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view libraries/json/json.c @ 157:004d2d50419e
Allow direct usage of json.null values in JSON library (for writing, not reading)
| author | jbe |
|---|---|
| date | Thu Jul 31 03:45:33 2014 +0200 (2014-07-31) |
| parents | 185e944182cb |
| children | d42a7a840358 |
line source
1 #include <lua.h>
2 #include <lauxlib.h>
3 #include <stdlib.h>
4 #include <string.h>
5 #include <math.h>
7 // maximum number of nested JSON values (objects and arrays):
8 // NOTE: The Lua reference states that the stack may typically contain at least
9 // "a few thousand elements". Since every nested level consumes
10 // 3 elements on the Lua stack (the object/array, its shadow table,
11 // a string key or a placeholder), we limit the number of nested levels
12 // to 500. If a stack overflow would still happen in the import function,
13 // this is detected nevertheless and an error is thrown (instead of
14 // returning nil and an error string).
15 #define JSON_MAXDEPTH 500
17 // generate dummy memory addresses that represents null values:
18 char json_nullmark;
19 #define json_isnullmark(L, i) (lua_touserdata((L), (i)) == &json_nullmark)
20 #define json_pushnullmark(L) lua_pushlightuserdata((L), &json_nullmark)
22 // macros for usage of Lua registry:
23 #define JSON_REGENT char
24 #define JSON_REGPOINTER void *
25 #define json_regpointer(x) (&json_registry.x)
26 #define json_regfetchpointer(L, x) lua_rawgetp((L), LUA_REGISTRYINDEX, (x))
27 #define json_regfetch(L, x) json_regfetchpointer(L, json_regpointer(x))
28 #define json_regstore(L, x) lua_rawsetp(L, LUA_REGISTRYINDEX, json_regpointer(x))
30 // generate dummy memory addresses that represent Lua objects
31 // via lightuserdata keys and LUA_REGISTRYINDEX:
32 static struct {
33 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
34 JSON_REGENT unknownmt; // metatable for tables that may be either JSON objects or JSON arrays
35 JSON_REGENT objectmt; // metatable for JSON objects
36 JSON_REGENT arraymt; // metatable for JSON arrays
37 } json_registry;
39 // returns the string "<JSON null marker>":
40 static int json_nullmark_tostring(lua_State *L) {
41 lua_pushliteral(L, "<JSON null marker>");
42 return 1;
43 }
45 // marks a Lua table as JSON object or JSON array:
46 // (returns its modified argument or a new table if argument is nil)
47 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
48 // check if argument is nil
49 if (lua_isnoneornil(L, 1)) {
50 // create new table at stack position 1:
51 lua_settop(L, 0);
52 lua_newtable(L);
53 // create shadow table (leaving previously created table on stack position 1):
54 json_regfetch(L, shadowtbl);
55 lua_pushvalue(L, 1);
56 lua_newtable(L);
57 lua_rawset(L, -3);
58 } else {
59 // push shadow table on top of stack:
60 json_regfetch(L, shadowtbl);
61 lua_pushvalue(L, 1);
62 lua_rawget(L, -2);
63 // if shadow table does not exist:
64 if (lua_isnil(L, -1)) {
65 // create shadow table and leave it on top of stack:
66 lua_newtable(L);
67 lua_pushvalue(L, 1);
68 lua_pushvalue(L, -2);
69 lua_rawset(L, -5);
70 }
71 // move elements from original table to shadow table (that's expected on top of stack):
72 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
73 lua_pushvalue(L, -2);
74 lua_pushnil(L);
75 lua_rawset(L, 1);
76 lua_pushvalue(L, -2);
77 lua_pushvalue(L, -2);
78 lua_rawset(L, -5);
79 }
80 }
81 // discard everything but table to return:
82 lua_settop(L, 1);
83 // set metatable:
84 json_regfetchpointer(L, mt);
85 lua_setmetatable(L, 1);
86 // return table:
87 return 1;
88 }
90 // marks a table as JSON object:
91 // (returns its modified argument or a new table if argument is nil)
92 static int json_object(lua_State *L) {
93 return json_mark(L, json_regpointer(objectmt));
94 }
96 // marks a table as JSON array:
97 // (returns its modified argument or a new table if argument is nil)
98 static int json_array(lua_State *L) {
99 return json_mark(L, json_regpointer(arraymt));
100 }
102 // internal states of JSON parser:
103 #define JSON_STATE_VALUE 0
104 #define JSON_STATE_OBJECT_KEY 1
105 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
