webmcp
view libraries/json/json.c @ 215:ba3dd4a17e3d
Some code cleanup/rearrangement for request handling
| author | jbe |
|---|---|
| date | Mon Jan 12 01:48:11 2015 +0100 (2015-01-12) |
| parents | eceb6f56e9ed |
| children | f0303fca9218 |
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: json_import can store 2^32 / 3 levels on stack swap (using
9 // also negative indicies after integer wraparound), and
10 // json_export can store even more levels, so 1024^3 =
11 // 1073741824 is a safe value and allows practically unlimited
12 // levels for JSON documents <= 2 GiB.
13 #define JSON_MAXDEPTH (1024*1024*1024)
15 // define type JSON_LIGHTUSERDATA and
16 // generate dummy memory addresses for lightuserdata values:
17 #define JSON_LIGHTUSERDATA char
18 static struct {
19 JSON_LIGHTUSERDATA nullmark; // lightuserdata value represents a NULL value
20 JSON_LIGHTUSERDATA shadowtbl; // lightuserdata key for shadow table
21 } json_lightuserdata;
23 // macros for special nullmark value:
24 #define json_isnullmark(L, i) (lua_touserdata((L), (i)) == &json_lightuserdata.nullmark)
25 #define json_pushnullmark(L) lua_pushlightuserdata((L), &json_lightuserdata.nullmark)
27 // macros for getting and setting shadow tables
28 #define json_setshadow(L, i) lua_rawsetp((L), (i), &json_lightuserdata.shadowtbl)
29 #define json_getshadow(L, i) lua_rawgetp((L), (i), &json_lightuserdata.shadowtbl)
30 #define json_createproxy(L) lua_createtable((L), 0, 1)
32 // generate additional dummy memory addresses that represent Lua objects
33 // via lightuserdata keys and LUA_REGISTRYINDEX:
34 static struct {
35 JSON_LIGHTUSERDATA objectmt; // metatable for JSON objects
36 JSON_LIGHTUSERDATA arraymt; // metatable for JSON arrays
37 } json_registry;
39 // macros for usage of Lua registry:
40 #define json_regpointer(x) (&json_registry.x)
41 #define json_regfetchpointer(L, x) lua_rawgetp((L), LUA_REGISTRYINDEX, (x))
42 #define json_regfetch(L, x) json_regfetchpointer(L, json_regpointer(x))
43 #define json_regstore(L, x) lua_rawsetp(L, LUA_REGISTRYINDEX, json_regpointer(x))
45 // returns the string "<JSON null marker>":
46 static int json_nullmark_tostring(lua_State *L) {
47 lua_pushliteral(L, "<JSON null marker>");
48 return 1;
49 }
51 #define json_object_source_idx 1
52 #define json_object_iterator_idx 2
53 #define json_object_output_idx 3
54 #define json_object_shadow_idx 4
55 #define json_object_iterfun_idx 5
56 #define json_object_itertbl_idx 6
58 // converts a Lua table (or any other iterable value) to a JSON object:
59 // (does never modify the argument, returns an empty object or array if argument is nil)
60 static int json_object(lua_State *L) {
61 // determine is argument is given:
62 if (lua_isnoneornil(L, json_object_source_idx)) {
63 // if no argument is given (or if argument is nil),
64 // create proxy table with shadow table, and leave proxy table on top of stack:
65 json_createproxy(L);
66 lua_newtable(L);
67 json_setshadow(L, -2);
68 } else {
69 // if an argument was given,
70 // stack shall contain only one function argument:
71 lua_settop(L, 1);
72 // check if there is an iterator function in its metatable:
73 if (luaL_getmetafield(L, json_object_source_idx, "__pairs")) {
74 // if there is an iterator function,
75 // leave it on stack position 2 and verify its type:
76 if (lua_type(L, json_object_iterator_idx) != LUA_TFUNCTION)
77 return luaL_error(L, "__pairs metamethod is not a function");
78 } else {
79 // if there is no iterator function,
80 // verify the type of the argument itself:
81 luaL_checktype(L, json_object_source_idx, LUA_TTABLE);
82 // push nil onto stack position 2:
83 lua_pushnil(L);
84 }
85 // create result table on stack position 3:
86 json_createproxy(L);
87 // create shadow table on stack position 4:
88 lua_newtable(L);
89 lua_pushvalue(L, -1);
90 json_setshadow(L, -3);
91 // check if iterator function exists:
92 if (lua_isnil(L, json_object_iterator_idx)) {
93 // if there is no iterator function,
94 // copy all string key value pairs to shadow table:
95 for (lua_pushnil(L); lua_next(L, json_object_source_idx); lua_pop(L, 1)) {
96 if (lua_type(L, -2) == LUA_TSTRING) {
97 lua_pushvalue(L, -2);
98 lua_pushvalue(L, -2);
99 lua_rawset(L, json_object_shadow_idx);
100 }
101 }
102 } else {
103 // if there is an iterator function,
104 // call iterator function with source value (first argument)
105 // and store 3 result values on stack positions 5 through 7:
106 lua_pushvalue(L, json_object_iterator_idx);
107 lua_pushvalue(L, 1);
108 lua_call(L, 1, 3);
109 // iterate through key value pairs and store some of them in shadow table
110 // while replacing nil values with null-marker:
111 while (1) {
112 // call iterfun function:
113 lua_pushvalue(L, json_object_iterfun_idx);
114 lua_pushvalue(L, json_object_itertbl_idx);
115 lua_pushvalue(L, -3);
116 lua_remove(L, -4);
117 lua_call(L, 2, 2);
118 // break iteration loop if key is nil:
119 if (lua_isnil(L, -2)) break;
120 // store key value pair only if key type is correct:
121 if (lua_type(L, -2) == LUA_TSTRING) {
122 // if key type is correct,
123 // push key onto stack:
124 lua_pushvalue(L, -2);
125 // if value is nil, push null-marker onto stack (as value):
126 if (lua_isnil(L, -2)) json_pushnullmark(L);
127 // else push value onto stack:
128 else lua_pushvalue(L, -2);
129 // set key value pair in shadow table:
130 lua_rawset(L, json_object_shadow_idx);
131 }
132 // pop value from stack, but leave key on stack:
133 lua_pop(L, 1);
134 }
135 }
136 // let result table be on top of stack:
137 lua_settop(L, json_object_output_idx);
138 }
139 // set metatable (for result table on top of stack):
140 json_regfetch(L, objectmt);
141 lua_setmetatable(L, -2);
142 // return table on top of stack:
143 return 1;
144 }
146 #define json_array_source_idx 1
147 #define json_array_output_idx 2
148 #define json_array_shadow_idx 3
150 // converts a Lua table (or any other iterable value) to a JSON array:
151 // (does never modify the argument, returns an empty object or array if argument is nil)
152 static int json_array(lua_State *L) {
153 // determine is argument is given:
154 if (lua_isnoneornil(L, json_array_source_idx)) {
155 // if no argument is given (or if argument is nil),
156 // create proxy table with shadow table, and leave proxy table on top of stack:
157 json_createproxy(L);
158 lua_newtable(L);
159 json_setshadow(L, -2);
160 } else {
161 lua_Integer arrayidx, arraylen;
162 // if an argument was given,
163 // stack shall contain only one function argument:
164 lua_settop(L, 1);
