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view libraries/json/json.c @ 175:20e393d2e6e1
Completed comments and minor code cleanup in JSON library; Added emergency garbage collection for memory allocation in json.export function
| author | jbe |
|---|---|
| date | Fri Aug 01 21:54:45 2014 +0200 (2014-08-01) |
| parents | 070edea2a92f |
| children | 461e5353ffb1 |
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 objectmt; // metatable for JSON objects
35 JSON_REGENT arraymt; // metatable for JSON arrays
36 } json_registry;
38 // returns the string "<JSON null marker>":
39 static int json_nullmark_tostring(lua_State *L) {
40 lua_pushliteral(L, "<JSON null marker>");
41 return 1;
42 }
44 #define json_convert_source_idx 1
45 #define json_convert_iterator_idx 2
46 #define json_convert_output_idx 3
47 #define json_convert_shadow_idx 4
48 #define json_convert_iterfun_idx 5
49 #define json_convert_itertbl_idx 6
51 // converts a Lua table (or any other iterable value) to a JSON object or JSON array:
52 // (does never modify the argument, returns an empty object or array if argument is nil)
53 static int json_convert(lua_State *L, int array) {
54 int arrayidx = 0;
55 // determine is argument is given:
56 if (lua_isnoneornil(L, json_convert_source_idx)) {
57 // if no argument is given (or if argument is nil),
58 // create table with shadow table, and leave first table on top of stack:
59 json_regfetch(L, shadowtbl);
60 lua_newtable(L);
61 lua_pushvalue(L, -1);
62 lua_newtable(L);
63 lua_rawset(L, -4);
64 } else {
65 // if an argument was given,
66 // push its iterator function on stack position 2 if existent,
67 // else push null for normal tables:
68 lua_settop(L, 1);
69 if (lua_getmetatable(L, json_convert_source_idx)) {
70 lua_getfield(L, -1, array ? "__ipairs" : "__pairs");
71 if (lua_isnil(L, -1)) luaL_checktype(L, 1, LUA_TTABLE);
72 else if (lua_type(L, -1) != LUA_TFUNCTION)
73 return luaL_error(L, "%s metamethod is not a function", array ? "__ipairs" : "__pairs");
74 lua_replace(L, -2);
75 } else {
76 lua_pushnil(L);
77 }
78 // create result table on stack position 3:
79 lua_newtable(L);
80 // create shadow table on stack position 4:
81 json_regfetch(L, shadowtbl);
82 lua_newtable(L);
83 lua_pushvalue(L, json_convert_output_idx);
84 lua_pushvalue(L, -2);
85 lua_rawset(L, -4);
86 lua_replace(L, -2);
87 // check if iterator function exists:
88 if (lua_isnil(L, json_convert_iterator_idx)) {
89 // if there is no iterator function,
90 // distinguish between objects and arrays:
91 if (array == 0) {
92 // for an object, copy all string key value pairs to shadow table:
93 for (lua_pushnil(L); lua_next(L, json_convert_source_idx); lua_pop(L, 1)) {
94 if (lua_type(L, -2) == LUA_TSTRING) {
95 lua_pushvalue(L, -2);
96 lua_pushvalue(L, -2);
97 lua_rawset(L, json_convert_shadow_idx);
98 }
99 }
100 } else {
101 // for an array, copy consecutive integer value pairs to shadow table:
102 while (1) {
103 // throw error if array would exceed INT_MAX elements:
104 // TODO: Lua 5.3 may support more elements
105 if (arrayidx == INT_MAX) {
106 lua_pushnumber(L, (size_t)INT_MAX+1);
107 lua_rawget(L, json_convert_source_idx);
108 if (lua_isnil(L, -1)) break;
109 return luaL_error(L, "Array exceeded length of %d elements", INT_MAX);
110 }
111 // get next array entry:
112 arrayidx++;
113 lua_rawgeti(L, json_convert_source_idx, arrayidx);
114 // break if value is nil:
115 if (lua_isnil(L, -1)) break;
116 // store value in shadow table:
117 lua_rawseti(L, json_convert_shadow_idx, arrayidx);
118 }
119 }
120 } else {
121 // if there is an iterator function,
122 // call iterator function with source value (first argument)
