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annotate libraries/json/json.c @ 155:185e944182cb

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Better C macros for null-marker in JSON library
author jbe
date Thu Jul 31 03:18:04 2014 +0200 (2014-07-31)
parents c8669dde9ce2
children 004d2d50419e
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@154 5 #include <math.h>
jbe@121 6
jbe@144 7 // maximum number of nested JSON values (objects and arrays):
jbe@150 8 // NOTE: The Lua reference states that the stack may typically contain at least
jbe@150 9 // "a few thousand elements". Since every nested level consumes
jbe@150 10 // 3 elements on the Lua stack (the object/array, its shadow table,
jbe@150 11 // a string key or a placeholder), we limit the number of nested levels
jbe@150 12 // to 500. If a stack overflow would still happen in the import function,
jbe@150 13 // this is detected nevertheless and an error is thrown (instead of
jbe@150 14 // returning nil and an error string).
jbe@150 15 #define JSON_MAXDEPTH 500
jbe@142 16
jbe@155 17 // generate dummy memory addresses that represents null values:
jbe@155 18 char json_nullmark;
jbe@155 19 #define json_isnullmark(L, i) (lua_touserdata((L), (i)) == &json_nullmark)
jbe@155 20 #define json_pushnullmark(L) lua_pushlightuserdata((L), &json_nullmark)
jbe@155 21
jbe@144 22 // macros for usage of Lua registry:
jbe@144 23 #define JSON_REGENT char
jbe@145 24 #define JSON_REGPOINTER void *
jbe@145 25 #define json_regpointer(x) (&json_registry.x)
jbe@151 26 #define json_regfetchpointer(L, x) lua_rawgetp((L), LUA_REGISTRYINDEX, (x))
jbe@151 27 #define json_regfetch(L, x) json_regfetchpointer(L, json_regpointer(x))
jbe@151 28 #define json_regstore(L, x) lua_rawsetp(L, LUA_REGISTRYINDEX, json_regpointer(x))
jbe@145 29
jbe@144 30 // generate dummy memory addresses that represent Lua objects
jbe@145 31 // via lightuserdata keys and LUA_REGISTRYINDEX:
jbe@144 32 static struct {
jbe@145 33 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
jbe@145 34 JSON_REGENT unknownmt; // metatable for tables that may be either JSON objects or JSON arrays
jbe@145 35 JSON_REGENT objectmt; // metatable for JSON objects
jbe@145 36 JSON_REGENT arraymt; // metatable for JSON arrays
jbe@144 37 } json_registry;
jbe@138 38
jbe@145 39 // marks a Lua table as JSON object or JSON array:
jbe@136 40 // (returns its modified argument or a new table if argument is nil)
jbe@145 41 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
jbe@145 42 // check if argument is nil
jbe@136 43 if (lua_isnoneornil(L, 1)) {
jbe@145 44 // create new table at stack position 1:
jbe@136 45 lua_settop(L, 0);
jbe@136 46 lua_newtable(L);
jbe@145 47 // create shadow table (leaving previously created table on stack position 1):
jbe@144 48 json_regfetch(L, shadowtbl);
jbe@136 49 lua_pushvalue(L, 1);
jbe@136 50 lua_newtable(L);
jbe@143 51 lua_rawset(L, -3);
jbe@143 52 } else {
jbe@145 53 // push shadow table on top of stack:
jbe@144 54 json_regfetch(L, shadowtbl);
jbe@143 55 lua_pushvalue(L, 1);
jbe@143 56 lua_rawget(L, -2);
jbe@145 57 // if shadow table does not exist:
jbe@143 58 if (lua_isnil(L, -1)) {
jbe@145 59 // create shadow table and leave it on top of stack:
jbe@143 60 lua_newtable(L);
jbe@143 61 lua_pushvalue(L, 1);
jbe@143 62 lua_pushvalue(L, -2);
jbe@143 63 lua_rawset(L, -5);
jbe@143 64 }
jbe@145 65 // move elements from original table to shadow table (that's expected on top of stack):
jbe@143 66 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@143 67 lua_pushvalue(L, -2);
jbe@143 68 lua_pushnil(L);
jbe@143 69 lua_rawset(L, 1);
jbe@143 70 lua_pushvalue(L, -2);
jbe@143 71 lua_pushvalue(L, -2);
jbe@143 72 lua_rawset(L, -5);
jbe@143 73 }
jbe@136 74 }
jbe@138 75 // discard everything but table to return:
jbe@138 76 lua_settop(L, 1);
jbe@136 77 // set metatable:
jbe@145 78 json_regfetchpointer(L, mt);
jbe@136 79 lua_setmetatable(L, 1);
jbe@138 80 // return table:
jbe@136 81 return 1;
jbe@136 82 }
jbe@136 83
jbe@136 84 // marks a table as JSON object:
jbe@136 85 // (returns its modified argument or a new table if argument is nil)