165 // create result table on stack position 2:
166 json_createproxy(L);
167 // create shadow table on stack position 3:
168 lua_newtable(L);
169 lua_pushvalue(L, -1);
170 json_setshadow(L, -3);
171 // determine length of array:
172 arraylen = luaL_len(L, json_array_source_idx);
173 // for an array, copy consecutive integer value pairs to shadow table:
174 for (arrayidx=0; arrayidx<arraylen; ) {
175 // increment arrayidx at head of loop:
176 arrayidx++;
177 // get next array entry:
178 lua_pushinteger(L, arrayidx);
179 lua_gettable(L, json_array_source_idx);
180 // check if value is nil:
181 if (lua_isnil(L, -1)) {
182 // if yes, replace it with null-marker:
183 lua_pop(L, 1);
184 json_pushnullmark(L);
185 }
186 // store value in shadow table:
187 lua_rawseti(L, json_array_shadow_idx, arrayidx);
188 }
189 // let result table be on top of stack:
190 lua_settop(L, json_array_output_idx);
191 }
192 // set metatable (for result table on top of stack):
193 json_regfetch(L, arraymt);
194 lua_setmetatable(L, -2);
195 // return table on top of stack:
196 return 1;
197 }
199 // internal states of JSON parser:
200 #define JSON_STATE_VALUE 0
201 #define JSON_STATE_OBJECT_KEY 1
202 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
203 #define JSON_STATE_OBJECT_VALUE 3
204 #define JSON_STATE_OBJECT_SEPARATOR 4
205 #define JSON_STATE_ARRAY_VALUE 5
206 #define JSON_STATE_ARRAY_SEPARATOR 6
207 #define JSON_STATE_END 7
209 // special Lua stack indicies for json_import function:
210 #define json_import_objectmt_idx 2
211 #define json_import_arraymt_idx 3
212 #define json_import_stackswap_idx 4
214 // macros for hex decoding:
215 #define json_utf16_surrogate(x) ((x) >= 0xD800 && (x) <= 0xDFFF)
216 #define json_utf16_lead(x) ((x) >= 0xD800 && (x) <= 0xDBFF)
217 #define json_utf16_tail(x) ((x) >= 0xDC00 && (x) <= 0xDFFF)
218 #define json_import_readhex(x) \
219 do { \
220 x = 0; \
221 for (i=0; i<4; i++) { \
222 x <<= 4; \
223 c = str[pos++]; \
224 if (c >= '0' && c <= '9') x += c - '0'; \
225 else if (c >= 'A' && c <= 'F') x += c - 'A' + 10; \
226 else if (c >= 'a' && c <= 'f') x += c - 'a' + 10; \
227 else if (c == 0) goto json_import_unexpected_eof; \
228 else goto json_import_unexpected_escape; \
229 } \
230 } while (0)
232 // decodes a JSON document:
233 static int json_import(lua_State *L) {
234 int stackswapidx = 0; // elements in stack swap table
235 int i; // loop variable
236 const char *str; // string to parse
237 size_t total; // total length of string to parse
238 size_t pos = 0; // current position in string to parse
239 size_t level = 0; // nested levels of objects/arrays currently being processed
240 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
241 unsigned char c; // variable to store a single character to be processed (unsigned!)
242 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
243 char *cbuf; // C buffer to decode JSON string values
244 size_t outlen; // maximum length or write position of C buffer
245 long codepoint; // decoded UTF-16 character or higher codepoint
246 long utf16tail; // second decoded UTF-16 character (surrogate tail)
247 size_t arraylen; // variable to temporarily store the array length
248 // require string as argument and convert to C string with length information:
249 str = luaL_checklstring(L, 1, &total);
250 // if string contains a NULL byte, this is a syntax error
251 if (strlen(str) != total) goto json_import_syntax_error;
252 // stack shall contain one function argument:
253 lua_settop(L, 1);
254 // push objectmt onto stack position 2:
255 json_regfetch(L, objectmt);
256 // push arraymt onto stack position 3:
257 json_regfetch(L, arraymt);
258 // push table for stack swapping onto stack position 5:
259 // (needed to avoid Lua stack overflows)
260 lua_newtable(L);
261 // main loop of parser:
262 json_import_loop:
263 // skip whitespace and store next character in variable 'c':
264 while (c = str[pos],
265 c == ' ' ||
266 c == '\f' ||
267 c == '\n' ||
268 c == '\r' ||
269 c == '\t' ||
270 c == '\v'
271 ) pos++;
272 // NOTE: variable c needs to be unsigned in the following code
273 // switch statement to handle certain (single) characters:
274 switch (c) {
275 // handle end of JSON document:
276 case 0:
277 // if end of JSON document was expected, then return top element of stack as result:
278 if (mode == JSON_STATE_END) return 1;
279 // otherwise, the JSON document was malformed:
280 if (level == 0) {
281 lua_pushnil(L);
282 lua_pushliteral(L, "Empty string");
283 } else {
284 json_import_unexpected_eof:
285 lua_pushnil(L);
286 lua_pushliteral(L, "Unexpected end of JSON document");
287 }
288 return 2;
289 // new JSON object or JSON array:
290 case '{':
291 case '[':
292 // if an encountered JSON object is not expected here, then return an error:
293 if (
294 c == '{' &&
295 mode != JSON_STATE_VALUE &&
296 mode != JSON_STATE_OBJECT_VALUE &&
297 mode != JSON_STATE_ARRAY_VALUE
298 ) goto json_import_syntax_error;
299 // if an encountered JSON array is not expected here, then return an error:
300 if (
301 c == '[' &&
302 mode != JSON_STATE_VALUE &&
303 mode != JSON_STATE_OBJECT_VALUE &&
304 mode != JSON_STATE_ARRAY_VALUE
305 ) goto json_import_syntax_error;
306 // consume input character:
307 pos++;
308 // limit nested levels:
309 if (level >= JSON_MAXDEPTH) {
310 lua_pushnil(L);
311 lua_pushfstring(L, "More than %d nested JSON levels", JSON_MAXDEPTH);
312 return 2;
313 }
314 // swap Lua stack entries for previous level to swap table:
315 // (avoids depth limitations due to Lua stack size)
316 if (level) {
317 lua_rawseti(L, json_import_stackswap_idx, ++stackswapidx);
318 lua_rawseti(L, json_import_stackswap_idx, ++stackswapidx);
319 lua_rawseti(L, json_import_stackswap_idx, ++stackswapidx);
320 }
321 // increment level:
322 level++;
323 // create JSON object or JSON array on stack:
324 lua_newtable(L);
325 // set metatable of JSON object or JSON array:
326 lua_pushvalue(L, c == '{' ? json_import_objectmt_idx : json_import_arraymt_idx);
327 lua_setmetatable(L, -2);
328 // create internal shadow table on stack:
329 lua_newtable(L);
330 // register internal shadow table:
331 lua_pushvalue(L, -1);
332 json_setshadow(L, -3);
333 // distinguish between JSON objects and JSON arrays:
334 if (c == '{') {
335 // if JSON object,
336 // expect object key (or end of object) to follow:
337 mode = JSON_STATE_OBJECT_KEY;
338 } else {
339 // if JSON array,
340 // expect array value (or end of array) to follow:
341 mode = JSON_STATE_ARRAY_VALUE;