123 // and store 3 result values on stack positions 5 through 7:
124 lua_pushvalue(L, json_convert_iterator_idx);
125 lua_pushvalue(L, 1);
126 lua_call(L, 1, 3);
127 // iterate through key value pairs and store some of them in shadow table
128 // while replacing nil values with null-marker:
129 while (1) {
130 // call iterfun function:
131 lua_pushvalue(L, json_convert_iterfun_idx);
132 lua_pushvalue(L, json_convert_itertbl_idx);
133 lua_pushvalue(L, -3);
134 lua_remove(L, -4);
135 lua_call(L, 2, 2);
136 // break iteration loop if key is nil:
137 if (lua_isnil(L, -2)) break;
138 // store key value pair only if key type is correct:
139 if (lua_type(L, -2) == (array ? LUA_TNUMBER : LUA_TSTRING)) {
140 // if key type is correct,
141 // push key onto stack:
142 lua_pushvalue(L, -2);
143 // if value is nil, push null-marker onto stack (as value):
144 if (lua_isnil(L, -2)) json_pushnullmark(L);
145 // else push value onto stack:
146 else lua_pushvalue(L, -2);
147 // set key value pair in shadow table:
148 lua_rawset(L, json_convert_shadow_idx);
149 }
150 // pop value from stack, but leave key on stack:
151 lua_pop(L, 1);
152 }
153 }
154 // let result table be on top of stack:
155 lua_settop(L, json_convert_output_idx);
156 }
157 // set metatable (for result table on top of stack):
158 if (array == 0) json_regfetch(L, objectmt);
159 else json_regfetch(L, arraymt);
160 lua_setmetatable(L, -2);
161 // return table on top of stack:
162 return 1;
163 }
165 // converts a Lua table (or any other iterable value) to a JSON object:
166 // (does never modify the argument, returns an empty object or array if argument is nil)
167 static int json_object(lua_State *L) {
168 return json_convert(L, 0);
169 }
171 // converts a Lua table (or any other iterable value) to a JSON array:
172 // (does never modify the argument, returns an empty object or array if argument is nil)
173 static int json_array(lua_State *L) {
174 return json_convert(L, 1);
175 }
177 // internal states of JSON parser:
178 #define JSON_STATE_VALUE 0
179 #define JSON_STATE_OBJECT_KEY 1
180 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
181 #define JSON_STATE_OBJECT_VALUE 3
182 #define JSON_STATE_OBJECT_SEPARATOR 4
183 #define JSON_STATE_ARRAY_VALUE 5
184 #define JSON_STATE_ARRAY_SEPARATOR 6
185 #define JSON_STATE_END 7
187 // special Lua stack indicies for json_import function:
188 #define json_import_objectmt_idx 2
189 #define json_import_arraymt_idx 3
190 #define json_import_shadowtbl_idx 4
192 // macros for hex decoding:
193 #define json_utf16_surrogate(x) ((x) >= 0xD800 && (x) <= 0xDFFF)
194 #define json_utf16_lead(x) ((x) >= 0xD800 && (x) <= 0xDBFF)
195 #define json_utf16_tail(x) ((x) >= 0xDC00 && (x) <= 0xDFFF)
196 #define json_import_readhex(x) \
197 do { \
198 x = 0; \
199 for (i=0; i<4; i++) { \
200 x <<= 4; \
201 c = str[pos++]; \
202 if (c >= '0' && c <= '9') x += c - '0'; \
203 else if (c >= 'A' && c <= 'F') x += c - 'A' + 10; \
204 else if (c >= 'a' && c <= 'f') x += c - 'a' + 10; \
205 else if (c == 0) goto json_import_unexpected_eof; \
206 else goto json_import_unexpected_escape; \
207 } \
208 } while (0)
210 // decodes a JSON document:
211 static int json_import(lua_State *L) {
212 int i; // loop variable
213 const char *str; // string to parse
214 size_t total; // total length of string to parse
215 size_t pos = 0; // current position in string to parse
216 size_t level = 0; // nested levels of objects/arrays currently being processed
217 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
218 unsigned char c; // variable to store a single character to be processed (unsigned!)