jbe@136 86 static int json_object(lua_State *L) {
jbe@145 87 return json_mark(L, json_regpointer(objectmt));
jbe@136 88 }
jbe@136 89
jbe@136 90 // marks a table as JSON array:
jbe@136 91 // (returns its modified argument or a new table if argument is nil)
jbe@136 92 static int json_array(lua_State *L) {
jbe@145 93 return json_mark(L, json_regpointer(arraymt));
jbe@136 94 }
jbe@136 95
jbe@145 96 // internal states of JSON parser:
jbe@124 97 #define JSON_STATE_VALUE 0
jbe@124 98 #define JSON_STATE_OBJECT_KEY 1
jbe@124 99 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
jbe@124 100 #define JSON_STATE_OBJECT_VALUE 3
jbe@124 101 #define JSON_STATE_OBJECT_SEPARATOR 4
jbe@124 102 #define JSON_STATE_ARRAY_VALUE 5
jbe@124 103 #define JSON_STATE_ARRAY_SEPARATOR 6
jbe@124 104 #define JSON_STATE_END 7
jbe@121 105
jbe@145 106 // special Lua stack indicies for json_import function:
jbe@138 107 #define json_import_objectmt_idx 2
jbe@138 108 #define json_import_arraymt_idx 3
jbe@138 109 #define json_import_shadowtbl_idx 4
jbe@138 110
jbe@136 111 // decodes a JSON document:
jbe@121 112 static int json_import(lua_State *L) {
jbe@136 113 const char *str; // string to parse
jbe@136 114 size_t total; // total length of string to parse
jbe@136 115 size_t pos = 0; // current position in string to parse
jbe@136 116 size_t level = 0; // nested levels of objects/arrays currently being processed
jbe@145 117 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
jbe@136 118 char c; // variable to store a single character to be processed
jbe@145 119 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
jbe@145 120 char *cbuf; // C buffer to decode JSON string values
jbe@136 121 size_t writepos; // write position of decoded strings in C buffer
jbe@152 122 size_t arraylen; // variable to temporarily store the array length
jbe@147 123 // stack shall contain one function argument:
jbe@138 124 lua_settop(L, 1);
jbe@147 125 // push objectmt onto stack position 2:
jbe@144 126 json_regfetch(L, objectmt);
jbe@147 127 // push arraymt onto stack position 3:
jbe@144 128 json_regfetch(L, arraymt);
jbe@147 129 // push shadowtbl onto stack position 4:
jbe@144 130 json_regfetch(L, shadowtbl);
jbe@136 131 // require string as first argument:
jbe@136 132 str = luaL_checklstring(L, 1, &total);
jbe@136 133 // if string contains a NULL byte, this is a syntax error
jbe@136 134 if (strlen(str) != total) goto json_import_syntax_error;
jbe@136 135 // main loop of parser:
jbe@136 136 json_import_loop:
jbe@136 137 // skip whitespace and store next character in variable 'c':
jbe@146 138 while (c = str[pos],
jbe@146 139 c == ' ' ||
jbe@146 140 c == '\f' ||
jbe@146 141 c == '\n' ||
jbe@146 142 c == '\r' ||
jbe@146 143 c == '\t' ||
jbe@146 144 c == '\v'
jbe@146 145 ) pos++;
jbe@136 146 // switch statement to handle certain (single) characters:
jbe@121 147 switch (c) {
jbe@136 148 // handle end of JSON document:
jbe@121 149 case 0:
jbe@136 150 // if end of JSON document was expected, then return top element of stack as result:
jbe@124 151 if (mode == JSON_STATE_END) return 1;
jbe@136 152 // otherwise, the JSON document was malformed:
jbe@121 153 json_import_unexpected_eof:
jbe@121 154 lua_pushnil(L);
jbe@121 155 if (level == 0) lua_pushliteral(L, "Empty string");
jbe@121 156 else lua_pushliteral(L, "Unexpected end of JSON document");
jbe@121 157 return 2;
jbe@136 158 // new JSON object:
jbe@121 159 case '{':
jbe@136 160 // if a JSON object is not expected here, then return an error:
jbe@146 161 if (
jbe@146 162 mode != JSON_STATE_VALUE &&
jbe@146 163 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 164 mode != JSON_STATE_ARRAY_VALUE
jbe@146 165 ) goto json_import_syntax_error;
jbe@136 166 // create JSON object on stack:
jbe@136 167 lua_newtable(L);
jbe@136 168 // set metatable of JSON object:
jbe@138 169 lua_pushvalue(L, json_import_objectmt_idx);
jbe@125 170 lua_setmetatable(L, -2);
jbe@136 171 // create internal shadow table on stack:
jbe@136 172 lua_newtable(L);
jbe@146 173 // register internal shadow table:
jbe@123 174 lua_pushvalue(L, -2);
jbe@123 175 lua_pushvalue(L, -2);