342 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
343 if (c == '[') lua_pushnil(L);
344 }
345 goto json_import_loop;
346 // end of JSON object:
347 case '}':
348 // if end of JSON object is not expected here, then return an error:
349 if (
350 mode != JSON_STATE_OBJECT_KEY &&
351 mode != JSON_STATE_OBJECT_SEPARATOR
352 ) goto json_import_syntax_error;
353 // jump to common code for end of JSON object and JSON array:
354 goto json_import_close;
355 // end of JSON array:
356 case ']':
357 // if end of JSON array is not expected here, then return an error:
358 if (
359 mode != JSON_STATE_ARRAY_VALUE &&
360 mode != JSON_STATE_ARRAY_SEPARATOR
361 ) goto json_import_syntax_error;
362 // pop nil key/magic (that was needed to keep stack balance):
363 lua_pop(L, 1);
364 // continue with common code for end of JSON object and JSON array:
365 // common code for end of JSON object or JSON array:
366 json_import_close:
367 // consume input character:
368 pos++;
369 // pop shadow table:
370 lua_pop(L, 1);
371 // check if nested:
372 if (--level) {
373 // if nested,
374 // restore previous stack elements from stack swap:
375 lua_rawgeti(L, json_import_stackswap_idx, stackswapidx--);
376 lua_insert(L, -2);
377 lua_rawgeti(L, json_import_stackswap_idx, stackswapidx--);
378 lua_insert(L, -2);
379 lua_rawgeti(L, json_import_stackswap_idx, stackswapidx--);
380 lua_insert(L, -2);
381 // check if outer(!) structure is an array or object:
382 if (lua_isnil(L, -2)) {
383 // select array value processing:
384 mode = JSON_STATE_ARRAY_VALUE;
385 } else {
386 // select object value processing:
387 mode = JSON_STATE_OBJECT_VALUE;
388 }
389 // store value in outer structure:
390 goto json_import_process_value;
391 }
392 // if not nested, then expect end of JSON document and continue with loop:
393 mode = JSON_STATE_END;
394 goto json_import_loop;
395 // key terminator:
396 case ':':
397 // if key terminator is not expected here, then return an error:
398 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
399 goto json_import_syntax_error;
400 // consume input character:
401 pos++;
402 // expect object value to follow:
403 mode = JSON_STATE_OBJECT_VALUE;
404 // continue with loop:
405 goto json_import_loop;
406 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
407 case ',':
408 // branch according to parser state:
409 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
410 // expect an object key to follow:
411 mode = JSON_STATE_OBJECT_KEY;
412 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
413 // expect an array value to follow:
414 mode = JSON_STATE_ARRAY_VALUE;
415 } else {
416 // if value terminator is not expected here, then return an error:
417 goto json_import_syntax_error;
418 }
419 // consume input character:
420 pos++;
421 // continue with loop:
422 goto json_import_loop;
423 // string literal:
424 case '"':
425 // consume quote character:
426 pos++;
427 // find last character in input string:
428 outlen = pos;
429 while ((c = str[outlen]) != '"') {
430 // consume one character:
431 outlen++;
432 // handle unexpected end of JSON document:
433 if (c == 0) goto json_import_unexpected_eof;
434 // consume one extra character when encountering an escaped quote:
435 else if (c == '\\' && str[outlen] == '"') outlen++;
436 }
437 // determine buffer length:
438 outlen -= pos;
439 // check if string is non empty:
440 if (outlen) {
441 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
442 cbuf = luaL_buffinitsize(L, &luabuf, outlen);
443 outlen = 0;
444 // loop through the characters until encountering end quote:
445 while ((c = str[pos++]) != '"') {
446 // NOTE: unexpected end cannot happen anymore
447 if (c < 32 || c == 127) {
448 // do not allow ASCII control characters:
449 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
450 // by this parser to allow different encodings than Unicode
451 lua_pushnil(L);
452 lua_pushliteral(L, "Unexpected control character in JSON string");
453 return 2;
454 } else if (c == '\\') {
455 // read next char after backslash escape:
456 c = str[pos++];
457 switch (c) {
458 // unexpected end-of-string:
459 case 0:
460 goto json_import_unexpected_eof;
461 // unescaping of quotation mark, slash, and backslash:
462 case '"':
463 case '/':
464 case '\\':
465 cbuf[outlen++] = c;
466 break;
467 // unescaping of backspace:
468 case 'b': cbuf[outlen++] = '\b'; break;
469 // unescaping of form-feed:
470 case 'f': cbuf[outlen++] = '\f'; break;
471 // unescaping of new-line:
472 case 'n': cbuf[outlen++] = '\n'; break;
473 // unescaping of carriage-return:
474 case 'r': cbuf[outlen++] = '\r'; break;
475 // unescaping of tabulator:
476 case 't': cbuf[outlen++] = '\t'; break;
477 // unescaping of UTF-16 characters
478 case 'u':
479 // decode 4 hex nibbles:
480 json_import_readhex(codepoint);
481 // handle surrogate character:
482 if (json_utf16_surrogate(codepoint)) {
483 // check if first surrogate is in valid range:
484 if (json_utf16_lead(codepoint)) {
485 // require second surrogate:
486 if ((c = str[pos++]) != '\\' || (c = str[pos++]) != 'u') {
487 if (c == 0) goto json_import_unexpected_eof;
488 else goto json_import_wrong_surrogate;
489 }
490 // read 4 hex nibbles of second surrogate character:
491 json_import_readhex(utf16tail);
492 // check if second surrogate is in valid range:
493 if (!json_utf16_tail(utf16tail)) goto json_import_wrong_surrogate;
494 // calculate codepoint:
495 codepoint = 0x10000 + (utf16tail - 0xDC00) + (codepoint - 0xD800) * 0x400;
496 } else {
497 // throw error for wrong surrogates:
498 json_import_wrong_surrogate:
499 lua_pushnil(L);
500 lua_pushliteral(L, "Illegal UTF-16 surrogate in JSON string escape sequence");
501 return 2;
502 }
503 }
504 // encode as UTF-8:
505 if (codepoint < 0x80) {
506 cbuf[outlen++] = (char)codepoint;
507 } else if (codepoint < 0x800) {
508 cbuf[outlen++] = (char)(0xc0 | (codepoint >> 6));
509 cbuf[outlen++] = (char)(0x80 | (codepoint & 0x3f));
510 } else if (codepoint < 0x10000) {
511 cbuf[outlen++] = (char)(0xe0 | (codepoint >> 12));
512 cbuf[outlen++] = (char)(0x80 | ((codepoint >> 6) & 0x3f));
513 cbuf[outlen++] = (char)(0x80 | (codepoint & 0x3f));
514 } else {
515 cbuf[outlen++] = (char)(0xf0 | (codepoint >> 18));
516 cbuf[outlen++] = (char)(0x80 | ((codepoint >> 12) & 0x3f));
517 cbuf[outlen++] = (char)(0x80 | ((codepoint >> 6) & 0x3f));
518 cbuf[outlen++] = (char)(0x80 | (codepoint & 0x3f));
519 }
520 break;
521 // unexpected escape sequence:
522 default:
523 json_import_unexpected_escape:
524 lua_pushnil(L);
525 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