219 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
220 char *cbuf; // C buffer to decode JSON string values
221 size_t outlen; // maximum length or write position of C buffer
222 long codepoint; // decoded UTF-16 character or higher codepoint
223 long utf16tail; // second decoded UTF-16 character (surrogate tail)
224 size_t arraylen; // variable to temporarily store the array length
225 // require string as argument and convert to C string with length information:
226 str = luaL_checklstring(L, 1, &total);
227 // if string contains a NULL byte, this is a syntax error
228 if (strlen(str) != total) goto json_import_syntax_error;
229 // stack shall contain one function argument:
230 lua_settop(L, 1);
231 // push objectmt onto stack position 2:
232 json_regfetch(L, objectmt);
233 // push arraymt onto stack position 3:
234 json_regfetch(L, arraymt);
235 // push shadowtbl onto stack position 4:
236 json_regfetch(L, shadowtbl);
237 // main loop of parser:
238 json_import_loop:
239 // skip whitespace and store next character in variable 'c':
240 while (c = str[pos],
241 c == ' ' ||
242 c == '\f' ||
243 c == '\n' ||
244 c == '\r' ||
245 c == '\t' ||
246 c == '\v'
247 ) pos++;
248 // NOTE: variable c needs to be unsigned in the following code
249 // switch statement to handle certain (single) characters:
250 switch (c) {
251 // handle end of JSON document:
252 case 0:
253 // if end of JSON document was expected, then return top element of stack as result:
254 if (mode == JSON_STATE_END) return 1;
255 // otherwise, the JSON document was malformed:
256 if (level == 0) {
257 lua_pushnil(L);
258 lua_pushliteral(L, "Empty string");
259 } else {
260 json_import_unexpected_eof:
261 lua_pushnil(L);
262 lua_pushliteral(L, "Unexpected end of JSON document");
263 }
264 return 2;
265 // new JSON object:
266 case '{':
267 // if a JSON object is not expected here, then return an error:
268 if (
269 mode != JSON_STATE_VALUE &&
270 mode != JSON_STATE_OBJECT_VALUE &&
271 mode != JSON_STATE_ARRAY_VALUE
272 ) goto json_import_syntax_error;
273 // create JSON object on stack:
274 lua_newtable(L);
275 // set metatable of JSON object:
276 lua_pushvalue(L, json_import_objectmt_idx);
277 lua_setmetatable(L, -2);
278 // create internal shadow table on stack:
279 lua_newtable(L);
280 // register internal shadow table:
281 lua_pushvalue(L, -2);
282 lua_pushvalue(L, -2);
283 lua_rawset(L, json_import_shadowtbl_idx);
284 // expect object key (or end of object) to follow:
285 mode = JSON_STATE_OBJECT_KEY;
286 // jump to common code for opening JSON object and JSON array:
287 goto json_import_open;
288 // new JSON array:
289 case '[':
290 // if a JSON array is not expected here, then return an error:
291 if (
292 mode != JSON_STATE_VALUE &&
293 mode != JSON_STATE_OBJECT_VALUE &&
294 mode != JSON_STATE_ARRAY_VALUE
295 ) goto json_import_syntax_error;
296 // create JSON array on stack:
297 lua_newtable(L);
298 // set metatable of JSON array:
299 lua_pushvalue(L, json_import_arraymt_idx);
300 lua_setmetatable(L, -2);
301 // create internal shadow table on stack:
302 lua_newtable(L);
303 // register internal shadow table:
304 lua_pushvalue(L, -2);
305 lua_pushvalue(L, -2);
306 lua_rawset(L, json_import_shadowtbl_idx);
307 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
308 lua_pushnil(L);
309 // expect array value (or end of array) to follow:
310 mode = JSON_STATE_ARRAY_VALUE;
311 // continue with common code for opening JSON object and JSON array:
312 // common code for opening JSON object or JSON array:
313 json_import_open:
314 // limit nested levels:
315 if (level >= JSON_MAXDEPTH) {
316 lua_pushnil(L);
317 lua_pushfstring(L, "More than %d nested JSON levels", JSON_MAXDEPTH);
318 return 2;
319 }
320 // additional buffer overflow protection:
321 if (!lua_checkstack(L, LUA_MINSTACK))