jbe@138 176 lua_rawset(L, json_import_shadowtbl_idx);
jbe@146 177 // expect object key (or end of object) to follow:
jbe@136 178 mode = JSON_STATE_OBJECT_KEY;
jbe@146 179 // jump to common code for opening JSON object and JSON array:
jbe@142 180 goto json_import_open;
jbe@136 181 // new JSON array:
jbe@121 182 case '[':
jbe@136 183 // if a JSON array is not expected here, then return an error:
jbe@146 184 if (
jbe@146 185 mode != JSON_STATE_VALUE &&
jbe@146 186 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 187 mode != JSON_STATE_ARRAY_VALUE
jbe@146 188 ) goto json_import_syntax_error;
jbe@136 189 // create JSON array on stack:
jbe@136 190 lua_newtable(L);
jbe@136 191 // set metatable of JSON array:
jbe@138 192 lua_pushvalue(L, json_import_arraymt_idx);
jbe@125 193 lua_setmetatable(L, -2);
jbe@136 194 // create internal shadow table on stack:
jbe@136 195 lua_newtable(L);
jbe@146 196 // register internal shadow table:
jbe@123 197 lua_pushvalue(L, -2);
jbe@123 198 lua_pushvalue(L, -2);
jbe@138 199 lua_rawset(L, json_import_shadowtbl_idx);
jbe@140 200 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
jbe@140 201 lua_pushnil(L);
jbe@146 202 // expect array value (or end of array) to follow:
jbe@142 203 mode = JSON_STATE_ARRAY_VALUE;
jbe@142 204 // continue with common code for opening JSON object and JSON array:
jbe@146 205 // common code for opening JSON object or JSON array:
jbe@142 206 json_import_open:
jbe@142 207 // limit nested levels:
jbe@142 208 if (level >= JSON_MAXDEPTH) {
jbe@142 209 lua_pushnil(L);
jbe@142 210 lua_pushliteral(L, "Too many nested JSON levels");
jbe@142 211 return 2;
jbe@142 212 }
jbe@142 213 // additional buffer overflow protection:
jbe@142 214 if (!lua_checkstack(L, LUA_MINSTACK))
jbe@142 215 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
jbe@136 216 // increment level:
jbe@121 217 level++;
jbe@142 218 // consume input character:
jbe@142 219 pos++;
jbe@121 220 goto json_import_loop;
jbe@136 221 // end of JSON object:
jbe@121 222 case '}':
jbe@136 223 // if end of JSON object is not expected here, then return an error:
jbe@146 224 if (
jbe@146 225 mode != JSON_STATE_OBJECT_KEY &&
jbe@146 226 mode != JSON_STATE_OBJECT_SEPARATOR
jbe@146 227 ) goto json_import_syntax_error;
jbe@136 228 // jump to common code for end of JSON object and JSON array:
jbe@121 229 goto json_import_close;
jbe@136 230 // end of JSON array:
jbe@121 231 case ']':
jbe@136 232 // if end of JSON array is not expected here, then return an error:
jbe@146 233 if (
jbe@146 234 mode != JSON_STATE_ARRAY_VALUE &&
jbe@146 235 mode != JSON_STATE_ARRAY_SEPARATOR
jbe@146 236 ) goto json_import_syntax_error;
jbe@146 237 // pop nil key/magic (that was needed to keep stack balance):
jbe@140 238 lua_pop(L, 1);
jbe@136 239 // continue with common code for end of JSON object and JSON array:
jbe@136 240 // common code for end of JSON object or JSON array:
jbe@121 241 json_import_close:
jbe@136 242 // consume input character:
jbe@121 243 pos++;
jbe@136 244 // pop shadow table:
jbe@136 245 lua_pop(L, 1);
jbe@136 246 // check if nested:
jbe@121 247 if (--level) {
jbe@146 248 // if nested,
jbe@146 249 // check if outer(!) structure is an array or object:
jbe@140 250 if (lua_isnil(L, -2)) {
jbe@136 251 // select array value processing:
jbe@124 252 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 253 } else {
jbe@136 254 // select object value processing:
jbe@124 255 mode = JSON_STATE_OBJECT_VALUE;
jbe@121 256 }
jbe@136 257 // store value in outer structure:
jbe@121 258 goto json_import_process_value;
jbe@121 259 }
jbe@136 260 // if not nested, then expect end of JSON document and continue with loop:
jbe@136 261 mode = JSON_STATE_END;
jbe@121 262 goto json_import_loop;
jbe@136 263 // key terminator:
jbe@121 264 case ':':
jbe@136 265 // if key terminator is not expected here, then return an error:
jbe@124 266 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
jbe@121 267 goto json_import_syntax_error;
jbe@136 268 // consume input character:
jbe@121 269 pos++;
jbe@146 270 // expect object value to follow:
jbe@124 271 mode = JSON_STATE_OBJECT_VALUE;
jbe@146 272 // continue with loop:
jbe@121 273 goto json_import_loop;
jbe@136 274 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
jbe@121 275 case ',':
jbe@146 276 // branch according to parser state:
jbe@124 277 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
jbe@146 278 // expect an object key to follow:
jbe@124 279 mode = JSON_STATE_OBJECT_KEY;
jbe@124 280 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
jbe@146 281 // expect an array value to follow:
jbe@124 282 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 283 } else {
jbe@136 284 // if value terminator is not expected here, then return an error:
jbe@136 285 goto json_import_syntax_error;
jbe@121 286 }
jbe@136 287 // consume input character:
jbe@121 288 pos++;
jbe@136 289 // continue with loop:
jbe@121 290 goto json_import_loop;
jbe@136 291 // string literal:
jbe@121 292 case '"':
jbe@146 293 // consume quote character:
jbe@146 294 pos++;
jbe@136 295 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
jbe@121 296 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
jbe@121 297 writepos = 0;
jbe@146 298 // loop through the characters until encountering end quote:
jbe@121 299 while ((c = str[pos++]) != '"') {
jbe@121 300 if (c == 0) {
jbe@146 301 // handle unexpected end of JSON document:
jbe@121 302 goto json_import_unexpected_eof;
jbe@121 303 } else if (c < 32 || c == 127) {
jbe@136 304 // do not allow ASCII control characters:
jbe@136 305 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
jbe@136 306 // by this parser to allow different encodings than Unicode
jbe@121 307 lua_pushnil(L);
jbe@121 308 lua_pushliteral(L, "Unexpected control character in JSON string");
jbe@121 309 return 2;
jbe@121 310 } else if (c == '\\') {
jbe@136 311 // read next char after backslash escape:
jbe@121 312 c = str[pos++];
jbe@121 313 switch (c) {
jbe@136 314 // unexpected end-of-string:
jbe@121 315 case 0:
jbe@121 316 goto json_import_unexpected_eof;
jbe@136 317 // unescaping of quotation mark, slash, and backslash:
jbe@121 318 case '"':
jbe@121 319 case '/':
jbe@121 320 case '\\':
jbe@121 321 cbuf[writepos++] = c;
jbe@121 322 break;
jbe@136 323 // unescaping of backspace:
jbe@146 324 case 'b': cbuf[writepos++] = '\b'; break;
jbe@136 325 // unescaping of form-feed:
jbe@146 326 case 'f': cbuf[writepos++] = '\f'; break;
jbe@136 327 // unescaping of new-line:
jbe@146 328 case 'n': cbuf[writepos++] = '\n'; break;
jbe@136 329 // unescaping of carriage-return:
jbe@146 330 case 'r': cbuf[writepos++] = '\r'; break;
jbe@136 331 // unescaping of tabulator:
jbe@146 332 case 't': cbuf[writepos++] = '\t'; break;
jbe@136 333 // unescaping of UTF-16 characters
jbe@121 334 case 'u':
jbe@121 335 lua_pushnil(L);
jbe@121 336 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
jbe@121 337 return 2;
jbe@136 338 // unexpected escape sequence:
jbe@121 339 default:
jbe@121 340 lua_pushnil(L);
jbe@121 341 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
jbe@121 342 return 2;
jbe@121 343 }
jbe@121 344 } else {
jbe@136 345 // normal character:
jbe@121 346 cbuf[writepos++] = c;
jbe@121 347 }
jbe@121 348 }
jbe@136 349 // process buffer to Lua string:
jbe@121 350 luaL_pushresultsize(&luabuf, writepos);
jbe@136 351 // continue with processing of decoded string:
jbe@121 352 goto json_import_process_value;
jbe@121 353 }
jbe@136 354 // process values whose type is is not deducible from a single character:
jbe@136 355 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
jbe@146 356 // for numbers,
jbe@146 357 // use strtod() call to parse a (double precision) floating point number:
jbe@122 358 char *endptr;
jbe@122 359 double numval;
jbe@122 360 numval = strtod(str+pos, &endptr);
jbe@146 361 // catch parsing errors:
jbe@122 362 if (endptr == str+pos) goto json_import_syntax_error;
jbe@146 363 // consume characters that were parsed:
jbe@122 364 pos += endptr - (str+pos);
jbe@146 365 // push parsed (double precision) floating point number on Lua stack:
jbe@122 366 lua_pushnumber(L, numval);
jbe@122 367 } else if (!strncmp(str+pos, "true", 4)) {
jbe@136 368 // consume 4 input characters for "true":
jbe@121 369 pos += 4;
