webmcp
view libraries/json/json.c @ 145:0edc2f05c66a
Use lightuserdata directly to store JSON null values in JSON library
| author | jbe |
|---|---|
| date | Wed Jul 30 19:59:11 2014 +0200 (2014-07-30) |
| parents | 0690fe79b673 |
| children | 7912a05ebc3f |
line source
1 #include <lua.h>
2 #include <lauxlib.h>
3 #include <stdlib.h>
4 #include <string.h>
6 // maximum number of nested JSON values (objects and arrays):
7 #define JSON_MAXDEPTH 100
9 // macros for usage of Lua registry:
10 #define JSON_REGENT char
11 #define JSON_REGPOINTER void *
12 #define json_pushlightref(L, x) (lua_pushlightuserdata((L), &json_reference.x))
13 #define json_regpointer(x) (&json_registry.x)
14 #define json_regfetchpointer(L, x) (lua_pushlightuserdata((L), (x)), lua_rawget((L), LUA_REGISTRYINDEX))
15 #define json_regfetch(L, x) (json_regfetchpointer(L, json_regpointer(x)))
16 #define json_regstore(L, x) (lua_pushlightuserdata(L, json_regpointer(x)), lua_pushvalue(L, -2), lua_rawset(L, LUA_REGISTRYINDEX));
18 // generate dummy memory addresses that represent Lua objects
19 // directly via lightuserdata values (not using the Lua registry):
20 static struct {
21 JSON_REGENT nullmark; // magic value to indicate JSON null value
22 } json_reference;
25 // generate dummy memory addresses that represent Lua objects
26 // via lightuserdata keys and LUA_REGISTRYINDEX:
27 static struct {
28 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
29 JSON_REGENT unknownmt; // metatable for tables that may be either JSON objects or JSON arrays
30 JSON_REGENT objectmt; // metatable for JSON objects
31 JSON_REGENT arraymt; // metatable for JSON arrays
32 } json_registry;
34 // marks a Lua table as JSON object or JSON array:
35 // (returns its modified argument or a new table if argument is nil)
36 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
37 // check if argument is nil
38 if (lua_isnoneornil(L, 1)) {
39 // create new table at stack position 1:
40 lua_settop(L, 0);
41 lua_newtable(L);
42 // create shadow table (leaving previously created table on stack position 1):
43 json_regfetch(L, shadowtbl);
44 lua_pushvalue(L, 1);
45 lua_newtable(L);
46 lua_rawset(L, -3);
47 } else {
48 // push shadow table on top of stack:
49 json_regfetch(L, shadowtbl);
50 lua_pushvalue(L, 1);
51 lua_rawget(L, -2);
52 // if shadow table does not exist:
53 if (lua_isnil(L, -1)) {
54 // create shadow table and leave it on top of stack:
55 lua_newtable(L);
56 lua_pushvalue(L, 1);
57 lua_pushvalue(L, -2);
58 lua_rawset(L, -5);
59 }
60 // move elements from original table to shadow table (that's expected on top of stack):
61 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
62 lua_pushvalue(L, -2);
63 lua_pushnil(L);
64 lua_rawset(L, 1);
65 lua_pushvalue(L, -2);
66 lua_pushvalue(L, -2);
67 lua_rawset(L, -5);
68 }
69 }
70 // discard everything but table to return:
71 lua_settop(L, 1);
72 // set metatable:
73 json_regfetchpointer(L, mt);
74 lua_setmetatable(L, 1);
75 // return table:
76 return 1;
77 }
79 // marks a table as JSON object:
80 // (returns its modified argument or a new table if argument is nil)
81 static int json_object(lua_State *L) {
82 return json_mark(L, json_regpointer(objectmt));
83 }
85 // marks a table as JSON array:
86 // (returns its modified argument or a new table if argument is nil)
87 static int json_array(lua_State *L) {
88 return json_mark(L, json_regpointer(arraymt));
89 }
91 // internal states of JSON parser:
92 #define JSON_STATE_VALUE 0
93 #define JSON_STATE_OBJECT_KEY 1
94 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
95 #define JSON_STATE_OBJECT_VALUE 3
96 #define JSON_STATE_OBJECT_SEPARATOR 4
97 #define JSON_STATE_ARRAY_VALUE 5
98 #define JSON_STATE_ARRAY_SEPARATOR 6
99 #define JSON_STATE_END 7
101 // special Lua stack indicies for json_import function:
102 #define json_import_objectmt_idx 2
103 #define json_import_arraymt_idx 3
104 #define json_import_shadowtbl_idx 4
105 #define json_import_nullmark_idx 5