526 return 2;
527 }
528 } else {
529 // normal character:
530 cbuf[outlen++] = c;
531 }
532 }
533 // process buffer to Lua string:
534 luaL_pushresultsize(&luabuf, outlen);
535 } else {
536 // if JSON string is empty,
537 // push empty Lua string:
538 lua_pushliteral(L, "");
539 // consume closing quote:
540 pos++;
541 }
542 // continue with processing of decoded string:
543 goto json_import_process_value;
544 }
545 // process values whose type is is not deducible from a single character:
546 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
547 // for numbers,
548 // use strtod() call to parse a (double precision) floating point number:
549 double numval;
550 char *endptr;
551 numval = strtod(str+pos, &endptr);
552 // catch parsing errors:
553 if (endptr == str+pos) goto json_import_syntax_error;
554 // consume characters that were parsed:
555 pos += endptr - (str+pos);
556 // push parsed (double precision) floating point number on Lua stack:
557 lua_pushnumber(L, numval);
558 } else if (!strncmp(str+pos, "true", 4)) {
559 // consume 4 input characters for "true":
560 pos += 4;
561 // put Lua true value onto stack:
562 lua_pushboolean(L, 1);
563 } else if (!strncmp(str+pos, "false", 5)) {
564 // consume 5 input characters for "false":
565 pos += 5;
566 // put Lua false value onto stack:
567 lua_pushboolean(L, 0);
568 } else if (!strncmp(str+pos, "null", 4)) {
569 // consume 4 input characters for "null":
570 pos += 4;
571 // push special null-marker onto stack:
572 json_pushnullmark(L);
573 } else {
574 // all other cases are a syntax error:
575 goto json_import_syntax_error;
576 }
577 // process a decoded value or key value pair (expected on top of Lua stack):
578 json_import_process_value:
579 switch (mode) {
580 // an object key has been read:
581 case JSON_STATE_OBJECT_KEY:
582 // if an object key is not a string, then this is a syntax error:
583 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
584 // expect key terminator to follow:
585 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
586 // continue with loop:
587 goto json_import_loop;
588 // a key value pair has been read:
589 case JSON_STATE_OBJECT_VALUE:
590 // store key value pair in outer shadow table:
591 lua_rawset(L, -3);
592 // expect value terminator (or end of object) to follow:
593 mode = JSON_STATE_OBJECT_SEPARATOR;
594 // continue with loop:
595 goto json_import_loop;
596 // an array value has been read:
597 case JSON_STATE_ARRAY_VALUE:
598 // get current array length:
599 arraylen = lua_rawlen(L, -3);
600 // throw error if array would exceed INT_MAX elements:
601 // TODO: Lua 5.3 may support more elements
602 if (arraylen >= INT_MAX) {
603 lua_pushnil(L);
604 lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
605 }
606 // store value in outer shadow table:
607 lua_rawseti(L, -3, arraylen + 1);
608 // expect value terminator (or end of object) to follow:
609 mode = JSON_STATE_ARRAY_SEPARATOR;
610 // continue with loop
611 goto json_import_loop;
612 // a single value has been read:
613 case JSON_STATE_VALUE:
614 // leave value on top of stack, expect end of JSON document, and continue with loop:
615 mode = JSON_STATE_END;
616 goto json_import_loop;
617 }
618 // syntax error handling (reachable by goto statement):
619 json_import_syntax_error:
620 lua_pushnil(L);
621 lua_pushliteral(L, "Syntax error in JSON document");
622 return 2;
623 }
625 // gets a value or its type from a JSON document (passed as first argument)
626 // using a path (passed as variable number of keys after the first argument):
627 static int json_path(lua_State *L, int type_mode) {
628 int stacktop; // number of arguments
629 int idx = 2; // stack index of current argument to process
630 // require at least one argument:
631 luaL_checkany(L, 1);
632 // store stack index of top of stack (number of arguments):
633 stacktop = lua_gettop(L);
634 // use first argument as "current value" (stored on top of stack):
635 lua_pushvalue(L, 1);
636 // process each "path key" (2nd argument and following arguments):
637 while (idx <= stacktop) {
638 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
639 if (lua_isnil(L, -1)) return 1;
640 // try to get shadow table of "current value":
641 json_getshadow(L, -1);
642 if (lua_isnil(L, -1)) {
643 // if no shadow table is found,
644 if (lua_type(L, -2) == LUA_TTABLE) {
645 // and if "current value" is a table,
646 // pop nil from stack:
647 lua_pop(L, 1);
648 // get "next value" using the "path key":
649 lua_pushvalue(L, idx++);
650 lua_gettable(L, -2);
651 } else {
652 // if "current value" is not a table,
653 // then the path cannot be walked and nil (already on top of stack) is returned:
654 return 1;
655 }
656 } else {
657 // if a shadow table is found,
658 // set "current value" to its shadow table:
659 lua_replace(L, -2);
660 // get "next value" using the "path key":
661 lua_pushvalue(L, idx++);
662 lua_rawget(L, -2);
663 }
664 // the "next value" replaces the "current value":
665 lua_replace(L, -2);
666 }
667 if (!type_mode) {
668 // if a value (and not its type) was requested,
669 // check if value is the null-marker, and store nil on top of Lua stack in that case:
670 if (json_isnullmark(L, -1)) lua_pushnil(L);
671 } else {
672 // if the type was requested,
673 // check if value is the null-marker:
674 if (json_isnullmark(L, -1)) {
675 // if yes, store string "null" on top of Lua stack:
676 lua_pushliteral(L, "null");
677 } else {
678 // otherwise,
679 // check if metatable indicates "object" or "array":
680 if (lua_getmetatable(L, -1)) {
681 json_regfetch(L, objectmt);
682 if (lua_rawequal(L, -2, -1)) {
683 // if value has metatable for JSON objects,
684 // return string "object":
685 lua_pushliteral(L, "object");
686 return 1;
687 }
688 json_regfetch(L, arraymt);
689 if (lua_rawequal(L, -3, -1)) {
690 // if value has metatable for JSON arrays,
691 // return string "object":
692 lua_pushliteral(L, "array");
693 return 1;
694 }
695 // remove 3 metatables (one of the value, two for comparison) from stack:
696 lua_pop(L, 3);
697 }
698 // otherwise, get the Lua type:
699 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
700 }
701 }
702 // return the top most value on the Lua stack:
703 return 1;
704 }
706 // gets a value from a JSON document (passed as first argument)
707 // using a path (passed as variable number of keys after the first argument):
708 static int json_get(lua_State *L) {
709 return json_path(L, 0);
710 }
712 // gets a value's type from a JSON document (passed as first argument)