jbe@147 370 // put Lua true value onto stack:
jbe@136 371 lua_pushboolean(L, 1);
jbe@121 372 } else if (!strncmp(str+pos, "false", 5)) {
jbe@136 373 // consume 5 input characters for "false":
jbe@121 374 pos += 5;
jbe@147 375 // put Lua false value onto stack:
jbe@136 376 lua_pushboolean(L, 0);
jbe@121 377 } else if (!strncmp(str+pos, "null", 4)) {
jbe@136 378 // consume 4 input characters for "null":
jbe@136 379 pos += 4;
jbe@153 380 // different behavor for top-level and sub-levels:
jbe@153 381 if (level) {
jbe@153 382 // if sub-level,
jbe@153 383 // push special null-marker onto stack:
jbe@155 384 json_pushnullmark(L);
jbe@153 385 } else {
jbe@153 386 // if top-level,
jbe@153 387 // push nil onto stack:
jbe@153 388 lua_pushnil(L);
jbe@153 389 }
jbe@121 390 } else {
jbe@136 391 // all other cases are a syntax error:
jbe@121 392 goto json_import_syntax_error;
jbe@121 393 }
jbe@136 394 // process a decoded value or key value pair (expected on top of Lua stack):
jbe@136 395 json_import_process_value:
jbe@121 396 switch (mode) {
jbe@136 397 // an object key has been read:
jbe@124 398 case JSON_STATE_OBJECT_KEY:
jbe@136 399 // if an object key is not a string, then this is a syntax error:
jbe@121 400 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
jbe@146 401 // expect key terminator to follow:
jbe@124 402 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
jbe@146 403 // continue with loop:
jbe@121 404 goto json_import_loop;
jbe@136 405 // a key value pair has been read:
jbe@124 406 case JSON_STATE_OBJECT_VALUE:
jbe@136 407 // store key value pair in outer shadow table:
jbe@130 408 lua_rawset(L, -3);
jbe@146 409 // expect value terminator (or end of object) to follow:
jbe@124 410 mode = JSON_STATE_OBJECT_SEPARATOR;
jbe@146 411 // continue with loop:
jbe@121 412 goto json_import_loop;
jbe@136 413 // an array value has been read:
jbe@124 414 case JSON_STATE_ARRAY_VALUE:
jbe@152 415 // get current array length:
jbe@152 416 arraylen = lua_rawlen(L, -3);
jbe@152 417 // throw error if array would exceed INT_MAX elements:
jbe@152 418 // TODO: Lua 5.3 may support more elements
jbe@152 419 if (arraylen >= INT_MAX) {
jbe@152 420 lua_pushnil(L);
jbe@152 421 lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
jbe@152 422 }
jbe@136 423 // store value in outer shadow table:
jbe@152 424 lua_rawseti(L, -3, arraylen + 1);
jbe@146 425 // expect value terminator (or end of object) to follow:
jbe@124 426 mode = JSON_STATE_ARRAY_SEPARATOR;
jbe@146 427 // continue with loop
jbe@121 428 goto json_import_loop;
jbe@136 429 // a single value has been read:
jbe@124 430 case JSON_STATE_VALUE:
jbe@136 431 // leave value on top of stack, expect end of JSON document, and continue with loop:
jbe@124 432 mode = JSON_STATE_END;
jbe@121 433 goto json_import_loop;
jbe@121 434 }
jbe@146 435 // syntax error handling (reachable by goto statement):
jbe@136 436 json_import_syntax_error:
jbe@121 437 lua_pushnil(L);
jbe@121 438 lua_pushliteral(L, "Syntax error in JSON document");
jbe@121 439 return 2;
jbe@121 440 }
jbe@121 441
jbe@146 442 // special Lua stack indicies for json_path function:
jbe@138 443 #define json_path_shadowtbl_idx 1
jbe@146 444
jbe@146 445 // stack offset of arguments to json_path function:
jbe@155 446 #define json_path_idxshift 1
jbe@138 447
jbe@146 448 // gets a value or its type from a JSON document (passed as first argument)
jbe@147 449 // using a path (passed as variable number of keys after first argument):
jbe@137 450 static int json_path(lua_State *L, int type_mode) {
jbe@146 451 int stacktop; // stack index of top of stack (after shifting)
jbe@146 452 int idx = 2 + json_path_idxshift; // stack index of current argument to process
jbe@148 453 // insert shadowtbl into stack at position 1 (shifting the arguments):
jbe@144 454 json_regfetch(L, shadowtbl);
jbe@138 455 lua_insert(L, 1);
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@155 495 if (json_isnullmark(L, -1)) 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@155 499 if (json_isnullmark(L, -1)) {
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@155 602 json_pushnullmark(L);