106 #define JSON_STATE_OBJECT_VALUE 3
107 #define JSON_STATE_OBJECT_SEPARATOR 4
108 #define JSON_STATE_ARRAY_VALUE 5
109 #define JSON_STATE_ARRAY_SEPARATOR 6
110 #define JSON_STATE_END 7
112 // special Lua stack indicies for json_import function:
113 #define json_import_objectmt_idx 2
114 #define json_import_arraymt_idx 3
115 #define json_import_shadowtbl_idx 4
117 // decodes a JSON document:
118 static int json_import(lua_State *L) {
119 const char *str; // string to parse
120 size_t total; // total length of string to parse
121 size_t pos = 0; // current position in string to parse
122 size_t level = 0; // nested levels of objects/arrays currently being processed
123 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
124 char c; // variable to store a single character to be processed
125 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
126 char *cbuf; // C buffer to decode JSON string values
127 size_t writepos; // write position of decoded strings in C buffer
128 size_t arraylen; // variable to temporarily store the array length
129 // stack shall contain one function argument:
130 lua_settop(L, 1);
131 // push objectmt onto stack position 2:
132 json_regfetch(L, objectmt);
133 // push arraymt onto stack position 3:
134 json_regfetch(L, arraymt);
135 // push shadowtbl onto stack position 4:
136 json_regfetch(L, shadowtbl);
137 // require string as first argument:
138 str = luaL_checklstring(L, 1, &total);
139 // if string contains a NULL byte, this is a syntax error
140 if (strlen(str) != total) goto json_import_syntax_error;
141 // main loop of parser:
142 json_import_loop:
143 // skip whitespace and store next character in variable 'c':
144 while (c = str[pos],
145 c == ' ' ||
146 c == '\f' ||
147 c == '\n' ||
148 c == '\r' ||
149 c == '\t' ||
150 c == '\v'
151 ) pos++;
152 // switch statement to handle certain (single) characters:
153 switch (c) {
154 // handle end of JSON document:
155 case 0:
156 // if end of JSON document was expected, then return top element of stack as result:
157 if (mode == JSON_STATE_END) return 1;
158 // otherwise, the JSON document was malformed:
159 json_import_unexpected_eof:
160 lua_pushnil(L);
161 if (level == 0) lua_pushliteral(L, "Empty string");
162 else lua_pushliteral(L, "Unexpected end of JSON document");
163 return 2;
164 // new JSON object:
165 case '{':
166 // if a JSON object is not expected here, then return an error:
167 if (
168 mode != JSON_STATE_VALUE &&
169 mode != JSON_STATE_OBJECT_VALUE &&
170 mode != JSON_STATE_ARRAY_VALUE
171 ) goto json_import_syntax_error;
172 // create JSON object on stack:
173 lua_newtable(L);
174 // set metatable of JSON object:
175 lua_pushvalue(L, json_import_objectmt_idx);
176 lua_setmetatable(L, -2);
177 // create internal shadow table on stack:
178 lua_newtable(L);
179 // register internal shadow table:
180 lua_pushvalue(L, -2);
181 lua_pushvalue(L, -2);
182 lua_rawset(L, json_import_shadowtbl_idx);
183 // expect object key (or end of object) to follow:
184 mode = JSON_STATE_OBJECT_KEY;
185 // jump to common code for opening JSON object and JSON array:
186 goto json_import_open;
187 // new JSON array:
188 case '[':
189 // if a JSON array is not expected here, then return an error:
190 if (
191 mode != JSON_STATE_VALUE &&
192 mode != JSON_STATE_OBJECT_VALUE &&
193 mode != JSON_STATE_ARRAY_VALUE
194 ) goto json_import_syntax_error;
195 // create JSON array on stack:
196 lua_newtable(L);
197 // set metatable of JSON array:
198 lua_pushvalue(L, json_import_arraymt_idx);
199 lua_setmetatable(L, -2);
200 // create internal shadow table on stack:
201 lua_newtable(L);
202 // register internal shadow table:
203 lua_pushvalue(L, -2);
204 lua_pushvalue(L, -2);
205 lua_rawset(L, json_import_shadowtbl_idx);
206 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
207 lua_pushnil(L);
208 // expect array value (or end of array) to follow:
209 mode = JSON_STATE_ARRAY_VALUE;
210 // continue with common code for opening JSON object and JSON array:
211 // common code for opening JSON object or JSON array:
212 json_import_open:
213 // limit nested levels:
214 if (level >= JSON_MAXDEPTH) {
215 lua_pushnil(L);
216 lua_pushliteral(L, "Too many nested JSON levels");
217 return 2;
218 }
219 // additional buffer overflow protection:
220 if (!lua_checkstack(L, LUA_MINSTACK))
221 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
222 // increment level:
223 level++;
224 // consume input character:
225 pos++;
226 goto json_import_loop;
227 // end of JSON object:
228 case '}':
229 // if end of JSON object is not expected here, then return an error:
230 if (
231 mode != JSON_STATE_OBJECT_KEY &&
232 mode != JSON_STATE_OBJECT_SEPARATOR
233 ) goto json_import_syntax_error;
234 // jump to common code for end of JSON object and JSON array:
235 goto json_import_close;
236 // end of JSON array:
237 case ']':
238 // if end of JSON array is not expected here, then return an error:
239 if (
240 mode != JSON_STATE_ARRAY_VALUE &&
241 mode != JSON_STATE_ARRAY_SEPARATOR
242 ) goto json_import_syntax_error;
243 // pop nil key/magic (that was needed to keep stack balance):
244 lua_pop(L, 1);
245 // continue with common code for end of JSON object and JSON array:
246 // common code for end of JSON object or JSON array:
247 json_import_close:
248 // consume input character:
249 pos++;
250 // pop shadow table:
251 lua_pop(L, 1);
252 // check if nested:
253 if (--level) {
254 // if nested,
255 // check if outer(!) structure is an array or object:
256 if (lua_isnil(L, -2)) {
257 // select array value processing:
258 mode = JSON_STATE_ARRAY_VALUE;
259 } else {
260 // select object value processing:
261 mode = JSON_STATE_OBJECT_VALUE;
262 }
263 // store value in outer structure:
264 goto json_import_process_value;
265 }
266 // if not nested, then expect end of JSON document and continue with loop:
267 mode = JSON_STATE_END;
268 goto json_import_loop;
269 // key terminator:
270 case ':':
271 // if key terminator is not expected here, then return an error:
272 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
273 goto json_import_syntax_error;
274 // consume input character:
275 pos++;
276 // expect object value to follow:
277 mode = JSON_STATE_OBJECT_VALUE;
278 // continue with loop:
279 goto json_import_loop;
280 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
281 case ',':
282 // branch according to parser state:
283 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
284 // expect an object key to follow:
285 mode = JSON_STATE_OBJECT_KEY;
286 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
287 // expect an array value to follow:
288 mode = JSON_STATE_ARRAY_VALUE;
289 } else {
290 // if value terminator is not expected here, then return an error:
291 goto json_import_syntax_error;
292 }
293 // consume input character:
294 pos++;
295 // continue with loop:
296 goto json_import_loop;
297 // string literal:
298 case '"':
299 // consume quote character:
300 pos++;
301 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
302 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
303 writepos = 0;
304 // loop through the characters until encountering end quote:
305 while ((c = str[pos++]) != '"') {
306 if (c == 0) {
307 // handle unexpected end of JSON document:
308 goto json_import_unexpected_eof;
309 } else if (c < 32 || c == 127) {
310 // do not allow ASCII control characters:
311 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
312 // by this parser to allow different encodings than Unicode
313 lua_pushnil(L);
314 lua_pushliteral(L, "Unexpected control character in JSON string");
315 return 2;
316 } else if (c == '\\') {
317 // read next char after backslash escape:
318 c = str[pos++];
319 switch (c) {
320 // unexpected end-of-string:
321 case 0:
322 goto json_import_unexpected_eof;
323 // unescaping of quotation mark, slash, and backslash:
324 case '"':
325 case '/':
326 case '\\':
327 cbuf[writepos++] = c;
328 break;
329 // unescaping of backspace:
330 case 'b': cbuf[writepos++] = '\b'; break;
331 // unescaping of form-feed:
332 case 'f': cbuf[writepos++] = '\f'; break;
333 // unescaping of new-line:
334 case 'n': cbuf[writepos++] = '\n'; break;
335 // unescaping of carriage-return:
336 case 'r': cbuf[writepos++] = '\r'; break;
337 // unescaping of tabulator:
338 case 't': cbuf[writepos++] = '\t'; break;
339 // unescaping of UTF-16 characters
340 case 'u':
341 lua_pushnil(L);
342 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
343 return 2;
344 // unexpected escape sequence:
345 default:
346 lua_pushnil(L);
347 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
348 return 2;
349 }
350 } else {
351 // normal character:
352 cbuf[writepos++] = c;
353 }
354 }
355 // process buffer to Lua string:
356 luaL_pushresultsize(&luabuf, writepos);
357 // continue with processing of decoded string:
358 goto json_import_process_value;
359 }
360 // process values whose type is is not deducible from a single character:
361 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
362 // for numbers,
363 // use strtod() call to parse a (double precision) floating point number:
364 char *endptr;
365 double numval;
366 numval = strtod(str+pos, &endptr);
367 // catch parsing errors:
368 if (endptr == str+pos) goto json_import_syntax_error;
369 // consume characters that were parsed:
370 pos += endptr - (str+pos);
371 // push parsed (double precision) floating point number on Lua stack:
372 lua_pushnumber(L, numval);
373 } else if (!strncmp(str+pos, "true", 4)) {
374 // consume 4 input characters for "true":
375 pos += 4;
376 // put Lua true value onto stack:
377 lua_pushboolean(L, 1);
378 } else if (!strncmp(str+pos, "false", 5)) {
379 // consume 5 input characters for "false":
380 pos += 5;
381 // put Lua false value onto stack:
382 lua_pushboolean(L, 0);
383 } else if (!strncmp(str+pos, "null", 4)) {
384 // consume 4 input characters for "null":
385 pos += 4;
386 // different behavor for top-level and sub-levels:
387 if (level) {
388 // if sub-level,
389 // push special null-marker onto stack:
390 json_pushnullmark(L);
391 } else {
392 // if top-level,
393 // push nil onto stack:
394 lua_pushnil(L);
395 }
396 } else {
397 // all other cases are a syntax error:
398 goto json_import_syntax_error;
399 }
400 // process a decoded value or key value pair (expected on top of Lua stack):
401 json_import_process_value:
402 switch (mode) {
403 // an object key has been read:
404 case JSON_STATE_OBJECT_KEY:
405 // if an object key is not a string, then this is a syntax error:
406 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
407 // expect key terminator to follow:
408 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
409 // continue with loop:
410 goto json_import_loop;
411 // a key value pair has been read:
412 case JSON_STATE_OBJECT_VALUE:
413 // store key value pair in outer shadow table:
414 lua_rawset(L, -3);
415 // expect value terminator (or end of object) to follow:
416 mode = JSON_STATE_OBJECT_SEPARATOR;
417 // continue with loop:
418 goto json_import_loop;
419 // an array value has been read:
420 case JSON_STATE_ARRAY_VALUE:
421 // get current array length:
422 arraylen = lua_rawlen(L, -3);
423 // throw error if array would exceed INT_MAX elements:
424 // TODO: Lua 5.3 may support more elements
425 if (arraylen >= INT_MAX) {
426 lua_pushnil(L);
427 lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
428 }
429 // store value in outer shadow table:
430 lua_rawseti(L, -3, arraylen + 1);
431 // expect value terminator (or end of object) to follow:
432 mode = JSON_STATE_ARRAY_SEPARATOR;
433 // continue with loop
434 goto json_import_loop;
435 // a single value has been read:
436 case JSON_STATE_VALUE:
437 // leave value on top of stack, expect end of JSON document, and continue with loop:
438 mode = JSON_STATE_END;
439 goto json_import_loop;
440 }
441 // syntax error handling (reachable by goto statement):
442 json_import_syntax_error:
443 lua_pushnil(L);
444 lua_pushliteral(L, "Syntax error in JSON document");
445 return 2;
446 }
448 // special Lua stack indicies for json_path function:
449 #define json_path_shadowtbl_idx 1
451 // stack offset of arguments to json_path function:
452 #define json_path_idxshift 1
454 // gets a value or its type from a JSON document (passed as first argument)
455 // using a path (passed as variable number of keys after first argument):
