_rawlen(L, -3);
jbe@152 413 // throw error if array would exceed INT_MAX elements:
jbe@152 414 // TODO: Lua 5.3 may support more elements
jbe@152 415 if (arraylen >= INT_MAX) {
jbe@152 416 lua_pushnil(L);
jbe@152 417 lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
jbe@152 418 }
jbe@136 419 // store value in outer shadow table:
jbe@152 420 lua_rawseti(L, -3, arraylen + 1);
jbe@146 421 // expect value terminator (or end of object) to follow:
jbe@124 422 mode = JSON_STATE_ARRAY_SEPARATOR;
jbe@146 423 // continue with loop
jbe@121 424 goto json_import_loop;
jbe@136 425 // a single value has been read:
jbe@124 426 case JSON_STATE_VALUE:
jbe@136 427 // leave value on top of stack, expect end of JSON document, and continue with loop:
jbe@124 428 mode = JSON_STATE_END;
jbe@121 429 goto json_import_loop;
jbe@121 430 }
jbe@146 431 // syntax error handling (reachable by goto statement):
jbe@136 432 json_import_syntax_error:
jbe@121 433 lua_pushnil(L);
jbe@121 434 lua_pushliteral(L, "Syntax error in JSON document");
jbe@121 435 return 2;
jbe@121 436 }
jbe@121 437
jbe@146 438 // special Lua stack indicies for json_path function:
jbe@138 439 #define json_path_shadowtbl_idx 1
jbe@138 440 #define json_path_nullmark_idx 2
jbe@146 441
jbe@146 442 // stack offset of arguments to json_path function:
jbe@138 443 #define json_path_idxshift 2
jbe@138 444
jbe@146 445 // gets a value or its type from a JSON document (passed as first argument)
jbe@147 446 // using a path (passed as variable number of keys after first argument):
jbe@137 447 static int json_path(lua_State *L, int type_mode) {
jbe@146 448 int stacktop; // stack index of top of stack (after shifting)
jbe@146 449 int idx = 2 + json_path_idxshift; // stack index of current argument to process
jbe@148 450 // insert shadowtbl into stack at position 1 (shifting the arguments):
jbe@144 451 json_regfetch(L, shadowtbl);
jbe@138 452 lua_insert(L, 1);
jbe@148 453 // insert nullmark into stack at position 2 (shifting the arguments):
jbe@145 454 json_pushlightref(L, nullmark);
jbe@138 455 lua_insert(L, 2);
jbe@146 456 // store stack index of top of stack:
jbe@138 457 stacktop = lua_gettop(L);
jbe@146 458 // use first argument as "current value" (stored on top of stack):
jbe@138 459 lua_pushvalue(L, 1 + json_path_idxshift);
jbe@146 460 // process each "path key" (2nd argument and following arguments):
jbe@138 461 while (idx <= stacktop) {
jbe@146 462 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
jbe@137 463 if (lua_isnil(L, -1)) return 1;
jbe@137 464 // try to get shadow table of "current value":
jbe@130 465 lua_pushvalue(L, -1);
jbe@138 466 lua_rawget(L, json_path_shadowtbl_idx);
jbe@126 467 if (lua_isnil(L, -1)) {
jbe@137 468 // if no shadow table is found,
jbe@130 469 if (lua_type(L, -1) == LUA_TTABLE) {
jbe@146 470 // and if "current value" is a table,
jbe@146 471 // drop nil from stack:
jbe@146 472 lua_pop(L, 1);
jbe@137 473 // get "next value" using the "path key":
jbe@130 474 lua_pushvalue(L, idx++);
jbe@130 475 lua_gettable(L, -2);
jbe@130 476 } else {
jbe@137 477 // if "current value" is not a table,
jbe@146 478 // then the path cannot be walked and nil (already on top of stack) is returned:
jbe@137 479 return 1;
jbe@130 480 }
jbe@130 481 } else {
jbe@137 482 // if a shadow table is found,
jbe@137 483 // set "current value" to its shadow table:
jbe@130 484 lua_replace(L, -2);
jbe@137 485 // get "next value" using the "path key":
