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view libraries/json/json.c @ 148:5354d836e6fb
Minor bugfix in json_newindex function of JSON library (should return nothing)
| author | jbe |
|---|---|
| date | Wed Jul 30 22:32:33 2014 +0200 (2014-07-30) |
| parents | da5ab2c226dc |
| children | 5229687c7601 |
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 non-modifiable lightuserdata (dummy) objects:
19 static struct {
20 JSON_REGENT nullmark; // magic value to indicate JSON null value in shadow table
21 } json_reference;
24 // generate dummy memory addresses that represent Lua objects
25 // via lightuserdata keys and LUA_REGISTRYINDEX:
26 static struct {
27 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
28 JSON_REGENT unknownmt; // metatable for tables that may be either JSON objects or JSON arrays
29 JSON_REGENT objectmt; // metatable for JSON objects
30 JSON_REGENT arraymt; // metatable for JSON arrays
31 } json_registry;
33 // marks a Lua table as JSON object or JSON array:
34 // (returns its modified argument or a new table if argument is nil)
35 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
36 // check if argument is nil
37 if (lua_isnoneornil(L, 1)) {
38 // create new table at stack position 1:
39 lua_settop(L, 0);
40 lua_newtable(L);
41 // create shadow table (leaving previously created table on stack position 1):
42 json_regfetch(L, shadowtbl);
43 lua_pushvalue(L, 1);
44 lua_newtable(L);
45 lua_rawset(L, -3);
46 } else {
47 // push shadow table on top of stack:
48 json_regfetch(L, shadowtbl);
49 lua_pushvalue(L, 1);
50 lua_rawget(L, -2);
51 // if shadow table does not exist:
52 if (lua_isnil(L, -1)) {
53 // create shadow table and leave it on top of stack:
54 lua_newtable(L);
55 lua_pushvalue(L, 1);
56 lua_pushvalue(L, -2);
57 lua_rawset(L, -5);
58 }
59 // move elements from original table to shadow table (that's expected on top of stack):
60 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
61 lua_pushvalue(L, -2);
62 lua_pushnil(L);
63 lua_rawset(L, 1);
64 lua_pushvalue(L, -2);
65 lua_pushvalue(L, -2);
66 lua_rawset(L, -5);
67 }
68 }
69 // discard everything but table to return:
70 lua_settop(L, 1);
71 // set metatable:
72 json_regfetchpointer(L, mt);
73 lua_setmetatable(L, 1);
74 // return table:
75 return 1;
76 }
78 // marks a table as JSON object:
79 // (returns its modified argument or a new table if argument is nil)
80 static int json_object(lua_State *L) {
81 return json_mark(L, json_regpointer(objectmt));
82 }
84 // marks a table as JSON array:
85 // (returns its modified argument or a new table if argument is nil)
86 static int json_array(lua_State *L) {
87 return json_mark(L, json_regpointer(arraymt));
88 }
90 // internal states of JSON parser:
91 #define JSON_STATE_VALUE 0
92 #define JSON_STATE_OBJECT_KEY 1
93 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
94 #define JSON_STATE_OBJECT_VALUE 3
95 #define JSON_STATE_OBJECT_SEPARATOR 4
96 #define JSON_STATE_ARRAY_VALUE 5
97 #define JSON_STATE_ARRAY_SEPARATOR 6
98 #define JSON_STATE_END 7
100 // special Lua stack indicies for json_import function:
101 #define json_import_objectmt_idx 2
102 #define json_import_arraymt_idx 3
103 #define json_import_shadowtbl_idx 4
104 #define json_import_nullmark_idx 5
106 // decodes a JSON document:
107 static int json_import(lua_State *L) {
108 const char *str; // string to parse
109 size_t total; // total length of string to parse
110 size_t pos = 0; // current position in string to parse
111 size_t level = 0; // nested levels of objects/arrays currently being processed
112 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
113 char c; // variable to store a single character to be processed