107 // decodes a JSON document:
108 static int json_import(lua_State *L) {
109 const char *str; // string to parse
110 size_t total; // total length of string to parse
111 size_t pos = 0; // current position in string to parse
112 size_t level = 0; // nested levels of objects/arrays currently being processed
113 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
114 char c; // variable to store a single character to be processed
115 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
116 char *cbuf; // C buffer to decode JSON string values
117 size_t writepos; // write position of decoded strings in C buffer
118 // stack shall only contain one function argument:
119 lua_settop(L, 1);
120 // push objectmt on stack position 2:
121 json_regfetch(L, objectmt);
122 // push arraymt on stack position 3:
123 json_regfetch(L, arraymt);
124 // push shadowtbl on stack position 4:
125 json_regfetch(L, shadowtbl);
126 // push nullmark on stack position 5:
127 json_pushlightref(L, nullmark);
128 // require string as first argument:
129 str = luaL_checklstring(L, 1, &total);
130 // if string contains a NULL byte, this is a syntax error
131 if (strlen(str) != total) goto json_import_syntax_error;
132 // main loop of parser:
133 json_import_loop:
134 // skip whitespace and store next character in variable 'c':
135 while (c = str[pos], c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == '\f') pos++;
136 // switch statement to handle certain (single) characters:
137 switch (c) {
138 // handle end of JSON document:
139 case 0:
140 // if end of JSON document was expected, then return top element of stack as result:
141 if (mode == JSON_STATE_END) return 1;
142 // otherwise, the JSON document was malformed:
143 json_import_unexpected_eof:
144 lua_pushnil(L);
145 if (level == 0) lua_pushliteral(L, "Empty string");
146 else lua_pushliteral(L, "Unexpected end of JSON document");
147 return 2;
148 // new JSON object:
149 case '{':
150 // if a JSON object is not expected here, then return an error:
151 if (mode != JSON_STATE_VALUE && mode != JSON_STATE_OBJECT_VALUE && mode != JSON_STATE_ARRAY_VALUE)
152 goto json_import_syntax_error;
153 // create JSON object on stack:
154 lua_newtable(L);
155 // set metatable of JSON object:
156 lua_pushvalue(L, json_import_objectmt_idx);
157 lua_setmetatable(L, -2);
158 // create internal shadow table on stack:
159 lua_newtable(L);
160 // register internal shadow table (and cleanup stack afterwards):
161 lua_pushvalue(L, -2);
162 lua_pushvalue(L, -2);
163 lua_rawset(L, json_import_shadowtbl_idx);
164 // expect object key (or end of object) and continue with loop:
165 mode = JSON_STATE_OBJECT_KEY;
166 goto json_import_open;
167 // new JSON array:
168 case '[':
169 // if a JSON array is not expected here, then return an error:
170 if (mode != JSON_STATE_VALUE && mode != JSON_STATE_OBJECT_VALUE && mode != JSON_STATE_ARRAY_VALUE)
171 goto json_import_syntax_error;
172 // create JSON array on stack:
173 lua_newtable(L);
174 // set metatable of JSON array:
175 lua_pushvalue(L, json_import_arraymt_idx);
176 lua_setmetatable(L, -2);
177 // create internal shadow table on stack:
178 lua_newtable(L);
179 // register internal shadow table (and cleanup stack afterwards):
180 lua_pushvalue(L, -2);
181 lua_pushvalue(L, -2);
182 lua_rawset(L, json_import_shadowtbl_idx);
183 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
184 lua_pushnil(L);
185 // expect array value (or end of array) and continue with loop:
186 mode = JSON_STATE_ARRAY_VALUE;
187 // continue with common code for opening JSON object and JSON array:
188 // commn code for opening JSON object or JSON array:
189 json_import_open:
190 // limit nested levels:
191 if (level >= JSON_MAXDEPTH) {
192 lua_pushnil(L);
193 lua_pushliteral(L, "Too many nested JSON levels");
194 return 2;
195 }
196 // additional buffer overflow protection:
197 if (!lua_checkstack(L, LUA_MINSTACK))