322 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
323 // increment level:
324 level++;
325 // consume input character:
326 pos++;
327 goto json_import_loop;
328 // end of JSON object:
329 case '}':
330 // if end of JSON object is not expected here, then return an error:
331 if (
332 mode != JSON_STATE_OBJECT_KEY &&
333 mode != JSON_STATE_OBJECT_SEPARATOR
334 ) goto json_import_syntax_error;
335 // jump to common code for end of JSON object and JSON array:
336 goto json_import_close;
337 // end of JSON array:
338 case ']':
339 // if end of JSON array is not expected here, then return an error:
340 if (
341 mode != JSON_STATE_ARRAY_VALUE &&
342 mode != JSON_STATE_ARRAY_SEPARATOR
343 ) goto json_import_syntax_error;
344 // pop nil key/magic (that was needed to keep stack balance):
345 lua_pop(L, 1);
346 // continue with common code for end of JSON object and JSON array:
347 // common code for end of JSON object or JSON array:
348 json_import_close:
349 // consume input character:
350 pos++;
351 // pop shadow table:
352 lua_pop(L, 1);
353 // check if nested:
354 if (--level) {
355 // if nested,
356 // check if outer(!) structure is an array or object:
357 if (lua_isnil(L, -2)) {
358 // select array value processing:
359 mode = JSON_STATE_ARRAY_VALUE;
360 } else {
361 // select object value processing:
362 mode = JSON_STATE_OBJECT_VALUE;
363 }
364 // store value in outer structure:
365 goto json_import_process_value;
366 }
367 // if not nested, then expect end of JSON document and continue with loop:
368 mode = JSON_STATE_END;
369 goto json_import_loop;
370 // key terminator:
371 case ':':
372 // if key terminator is not expected here, then return an error:
373 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
374 goto json_import_syntax_error;
375 // consume input character:
376 pos++;
377 // expect object value to follow:
378 mode = JSON_STATE_OBJECT_VALUE;
379 // continue with loop:
380 goto json_import_loop;
381 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
382 case ',':
383 // branch according to parser state:
384 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
385 // expect an object key to follow:
386 mode = JSON_STATE_OBJECT_KEY;
387 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
388 // expect an array value to follow:
389 mode = JSON_STATE_ARRAY_VALUE;
390 } else {
391 // if value terminator is not expected here, then return an error:
392 goto json_import_syntax_error;
393 }
394 // consume input character:
395 pos++;
396 // continue with loop:
397 goto json_import_loop;
398 // string literal:
399 case '"':
400 // consume quote character:
401 pos++;
402 // find last character in input string:
403 outlen = pos;
404 while ((c = str[outlen]) != '"') {
405 // consume one character:
406 outlen++;
407 // handle unexpected end of JSON document:
408 if (c == 0) goto json_import_unexpected_eof;
409 // consume one extra character when encountering an escaped quote:
410 else if (c == '\\' && str[outlen] == '"') outlen++;
411 }
412 // determine buffer length:
413 outlen -= pos;
414 // check if string is non empty:
415 if (outlen) {
416 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
417 cbuf = luaL_buffinitsize(L, &luabuf, outlen);
418 outlen = 0;
419 // loop through the characters until encountering end quote:
420 while ((c = str[pos++]) != '"') {
421 // NOTE: unexpected end cannot happen anymore
422 if (c < 32 || c == 127) {
423 // do not allow ASCII control characters:
424 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
425 // by this parser to allow different encodings than Unicode
426 lua_pushnil(L);
427 lua_pushliteral(L, "Unexpected control character in JSON string");
428 return 2;
429 } else if (c == '\\') {
430 // read next char after backslash escape:
431 c = str[pos++];
432 switch (c) {
433 // unexpected end-of-string:
434 case 0:
435 goto json_import_unexpected_eof;
436 // unescaping of quotation mark, slash, and backslash:
437 case '"':
438 case '/':
439 case '\\':
440 cbuf[outlen++] = c;
441 break;
442 // unescaping of backspace:
443 case 'b': cbuf[outlen++] = '\b'; break;
444 // unescaping of form-feed:
445 case 'f': cbuf[outlen++] = '\f'; break;
446 // unescaping of new-line:
447 case 'n': cbuf[outlen++] = '\n'; break;
448 // unescaping of carriage-return:
449 case 'r': cbuf[outlen++] = '\r'; break;
450 // unescaping of tabulator:
451 case 't': cbuf[outlen++] = '\t'; break;
452 // unescaping of UTF-16 characters
453 case 'u':
454 // decode 4 hex nibbles:
455 json_import_readhex(codepoint);
456 // handle surrogate character:
457 if (json_utf16_surrogate(codepoint)) {
458 // check if first surrogate is in valid range:
459 if (json_utf16_lead(codepoint)) {
460 // require second surrogate:
461 if ((c = str[pos++]) != '\\' || (c = str[pos++]) != 'u') {
462 if (c == 0) goto json_import_unexpected_eof;
463 else goto json_import_wrong_surrogate;
464 }
465 // read 4 hex nibbles of second surrogate character:
466 json_import_readhex(utf16tail);
467 // check if second surrogate is in valid range:
468 if (!json_utf16_tail(utf16tail)) goto json_import_wrong_surrogate;
469 // calculate codepoint:
470 codepoint = 0x10000 + (utf16tail - 0xDC00) + (codepoint - 0xD800) * 0x400;
471 } else {
472 // throw error for wrong surrogates:
473 json_import_wrong_surrogate:
474 lua_pushnil(L);
475 lua_pushliteral(L, "Illegal UTF-16 surrogate in JSON string escape sequence");
476 return 2;
477 }
478 }
479 // encode as UTF-8:
480 if (codepoint < 0x80) {
481 cbuf[outlen++] = (char)codepoint;
482 } else if (codepoint < 0x800) {
483 cbuf[outlen++] = (char)(0xc0 | (codepoint >> 6));
484 cbuf[outlen++] = (char)(0x80 | (codepoint & 0x3f));
485 } else if (codepoint < 0x10000) {
486 cbuf[outlen++] = (char)(0xe0 | (codepoint >> 12));
487 cbuf[outlen++] = (char)(0x80 | ((codepoint >> 6) & 0x3f));
488 cbuf[outlen++] = (char)(0x80 | (codepoint & 0x3f));
489 } else {
490 cbuf[outlen++] = (char)(0xf0 | (codepoint >> 18));
491 cbuf[outlen++] = (char)(0x80 | ((codepoint >> 12) & 0x3f));
492 cbuf[outlen++] = (char)(0x80 | ((codepoint >> 6) & 0x3f));
493 cbuf[outlen++] = (char)(0x80 | (codepoint & 0x3f));
494 }
495 break;
496 // unexpected escape sequence:
497 default:
498 json_import_unexpected_escape:
499 lua_pushnil(L);
500 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
501 return 2;
502 }
503 } else {
504 // normal character:
505 cbuf[outlen++] = c;
506 }
507 }
508 // process buffer to Lua string:
509 luaL_pushresultsize(&luabuf, outlen);
510 } else {
511 // if JSON string is empty,
512 // push empty Lua string:
513 lua_pushliteral(L, "");
514 // consume closing quote:
515 pos++;
516 }
517 // continue with processing of decoded string:
518 goto json_import_process_value;
519 }
520 // process values whose type is is not deducible from a single character:
521 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
522 // for numbers,
523 // use strtod() call to parse a (double precision) floating point number:
524 double numval;
525 char *endptr;
526 numval = strtod(str+pos, &endptr);
527 // catch parsing errors:
528 if (endptr == str+pos) goto json_import_syntax_error;
529 // consume characters that were parsed:
530 pos += endptr - (str+pos);
531 // push parsed (double precision) floating point number on Lua stack:
532 lua_pushnumber(L, numval);
533 } else if (!strncmp(str+pos, "true", 4)) {
534 // consume 4 input characters for "true":
535 pos += 4;
536 // put Lua true value onto stack:
537 lua_pushboolean(L, 1);
538 } else if (!strncmp(str+pos, "false", 5)) {
539 // consume 5 input characters for "false":
540 pos += 5;
541 // put Lua false value onto stack:
542 lua_pushboolean(L, 0);
543 } else if (!strncmp(str+pos, "null", 4)) {