jbe@130 486 lua_pushvalue(L, idx++);
jbe@130 487 lua_rawget(L, -2);
jbe@126 488 }
jbe@137 489 // the "next value" replaces the "current value":
jbe@130 490 lua_replace(L, -2);
jbe@126 491 }
jbe@137 492 if (!type_mode) {
jbe@137 493 // if a value (and not its type) was requested,
jbe@137 494 // check if value is the null-marker, and store nil on top of Lua stack in that case:
jbe@138 495 if (lua_rawequal(L, -1, json_path_nullmark_idx)) lua_pushnil(L);
jbe@137 496 } else {
jbe@137 497 // if the type was requested,
jbe@137 498 // check if value is the null-marker:
jbe@138 499 if (lua_rawequal(L, -1, json_path_nullmark_idx)) {
jbe@137 500 // if yes, store string "null" on top of Lua stack:
jbe@130 501 lua_pushliteral(L, "null");
jbe@137 502 } else {
jbe@137 503 // otherwise,
jbe@138 504 // check if metatable indicates "object" or "array":
jbe@138 505 if (lua_getmetatable(L, -1)) {
jbe@144 506 json_regfetch(L, objectmt);
jbe@138 507 if (lua_rawequal(L, -2, -1)) {
jbe@146 508 // if value has metatable for JSON objects,
jbe@138 509 // return string "object":
jbe@138 510 lua_pushliteral(L, "object");
jbe@138 511 return 1;
jbe@138 512 }
jbe@144 513 json_regfetch(L, arraymt);
jbe@138 514 if (lua_rawequal(L, -3, -1)) {
jbe@146 515 // if value has metatable for JSON arrays,
jbe@146 516 // return string "object":
jbe@138 517 lua_pushliteral(L, "array");
jbe@138 518 return 1;
jbe@138 519 }
jbe@146 520 // remove 3 metatables (one of the value, two for comparison) from stack:
jbe@138 521 lua_pop(L, 3);
jbe@138 522 }
jbe@138 523 // otherwise, get the Lua type:
jbe@138 524 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
jbe@126 525 }
jbe@126 526 }
jbe@137 527 // return the top most value on the Lua stack:
jbe@137 528 return 1;
jbe@130 529 }
jbe@130 530
jbe@147 531 // gets a value from a JSON document (passed as first argument)
jbe@147 532 // using a path (passed as variable number of keys after first argument):
jbe@130 533 static int json_get(lua_State *L) {
jbe@137 534 return json_path(L, 0);
jbe@130 535 }
jbe@130 536
jbe@147 537 // gets a value's type from a JSON document (passed as first argument)
jbe@147 538 // using a path (variable number of keys after first argument):
jbe@130 539 static int json_type(lua_State *L) {
jbe@137 540 return json_path(L, 1);
jbe@130 541 }
jbe@130 542
jbe@147 543 // checks if a value in a JSON document (first argument) is
jbe@147 544 // explicitly set to null:
jbe@130 545 static int json_isnull(lua_State *L) {
jbe@137 546 const char *jsontype;
jbe@147 547 // call json_type function with variable arguments:
jbe@138 548 lua_pushcfunction(L, json_type);
jbe@137 549 lua_insert(L, 1);
jbe@137 550 lua_call(L, lua_gettop(L) - 1, 1);
jbe@147 551 // return true if result equals to string "null", otherwise return false:
jbe@137 552 jsontype = lua_tostring(L, -1);
jbe@137 553 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
jbe@137 554 else lua_pushboolean(L, 0);
jbe@137 555 return 1;
jbe@130 556 }
jbe@130 557
jbe@146 558 // special Lua stack indicies for json_setnull function:
jbe@138 559 #define json_setnull_unknownmt_idx 3
jbe@138 560 #define json_setnull_objectmt_idx 4
jbe@138 561 #define json_setnull_arraymt_idx 5
jbe@138 562 #define json_setnull_shadowtbl_idx 6
jbe@138 563
jbe@147 564 // sets a value in a JSON object or JSON array explicitly to null:
jbe@147 565 // NOTE: JSON null is different than absence of a key
jbe@131 566 static int json_setnull(lua_State *L) {