114 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
115 char *cbuf; // C buffer to decode JSON string values
116 size_t writepos; // write position of decoded strings in C buffer
117 // stack shall contain one function argument:
118 lua_settop(L, 1);
119 // push objectmt onto stack position 2:
120 json_regfetch(L, objectmt);
121 // push arraymt onto stack position 3:
122 json_regfetch(L, arraymt);
123 // push shadowtbl onto stack position 4:
124 json_regfetch(L, shadowtbl);
125 // push nullmark onto stack position 5:
126 json_pushlightref(L, nullmark);
127 // require string as first argument:
128 str = luaL_checklstring(L, 1, &total);
129 // if string contains a NULL byte, this is a syntax error
130 if (strlen(str) != total) goto json_import_syntax_error;
131 // main loop of parser:
132 json_import_loop:
133 // skip whitespace and store next character in variable 'c':
134 while (c = str[pos],
135 c == ' ' ||
136 c == '\f' ||
137 c == '\n' ||
138 c == '\r' ||
139 c == '\t' ||
140 c == '\v'
141 ) pos++;
142 // switch statement to handle certain (single) characters:
143 switch (c) {
144 // handle end of JSON document:
145 case 0:
146 // if end of JSON document was expected, then return top element of stack as result:
147 if (mode == JSON_STATE_END) return 1;
148 // otherwise, the JSON document was malformed:
149 json_import_unexpected_eof:
150 lua_pushnil(L);
151 if (level == 0) lua_pushliteral(L, "Empty string");
152 else lua_pushliteral(L, "Unexpected end of JSON document");
153 return 2;
154 // new JSON object:
155 case '{':
156 // if a JSON object is not expected here, then return an error:
157 if (
158 mode != JSON_STATE_VALUE &&
159 mode != JSON_STATE_OBJECT_VALUE &&
160 mode != JSON_STATE_ARRAY_VALUE
161 ) goto json_import_syntax_error;
162 // create JSON object on stack:
163 lua_newtable(L);
164 // set metatable of JSON object:
165 lua_pushvalue(L, json_import_objectmt_idx);
166 lua_setmetatable(L, -2);
167 // create internal shadow table on stack:
168 lua_newtable(L);
169 // register internal shadow table:
170 lua_pushvalue(L, -2);
171 lua_pushvalue(L, -2);
172 lua_rawset(L, json_import_shadowtbl_idx);
173 // expect object key (or end of object) to follow:
174 mode = JSON_STATE_OBJECT_KEY;
175 // jump to common code for opening JSON object and JSON array:
176 goto json_import_open;
177 // new JSON array:
178 case '[':
179 // if a JSON array is not expected here, then return an error:
180 if (
181 mode != JSON_STATE_VALUE &&
182 mode != JSON_STATE_OBJECT_VALUE &&
183 mode != JSON_STATE_ARRAY_VALUE
184 ) goto json_import_syntax_error;
185 // create JSON array on stack:
186 lua_newtable(L);
187 // set metatable of JSON array:
188 lua_pushvalue(L, json_import_arraymt_idx);
189 lua_setmetatable(L, -2);
190 // create internal shadow table on stack:
191 lua_newtable(L);
192 // register internal shadow table:
193 lua_pushvalue(L, -2);
194 lua_pushvalue(L, -2);
195 lua_rawset(L, json_import_shadowtbl_idx);
196 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
197 lua_pushnil(L);
198 // expect array value (or end of array) to follow:
199 mode = JSON_STATE_ARRAY_VALUE;
200 // continue with common code for opening JSON object and JSON array:
201 // common code for opening JSON object or JSON array:
202 json_import_open:
203 // limit nested levels:
204 if (level >= JSON_MAXDEPTH) {
205 lua_pushnil(L);
206 lua_pushliteral(L, "Too many nested JSON levels");
207 return 2;
208 }
209 // additional buffer overflow protection:
210 if (!lua_checkstack(L, LUA_MINSTACK))
211 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
212 // increment level:
213 level++;
214 // consume input character:
215 pos++;
216 goto json_import_loop;