198 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
199 // increment level:
200 level++;
201 // consume input character:
202 pos++;
203 goto json_import_loop;
204 // end of JSON object:
205 case '}':
206 // if end of JSON object is not expected here, then return an error:
207 if (mode != JSON_STATE_OBJECT_KEY && mode != JSON_STATE_OBJECT_SEPARATOR)
208 goto json_import_syntax_error;
209 // jump to common code for end of JSON object and JSON array:
210 goto json_import_close;
211 // end of JSON array:
212 case ']':
213 // if end of JSON array is not expected here, then return an error:
214 if (mode != JSON_STATE_ARRAY_VALUE && mode != JSON_STATE_ARRAY_SEPARATOR)
215 goto json_import_syntax_error;
216 // pop nil key/magic:
217 lua_pop(L, 1);
218 // continue with common code for end of JSON object and JSON array:
219 // common code for end of JSON object or JSON array:
220 json_import_close:
221 // consume input character:
222 pos++;
223 // pop shadow table:
224 lua_pop(L, 1);
225 // check if nested:
226 if (--level) {
227 // if nested, then check if outer(!) structure is an array or object:
228 if (lua_isnil(L, -2)) {
229 // select array value processing:
230 mode = JSON_STATE_ARRAY_VALUE;
231 } else {
232 // select object value processing:
233 mode = JSON_STATE_OBJECT_VALUE;
234 }
235 // store value in outer structure:
236 goto json_import_process_value;
237 }
238 // if not nested, then expect end of JSON document and continue with loop:
239 mode = JSON_STATE_END;
240 goto json_import_loop;
241 // key terminator:
242 case ':':
243 // if key terminator is not expected here, then return an error:
244 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
245 goto json_import_syntax_error;
246 // consume input character:
247 pos++;
248 // set state of parser and continue with loop:
249 mode = JSON_STATE_OBJECT_VALUE;
250 goto json_import_loop;
251 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
252 case ',':
253 // change parser state accordingly:
254 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
255 mode = JSON_STATE_OBJECT_KEY;
256 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
257 mode = JSON_STATE_ARRAY_VALUE;
258 } else {
259 // if value terminator is not expected here, then return an error:
260 goto json_import_syntax_error;
261 }
262 // consume input character:
263 pos++;
264 // continue with loop:
265 goto json_import_loop;
266 // string literal:
267 case '"':
268 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
269 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
270 writepos = 0;
271 // consume quote character:
272 pos++;
273 // read next character until encountering end quote:
274 while ((c = str[pos++]) != '"') {
275 if (c == 0) {
276 // handle unexpected end-of-string:
277 goto json_import_unexpected_eof;
278 } else if (c < 32 || c == 127) {
279 // do not allow ASCII control characters:
280 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
281 // by this parser to allow different encodings than Unicode
282 lua_pushnil(L);
283 lua_pushliteral(L, "Unexpected control character in JSON string");
284 return 2;
285 } else if (c == '\\') {
286 // read next char after backslash escape:
287 c = str[pos++];
288 switch (c) {
289 // unexpected end-of-string:
290 case 0:
291 goto json_import_unexpected_eof;
292 // unescaping of quotation mark, slash, and backslash:
293 case '"':
294 case '/':
295 case '\\':
296 cbuf[writepos++] = c;
297 break;
298 // unescaping of backspace:
299 case 'b':
300 cbuf[writepos++] = '\b';
301 break;
302 // unescaping of form-feed:
303 case 'f':
304 cbuf[writepos++] = '\f';
305 break;
306 // unescaping of new-line:
307 case 'n':
308 cbuf[writepos++] = '\n';
309 break;
310 // unescaping of carriage-return:
311 case 'r':
312 cbuf[writepos++] = '\r';
313 break;
314 // unescaping of tabulator:
315 case 't':
316 cbuf[writepos++] = '\t';
317 break;
318 // unescaping of UTF-16 characters
319 case 'u':
320 lua_pushnil(L);
321 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