jbe@147 567 // stack shall contain two function arguments:
jbe@131 568 lua_settop(L, 2);
jbe@148 569 // push unknownmt onto stack position 3:
jbe@144 570 json_regfetch(L, unknownmt);
jbe@148 571 // push objectmt onto stack position 4:
jbe@144 572 json_regfetch(L, objectmt);
jbe@148 573 // push arraymt onto stack position 5:
jbe@144 574 json_regfetch(L, arraymt);
jbe@148 575 // push shadowtbl onto stack position 6:
jbe@144 576 json_regfetch(L, shadowtbl);
jbe@147 577 // set metatable if necessary (leaves unknown number of elements on stack):
jbe@138 578 if (
jbe@147 579 !lua_getmetatable(L, 1) || (
jbe@147 580 !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
jbe@147 581 !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
jbe@147 582 !lua_rawequal(L, -1, json_setnull_arraymt_idx)
jbe@147 583 )
jbe@138 584 ) {
jbe@138 585 lua_pushvalue(L, json_setnull_unknownmt_idx);
jbe@138 586 lua_setmetatable(L, 1);
jbe@138 587 }
jbe@147 588 // try to get shadow table:
jbe@131 589 lua_pushvalue(L, 1);
jbe@138 590 lua_rawget(L, json_setnull_shadowtbl_idx);
jbe@131 591 if (lua_isnil(L, -1)) {
jbe@147 592 // if no shadow table is found,
jbe@147 593 // create new shadow table (and leave it on top of stack):
jbe@131 594 lua_newtable(L);
jbe@147 595 // register shadow table:
jbe@131 596 lua_pushvalue(L, 1);
jbe@131 597 lua_pushvalue(L, -2);
jbe@138 598 lua_rawset(L, json_setnull_shadowtbl_idx);
jbe@131 599 }
jbe@147 600 // push key (second argument) and null-marker after shadow table onto stack:
jbe@131 601 lua_pushvalue(L, 2);
jbe@145 602 json_pushlightref(L, nullmark);
jbe@147 603 // store key and null-marker in shadow table:
jbe@131 604 lua_rawset(L, -3);
jbe@147 605 // return nothing:
jbe@131 606 return 0;
jbe@131 607 }
jbe@131 608
jbe@147 609 // returns the length of a JSON array (or zero for a table without numeric keys):
jbe@130 610 static int json_len(lua_State *L) {
jbe@147 611 // stack shall contain one function argument:
jbe@130 612 lua_settop(L, 1);
jbe@148 613 // try to get corresponding shadow table for first argument:
jbe@144 614 json_regfetch(L, shadowtbl);
jbe@130 615 lua_pushvalue(L, 1);
jbe@138 616 lua_rawget(L, -2);
jbe@147 617 // if shadow table does not exist, return length of argument, else length of shadow table:
jbe@147 618 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
jbe@123 619 return 1;
jbe@123 620 }
jbe@123 621
jbe@146 622 // special Lua stack indicies for json_index function:
jbe@141 623 #define json_index_nullmark_idx 3
jbe@141 624 #define json_index_shadowtbl_idx 4
jbe@141 625
jbe@130 626 static int json_index(lua_State *L) {
jbe@148 627 // stack shall contain two function arguments:
jbe@130 628 lua_settop(L, 2);
jbe@148 629 // push nullmark onto stack position 3:
jbe@148 630 json_pushlightref(L, nullmark);
jbe@148 631 // push shadowtbl onto stack position 4:
jbe@144 632 json_regfetch(L, shadowtbl);
jbe@148 633 // get corresponding shadow table for first argument:
jbe@130 634 lua_pushvalue(L, 1);
jbe@141 635 lua_rawget(L, json_index_shadowtbl_idx);
jbe@148 636 // throw error if no shadow table was found:
jbe@139 637 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 638 // use key passed as second argument to lookup value in shadow table:
jbe@130 639 lua_pushvalue(L, 2);
jbe@130 640 lua_rawget(L, -2);
jbe@148 641 // if value is null-marker, then push nil onto stack:
jbe@141 642 if (lua_rawequal(L, -1, json_index_nullmark_idx)) lua_pushnil(L);