713 // using a path (passed as variable number of keys after first the argument):
714 static int json_type(lua_State *L) {
715 return json_path(L, 1);
716 }
718 // special Lua stack indicies for json_set function:
719 #define json_set_objectmt_idx 1
720 #define json_set_arraymt_idx 2
722 // stack offset of arguments to json_set function:
723 #define json_set_idxshift 2
725 // sets a value (passed as second argument) in a JSON document (passed as first argument)
726 // using a path (passed as variable number of keys starting at third argument):
727 static int json_set(lua_State *L) {
728 int stacktop; // stack index of top of stack (after shifting)
729 int idx; // stack index of current argument to process
730 // require at least three arguments:
731 luaL_checkany(L, 1);
732 luaL_checkany(L, 2);
733 luaL_checkany(L, 3);
734 // insert objectmt into stack at position 1 (shifting the arguments):
735 json_regfetch(L, objectmt);
736 lua_insert(L, 1);
737 // insert arraymt into stack at position 2 (shifting the arguments):
738 json_regfetch(L, arraymt);
739 lua_insert(L, 2);
740 // store stack index of top of stack:
741 stacktop = lua_gettop(L);
742 // use nil as initial "parent value":
743 lua_pushnil(L);
744 // use first argument as "current value":
745 lua_pushvalue(L, 1 + json_set_idxshift);
746 // set all necessary values in path:
747 for (idx = 3 + json_set_idxshift; idx<=stacktop; idx++) {
748 // push metatable of "current value" onto stack:
749 if (!lua_getmetatable(L, -1)) lua_pushnil(L);
750 // distinguish according to type of path key:
751 switch (lua_type(L, idx)) {
752 case LUA_TSTRING:
753 // if path key is a string,
754 // check if "current value" is a JSON object (or table without metatable):
755 if (
756 lua_rawequal(L, -1, json_set_objectmt_idx) ||
757 (lua_isnil(L, -1) && lua_type(L, -2) == LUA_TTABLE)
758 ) {
759 // if "current value" is acceptable,
760 // pop metatable and leave "current value" on top of stack:
761 lua_pop(L, 1);
762 } else {
763 // if "current value" is not acceptable:
764 // pop metatable and "current value":
765 lua_pop(L, 2);
766 // throw error if parent element does not exist:
767 if (lua_isnil(L, -1)) return luaL_error(L, "Root element is not a JSON object");
768 // push new JSON object as "current value" onto stack:
769 json_createproxy(L);
770 // create and register shadow table:
771 lua_newtable(L);
772 json_setshadow(L, -2);
773 // set metatable of JSON object:
774 lua_pushvalue(L, json_set_objectmt_idx);
775 lua_setmetatable(L, -2);
776 // set entry in "parent value":
777 lua_pushvalue(L, idx-1);
778 lua_pushvalue(L, -2);
779 lua_settable(L, -4);
780 }
781 break;
782 case LUA_TNUMBER:
783 // if path key is a number,
784 // check if "current value" is a JSON array (or table without metatable):
785 if (
786 lua_rawequal(L, -1, json_set_arraymt_idx) ||
787 (lua_isnil(L, -1) && lua_type(L, -2) == LUA_TTABLE)
788 ) {
789 // if "current value" is acceptable,
790 // pop metatable and leave "current value" on top of stack:
791 lua_pop(L, 1);
792 } else {
793 // if "current value" is not acceptable:
794 // pop metatable and "current value":
795 lua_pop(L, 2);
796 // throw error if parent element does not exist:
797 if (lua_isnil(L, -1)) return luaL_error(L, "Root element is not a JSON array");
798 // push new JSON array as "current value" onto stack:
799 json_createproxy(L);
800 // create and register shadow table:
801 lua_newtable(L);
802 json_setshadow(L, -2);
803 // set metatable of JSON array:
804 lua_pushvalue(L, json_set_arraymt_idx);
805 lua_setmetatable(L, -2);
806 // set entry in "parent value":
807 lua_pushvalue(L, idx-1);
808 lua_pushvalue(L, -2);
809 lua_settable(L, -4);
810 }
811 break;
812 default:
813 return luaL_error(L, "Invalid path key of type %s", lua_typename(L, lua_type(L, idx)));
814 }
815 // check if last path element is being processed:
816 if (idx == stacktop) {
817 // if the last path element is being processed,
818 // set last path value in "current value" container:
819 lua_pushvalue(L, idx);
820 lua_pushvalue(L, 2 + json_set_idxshift);
821 lua_settable(L, -3);
822 } else {
823 // if the processed path element is not the last,
824 // use old "current value" as new "parent value"
825 lua_remove(L, -2);
826 // push new "current value" onto stack by performing a lookup:
827 lua_pushvalue(L, idx);
828 lua_gettable(L, -2);
829 }
830 }
831 // return first argument for convenience:
832 lua_settop(L, 1 + json_set_idxshift);
833 return 1;
834 }
836 // returns the length of a JSON array (or zero for a table without numeric keys):
837 static int json_len(lua_State *L) {
838 // require table as first argument:
839 luaL_checktype(L, 1, LUA_TTABLE);
840 // stack shall contain one function argument:
841 lua_settop(L, 1);
842 // push shadow table or nil onto stack:
843 json_getshadow(L, 1);
844 // pop nil from stack if no shadow table has been found:
845 if (lua_isnil(L, -1)) lua_pop(L, 1);
846 // return length of argument or shadow table:
847 lua_pushnumber(L, lua_rawlen(L, -1));
848 return 1;
849 }
851 // __index metamethod for JSON objects and JSON arrays:
852 static int json_index(lua_State *L) {
853 // require table as first argument:
854 luaL_checktype(L, 1, LUA_TTABLE);
855 // stack shall contain two function arguments:
856 lua_settop(L, 2);
857 // replace first argument with its shadow table
858 // or throw error if no shadow table is found:
859 json_getshadow(L, 1);
860 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
861 lua_replace(L, 1);
862 // use key passed as second argument to lookup value in shadow table:
863 lua_rawget(L, 1);
864 // if value is null-marker, then push nil onto stack:
865 if (json_isnullmark(L, 2)) lua_pushnil(L);
866 // return either looked up value, or nil
867 return 1;
868 }
870 // __newindex metamethod for JSON objects and JSON arrays:
871 static int json_newindex(lua_State *L) {
872 // require table as first argument
873 luaL_checktype(L, 1, LUA_TTABLE);
874 // stack shall contain three function arguments:
875 lua_settop(L, 3);
876 // replace first argument with its shadow table
877 // or throw error if no shadow table is found:
878 json_getshadow(L, 1);
879 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
880 lua_replace(L, 1);
881 // second and third argument to write to shadow table:
882 lua_rawset(L, 1);
883 // return nothing:
884 return 0;
885 }
887 // function returned as first value by json_pairs function:
888 static int json_pairs_iterfunc(lua_State *L) {
889 // require table as first argument