322 return 2;
323 // unexpected escape sequence:
324 default:
325 lua_pushnil(L);
326 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
327 return 2;
328 }
329 } else {
330 // normal character:
331 cbuf[writepos++] = c;
332 }
333 }
334 // process buffer to Lua string:
335 luaL_pushresultsize(&luabuf, writepos);
336 // continue with processing of decoded string:
337 goto json_import_process_value;
338 }
339 // process values whose type is is not deducible from a single character:
340 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
341 // numbers:
342 char *endptr;
343 double numval;
344 numval = strtod(str+pos, &endptr);
345 if (endptr == str+pos) goto json_import_syntax_error;
346 pos += endptr - (str+pos);
347 lua_pushnumber(L, numval);
348 } else if (!strncmp(str+pos, "true", 4)) {
349 // consume 4 input characters for "true":
350 pos += 4;
351 // put Lua true value on stack:
352 lua_pushboolean(L, 1);
353 } else if (!strncmp(str+pos, "false", 5)) {
354 // consume 5 input characters for "false":
355 pos += 5;
356 // put Lua false value on stack:
357 lua_pushboolean(L, 0);
358 } else if (!strncmp(str+pos, "null", 4)) {
359 // consume 4 input characters for "null":
360 pos += 4;
361 // put special null-marker on stack:
362 lua_pushvalue(L, json_import_nullmark_idx);
363 } else {
364 // all other cases are a syntax error:
365 goto json_import_syntax_error;
366 }
367 // process a decoded value or key value pair (expected on top of Lua stack):
368 json_import_process_value:
369 switch (mode) {
370 // an object key has been read:
371 case JSON_STATE_OBJECT_KEY:
372 // if an object key is not a string, then this is a syntax error:
373 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
374 // expect key terminator and continue with loop:
375 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
376 goto json_import_loop;
377 // a key value pair has been read:
378 case JSON_STATE_OBJECT_VALUE:
379 // store key value pair in outer shadow table:
380 lua_rawset(L, -3);
381 // expect value terminator (or end of object) and continue with loop:
382 mode = JSON_STATE_OBJECT_SEPARATOR;
383 goto json_import_loop;
384 // an array value has been read:
385 case JSON_STATE_ARRAY_VALUE:
386 // store value in outer shadow table:
387 lua_rawseti(L, -3, lua_rawlen(L, -3) + 1);
388 // expect value terminator (or end of object) and continue with loop:
389 mode = JSON_STATE_ARRAY_SEPARATOR;
390 goto json_import_loop;
391 // a single value has been read:
392 case JSON_STATE_VALUE:
393 // leave value on top of stack, expect end of JSON document, and continue with loop:
394 mode = JSON_STATE_END;
395 goto json_import_loop;
396 }
397 // syntax error handling (only reachable by goto statement):
398 json_import_syntax_error:
399 lua_pushnil(L);
400 lua_pushliteral(L, "Syntax error in JSON document");
401 return 2;
402 }
404 #define json_path_shadowtbl_idx 1
405 #define json_path_nullmark_idx 2
406 #define json_path_idxshift 2
408 // gets a value or its type from a JSON document (first argument)
409 // optionally using a path (variable number of keys after first argument):
410 static int json_path(lua_State *L, int type_mode) {
411 int stacktop;
412 int idx = 2 + json_path_idxshift;
413 // insert json_shadowtbl on stack at position 1:
414 json_regfetch(L, shadowtbl);
415 lua_insert(L, 1);
416 // insert json_nullmark on stack at position 2:
417 json_pushlightref(L, nullmark);
418 lua_insert(L, 2);
419 // store number of arguments:
420 stacktop = lua_gettop(L);
421 // follow path, starting with first argument as "current value":
422 lua_pushvalue(L, 1 + json_path_idxshift);
423 // process each "path key":
424 while (idx <= stacktop) {
425 // if "current value" is nil, then the path cannot be walked and nil is returned:
426 if (lua_isnil(L, -1)) return 1;
427 // try to get shadow table of "current value":
428 lua_pushvalue(L, -1);
429 lua_rawget(L, json_path_shadowtbl_idx);