217 // end of JSON object:
218 case '}':
219 // if end of JSON object is not expected here, then return an error:
220 if (
221 mode != JSON_STATE_OBJECT_KEY &&
222 mode != JSON_STATE_OBJECT_SEPARATOR
223 ) goto json_import_syntax_error;
224 // jump to common code for end of JSON object and JSON array:
225 goto json_import_close;
226 // end of JSON array:
227 case ']':
228 // if end of JSON array is not expected here, then return an error:
229 if (
230 mode != JSON_STATE_ARRAY_VALUE &&
231 mode != JSON_STATE_ARRAY_SEPARATOR
232 ) goto json_import_syntax_error;
233 // pop nil key/magic (that was needed to keep stack balance):
234 lua_pop(L, 1);
235 // continue with common code for end of JSON object and JSON array:
236 // common code for end of JSON object or JSON array:
237 json_import_close:
238 // consume input character:
239 pos++;
240 // pop shadow table:
241 lua_pop(L, 1);
242 // check if nested:
243 if (--level) {
244 // if nested,
245 // check if outer(!) structure is an array or object:
246 if (lua_isnil(L, -2)) {
247 // select array value processing:
248 mode = JSON_STATE_ARRAY_VALUE;
249 } else {
250 // select object value processing:
251 mode = JSON_STATE_OBJECT_VALUE;
252 }
253 // store value in outer structure:
254 goto json_import_process_value;
255 }
256 // if not nested, then expect end of JSON document and continue with loop:
257 mode = JSON_STATE_END;
258 goto json_import_loop;
259 // key terminator:
260 case ':':
261 // if key terminator is not expected here, then return an error:
262 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
263 goto json_import_syntax_error;
264 // consume input character:
265 pos++;
266 // expect object value to follow:
267 mode = JSON_STATE_OBJECT_VALUE;
268 // continue with loop:
269 goto json_import_loop;
270 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
271 case ',':
272 // branch according to parser state:
273 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
274 // expect an object key to follow:
275 mode = JSON_STATE_OBJECT_KEY;
276 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
277 // expect an array value to follow:
278 mode = JSON_STATE_ARRAY_VALUE;
279 } else {
280 // if value terminator is not expected here, then return an error:
281 goto json_import_syntax_error;
282 }
283 // consume input character:
284 pos++;
285 // continue with loop:
286 goto json_import_loop;
287 // string literal:
288 case '"':
289 // consume quote character:
290 pos++;
291 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
292 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
293 writepos = 0;
294 // loop through the characters until encountering end quote:
295 while ((c = str[pos++]) != '"') {
296 if (c == 0) {
297 // handle unexpected end of JSON document:
298 goto json_import_unexpected_eof;
299 } else if (c < 32 || c == 127) {
300 // do not allow ASCII control characters:
301 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
302 // by this parser to allow different encodings than Unicode
303 lua_pushnil(L);
304 lua_pushliteral(L, "Unexpected control character in JSON string");
305 return 2;
306 } else if (c == '\\') {
307 // read next char after backslash escape:
308 c = str[pos++];
309 switch (c) {
310 // unexpected end-of-string:
311 case 0:
312 goto json_import_unexpected_eof;
313 // unescaping of quotation mark, slash, and backslash:
314 case '"':
315 case '/':
316 case '\\':
317 cbuf[writepos++] = c;
318 break;
319 // unescaping of backspace:
320 case 'b': cbuf[writepos++] = '\b'; break;
321 // unescaping of form-feed:
322 case 'f': cbuf[writepos++] = '\f'; break;
323 // unescaping of new-line:
324 case 'n': cbuf[writepos++] = '\n'; break;
325 // unescaping of carriage-return:
326 case 'r': cbuf[writepos++] = '\r'; break;
327 // unescaping of tabulator:
328 case 't': cbuf[writepos++] = '\t'; break;
329 // unescaping of UTF-16 characters
330 case 'u':
331 lua_pushnil(L);
332 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
333 return 2;
334 // unexpected escape sequence:
335 default:
336 lua_pushnil(L);
337 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
338 return 2;
339 }
340 } else {
341 // normal character:
342 cbuf[writepos++] = c;
343 }
344 }
345 // process buffer to Lua string:
346 luaL_pushresultsize(&luabuf, writepos);
347 // continue with processing of decoded string:
348 goto json_import_process_value;
349 }
350 // process values whose type is is not deducible from a single character:
351 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
352 // for numbers,
353 // use strtod() call to parse a (double precision) floating point number:
354 char *endptr;
355 double numval;
356 numval = strtod(str+pos, &endptr);
357 // catch parsing errors:
358 if (endptr == str+pos) goto json_import_syntax_error;
359 // consume characters that were parsed:
360 pos += endptr - (str+pos);
361 // push parsed (double precision) floating point number on Lua stack:
362 lua_pushnumber(L, numval);
363 } else if (!strncmp(str+pos, "true", 4)) {
364 // consume 4 input characters for "true":
365 pos += 4;
366 // put Lua true value onto stack:
367 lua_pushboolean(L, 1);
368 } else if (!strncmp(str+pos, "false", 5)) {
369 // consume 5 input characters for "false":
370 pos += 5;
371 // put Lua false value onto stack:
372 lua_pushboolean(L, 0);
373 } else if (!strncmp(str+pos, "null", 4)) {
374 // consume 4 input characters for "null":
375 pos += 4;
376 // put special null-marker onto stack:
377 lua_pushvalue(L, json_import_nullmark_idx);
378 } else {
379 // all other cases are a syntax error:
380 goto json_import_syntax_error;
381 }
382 // process a decoded value or key value pair (expected on top of Lua stack):
383 json_import_process_value:
384 switch (mode) {
385 // an object key has been read:
386 case JSON_STATE_OBJECT_KEY:
387 // if an object key is not a string, then this is a syntax error:
388 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
389 // expect key terminator to follow:
390 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
391 // continue with loop:
392 goto json_import_loop;
393 // a key value pair has been read:
394 case JSON_STATE_OBJECT_VALUE:
395 // store key value pair in outer shadow table:
396 lua_rawset(L, -3);
397 // expect value terminator (or end of object) to follow:
398 mode = JSON_STATE_OBJECT_SEPARATOR;
399 // continue with loop:
400 goto json_import_loop;
401 // an array value has been read:
402 case JSON_STATE_ARRAY_VALUE:
403 // store value in outer shadow table:
404 lua_rawseti(L, -3, lua_rawlen(L, -3) + 1);
405 // expect value terminator (or end of object) to follow:
406 mode = JSON_STATE_ARRAY_SEPARATOR;
407 // continue with loop
408 goto json_import_loop;
409 // a single value has been read:
410 case JSON_STATE_VALUE:
411 // leave value on top of stack, expect end of JSON document, and continue with loop:
412 mode = JSON_STATE_END;
413 goto json_import_loop;
414 }
415 // syntax error handling (reachable by goto statement):
416 json_import_syntax_error:
417 lua_pushnil(L);
418 lua_pushliteral(L, "Syntax error in JSON document");
419 return 2;
420 }
422 // special Lua stack indicies for json_path function:
423 #define json_path_shadowtbl_idx 1
424 #define json_path_nullmark_idx 2
426 // stack offset of arguments to json_path function:
427 #define json_path_idxshift 2
429 // gets a value or its type from a JSON document (passed as first argument)