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@130 622 static int json_index(lua_State *L) {
jbe@148 623 // stack shall contain two function arguments:
jbe@130 624 lua_settop(L, 2);
jbe@155 625 // get corresponding shadow table for first argument:
jbe@144 626 json_regfetch(L, shadowtbl);
jbe@130 627 lua_pushvalue(L, 1);
jbe@155 628 lua_rawget(L, -2);
jbe@148 629 // throw error if no shadow table was found:
jbe@139 630 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 631 // use key passed as second argument to lookup value in shadow table:
jbe@130 632 lua_pushvalue(L, 2);
jbe@130 633 lua_rawget(L, -2);
jbe@148 634 // if value is null-marker, then push nil onto stack:
jbe@155 635 if (json_isnullmark(L, -1)) lua_pushnil(L);
jbe@148 636 // return either looked up value, or nil
jbe@127 637 return 1;
jbe@127 638 }
jbe@127 639
jbe@130 640 static int json_newindex(lua_State *L) {
jbe@148 641 // stack shall contain three function arguments:
jbe@130 642 lua_settop(L, 3);
jbe@148 643 // get corresponding shadow table for first argument:
jbe@144 644 json_regfetch(L, shadowtbl);
jbe@123 645 lua_pushvalue(L, 1);
jbe@143 646 lua_rawget(L, -2);
jbe@148 647 // throw error if no shadow table was found:
jbe@130 648 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 649 // replace first argument with shadow table:
jbe@130 650 lua_replace(L, 1);
jbe@148 651 // reset stack and use second and third argument to write to shadow table:
jbe@139 652 lua_settop(L, 3);
jbe@130 653 lua_rawset(L, 1);
jbe@148 654 // return nothing:
jbe@148 655 return 0;
jbe@121 656 }
jbe@121 657
jbe@135 658 static int json_pairs_iterfunc(lua_State *L) {
jbe@149 659 // stack shall contain two function arguments:
jbe@135 660 lua_settop(L, 2);
jbe@155 661 // get corresponding shadow table for first argument:
jbe@144 662 json_regfetch(L, shadowtbl);
jbe@135 663 lua_pushvalue(L, 1);
jbe@155 664 lua_rawget(L, -2);
jbe@149 665 // throw error if no shadow table was found:
jbe@135 666 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 667 // get next key value pair from shadow table (using previous key from argument 2)
jbe@149 668 // and return nothing if there is no next pair:
jbe@135 669 lua_pushvalue(L, 2);
jbe@135 670 if (!lua_next(L, -2)) return 0;
jbe@149 671 // replace null-marker with nil:
jbe@155 672 if (json_isnullmark(L, -1)) {
jbe@135 673 lua_pop(L, 1);
jbe@135 674 lua_pushnil(L);
jbe@135 675 }
jbe@149 676 // return key and value (or key and nil, if null-marker was found):
jbe@135 677 return 2;
jbe@135 678 }
jbe@135 679
jbe@149 680 // returns a triple such that 'for key, value in pairs(obj) do ... end'
jbe@149 681 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
jbe@135 682 static int json_pairs(lua_State *L) {
jbe@149 683 // return triple of function json_pairs_iterfunc, first argument, and nil:
jbe@139 684 lua_pushcfunction(L, json_pairs_iterfunc);
jbe@135 685 lua_pushvalue(L, 1);
jbe@135 686 lua_pushnil(L);
jbe@135 687 return 3;
jbe@135 688 }
jbe@135 689
jbe@134 690 static int json_ipairs_iterfunc(lua_State *L) {
jbe@152 691 lua_Integer idx;
jbe@149 692 // stack shall contain two function arguments:
jbe@134 693 lua_settop(L, 2);
jbe@149 694 // calculate new index by incrementing second argument:
jbe@134 695 idx = lua_tointeger(L, 2) + 1;
jbe@149 696 // get corresponding shadow table for first argument:
jbe@155 697 json_regfetch(L, shadowtbl);
jbe@134 698 lua_pushvalue(L, 1);
jbe@155 699 lua_rawget(L, -2);
jbe@149 700 // throw error if no shadow table was found:
jbe@134 701 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 702 // do integer lookup in shadow table:
jbe@134 703 lua_rawgeti(L, -1, idx);
jbe@149 704 // return nothing if there was no value:
jbe@134 705 if (lua_isnil(L, -1)) return 0;
jbe@149 706 // return new index and
jbe@149 707 // either the looked up value if it is not equal to the null-marker
jbe@149 708 // or nil instead of null-marker:
jbe@134 709 lua_pushinteger(L, idx);
jbe@155 710 if (json_isnullmark(L, -2)) lua_pushnil(L);
jbe@134 711 else lua_pushvalue(L, -2);
jbe@134 712 return 2;
jbe@134 713 }
jbe@134 714
jbe@149 715 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