890 luaL_checktype(L, 1, LUA_TTABLE);
891 // stack shall contain two function arguments:
892 lua_settop(L, 2);
893 // get next key value pair from shadow table (argument 1) using previous key (argument 2)
894 // and return nothing if there is no next pair:
895 if (!lua_next(L, 1)) return 0;
896 // replace null-marker with nil:
897 if (json_isnullmark(L, -1)) {
898 lua_pop(L, 1);
899 lua_pushnil(L);
900 }
901 // return key and value (or key and nil, if null-marker was found):
902 return 2;
903 }
905 // returns a triple such that 'for key, value in pairs(obj) do ... end'
906 // iterates through all key value pairs (including JSON null values represented as Lua nil):
907 static int json_pairs(lua_State *L) {
908 // require table as first argument
909 luaL_checktype(L, 1, LUA_TTABLE);
910 // return triple of function json_pairs_iterfunc, shadow table of first argument, and nil:
911 lua_pushcfunction(L, json_pairs_iterfunc);
912 json_getshadow(L, 1);
913 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
914 lua_pushnil(L);
915 return 3;
916 }
918 // function returned as first value by json_ipairs function:
919 static int json_ipairs_iterfunc(lua_State *L) {
920 lua_Integer idx;
921 // require table as first argument
922 luaL_checktype(L, 1, LUA_TTABLE);
923 // stack shall contain two function arguments:
924 lua_settop(L, 2);
925 // calculate new index by incrementing second argument:
926 idx = lua_tointeger(L, 2) + 1;
927 // do integer lookup in shadow table and store result on stack position 3:
928 lua_rawgeti(L, 1, idx);
929 // return nothing if there was no value:
930 if (lua_isnil(L, 3)) return 0;
931 // return new index and
932 // either the looked up value if it is not equal to the null-marker
933 // or nil instead of null-marker:
934 lua_pushinteger(L, idx);
935 if (json_isnullmark(L, 3)) lua_pushnil(L);
936 else lua_pushvalue(L, 3);
937 return 2;
938 }
940 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
941 // iterates through all values (including JSON null values represented as Lua nil):
942 static int json_ipairs(lua_State *L) {
943 // require table as first argument
944 luaL_checktype(L, 1, LUA_TTABLE);
945 // return triple of function json_ipairs_iterfunc, shadow table of first argument, and zero:
946 lua_pushcfunction(L, json_ipairs_iterfunc);
947 json_getshadow(L, 1);
948 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
949 lua_pushinteger(L, 0);
950 return 3;
951 }
953 // datatype representing a table key:
954 // (used for sorting)
955 typedef struct {
956 size_t length;
957 const char *data;
958 } json_key_t;
960 // comparation function for table keys to be passed to qsort function:
961 static int json_key_cmp(json_key_t *key1, json_key_t *key2) {
962 size_t pos = 0;
963 unsigned char c1, c2;
964 while (1) {
965 if (key1->length > pos) {
966 if (key2->length > pos) {
967 c1 = key1->data[pos];
968 c2 = key2->data[pos];
969 if (c1 < c2) return -1;
970 else if (c1 > c2) return 1;
971 } else {
972 return 1;
973 }
974 } else {
975 if (key2->length > pos) {
976 return -1;
977 } else {
978 return 0;
979 }
980 }
981 pos++;
982 }
983 }
985 // constants for type detection of ambiguous tables:
986 #define JSON_TABLETYPE_UNKNOWN 0
987 #define JSON_TABLETYPE_OBJECT 1
988 #define JSON_TABLETYPE_ARRAY 2
990 typedef struct {
991 int type;
992 int pos;
993 int count;
994 json_key_t keys[1]; // or more
995 } json_container_t;
997 // special Lua stack indicies for json_export function:
998 #define json_export_value_idx 1
999 #define json_export_indentstring_idx 2
1000 #define json_export_objectmt_idx 3
1001 #define json_export_arraymt_idx 4
1002 #define json_export_stackswap_idx 5
1003 #define json_export_luacontainer_idx 6
1004 #define json_export_ccontainer_idx 7
1005 #define json_export_buffer_idx 8
1007 // encodes a JSON document (passed as first argument)
1008 // optionally using indentation (indentation string or true passed as second argument)
1009 static int json_export(lua_State *L) {
1010 int pretty; // pretty printing on? (i.e. printing with indentation)
1011 luaL_Buffer buf; // Lua buffer containing result string
1012 lua_Number num; // number to encode
1013 char numstr[21]; // encoded number (sign, zero, point, 17 significant digits, and terminating NULL byte)
1014 const char *str; // string to encode
1015 size_t strlen; // length of string to encode
1016 size_t strpos ; // position in string or position of current key
1017 unsigned char c; // character to encode (unsigned!)
1018 char hexcode[7]; // store for unicode hex escape sequence
1019 // NOTE: 7 bytes due to backslash, character 'u', 4 hex digits, and terminating NULL byte
1020 int tabletype; // table type: unknown, JSON object, or JSON array
1021 size_t keycount = 0; // number of string keys in object
1022 json_key_t *key; // pointer to C structure containing a string key
1023 int level = 0; // current depth level
1024 int i; // iteration variable for level dependent repetitions
1025 int stackswapidx = 0; // elements in stack swap table
1026 int containerkey = 0; // temporarily set to 1, if a container key is being encoded
1027 json_container_t *container = NULL; // pointer to current C struct for container information
1028 // stack shall contain two function arguments:
1029 lua_settop(L, 2);
1030 // check if pretty printing (with indentation) is desired:
1031 if (lua_toboolean(L, json_export_indentstring_idx)) {
1032 // if yes,
1033 // set pretty variable to 1:
1034 pretty = 1;
1035 // check if second argument is a boolean (true):
1036 if (lua_isboolean(L, json_export_indentstring_idx)) {
1037 // if yes,
1038 // use default indentation if indentation argument is boolean true:
1039 lua_pushliteral(L, " ");
1040 lua_replace(L, json_export_indentstring_idx);
1041 } else {
1042 // if no,
1043 // require second argument to be a string:
1044 luaL_checktype(L, json_export_indentstring_idx, LUA_TSTRING);
1045 }
1046 } else {
1047 // if no,
1048 // set pretty variable to 0:
1049 pretty = 0;
1050 }
1051 // push objectmt onto stack position 3:
1052 json_regfetch(L, objectmt);
1053 // push arraymt onto stack position 4:
1054 json_regfetch(L, arraymt);
1055 // push table for stack swapping onto stack position 5:
1056 lua_newtable(L);
1057 // create placeholders on stack positions 6 through 7:
1058 lua_settop(L, json_export_buffer_idx);
1059 // create Lua string buffer:
1060 luaL_buffinit(L, &buf);
1061 // loop:
1062 while (1) {
1063 // if value to encode is the null-marker, then treat it the same as nil:
1064 if (json_isnullmark(L, json_export_value_idx)) {