430 // using a path (passed as variable number of keys after first argument):
431 static int json_path(lua_State *L, int type_mode) {
432 int stacktop; // stack index of top of stack (after shifting)
433 int idx = 2 + json_path_idxshift; // stack index of current argument to process
434 // insert shadowtbl into stack at position 1 (shifting the arguments):
435 json_regfetch(L, shadowtbl);
436 lua_insert(L, 1);
437 // insert nullmark into stack at position 2 (shifting the arguments):
438 json_pushlightref(L, nullmark);
439 lua_insert(L, 2);
440 // store stack index of top of stack:
441 stacktop = lua_gettop(L);
442 // use first argument as "current value" (stored on top of stack):
443 lua_pushvalue(L, 1 + json_path_idxshift);
444 // process each "path key" (2nd argument and following arguments):
445 while (idx <= stacktop) {
446 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
447 if (lua_isnil(L, -1)) return 1;
448 // try to get shadow table of "current value":
449 lua_pushvalue(L, -1);
450 lua_rawget(L, json_path_shadowtbl_idx);
451 if (lua_isnil(L, -1)) {
452 // if no shadow table is found,
453 if (lua_type(L, -1) == LUA_TTABLE) {
454 // and if "current value" is a table,
455 // drop nil from stack:
456 lua_pop(L, 1);
457 // get "next value" using the "path key":
458 lua_pushvalue(L, idx++);
459 lua_gettable(L, -2);
460 } else {
461 // if "current value" is not a table,
462 // then the path cannot be walked and nil (already on top of stack) is returned:
463 return 1;
464 }
465 } else {
466 // if a shadow table is found,
467 // set "current value" to its shadow table:
468 lua_replace(L, -2);
469 // get "next value" using the "path key":
470 lua_pushvalue(L, idx++);
471 lua_rawget(L, -2);
472 }
473 // the "next value" replaces the "current value":
474 lua_replace(L, -2);
475 }
476 if (!type_mode) {
477 // if a value (and not its type) was requested,
478 // check if value is the null-marker, and store nil on top of Lua stack in that case:
479 if (lua_rawequal(L, -1, json_path_nullmark_idx)) lua_pushnil(L);
480 } else {
481 // if the type was requested,
482 // check if value is the null-marker:
483 if (lua_rawequal(L, -1, json_path_nullmark_idx)) {
484 // if yes, store string "null" on top of Lua stack:
485 lua_pushliteral(L, "null");
486 } else {
487 // otherwise,
488 // check if metatable indicates "object" or "array":
489 if (lua_getmetatable(L, -1)) {
490 json_regfetch(L, objectmt);
491 if (lua_rawequal(L, -2, -1)) {
492 // if value has metatable for JSON objects,
493 // return string "object":
494 lua_pushliteral(L, "object");
495 return 1;
496 }
497 json_regfetch(L, arraymt);
498 if (lua_rawequal(L, -3, -1)) {
499 // if value has metatable for JSON arrays,
500 // return string "object":
501 lua_pushliteral(L, "array");
502 return 1;
503 }
504 // remove 3 metatables (one of the value, two for comparison) from stack:
505 lua_pop(L, 3);
506 }
507 // otherwise, get the Lua type:
508 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
509 }
510 }
511 // return the top most value on the Lua stack:
512 return 1;
513 }
515 // gets a value from a JSON document (passed as first argument)
516 // using a path (passed as variable number of keys after first argument):
517 static int json_get(lua_State *L) {
518 return json_path(L, 0);
519 }
521 // gets a value's type from a JSON document (passed as first argument)
522 // using a path (variable number of keys after first argument):
523 static int json_type(lua_State *L) {
524 return json_path(L, 1);
525 }
527 // checks if a value in a JSON document (first argument) is
528 // explicitly set to null:
529 static int json_isnull(lua_State *L) {
530 const char *jsontype;