544 // consume 4 input characters for "null":
545 pos += 4;
546 // different behavor for top-level and sub-levels:
547 if (level) {
548 // if sub-level,
549 // push special null-marker onto stack:
550 json_pushnullmark(L);
551 } else {
552 // if top-level,
553 // push nil onto stack:
554 lua_pushnil(L);
555 }
556 } else {
557 // all other cases are a syntax error:
558 goto json_import_syntax_error;
559 }
560 // process a decoded value or key value pair (expected on top of Lua stack):
561 json_import_process_value:
562 switch (mode) {
563 // an object key has been read:
564 case JSON_STATE_OBJECT_KEY:
565 // if an object key is not a string, then this is a syntax error:
566 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
567 // expect key terminator to follow:
568 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
569 // continue with loop:
570 goto json_import_loop;
571 // a key value pair has been read:
572 case JSON_STATE_OBJECT_VALUE:
573 // store key value pair in outer shadow table:
574 lua_rawset(L, -3);
575 // expect value terminator (or end of object) to follow:
576 mode = JSON_STATE_OBJECT_SEPARATOR;
577 // continue with loop:
578 goto json_import_loop;
579 // an array value has been read:
580 case JSON_STATE_ARRAY_VALUE:
581 // get current array length:
582 arraylen = lua_rawlen(L, -3);
583 // throw error if array would exceed INT_MAX elements:
584 // TODO: Lua 5.3 may support more elements
585 if (arraylen >= INT_MAX) {
586 lua_pushnil(L);
587 lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
588 }
589 // store value in outer shadow table:
590 lua_rawseti(L, -3, arraylen + 1);
591 // expect value terminator (or end of object) to follow:
592 mode = JSON_STATE_ARRAY_SEPARATOR;
593 // continue with loop
594 goto json_import_loop;
595 // a single value has been read:
596 case JSON_STATE_VALUE:
597 // leave value on top of stack, expect end of JSON document, and continue with loop:
598 mode = JSON_STATE_END;
599 goto json_import_loop;
600 }
601 // syntax error handling (reachable by goto statement):
602 json_import_syntax_error:
603 lua_pushnil(L);
604 lua_pushliteral(L, "Syntax error in JSON document");
605 return 2;
606 }
608 // special Lua stack indicies for json_path function:
609 #define json_path_shadowtbl_idx 1
611 // stack offset of arguments to json_path function:
612 #define json_path_idxshift 1
614 // gets a value or its type from a JSON document (passed as first argument)
615 // using a path (passed as variable number of keys after the first argument):
616 static int json_path(lua_State *L, int type_mode) {
617 int stacktop; // stack index of top of stack (after shifting)
618 int idx = 2 + json_path_idxshift; // stack index of current argument to process
619 // require at least one argument:
620 luaL_checkany(L, 1);
621 // insert shadowtbl into stack at position 1 (shifting the arguments):
622 json_regfetch(L, shadowtbl);
623 lua_insert(L, 1);
624 // store stack index of top of stack:
625 stacktop = lua_gettop(L);
626 // use first argument as "current value" (stored on top of stack):
627 lua_pushvalue(L, 1 + json_path_idxshift);
628 // process each "path key" (2nd argument and following arguments):
629 while (idx <= stacktop) {
630 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
631 if (lua_isnil(L, -1)) return 1;
632 // try to get shadow table of "current value":
633 lua_pushvalue(L, -1);
634 lua_rawget(L, json_path_shadowtbl_idx);
635 if (lua_isnil(L, -1)) {
636 // if no shadow table is found,
637 if (lua_type(L, -1) == LUA_TTABLE) {
638 // and if "current value" is a table,
639 // drop nil from stack:
640 lua_pop(L, 1);
641 // get "next value" using the "path key":
642 lua_pushvalue(L, idx++);
643 lua_gettable(L, -2);
644 } else {
645 // if "current value" is not a table,
646 // then the path cannot be walked and nil (already on top of stack) is returned:
647 return 1;
648 }
649 } else {
650 // if a shadow table is found,
651 // set "current value" to its shadow table:
652 lua_replace(L, -2);
653 // get "next value" using the "path key":
654 lua_pushvalue(L, idx++);
655 lua_rawget(L, -2);
656 }
657 // the "next value" replaces the "current value":
658 lua_replace(L, -2);
659 }
660 if (!type_mode) {
661 // if a value (and not its type) was requested,
662 // check if value is the null-marker, and store nil on top of Lua stack in that case:
663 if (json_isnullmark(L, -1)) lua_pushnil(L);
664 } else {
665 // if the type was requested,
666 // check if value is the null-marker:
667 if (json_isnullmark(L, -1)) {
668 // if yes, store string "null" on top of Lua stack:
669 lua_pushliteral(L, "null");
670 } else {
671 // otherwise,
672 // check if metatable indicates "object" or "array":
673 if (lua_getmetatable(L, -1)) {
674 json_regfetch(L, objectmt);
675 if (lua_rawequal(L, -2, -1)) {
676 // if value has metatable for JSON objects,
677 // return string "object":
678 lua_pushliteral(L, "object");
679 return 1;
680 }
681 json_regfetch(L, arraymt);
682 if (lua_rawequal(L, -3, -1)) {
683 // if value has metatable for JSON arrays,
684 // return string "object":
685 lua_pushliteral(L, "array");
686 return 1;
687 }
688 // remove 3 metatables (one of the value, two for comparison) from stack:
689 lua_pop(L, 3);
690 }
691 // otherwise, get the Lua type:
692 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
693 }
694 }
695 // return the top most value on the Lua stack:
696 return 1;
697 }
699 // gets a value from a JSON document (passed as first argument)
700 // using a path (passed as variable number of keys after the first argument):
701 static int json_get(lua_State *L) {
702 return json_path(L, 0);
703 }
705 // gets a value's type from a JSON document (passed as first argument)
706 // using a path (passed as variable number of keys after first the argument):
707 static int json_type(lua_State *L) {
708 return json_path(L, 1);
709 }
711 // special Lua stack indicies for json_set function:
712 #define json_set_shadowtbl_idx 1
713 #define json_set_objectmt_idx 2
714 #define json_set_arraymt_idx 3
716 // stack offset of arguments to json_set function:
717 #define json_set_idxshift 3
719 // sets a value (passed as second argument) in a JSON document (passed as first argument)
720 // using a path (passed as variable number of keys starting at third argument):
721 static int json_set(lua_State *L) {
722 int stacktop; // stack index of top of stack (after shifting)
723 int idx = 3; // stack index of current argument to process
724 // require at least two arguments:
725 luaL_checkany(L, 1);
726 luaL_checkany(L, 2);
727 // insert shadowtbl into stack at position 1 (shifting the arguments):
728 json_regfetch(L, shadowtbl);
729 lua_insert(L, 1);
730 // insert objectmt into stack at position 2 (shifting the arguments):
731 json_regfetch(L, objectmt);
732 lua_insert(L, 2);
733 // insert arraymt into stack at position 3 (shifting the arguments):
734 json_regfetch(L, arraymt);
735 lua_insert(L, 3);
736 // store stack index of top of stack:
737 stacktop = lua_gettop(L);
738 // use nil as initial "parent value":
739 lua_pushnil(L);
740 // use first argument as "current value":
741 lua_pushvalue(L, 1 + json_set_idxshift);
742 // set all necessary values in path:
743 for (idx = 3 + json_set_idxshift; idx<=stacktop; idx++) {
744 // push metatable of "current value" onto stack:
745 if (!lua_getmetatable(L, -1)) lua_pushnil(L);
746 // distinguish according to type of path key:
747 switch (lua_type(L, idx)) {
748 case LUA_TSTRING:
749 // if path key is a string,
750 // check if "current value" is a JSON object (or table without metatable):
751 if (
752 lua_rawequal(L, -1, json_set_objectmt_idx) ||
753 (lua_isnil(L, -1) && lua_type(L, -2) == LUA_TTABLE)