1065 lua_pushnil(L);
1066 lua_replace(L, json_export_value_idx);
1067 }
1068 // distinguish between different Lua types:
1069 switch (lua_type(L, json_export_value_idx)) {
1070 // value to encode is nil:
1071 case LUA_TNIL:
1072 // add string "null" to output buffer:
1073 luaL_addstring(&buf, "null");
1074 break;
1075 // value to encode is of type number:
1076 case LUA_TNUMBER:
1077 // convert value to double precision number:
1078 num = lua_tonumber(L, json_export_value_idx);
1079 // throw error if number is not-a-number:
1080 if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
1081 // throw error if number is positive or negative infinity:
1082 if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
1083 // determine necessary precision to represent double precision floating point number:
1084 sprintf(numstr, "%.16g", num);
1085 if (strtod(numstr, NULL) != num) sprintf(numstr, "%.17g", num);
1086 // add string encoding of the number to the output buffer:
1087 luaL_addstring(&buf, numstr);
1088 break;
1089 // value to encode is of type boolean:
1090 case LUA_TBOOLEAN:
1091 // add string "true" or "false" according to boolean value:
1092 luaL_addstring(&buf, lua_toboolean(L, json_export_value_idx) ? "true" : "false");
1093 break;
1094 // value to encode is of type string:
1095 case LUA_TSTRING:
1096 // add quoted and escaped string to output buffer:
1097 str = lua_tolstring(L, json_export_value_idx, &strlen);
1098 luaL_addchar(&buf, '"');
1099 strpos = 0;
1100 while (strpos < strlen) {
1101 c = str[strpos++];
1102 if (c == '"') luaL_addstring(&buf, "\\\"");
1103 else if (c == '\\') luaL_addstring(&buf, "\\\\");
1104 else if (c == 127) luaL_addstring(&buf, "\\u007F");
1105 else if (c >= 32) luaL_addchar(&buf, c);
1106 else if (c == '\b') luaL_addstring(&buf, "\\b");
1107 else if (c == '\f') luaL_addstring(&buf, "\\f");
1108 else if (c == '\n') luaL_addstring(&buf, "\\n");
1109 else if (c == '\r') luaL_addstring(&buf, "\\r");
1110 else if (c == '\t') luaL_addstring(&buf, "\\t");
1111 else if (c == '\v') luaL_addstring(&buf, "\\v");
1112 else {
1113 sprintf(hexcode, "\\u%04X", c);
1114 luaL_addstring(&buf, hexcode);
1115 }
1116 }
1117 luaL_addchar(&buf, '"');
1118 break;
1119 // value to encode is of type table (this includes JSON objects and JSON arrays):
1120 case LUA_TTABLE:
1121 // use table's metatable to try to determine type of table:
1122 tabletype = JSON_TABLETYPE_UNKNOWN;
1123 if (lua_getmetatable(L, json_export_value_idx)) {
1124 if (lua_rawequal(L, -1, json_export_objectmt_idx)) {
1125 tabletype = JSON_TABLETYPE_OBJECT;
1126 } else {
1127 if (lua_rawequal(L, -1, json_export_arraymt_idx)) {
1128 tabletype = JSON_TABLETYPE_ARRAY;
1129 } else {
1130 return luaL_error(L, "JSON export not possible for tables with nonsupported metatable");
1131 }
1132 }
1133 // reset stack (pop metatable from stack):
1134 lua_pop(L, 1);
1135 }
1136 // replace table with its shadow table if existent:
1137 json_getshadow(L, json_export_value_idx);
1138 if (lua_isnil(L, -1)) lua_pop(L, 1);
1139 else lua_replace(L, json_export_value_idx);
1140 // check if type of table is still undetermined
1141 // and optionally calculate number of string keys (keycount)
1142 // or set keycount to zero:
1143 keycount = 0;
1144 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
1145 // if type of table is undetermined,
1146 // iterate over all keys:
1147 for (lua_pushnil(L); lua_next(L, json_export_value_idx); lua_pop(L, 1)) {
1148 switch (lua_type(L, -2)) {
1149 case LUA_TSTRING:
1150 // for string keys,
1151 // increase keycount (may avoid another iteration):
1152 keycount++;
1153 // if type of table was unknown, then type of table is a JSON object now:
1154 if (tabletype == JSON_TABLETYPE_UNKNOWN) tabletype = JSON_TABLETYPE_OBJECT;
1155 // if type of table was a JSON array, then the type of table is ambiguous now
1156 // and an error is thrown:
1157 else if (tabletype == JSON_TABLETYPE_ARRAY) goto json_export_tabletype_error;
1158 break;
1159 case LUA_TNUMBER:
1160 // for numeric keys,
1161 // if type of table was unknown, then type of table is a JSON array now:
1162 if (tabletype == JSON_TABLETYPE_UNKNOWN) tabletype = JSON_TABLETYPE_ARRAY;
1163 // if type of table was a JSON object, then the type of table is ambiguous now
1164 // and an error is thrown:
1165 else if (tabletype == JSON_TABLETYPE_OBJECT) goto json_export_tabletype_error;
1166 break;
1167 }
1168 }
1169 }
1170 // raise error if too many nested levels:
1171 if (level >= JSON_MAXDEPTH) {
1172 return luaL_error(L, "More than %d nested JSON levels", JSON_MAXDEPTH);
1173 }
1174 // store previous container information (if existent) on stack swap
1175 // and increase level variable:
1176 if (level++) {
1177 lua_pushvalue(L, json_export_luacontainer_idx);
1178 lua_rawseti(L, json_export_stackswap_idx, ++stackswapidx);
1179 lua_pushvalue(L, json_export_ccontainer_idx);
1180 lua_rawseti(L, json_export_stackswap_idx, ++stackswapidx);
1181 }
1182 // use value as current container:
1183 lua_pushvalue(L, json_export_value_idx);
1184 lua_replace(L, json_export_luacontainer_idx);
1185 // distinguish between JSON objects and JSON arrays:
1186 switch (tabletype) {
1187 // JSON object:
1188 case JSON_TABLETYPE_OBJECT:
1189 // calculate count of string keys unless it has been calculated before:
1190 if (!keycount) {
1191 for (lua_pushnil(L); lua_next(L, json_export_luacontainer_idx); lua_pop(L, 1)) {
1192 if (lua_type(L, -2) == LUA_TSTRING) keycount++;
1193 }
1194 }
1195 // allocate memory for C structure containing string keys and container iteration state:
1196 container = lua_newuserdata(L, sizeof(json_container_t) + (keycount-1) * sizeof(json_key_t));
1197 // store reference to C structure on designated stack position:
1198 lua_replace(L, json_export_ccontainer_idx);
1199 // initialize C structure for container state:
1200 container->type = JSON_TABLETYPE_OBJECT;
1201 container->count = keycount;
1202 container->pos = 0;
1203 // check if object contains any keys:
1204 if (keycount) {
1205 // if yes,
1206 // copy all string keys to the C structure (and reset container->pos again):
1207 for (lua_pushnil(L); lua_next(L, json_export_luacontainer_idx); lua_pop(L, 1)) {
1208 if (lua_type(L, -2) == LUA_TSTRING) {
1209 json_key_t *key = &container->keys[container->pos++];
1210 key->data = lua_tolstring(L, -2, &key->length);
1211 }
1212 }
1213 container->pos = 0;
1214 // sort C array using quicksort:
1215 qsort(container->keys, keycount, sizeof(json_key_t), (void *)json_key_cmp);
1216 }