531 // call json_type function with variable arguments:
532 lua_pushcfunction(L, json_type);
533 lua_insert(L, 1);
534 lua_call(L, lua_gettop(L) - 1, 1);
535 // return true if result equals to string "null", otherwise return false:
536 jsontype = lua_tostring(L, -1);
537 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
538 else lua_pushboolean(L, 0);
539 return 1;
540 }
542 // special Lua stack indicies for json_setnull function:
543 #define json_setnull_unknownmt_idx 3
544 #define json_setnull_objectmt_idx 4
545 #define json_setnull_arraymt_idx 5
546 #define json_setnull_shadowtbl_idx 6
548 // sets a value in a JSON object or JSON array explicitly to null:
549 // NOTE: JSON null is different than absence of a key
550 static int json_setnull(lua_State *L) {
551 // stack shall contain two function arguments:
552 lua_settop(L, 2);
553 // push unknownmt onto stack position 3:
554 json_regfetch(L, unknownmt);
555 // push objectmt onto stack position 4:
556 json_regfetch(L, objectmt);
557 // push arraymt onto stack position 5:
558 json_regfetch(L, arraymt);
559 // push shadowtbl onto stack position 6:
560 json_regfetch(L, shadowtbl);
561 // set metatable if necessary (leaves unknown number of elements on stack):
562 if (
563 !lua_getmetatable(L, 1) || (
564 !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
565 !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
566 !lua_rawequal(L, -1, json_setnull_arraymt_idx)
567 )
568 ) {
569 lua_pushvalue(L, json_setnull_unknownmt_idx);
570 lua_setmetatable(L, 1);
571 }
572 // try to get shadow table:
573 lua_pushvalue(L, 1);
574 lua_rawget(L, json_setnull_shadowtbl_idx);
575 if (lua_isnil(L, -1)) {
576 // if no shadow table is found,
577 // create new shadow table (and leave it on top of stack):
578 lua_newtable(L);
579 // register shadow table:
580 lua_pushvalue(L, 1);
581 lua_pushvalue(L, -2);
582 lua_rawset(L, json_setnull_shadowtbl_idx);
583 }
584 // push key (second argument) and null-marker after shadow table onto stack:
585 lua_pushvalue(L, 2);
586 json_pushlightref(L, nullmark);
587 // store key and null-marker in shadow table:
588 lua_rawset(L, -3);
589 // return nothing:
590 return 0;
591 }
593 // returns the length of a JSON array (or zero for a table without numeric keys):
594 static int json_len(lua_State *L) {
595 // stack shall contain one function argument:
596 lua_settop(L, 1);
597 // try to get corresponding shadow table for first argument:
598 json_regfetch(L, shadowtbl);
599 lua_pushvalue(L, 1);
600 lua_rawget(L, -2);
601 // if shadow table does not exist, return length of argument, else length of shadow table:
602 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
603 return 1;
604 }
606 // special Lua stack indicies for json_index function:
607 #define json_index_nullmark_idx 3
608 #define json_index_shadowtbl_idx 4
610 static int json_index(lua_State *L) {
611 // stack shall contain two function arguments:
612 lua_settop(L, 2);
613 // push nullmark onto stack position 3:
614 json_pushlightref(L, nullmark);
615 // push shadowtbl onto stack position 4:
616 json_regfetch(L, shadowtbl);
617 // get corresponding shadow table for first argument:
618 lua_pushvalue(L, 1);
619 lua_rawget(L, json_index_shadowtbl_idx);
620 // throw error if no shadow table was found:
621 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
622 // use key passed as second argument to lookup value in shadow table:
623 lua_pushvalue(L, 2);
624 lua_rawget(L, -2);
625 // if value is null-marker, then push nil onto stack:
626 if (lua_rawequal(L, -1, json_index_nullmark_idx)) lua_pushnil(L);
627 // return either looked up value, or nil
628 return 1;
629 }
631 static int json_newindex(lua_State *L) {