456 static int json_path(lua_State *L, int type_mode) {
457 int stacktop; // stack index of top of stack (after shifting)
458 int idx = 2 + json_path_idxshift; // stack index of current argument to process
459 // insert shadowtbl into stack at position 1 (shifting the arguments):
460 json_regfetch(L, shadowtbl);
461 lua_insert(L, 1);
462 // store stack index of top of stack:
463 stacktop = lua_gettop(L);
464 // use first argument as "current value" (stored on top of stack):
465 lua_pushvalue(L, 1 + json_path_idxshift);
466 // process each "path key" (2nd argument and following arguments):
467 while (idx <= stacktop) {
468 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
469 if (lua_isnil(L, -1)) return 1;
470 // try to get shadow table of "current value":
471 lua_pushvalue(L, -1);
472 lua_rawget(L, json_path_shadowtbl_idx);
473 if (lua_isnil(L, -1)) {
474 // if no shadow table is found,
475 if (lua_type(L, -1) == LUA_TTABLE) {
476 // and if "current value" is a table,
477 // drop nil from stack:
478 lua_pop(L, 1);
479 // get "next value" using the "path key":
480 lua_pushvalue(L, idx++);
481 lua_gettable(L, -2);
482 } else {
483 // if "current value" is not a table,
484 // then the path cannot be walked and nil (already on top of stack) is returned:
485 return 1;
486 }
487 } else {
488 // if a shadow table is found,
489 // set "current value" to its shadow table:
490 lua_replace(L, -2);
491 // get "next value" using the "path key":
492 lua_pushvalue(L, idx++);
493 lua_rawget(L, -2);
494 }
495 // the "next value" replaces the "current value":
496 lua_replace(L, -2);
497 }
498 if (!type_mode) {
499 // if a value (and not its type) was requested,
500 // check if value is the null-marker, and store nil on top of Lua stack in that case:
501 if (json_isnullmark(L, -1)) lua_pushnil(L);
502 } else {
503 // if the type was requested,
504 // check if value is the null-marker:
505 if (json_isnullmark(L, -1)) {
506 // if yes, store string "null" on top of Lua stack:
507 lua_pushliteral(L, "null");
508 } else {
509 // otherwise,
510 // check if metatable indicates "object" or "array":
511 if (lua_getmetatable(L, -1)) {
512 json_regfetch(L, objectmt);
513 if (lua_rawequal(L, -2, -1)) {
514 // if value has metatable for JSON objects,
515 // return string "object":
516 lua_pushliteral(L, "object");
517 return 1;
518 }
519 json_regfetch(L, arraymt);
520 if (lua_rawequal(L, -3, -1)) {
521 // if value has metatable for JSON arrays,
522 // return string "object":
523 lua_pushliteral(L, "array");
524 return 1;
525 }
526 // remove 3 metatables (one of the value, two for comparison) from stack:
527 lua_pop(L, 3);
528 }
529 // otherwise, get the Lua type:
530 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
531 }
532 }
533 // return the top most value on the Lua stack:
534 return 1;
535 }
537 // gets a value from a JSON document (passed as first argument)
538 // using a path (passed as variable number of keys after first argument):
539 static int json_get(lua_State *L) {
540 return json_path(L, 0);
541 }
543 // gets a value's type from a JSON document (passed as first argument)
544 // using a path (variable number of keys after first argument):
545 static int json_type(lua_State *L) {
546 return json_path(L, 1);
547 }
549 // checks if a value in a JSON document (first argument) is
550 // explicitly set to null:
551 static int json_isnull(lua_State *L) {
552 const char *jsontype;
553 // call json_type function with variable arguments:
554 lua_pushcfunction(L, json_type);
555 lua_insert(L, 1);
556 lua_call(L, lua_gettop(L) - 1, 1);
557 // return true if result equals to string "null", otherwise return false:
558 jsontype = lua_tostring(L, -1);
559 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
560 else lua_pushboolean(L, 0);
561 return 1;
562 }
564 // special Lua stack indicies for json_setnull function:
565 #define json_setnull_unknownmt_idx 3
566 #define json_setnull_objectmt_idx 4
567 #define json_setnull_arraymt_idx 5
568 #define json_setnull_shadowtbl_idx 6
570 // sets a value in a JSON object or JSON array explicitly to null:
571 // NOTE: JSON null is different than absence of a key
572 static int json_setnull(lua_State *L) {
573 // stack shall contain two function arguments:
574 lua_settop(L, 2);
575 // push unknownmt onto stack position 3:
576 json_regfetch(L, unknownmt);
577 // push objectmt onto stack position 4:
578 json_regfetch(L, objectmt);
579 // push arraymt onto stack position 5:
580 json_regfetch(L, arraymt);
581 // push shadowtbl onto stack position 6:
582 json_regfetch(L, shadowtbl);
583 // set metatable if necessary (leaves unknown number of elements on stack):
584 if (
585 !lua_getmetatable(L, 1) || (
586 !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
587 !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
588 !lua_rawequal(L, -1, json_setnull_arraymt_idx)
589 )
590 ) {
591 lua_pushvalue(L, json_setnull_unknownmt_idx);
592 lua_setmetatable(L, 1);
593 }
594 // try to get shadow table:
595 lua_pushvalue(L, 1);
596 lua_rawget(L, json_setnull_shadowtbl_idx);
597 if (lua_isnil(L, -1)) {
598 // if no shadow table is found,
599 // create new shadow table (and leave it on top of stack):
600 lua_newtable(L);
601 // register shadow table:
602 lua_pushvalue(L, 1);
603 lua_pushvalue(L, -2);
604 lua_rawset(L, json_setnull_shadowtbl_idx);
605 }
606 // push key (second argument) and null-marker after shadow table onto stack:
607 lua_pushvalue(L, 2);
608 json_pushnullmark(L);
609 // store key and null-marker in shadow table:
610 lua_rawset(L, -3);
611 // return nothing:
612 return 0;
613 }
615 // returns the length of a JSON array (or zero for a table without numeric keys):
616 static int json_len(lua_State *L) {
617 // stack shall contain one function argument:
618 lua_settop(L, 1);
619 // try to get corresponding shadow table for first argument:
620 json_regfetch(L, shadowtbl);
621 lua_pushvalue(L, 1);
622 lua_rawget(L, -2);
623 // if shadow table does not exist, return length of argument, else length of shadow table:
624 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
625 return 1;
626 }
628 static int json_index(lua_State *L) {
629 // stack shall contain two function arguments:
630 lua_settop(L, 2);
631 // get corresponding shadow table for first argument:
632 json_regfetch(L, shadowtbl);
633 lua_pushvalue(L, 1);
634 lua_rawget(L, -2);
635 // throw error if no shadow table was found:
636 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
637 // use key passed as second argument to lookup value in shadow table:
638 lua_pushvalue(L, 2);
639 lua_rawget(L, -2);
640 // if value is null-marker, then push nil onto stack:
641 if (json_isnullmark(L, -1)) lua_pushnil(L);
642 // return either looked up value, or nil
643 return 1;
644 }
646 static int json_newindex(lua_State *L) {
647 // stack shall contain three function arguments:
648 lua_settop(L, 3);
649 // get corresponding shadow table for first argument:
650 json_regfetch(L, shadowtbl);
651 lua_pushvalue(L, 1);
652 lua_rawget(L, -2);
653 // throw error if no shadow table was found:
654 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
655 // replace first argument with shadow table:
656 lua_replace(L, 1);
657 // reset stack and use second and third argument to write to shadow table:
658 lua_settop(L, 3);
659 lua_rawset(L, 1);
660 // return nothing:
661 return 0;
662 }
664 static int json_pairs_iterfunc(lua_State *L) {
665 // stack shall contain two function arguments:
666 lua_settop(L, 2);
667 // get corresponding shadow table for first argument:
668 json_regfetch(L, shadowtbl);
669 lua_pushvalue(L, 1);
670 lua_rawget(L, -2);
671 // throw error if no shadow table was found:
672 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
673 // get next key value pair from shadow table (using previous key from argument 2)
674 // and return nothing if there is no next pair:
675 lua_pushvalue(L, 2);
676 if (!lua_next(L, -2)) return 0;
677 // replace null-marker with nil:
678 if (json_isnullmark(L, -1)) {
679 lua_pop(L, 1);
680 lua_pushnil(L);
681 }
682 // return key and value (or key and nil, if null-marker was found):
683 return 2;
684 }
686 // returns a triple such that 'for key, value in pairs(obj) do ... end'