1217 // add opening bracket to output buffer:
1218 luaL_addchar(&buf, '{');
1219 break;
1220 // JSON array:
1221 case JSON_TABLETYPE_ARRAY:
1222 // allocate memory for C structure for container iteration state:
1223 container = lua_newuserdata(L, sizeof(json_container_t) - sizeof(json_key_t));
1224 // store reference to C structure on designated stack position:
1225 lua_replace(L, json_export_ccontainer_idx);
1226 // initialize C structure for container state:
1227 container->type = JSON_TABLETYPE_ARRAY;
1228 container->pos = 0;
1229 // add opening bracket to output buffer:
1230 luaL_addchar(&buf, '[');
1231 break;
1232 default:
1233 // throw error if table type is unknown:
1234 json_export_tabletype_error:
1235 return luaL_error(L, "JSON export not possible for ambiguous table (cannot decide whether it is an object or array)");
1236 }
1237 break;
1238 default:
1239 // all other datatypes are considered an error:
1240 return luaL_error(L, "JSON export not possible for values of type \"%s\"", lua_typename(L, lua_type(L, json_export_value_idx)));
1241 }
1242 // check if a container is being processed:
1243 if (container) {
1244 // if yes,
1245 // execute code for container iteration:
1246 json_export_container:
1247 // distinguish between JSON objects and JSON arrays:
1248 switch (container->type) {
1249 // JSON object:
1250 case JSON_TABLETYPE_OBJECT:
1251 // finish iteration if all string keys have been processed:
1252 if (container->pos == container->count) goto json_export_close;
1253 // push current string key on top of stack:
1254 key = &container->keys[container->pos];
1255 lua_pushlstring(L, key->data, key->length);
1256 // check if the key has already been exported:
1257 if (!containerkey) {
1258 // if no,
1259 // add a comma to the output buffer if necessary:
1260 if (container->pos) luaL_addchar(&buf, ',');
1261 // set containerkey variable to true:
1262 containerkey = 1;
1263 } else {
1264 // if a key has already been exported,
1265 // add a colon to the output buffer:
1266 luaL_addchar(&buf, ':');
1267 // add a space to the output buffer for pretty results:
1268 if (pretty) luaL_addchar(&buf, ' ');
1269 // replace string key on top of stack with corresponding value:
1270 lua_rawget(L, json_export_luacontainer_idx);
1271 // reset containerkey variable
1272 containerkey = 0;
1273 // increase number of processed key value pairs:
1274 container->pos++;
1275 }
1276 // store key or value on top of stack in designated stack position:
1277 lua_replace(L, json_export_value_idx);
1278 break;
1279 // JSON array:
1280 case JSON_TABLETYPE_ARRAY:
1281 // store next value in designated stack position:
1282 lua_rawgeti(L, json_export_luacontainer_idx, container->pos+1);
1283 lua_replace(L, json_export_value_idx);
1284 // finish iteration if value is nil:
1285 if (lua_isnil(L, json_export_value_idx)) goto json_export_close;
1286 // add a comma to the output buffer if necessary:
1287 if (container->pos) luaL_addchar(&buf, ',');
1288 // increase number of processed values:
1289 container->pos++;
1290 break;
1291 // common code for closing JSON objects or JSON arrays:
1292 json_export_close:
1293 // decrement level variable:
1294 level--;
1295 // handle indentation for pretty results:
1296 if (pretty && container->pos) {
1297 luaL_addchar(&buf, '\n');
1298 for (i=0; i<level; i++) {
1299 lua_pushvalue(L, json_export_indentstring_idx);
1300 luaL_addvalue(&buf);
1301 }
1302 }
1303 // add closing bracket to output buffer:
1304 luaL_addchar(&buf, container->type == JSON_TABLETYPE_OBJECT ? '}' : ']');
1305 // finish export if last level has been closed:
1306 if (!level) goto json_export_finish;
1307 // otherwise,
1308 // recall previous container information from stack swap
1309 // and set C pointer to corresponding C struct:
1310 lua_rawgeti(L, json_export_stackswap_idx, stackswapidx--);
1311 lua_replace(L, json_export_ccontainer_idx);
1312 container = lua_touserdata(L, json_export_ccontainer_idx);
1313 lua_rawgeti(L, json_export_stackswap_idx, stackswapidx--);
1314 lua_replace(L, json_export_luacontainer_idx);
1315 // repeat code for container iteration:
1316 goto json_export_container;
1317 }
1318 // handle indentation for pretty results:
1319 if (pretty && (containerkey || container->type == JSON_TABLETYPE_ARRAY)) {
1320 luaL_addchar(&buf, '\n');
1321 for (i=0; i<level; i++) {
1322 lua_pushvalue(L, json_export_indentstring_idx);
1323 luaL_addvalue(&buf);
1324 }
1325 }
1326 } else {
1327 // if no container is being processed,
1328 // finish export:
1329 json_export_finish:
1330 // for pretty results, add final newline character if outermost container is processed:
1331 if (pretty) luaL_addchar(&buf, '\n');
1332 // create and return Lua string from buffer contents
1333 luaL_pushresult(&buf);
1334 return 1;
1335 }
1336 }
1337 }
1339 // functions in library module:
1340 static const struct luaL_Reg json_module_functions[] = {
1341 {"object", json_object},
1342 {"array", json_array},
1343 {"import", json_import},
1344 {"export", json_export},
1345 {"get", json_get},
1346 {"type", json_type},
1347 {"set", json_set},
1348 {NULL, NULL}
1349 };
1351 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
1352 static const struct luaL_Reg json_metatable_functions[] = {
1353 {"__len", json_len},
1354 {"__index", json_index},
1355 {"__newindex", json_newindex},
1356 {"__pairs", json_pairs},
1357 {"__ipairs", json_ipairs},
1358 {"__tostring", json_export},
1359 {NULL, NULL}
1360 };
1362 // metamethods for JSON null marker:
1363 static const struct luaL_Reg json_nullmark_metamethods[] = {
1364 {"__tostring", json_nullmark_tostring},
1365 {NULL, NULL}
1366 };
1368 // initializes json library:
1369 int luaopen_json(lua_State *L) {
1370 // empty stack:
1371 lua_settop(L, 0);
1372 // push library module onto stack position 1:
1373 lua_newtable(L);
1374 // register library functions:
1375 luaL_setfuncs(L, json_module_functions, 0);
1376 // create and store objectmt:
1377 lua_newtable(L);
1378 luaL_setfuncs(L, json_metatable_functions, 0);
1379 json_regstore(L, objectmt);
1380 // create and store arraymt:
1381 lua_newtable(L);
1382 luaL_setfuncs(L, json_metatable_functions, 0);
1383 json_regstore(L, arraymt);
1384 // set metatable of null marker and make it available through library module:
1385 json_pushnullmark(L);
1386 lua_newtable(L);
1387 luaL_setfuncs(L, json_nullmark_metamethods, 0);
1388 lua_setmetatable(L, -2);
1389 lua_setfield(L, 1, "null");
1390 // return library module (that's expected on top of stack):
1391 return 1;
1392 }