jbe@149 716 // iterates through all values (including JSON null represented as Lua nil):
jbe@134 717 static int json_ipairs(lua_State *L) {
jbe@149 718 // return triple of function json_ipairs_iterfunc, first argument, and zero:
jbe@139 719 lua_pushcfunction(L, json_ipairs_iterfunc);
jbe@134 720 lua_pushvalue(L, 1);
jbe@134 721 lua_pushinteger(L, 0);
jbe@134 722 return 3;
jbe@134 723 }
jbe@134 724
jbe@154 725 #define JSON_TABLETYPE_UNKNOWN 0
jbe@154 726 #define JSON_TABLETYPE_OBJECT 1
jbe@154 727 #define JSON_TABLETYPE_ARRAY 2
jbe@154 728
jbe@154 729 static int json_export(lua_State *L) {
jbe@154 730 lua_Number num;
jbe@154 731 const char *str;
jbe@154 732 unsigned char c;
jbe@154 733 size_t strlen;
jbe@154 734 size_t pos = 0;
jbe@154 735 luaL_Buffer buf;
jbe@154 736 char hexcode[7]; // backslash, character 'u', 4 hex digits, and terminating NULL byte
jbe@154 737 int luatype;
jbe@154 738 int tabletype = JSON_TABLETYPE_UNKNOWN;
jbe@154 739 int needsep = 0;
jbe@154 740 lua_Integer idx;
jbe@154 741 lua_settop(L, 1);
jbe@154 742 switch (lua_type(L, 1)) {
jbe@154 743 case LUA_TNIL:
jbe@154 744 lua_pushliteral(L, "null");
jbe@154 745 return 1;
jbe@154 746 case LUA_TNUMBER:
jbe@154 747 num = lua_tonumber(L, 1);
jbe@154 748 if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
jbe@154 749 if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
jbe@154 750 lua_tostring(L, 1);
jbe@154 751 return 1;
jbe@154 752 case LUA_TBOOLEAN:
jbe@154 753 if (lua_toboolean(L, 1)) lua_pushliteral(L, "true");
jbe@154 754 else lua_pushliteral(L, "false");
jbe@154 755 return 1;
jbe@154 756 case LUA_TSTRING:
jbe@154 757 str = lua_tolstring(L, 1, &strlen);
jbe@154 758 luaL_buffinit(L, &buf);
jbe@154 759 luaL_addchar(&buf, '"');
jbe@154 760 while (pos < strlen) {
jbe@154 761 c = str[pos++];
jbe@154 762 if (c == '"') luaL_addstring(&buf, "\\\"");
jbe@154 763 else if (c == '\\') luaL_addstring(&buf, "\\\\");
jbe@154 764 else if (c == 127) luaL_addstring(&buf, "\\u007F");
jbe@154 765 else if (c >= 32) luaL_addchar(&buf, c);
jbe@154 766 else if (c == '\b') luaL_addstring(&buf, "\\b");
jbe@154 767 else if (c == '\f') luaL_addstring(&buf, "\\f");
jbe@154 768 else if (c == '\n') luaL_addstring(&buf, "\\n");
jbe@154 769 else if (c == '\r') luaL_addstring(&buf, "\\r");
jbe@154 770 else if (c == '\t') luaL_addstring(&buf, "\\t");
jbe@154 771 else if (c == '\v') luaL_addstring(&buf, "\\v");
jbe@154 772 else {
jbe@154 773 sprintf(hexcode, "\\u%04X", c);
jbe@154 774 luaL_addstring(&buf, hexcode);
jbe@154 775 }
jbe@154 776 }
jbe@154 777 luaL_addchar(&buf, '"');
jbe@154 778 luaL_pushresult(&buf);
jbe@154 779 return 1;
jbe@154 780 case LUA_TTABLE:
jbe@154 781 if (lua_getmetatable(L, 1)) {
jbe@154 782 json_regfetch(L, objectmt);
jbe@154 783 if (lua_rawequal(L, -2, -1)) {
jbe@154 784 tabletype = JSON_TABLETYPE_OBJECT;
jbe@154 785 } else {
jbe@154 786 json_regfetch(L, arraymt);
jbe@154 787 if (lua_rawequal(L, -3, -1)) tabletype = JSON_TABLETYPE_ARRAY;
jbe@154 788 }
jbe@154 789 }
jbe@154 790 json_regfetch(L, shadowtbl);
jbe@154 791 lua_pushvalue(L, 1);
jbe@154 792 lua_rawget(L, -2);
jbe@154 793 if (!lua_isnil(L, -1)) lua_replace(L, 1);
jbe@154 794 lua_settop(L, 1);
jbe@154 795 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
jbe@154 796 for (lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@154 797 luatype = lua_type(L, -2);
jbe@154 798 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
jbe@154 799 if (luatype == LUA_TSTRING) tabletype = JSON_TABLETYPE_OBJECT;
jbe@154 800 else if (luatype == LUA_TNUMBER) tabletype = JSON_TABLETYPE_ARRAY;
jbe@154 801 } else if (
jbe@154 802 (tabletype == JSON_TABLETYPE_OBJECT && luatype == LUA_TNUMBER) ||
jbe@154 803 (tabletype == JSON_TABLETYPE_ARRAY && luatype == LUA_TSTRING)
jbe@154 804 ) {
jbe@154 805 goto json_export_tabletype_error;
jbe@154 806 }
jbe@154 807 }
jbe@154 808 }
jbe@154 809 switch (tabletype) {
jbe@154 810 case JSON_TABLETYPE_OBJECT:
jbe@154 811 lua_settop(L, 3);
jbe@154 812 luaL_buffinit(L, &buf);
jbe@154 813 luaL_addchar(&buf, '{');
jbe@154 814 for (lua_pushnil(L); lua_next(L, 1); ) {
jbe@154 815 if (lua_type(L, -2) == LUA_TSTRING) {