430 if (lua_isnil(L, -1)) {
431 // if no shadow table is found,
432 // drop nil from stack:
433 lua_pop(L, 1);
434 if (lua_type(L, -1) == LUA_TTABLE) {
435 // if "current value" is a table,
436 // get "next value" using the "path key":
437 lua_pushvalue(L, idx++);
438 lua_gettable(L, -2);
439 } else {
440 // if "current value" is not a table,
441 // then the path cannot be walked and nil is returned:
442 lua_pushnil(L);
443 return 1;
444 }
445 } else {
446 // if a shadow table is found,
447 // set "current value" to its shadow table:
448 lua_replace(L, -2);
449 // get "next value" using the "path key":
450 lua_pushvalue(L, idx++);
451 lua_rawget(L, -2);
452 }
453 // the "next value" replaces the "current value":
454 lua_replace(L, -2);
455 }
456 if (!type_mode) {
457 // if a value (and not its type) was requested,
458 // check if value is the null-marker, and store nil on top of Lua stack in that case:
459 if (lua_rawequal(L, -1, json_path_nullmark_idx)) lua_pushnil(L);
460 } else {
461 // if the type was requested,
462 // check if value is the null-marker:
463 if (lua_rawequal(L, -1, json_path_nullmark_idx)) {
464 // if yes, store string "null" on top of Lua stack:
465 lua_pushliteral(L, "null");
466 } else {
467 // otherwise,
468 // check if metatable indicates "object" or "array":
469 if (lua_getmetatable(L, -1)) {
470 json_regfetch(L, objectmt);
471 if (lua_rawequal(L, -2, -1)) {
472 // return string "object":
473 lua_pushliteral(L, "object");
474 return 1;
475 }
476 json_regfetch(L, arraymt);
477 if (lua_rawequal(L, -3, -1)) {
478 // return string "array":
479 lua_pushliteral(L, "array");
480 return 1;
481 }
482 lua_pop(L, 3);
483 }
484 // otherwise, get the Lua type:
485 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
486 }
487 }
488 // return the top most value on the Lua stack:
489 return 1;
490 }
492 // gets a value from a JSON document (first argument)
493 // optionally using a path (variable number of keys after first argument):
494 static int json_get(lua_State *L) {
495 return json_path(L, 0);
496 }
498 // gets a value's type from a JSON document (first argument)
499 // optionally using a path (variable number of keys after first argument):
500 static int json_type(lua_State *L) {
501 return json_path(L, 1);
502 }
504 // checks if a value in a JSON document (first argument) is null:
505 static int json_isnull(lua_State *L) {
506 const char *jsontype;
507 lua_pushcfunction(L, json_type);
508 lua_insert(L, 1);
509 lua_call(L, lua_gettop(L) - 1, 1);
510 jsontype = lua_tostring(L, -1);
511 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
512 else lua_pushboolean(L, 0);
513 return 1;
514 }
516 #define json_setnull_unknownmt_idx 3
517 #define json_setnull_objectmt_idx 4
518 #define json_setnull_arraymt_idx 5
519 #define json_setnull_shadowtbl_idx 6
521 static int json_setnull(lua_State *L) {
522 // truncate stack to two elements:
523 lua_settop(L, 2);
524 // push json_unknownmt to stack position 3:
525 json_regfetch(L, unknownmt);
526 // push json_objectmt to stack position 4:
527 json_regfetch(L, objectmt);
528 // push json_arraymt to stack position 5:
529 json_regfetch(L, arraymt);
530 // push json_shadowtbl to stack position 6:
531 json_regfetch(L, shadowtbl);
532 //
533 lua_getmetatable(L, 1);
534 if (
535 !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
536 !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
537 !lua_rawequal(L, -1, json_setnull_arraymt_idx)
538 ) {
539 lua_pushvalue(L, json_setnull_unknownmt_idx);
540 lua_setmetatable(L, 1);
541 }
542 lua_pushvalue(L, 1);
543 lua_rawget(L, json_setnull_shadowtbl_idx);
544 if (lua_isnil(L, -1)) {
545 lua_newtable(L);
546 lua_pushvalue(L, 1);
547 lua_pushvalue(L, -2);
548 lua_rawset(L, json_setnull_shadowtbl_idx);
549 }
550 lua_pushvalue(L, 2);
551 json_pushlightref(L, nullmark);
552 lua_rawset(L, -3);
553 return 0;
554 }
556 static int json_len(lua_State *L) {
557 lua_settop(L, 1);
558 json_regfetch(L, shadowtbl);