jbe@148 643 // return either looked up value, or nil
jbe@127 644 return 1;
jbe@127 645 }
jbe@127 646
jbe@130 647 static int json_newindex(lua_State *L) {
jbe@148 648 // stack shall contain three function arguments:
jbe@130 649 lua_settop(L, 3);
jbe@148 650 // get corresponding shadow table for first argument:
jbe@144 651 json_regfetch(L, shadowtbl);
jbe@123 652 lua_pushvalue(L, 1);
jbe@143 653 lua_rawget(L, -2);
jbe@148 654 // throw error if no shadow table was found:
jbe@130 655 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 656 // replace first argument with shadow table:
jbe@130 657 lua_replace(L, 1);
jbe@148 658 // reset stack and use second and third argument to write to shadow table:
jbe@139 659 lua_settop(L, 3);
jbe@130 660 lua_rawset(L, 1);
jbe@148 661 // return nothing:
jbe@148 662 return 0;
jbe@121 663 }
jbe@121 664
jbe@146 665 // special Lua stack indicies for json_pairs_iterfunc function:
jbe@139 666 #define json_pairs_iterfunc_nullmark_idx 3
jbe@139 667 #define json_pairs_iterfunc_shadowtbl_idx 4
jbe@139 668
jbe@135 669 static int json_pairs_iterfunc(lua_State *L) {
jbe@149 670 // stack shall contain two function arguments:
jbe@135 671 lua_settop(L, 2);
jbe@149 672 // push nullmark onto stack position 3:
jbe@149 673 json_pushlightref(L, nullmark);
jbe@149 674 // push shadowtbl onto stack position 4:
jbe@144 675 json_regfetch(L, shadowtbl);
jbe@149 676 // get corresponding shadow table for first argument:
jbe@135 677 lua_pushvalue(L, 1);
jbe@139 678 lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
jbe@149 679 // throw error if no shadow table was found:
jbe@135 680 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 681 // get next key value pair from shadow table (using previous key from argument 2)
jbe@149 682 // and return nothing if there is no next pair:
jbe@135 683 lua_pushvalue(L, 2);
jbe@135 684 if (!lua_next(L, -2)) return 0;
jbe@149 685 // replace null-marker with nil:
jbe@139 686 if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
jbe@135 687 lua_pop(L, 1);
jbe@135 688 lua_pushnil(L);
jbe@135 689 }
jbe@149 690 // return key and value (or key and nil, if null-marker was found):
jbe@135 691 return 2;
jbe@135 692 }
jbe@135 693
jbe@149 694 // returns a triple such that 'for key, value in pairs(obj) do ... end'
jbe@149 695 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
jbe@135 696 static int json_pairs(lua_State *L) {
jbe@149 697 // return triple of function json_pairs_iterfunc, first argument, and nil:
jbe@139 698 lua_pushcfunction(L, json_pairs_iterfunc);
jbe@135 699 lua_pushvalue(L, 1);
jbe@135 700 lua_pushnil(L);
jbe@135 701 return 3;
jbe@135 702 }
jbe@135 703
jbe@146 704 // special Lua stack indicies for json_ipairs_iterfunc function:
jbe@139 705 #define json_ipairs_iterfunc_nullmark_idx 3
jbe@139 706 #define json_ipairs_iterfunc_shadowtbl_idx 4
jbe@139 707
jbe@134 708 static int json_ipairs_iterfunc(lua_State *L) {
jbe@152 709 lua_Integer idx;
jbe@149 710 // stack shall contain two function arguments:
jbe@134 711 lua_settop(L, 2);
jbe@149 712 // push nullmark onto stack position 3:
jbe@149 713 json_pushlightref(L, nullmark);
jbe@149 714 // push shadowtbl onto stack position 4:
jbe@144 715 json_regfetch(L, shadowtbl);
jbe@149 716 // calculate new index by incrementing second argument:
jbe@134 717 idx = lua_tointeger(L, 2) + 1;
jbe@149 718 // get corresponding shadow table for first argument:
jbe@134 719 lua_pushvalue(L, 1);