632 // stack shall contain three function arguments:
633 lua_settop(L, 3);
634 // get corresponding shadow table for first argument:
635 json_regfetch(L, shadowtbl);
636 lua_pushvalue(L, 1);
637 lua_rawget(L, -2);
638 // throw error if no shadow table was found:
639 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
640 // replace first argument with shadow table:
641 lua_replace(L, 1);
642 // reset stack and use second and third argument to write to shadow table:
643 lua_settop(L, 3);
644 lua_rawset(L, 1);
645 // return nothing:
646 return 0;
647 }
649 // special Lua stack indicies for json_pairs_iterfunc function:
650 #define json_pairs_iterfunc_nullmark_idx 3
651 #define json_pairs_iterfunc_shadowtbl_idx 4
653 static int json_pairs_iterfunc(lua_State *L) {
654 lua_settop(L, 2);
655 json_pushlightref(L, nullmark); // on stack position 3
656 json_regfetch(L, shadowtbl);
657 lua_pushvalue(L, 1);
658 lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
659 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
660 lua_pushvalue(L, 2);
661 if (!lua_next(L, -2)) return 0;
662 if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
663 lua_pop(L, 1);
664 lua_pushnil(L);
665 }
666 return 2;
667 }
669 static int json_pairs(lua_State *L) {
670 lua_pushcfunction(L, json_pairs_iterfunc);
671 lua_pushvalue(L, 1);
672 lua_pushnil(L);
673 return 3;
674 }
676 // special Lua stack indicies for json_ipairs_iterfunc function:
677 #define json_ipairs_iterfunc_nullmark_idx 3
678 #define json_ipairs_iterfunc_shadowtbl_idx 4
680 static int json_ipairs_iterfunc(lua_State *L) {
681 int idx;
682 lua_settop(L, 2);
683 json_pushlightref(L, nullmark); // on stack position 3
684 json_regfetch(L, shadowtbl);
685 idx = lua_tointeger(L, 2) + 1;
686 lua_pushvalue(L, 1);
687 lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
688 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
689 lua_rawgeti(L, -1, idx);
690 if (lua_isnil(L, -1)) return 0;
691 lua_pushinteger(L, idx);
692 if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
693 else lua_pushvalue(L, -2);
694 return 2;
695 }
697 static int json_ipairs(lua_State *L) {
698 lua_pushcfunction(L, json_ipairs_iterfunc);
699 lua_pushvalue(L, 1);
700 lua_pushinteger(L, 0);
701 return 3;
702 }
704 static const struct luaL_Reg json_module_functions[] = {
705 {"object", json_object},
706 {"array", json_array},
707 {"import", json_import},
708 {"get", json_get},
709 {"type", json_type},
710 {"isnull", json_isnull},
711 {"setnull", json_setnull},
712 {NULL, NULL}
713 };
715 static const struct luaL_Reg json_metatable_functions[] = {
716 {"__len", json_len},
717 {"__index", json_index},
718 {"__newindex", json_newindex},
719 {"__pairs", json_pairs},
720 {"__ipairs", json_ipairs},
721 {NULL, NULL}
722 };
724 int luaopen_json(lua_State *L) {
725 lua_settop(L, 0);
726 lua_newtable(L); // library
727 lua_newtable(L);
728 luaL_setfuncs(L, json_metatable_functions, 0);
729 json_regstore(L, unknownmt);
730 lua_setfield(L, 1, "ambiguous_mt");
731 lua_newtable(L);
732 luaL_setfuncs(L, json_metatable_functions, 0);
733 json_regstore(L, objectmt);
734 lua_setfield(L, 1, "object_mt");
735 lua_newtable(L);
736 luaL_setfuncs(L, json_metatable_functions, 0);
737 json_regstore(L, arraymt);
738 lua_setfield(L, 1, "array_mt");
739 lua_newtable(L); // ephemeron table to store shadow tables for each JSON object/array to allow NULL values returned as nil
740 lua_newtable(L); // metatable for ephemeron table
741 lua_pushliteral(L, "__mode");
742 lua_pushliteral(L, "k");
743 lua_rawset(L, -3);
744 lua_setmetatable(L, -2);
745 json_regstore(L, shadowtbl);
746 lua_settop(L, 1);
747 luaL_setfuncs(L, json_module_functions, 0);
748 return 1;
749 }