jbe@154 816 lua_replace(L, 3);
jbe@154 817 lua_replace(L, 2);
jbe@154 818 if (needsep) luaL_addchar(&buf, ',');
jbe@154 819 else needsep = 1;
jbe@154 820 lua_pushcfunction(L, json_export);
jbe@154 821 lua_pushvalue(L, 2);
jbe@154 822 lua_call(L, 1, 1);
jbe@154 823 luaL_addvalue(&buf);
jbe@154 824 luaL_addchar(&buf, ':');
jbe@155 825 if (json_isnullmark(L, 3)) {
jbe@154 826 luaL_addstring(&buf, "null");
jbe@154 827 } else {
jbe@154 828 lua_pushcfunction(L, json_export);
jbe@154 829 lua_pushvalue(L, 3);
jbe@154 830 lua_call(L, 1, 1);
jbe@154 831 luaL_addvalue(&buf);
jbe@154 832 }
jbe@154 833 lua_pushvalue(L, 2);
jbe@154 834 } else {
jbe@154 835 lua_pop(L, 1);
jbe@154 836 }
jbe@154 837 }
jbe@154 838 luaL_addchar(&buf, '}');
jbe@154 839 luaL_pushresult(&buf);
jbe@154 840 return 1;
jbe@154 841 case JSON_TABLETYPE_ARRAY:
jbe@154 842 lua_settop(L, 2);
jbe@154 843 luaL_buffinit(L, &buf);
jbe@154 844 luaL_addchar(&buf, '[');
jbe@154 845 for (idx = 1; ; idx++) {
jbe@154 846 lua_rawgeti(L, 1, idx);
jbe@154 847 if (lua_isnil(L, -1)) {
jbe@154 848 lua_pop(L, 1);
jbe@154 849 break;
jbe@154 850 }
jbe@154 851 lua_replace(L, 2);
jbe@154 852 if (needsep) luaL_addchar(&buf, ',');
jbe@154 853 else needsep = 1;
jbe@154 854 lua_pushcfunction(L, json_export);
jbe@154 855 lua_pushvalue(L, 2);
jbe@154 856 lua_call(L, 1, 1);
jbe@154 857 luaL_addvalue(&buf);
jbe@154 858 }
jbe@154 859 luaL_addchar(&buf, ']');
jbe@154 860 luaL_pushresult(&buf);
jbe@154 861 return 1;
jbe@154 862 }
jbe@154 863 json_export_tabletype_error:
jbe@154 864 return luaL_error(L, "JSON export not possible for ambiguous table (cannot decide whether it is an object or array)");
jbe@154 865 }
jbe@154 866 return luaL_error(L, "JSON export not possible for values of type \"%s\"", lua_typename(L, lua_type(L, 1)));
jbe@154 867 }
jbe@154 868
jbe@149 869 // functions in library module:
jbe@121 870 static const struct luaL_Reg json_module_functions[] = {
jbe@133 871 {"object", json_object},
jbe@133 872 {"array", json_array},
jbe@121 873 {"import", json_import},
jbe@154 874 {"export", json_export},
jbe@130 875 {"get", json_get},
jbe@127 876 {"type", json_type},
jbe@123 877 {"isnull", json_isnull},
jbe@131 878 {"setnull", json_setnull},
jbe@121 879 {NULL, NULL}
jbe@121 880 };
jbe@121 881
jbe@149 882 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
jbe@126 883 static const struct luaL_Reg json_metatable_functions[] = {
jbe@130 884 {"__len", json_len},
jbe@130 885 {"__index", json_index},
jbe@130 886 {"__newindex", json_newindex},
jbe@135 887 {"__pairs", json_pairs},
jbe@134 888 {"__ipairs", json_ipairs},
jbe@126 889 {NULL, NULL}
jbe@126 890 };
jbe@126 891
jbe@149 892 // initializes json library:
jbe@121 893 int luaopen_json(lua_State *L) {
jbe@149 894 // empty stack:
jbe@126 895 lua_settop(L, 0);
jbe@149 896 // push library module onto stack position 1:
jbe@149 897 lua_newtable(L);
jbe@149 898 // register library functions:
jbe@149 899 luaL_setfuncs(L, json_module_functions, 0);
jbe@149 900 // create and store unknownmt:
jbe@138 901 lua_newtable(L);
jbe@138 902 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 903 json_regstore(L, unknownmt);
jbe@149 904 // create and store objectmt:
jbe@138 905 lua_newtable(L);
jbe@138 906 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 907 json_regstore(L, objectmt);
jbe@149 908 // create and store arraymt:
jbe@138 909 lua_newtable(L);
jbe@138 910 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 911 json_regstore(L, arraymt);
jbe@149 912 // create and store ephemeron table to store shadow tables for each JSON object/array
jbe@149 913 // to allow NULL values returned as nil
jbe@149 914 lua_newtable(L);
jbe@138 915 lua_newtable(L); // metatable for ephemeron table
jbe@121 916 lua_pushliteral(L, "__mode");
jbe@121 917 lua_pushliteral(L, "k");
jbe@138 918 lua_rawset(L, -3);
jbe@138 919 lua_setmetatable(L, -2);
jbe@144 920 json_regstore(L, shadowtbl);
jbe@149 921 // return library module stored on lowest stack position:
jbe@138 922 lua_settop(L, 1);
jbe@121 923 return 1;
jbe@121 924 }

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