jbe@139 720 lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
jbe@149 721 // throw error if no shadow table was found:
jbe@134 722 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 723 // do integer lookup in shadow table:
jbe@134 724 lua_rawgeti(L, -1, idx);
jbe@149 725 // return nothing if there was no value:
jbe@134 726 if (lua_isnil(L, -1)) return 0;
jbe@149 727 // return new index and
jbe@149 728 // either the looked up value if it is not equal to the null-marker
jbe@149 729 // or nil instead of null-marker:
jbe@134 730 lua_pushinteger(L, idx);
jbe@139 731 if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
jbe@134 732 else lua_pushvalue(L, -2);
jbe@134 733 return 2;
jbe@134 734 }
jbe@134 735
jbe@149 736 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
jbe@149 737 // iterates through all values (including JSON null represented as Lua nil):
jbe@134 738 static int json_ipairs(lua_State *L) {
jbe@149 739 // return triple of function json_ipairs_iterfunc, first argument, and zero:
jbe@139 740 lua_pushcfunction(L, json_ipairs_iterfunc);
jbe@134 741 lua_pushvalue(L, 1);
jbe@134 742 lua_pushinteger(L, 0);
jbe@134 743 return 3;
jbe@134 744 }
jbe@134 745
jbe@149 746 // functions in library module:
jbe@121 747 static const struct luaL_Reg json_module_functions[] = {
jbe@133 748 {"object", json_object},
jbe@133 749 {"array", json_array},
jbe@121 750 {"import", json_import},
jbe@130 751 {"get", json_get},
jbe@127 752 {"type", json_type},
jbe@123 753 {"isnull", json_isnull},
jbe@131 754 {"setnull", json_setnull},
jbe@121 755 {NULL, NULL}
jbe@121 756 };
jbe@121 757
jbe@149 758 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
jbe@126 759 static const struct luaL_Reg json_metatable_functions[] = {
jbe@130 760 {"__len", json_len},
jbe@130 761 {"__index", json_index},
jbe@130 762 {"__newindex", json_newindex},
jbe@135 763 {"__pairs", json_pairs},
jbe@134 764 {"__ipairs", json_ipairs},
jbe@126 765 {NULL, NULL}
jbe@126 766 };
jbe@126 767
jbe@149 768 // initializes json library:
jbe@121 769 int luaopen_json(lua_State *L) {
jbe@149 770 // empty stack:
jbe@126 771 lua_settop(L, 0);
jbe@149 772 // push library module onto stack position 1:
jbe@149 773 lua_newtable(L);
jbe@149 774 // register library functions:
jbe@149 775 luaL_setfuncs(L, json_module_functions, 0);
jbe@149 776 // create and store unknownmt:
jbe@138 777 lua_newtable(L);
jbe@138 778 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 779 json_regstore(L, unknownmt);
jbe@149 780 // create and store objectmt:
jbe@138 781 lua_newtable(L);
jbe@138 782 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 783 json_regstore(L, objectmt);
jbe@149 784 // create and store arraymt:
jbe@138 785 lua_newtable(L);
jbe@138 786 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 787 json_regstore(L, arraymt);
jbe@149 788 // create and store ephemeron table to store shadow tables for each JSON object/array
jbe@149 789 // to allow NULL values returned as nil
jbe@149 790 lua_newtable(L);
jbe@138 791 lua_newtable(L); // metatable for ephemeron table
jbe@121 792 lua_pushliteral(L, "__mode");
jbe@121 793 lua_pushliteral(L, "k");
jbe@138 794 lua_rawset(L, -3);
jbe@138 795 lua_setmetatable(L, -2);
jbe@144 796 json_regstore(L, shadowtbl);
jbe@149 797 // return library module stored on lowest stack position:
jbe@138 798 lua_settop(L, 1);
jbe@121 799 return 1;
jbe@121 800 }

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