687 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
688 static int json_pairs(lua_State *L) {
689 // return triple of function json_pairs_iterfunc, first argument, and nil:
690 lua_pushcfunction(L, json_pairs_iterfunc);
691 lua_pushvalue(L, 1);
692 lua_pushnil(L);
693 return 3;
694 }
696 static int json_ipairs_iterfunc(lua_State *L) {
697 lua_Integer idx;
698 // stack shall contain two function arguments:
699 lua_settop(L, 2);
700 // calculate new index by incrementing second argument:
701 idx = lua_tointeger(L, 2) + 1;
702 // get corresponding shadow table for first argument:
703 json_regfetch(L, shadowtbl);
704 lua_pushvalue(L, 1);
705 lua_rawget(L, -2);
706 // throw error if no shadow table was found:
707 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
708 // do integer lookup in shadow table:
709 lua_rawgeti(L, -1, idx);
710 // return nothing if there was no value:
711 if (lua_isnil(L, -1)) return 0;
712 // return new index and
713 // either the looked up value if it is not equal to the null-marker
714 // or nil instead of null-marker:
715 lua_pushinteger(L, idx);
716 if (json_isnullmark(L, -2)) lua_pushnil(L);
717 else lua_pushvalue(L, -2);
718 return 2;
719 }
721 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
722 // iterates through all values (including JSON null represented as Lua nil):
723 static int json_ipairs(lua_State *L) {
724 // return triple of function json_ipairs_iterfunc, first argument, and zero:
725 lua_pushcfunction(L, json_ipairs_iterfunc);
726 lua_pushvalue(L, 1);
727 lua_pushinteger(L, 0);
728 return 3;
729 }
731 #define JSON_TABLETYPE_UNKNOWN 0
732 #define JSON_TABLETYPE_OBJECT 1
733 #define JSON_TABLETYPE_ARRAY 2
735 static int json_export(lua_State *L) {
736 lua_Number num;
737 const char *str;
738 unsigned char c;
739 size_t strlen;
740 size_t pos = 0;
741 luaL_Buffer buf;
742 char hexcode[7]; // backslash, character 'u', 4 hex digits, and terminating NULL byte
743 int luatype;
744 int tabletype = JSON_TABLETYPE_UNKNOWN;
745 int needsep = 0;
746 lua_Integer idx;
747 lua_settop(L, 1);
748 if (json_isnullmark(L, 1)) {
749 lua_pushnil(L);
750 lua_replace(L, 1);
751 }
752 switch (lua_type(L, 1)) {
753 case LUA_TNIL:
754 lua_pushliteral(L, "null");
755 return 1;
756 case LUA_TNUMBER:
757 num = lua_tonumber(L, 1);
758 if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
759 if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
760 lua_tostring(L, 1);
761 return 1;
762 case LUA_TBOOLEAN:
763 if (lua_toboolean(L, 1)) lua_pushliteral(L, "true");
764 else lua_pushliteral(L, "false");
765 return 1;
766 case LUA_TSTRING:
767 str = lua_tolstring(L, 1, &strlen);
768 luaL_buffinit(L, &buf);
769 luaL_addchar(&buf, '"');
770 while (pos < strlen) {
771 c = str[pos++];
772 if (c == '"') luaL_addstring(&buf, "\\\"");
773 else if (c == '\\') luaL_addstring(&buf, "\\\\");
774 else if (c == 127) luaL_addstring(&buf, "\\u007F");
775 else if (c >= 32) luaL_addchar(&buf, c);
776 else if (c == '\b') luaL_addstring(&buf, "\\b");
777 else if (c == '\f') luaL_addstring(&buf, "\\f");
778 else if (c == '\n') luaL_addstring(&buf, "\\n");
779 else if (c == '\r') luaL_addstring(&buf, "\\r");
780 else if (c == '\t') luaL_addstring(&buf, "\\t");
781 else if (c == '\v') luaL_addstring(&buf, "\\v");
782 else {
783 sprintf(hexcode, "\\u%04X", c);
784 luaL_addstring(&buf, hexcode);
785 }
786 }
787 luaL_addchar(&buf, '"');
788 luaL_pushresult(&buf);
789 return 1;
790 case LUA_TTABLE:
791 if (lua_getmetatable(L, 1)) {
792 json_regfetch(L, objectmt);
793 if (lua_rawequal(L, -2, -1)) {
794 tabletype = JSON_TABLETYPE_OBJECT;
795 } else {
796 json_regfetch(L, arraymt);
797 if (lua_rawequal(L, -3, -1)) tabletype = JSON_TABLETYPE_ARRAY;
798 }
799 }
800 json_regfetch(L, shadowtbl);
801 lua_pushvalue(L, 1);
802 lua_rawget(L, -2);
803 if (!lua_isnil(L, -1)) lua_replace(L, 1);
804 lua_settop(L, 1);
805 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
806 for (lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
807 luatype = lua_type(L, -2);
808 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