559 lua_pushvalue(L, 1);
560 lua_rawget(L, -2);
561 lua_pushinteger(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
562 return 1;
563 }
565 #define json_index_nullmark_idx 3
566 #define json_index_shadowtbl_idx 4
568 static int json_index(lua_State *L) {
569 lua_settop(L, 2);
570 json_pushlightref(L, nullmark); // on stack position 3
571 json_regfetch(L, shadowtbl);
572 lua_pushvalue(L, 1);
573 lua_rawget(L, json_index_shadowtbl_idx);
574 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
575 lua_pushvalue(L, 2);
576 lua_rawget(L, -2);
577 if (lua_rawequal(L, -1, json_index_nullmark_idx)) lua_pushnil(L);
578 return 1;
579 }
581 static int json_newindex(lua_State *L) {
582 lua_settop(L, 3);
583 json_regfetch(L, shadowtbl);
584 lua_pushvalue(L, 1);
585 lua_rawget(L, -2);
586 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
587 lua_replace(L, 1);
588 lua_settop(L, 3);
589 lua_rawset(L, 1);
590 return 1;
591 }
593 #define json_pairs_iterfunc_nullmark_idx 3
594 #define json_pairs_iterfunc_shadowtbl_idx 4
596 static int json_pairs_iterfunc(lua_State *L) {
597 lua_settop(L, 2);
598 json_pushlightref(L, nullmark); // on stack position 3
599 json_regfetch(L, shadowtbl);
600 lua_pushvalue(L, 1);
601 lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
602 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
603 lua_pushvalue(L, 2);
604 if (!lua_next(L, -2)) return 0;
605 if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
606 lua_pop(L, 1);
607 lua_pushnil(L);
608 }
609 return 2;
610 }
612 static int json_pairs(lua_State *L) {
613 lua_pushcfunction(L, json_pairs_iterfunc);
614 lua_pushvalue(L, 1);
615 lua_pushnil(L);
616 return 3;
617 }
619 #define json_ipairs_iterfunc_nullmark_idx 3
620 #define json_ipairs_iterfunc_shadowtbl_idx 4
622 static int json_ipairs_iterfunc(lua_State *L) {
623 int idx;
624 lua_settop(L, 2);
625 json_pushlightref(L, nullmark); // on stack position 3
626 json_regfetch(L, shadowtbl);
627 idx = lua_tointeger(L, 2) + 1;
628 lua_pushvalue(L, 1);
629 lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
630 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
631 lua_rawgeti(L, -1, idx);
632 if (lua_isnil(L, -1)) return 0;
633 lua_pushinteger(L, idx);
634 if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
635 else lua_pushvalue(L, -2);
636 return 2;
637 }
639 static int json_ipairs(lua_State *L) {
640 lua_pushcfunction(L, json_ipairs_iterfunc);
641 lua_pushvalue(L, 1);
642 lua_pushinteger(L, 0);
643 return 3;
644 }
646 static const struct luaL_Reg json_module_functions[] = {
647 {"object", json_object},
648 {"array", json_array},
649 {"import", json_import},
650 {"get", json_get},
651 {"type", json_type},
652 {"isnull", json_isnull},
653 {"setnull", json_setnull},
654 {NULL, NULL}
655 };
657 static const struct luaL_Reg json_metatable_functions[] = {
658 {"__len", json_len},
659 {"__index", json_index},
660 {"__newindex", json_newindex},
661 {"__pairs", json_pairs},
662 {"__ipairs", json_ipairs},
663 {NULL, NULL}
664 };
666 int luaopen_json(lua_State *L) {
667 lua_settop(L, 0);
668 lua_newtable(L); // library
669 lua_newtable(L);
670 luaL_setfuncs(L, json_metatable_functions, 0);
671 json_regstore(L, unknownmt);
672 lua_setfield(L, 1, "ambiguous_mt");
673 lua_newtable(L);
674 luaL_setfuncs(L, json_metatable_functions, 0);
675 json_regstore(L, objectmt);
676 lua_setfield(L, 1, "object_mt");
677 lua_newtable(L);
678 luaL_setfuncs(L, json_metatable_functions, 0);
679 json_regstore(L, arraymt);
680 lua_setfield(L, 1, "array_mt");
681 lua_newtable(L); // ephemeron table to store shadow tables for each JSON object/array to allow NULL values returned as nil
682 lua_newtable(L); // metatable for ephemeron table
683 lua_pushliteral(L, "__mode");
684 lua_pushliteral(L, "k");
685 lua_rawset(L, -3);
686 lua_setmetatable(L, -2);
687 json_regstore(L, shadowtbl);
688 lua_settop(L, 1);
689 luaL_setfuncs(L, json_module_functions, 0);
690 return 1;
691 }