809 if (luatype == LUA_TSTRING) tabletype = JSON_TABLETYPE_OBJECT;
810 else if (luatype == LUA_TNUMBER) tabletype = JSON_TABLETYPE_ARRAY;
811 } else if (
812 (tabletype == JSON_TABLETYPE_OBJECT && luatype == LUA_TNUMBER) ||
813 (tabletype == JSON_TABLETYPE_ARRAY && luatype == LUA_TSTRING)
814 ) {
815 goto json_export_tabletype_error;
816 }
817 }
818 }
819 switch (tabletype) {
820 case JSON_TABLETYPE_OBJECT:
821 lua_settop(L, 3);
822 luaL_buffinit(L, &buf);
823 luaL_addchar(&buf, '{');
824 for (lua_pushnil(L); lua_next(L, 1); ) {
825 if (lua_type(L, -2) == LUA_TSTRING) {
826 lua_replace(L, 3);
827 lua_replace(L, 2);
828 if (needsep) luaL_addchar(&buf, ',');
829 else needsep = 1;
830 lua_pushcfunction(L, json_export);
831 lua_pushvalue(L, 2);
832 lua_call(L, 1, 1);
833 luaL_addvalue(&buf);
834 luaL_addchar(&buf, ':');
835 if (json_isnullmark(L, 3)) {
836 luaL_addstring(&buf, "null");
837 } else {
838 lua_pushcfunction(L, json_export);
839 lua_pushvalue(L, 3);
840 lua_call(L, 1, 1);
841 luaL_addvalue(&buf);
842 }
843 lua_pushvalue(L, 2);
844 } else {
845 lua_pop(L, 1);
846 }
847 }
848 luaL_addchar(&buf, '}');
849 luaL_pushresult(&buf);
850 return 1;
851 case JSON_TABLETYPE_ARRAY:
852 lua_settop(L, 2);
853 luaL_buffinit(L, &buf);
854 luaL_addchar(&buf, '[');
855 for (idx = 1; ; idx++) {
856 lua_rawgeti(L, 1, idx);
857 if (lua_isnil(L, -1)) {
858 lua_pop(L, 1);
859 break;
860 }
861 lua_replace(L, 2);
862 if (needsep) luaL_addchar(&buf, ',');
863 else needsep = 1;
864 lua_pushcfunction(L, json_export);
865 lua_pushvalue(L, 2);
866 lua_call(L, 1, 1);
867 luaL_addvalue(&buf);
868 }
869 luaL_addchar(&buf, ']');
870 luaL_pushresult(&buf);
871 return 1;
872 }
873 json_export_tabletype_error:
874 return luaL_error(L, "JSON export not possible for ambiguous table (cannot decide whether it is an object or array)");
875 }
876 return luaL_error(L, "JSON export not possible for values of type \"%s\"", lua_typename(L, lua_type(L, 1)));
877 }
879 // functions in library module:
880 static const struct luaL_Reg json_module_functions[] = {
881 {"object", json_object},
882 {"array", json_array},
883 {"import", json_import},
884 {"export", json_export},
885 {"get", json_get},
886 {"type", json_type},
887 {"isnull", json_isnull},
888 {"setnull", json_setnull},
889 {NULL, NULL}
890 };
892 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
893 static const struct luaL_Reg json_metatable_functions[] = {
894 {"__len", json_len},
895 {"__index", json_index},
896 {"__newindex", json_newindex},
897 {"__pairs", json_pairs},
898 {"__ipairs", json_ipairs},
899 {NULL, NULL}
900 };
902 // metamethods for JSON null marker:
903 static const struct luaL_Reg json_nullmark_metamethods[] = {
904 {"__tostring", json_nullmark_tostring},
905 {NULL, NULL}
906 };
908 // initializes json library:
909 int luaopen_json(lua_State *L) {
910 // empty stack:
911 lua_settop(L, 0);
912 // push library module onto stack position 1:
913 lua_newtable(L);
914 // register library functions:
915 luaL_setfuncs(L, json_module_functions, 0);
916 // create and store unknownmt:
917 lua_newtable(L);
918 luaL_setfuncs(L, json_metatable_functions, 0);
919 json_regstore(L, unknownmt);
920 // create and store objectmt:
921 lua_newtable(L);
922 luaL_setfuncs(L, json_metatable_functions, 0);
923 json_regstore(L, objectmt);
924 // create and store arraymt:
925 lua_newtable(L);
926 luaL_setfuncs(L, json_metatable_functions, 0);
927 json_regstore(L, arraymt);
928 // create and store ephemeron table to store shadow tables for each JSON object/array
929 // to allow NULL values returned as nil
930 lua_newtable(L);
931 lua_newtable(L); // metatable for ephemeron table
932 lua_pushliteral(L, "__mode");
933 lua_pushliteral(L, "k");
934 lua_rawset(L, -3);
935 lua_setmetatable(L, -2);
936 json_regstore(L, shadowtbl);
937 // set metatable of null marker and make it available through library module:
938 json_pushnullmark(L);
939 lua_newtable(L);
940 luaL_setfuncs(L, json_nullmark_metamethods, 0);
941 lua_setmetatable(L, -2);
942 lua_setfield(L, 1, "null");
943 // return library module (that's expected on top of stack):
944 return 1;
945 }