754 ) {
755 // if "current value" is acceptable,
756 // pop metatable and leave "current value" on top of stack:
757 lua_pop(L, 1);
758 } else {
759 // if "current value" is not acceptable:
760 // pop metatable and "current value":
761 lua_pop(L, 2);
762 // throw error if parent element does not exist:
763 if (lua_isnil(L, -1)) return luaL_error(L, "Root element is not a JSON object");
764 // push new JSON object as "current value" onto stack:
765 lua_newtable(L);
766 // create and register shadow table:
767 lua_pushvalue(L, -1);
768 lua_newtable(L);
769 lua_rawset(L, json_set_shadowtbl_idx);
770 // set metatable of JSON object:
771 lua_pushvalue(L, json_set_objectmt_idx);
772 lua_setmetatable(L, -2);
773 // set entry in "parent value":
774 lua_pushvalue(L, idx-1);
775 lua_pushvalue(L, -2);
776 lua_settable(L, -4);
777 }
778 break;
779 case LUA_TNUMBER:
780 // if path key is a number,
781 // check if "current value" is a JSON array (or table without metatable):
782 if (
783 lua_rawequal(L, -1, json_set_arraymt_idx) ||
784 (lua_isnil(L, -1) && lua_type(L, -2) == LUA_TTABLE)
785 ) {
786 // if "current value" is acceptable,
787 // pop metatable and leave "current value" on top of stack:
788 lua_pop(L, 1);
789 } else {
790 // if "current value" is not acceptable:
791 // pop metatable and "current value":
792 lua_pop(L, 2);
793 // throw error if parent element does not exist:
794 if (lua_isnil(L, -1)) return luaL_error(L, "Root element is not a JSON array");
795 // push new JSON array as "current value" onto stack:
796 lua_newtable(L);
797 // create and register shadow table:
798 lua_pushvalue(L, -1);
799 lua_newtable(L);
800 lua_rawset(L, json_set_shadowtbl_idx);
801 // set metatable of JSON array:
802 lua_pushvalue(L, json_set_arraymt_idx);
803 lua_setmetatable(L, -2);
804 // set entry in "parent value":
805 lua_pushvalue(L, idx-1);
806 lua_pushvalue(L, -2);
807 lua_settable(L, -4);
808 }
809 break;
810 default:
811 return luaL_error(L, "Invalid path key of type %s", lua_typename(L, lua_type(L, idx)));
812 }
813 // check if last path element is being processed:
814 if (idx == stacktop) {
815 // if the last path element is being processed,
816 // set last path value in "current value" container:
817 lua_pushvalue(L, idx);
818 lua_pushvalue(L, 2 + json_set_idxshift);
819 lua_settable(L, -3);
820 } else {
821 // if the processed path element is not the last,
822 // use old "current value" as new "parent value"
823 lua_remove(L, -2);
824 // push new "current value" onto stack by performing a lookup:
825 lua_pushvalue(L, idx);
826 lua_gettable(L, -2);
827 }
828 }
829 // return first argument for convenience:
830 lua_settop(L, 1 + json_set_idxshift);
831 return 1;
832 }
834 // returns the length of a JSON array (or zero for a table without numeric keys):
835 static int json_len(lua_State *L) {
836 // stack shall contain one function argument:
837 lua_settop(L, 1);
838 // try to get corresponding shadow table for first argument:
839 json_regfetch(L, shadowtbl);
840 lua_pushvalue(L, 1);
841 lua_rawget(L, -2);
842 // if shadow table does not exist, return length of argument, else length of shadow table:
843 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
844 return 1;
845 }
847 // __index metamethod for JSON objects and JSON arrays:
848 static int json_index(lua_State *L) {
849 // stack shall contain two function arguments:
850 lua_settop(L, 2);
851 // get corresponding shadow table for first argument:
852 json_regfetch(L, shadowtbl);
853 lua_pushvalue(L, 1);
854 lua_rawget(L, -2);
855 // throw error if no shadow table was found:
856 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
857 // use key passed as second argument to lookup value in shadow table:
858 lua_pushvalue(L, 2);
859 lua_rawget(L, -2);
860 // if value is null-marker, then push nil onto stack:
861 if (json_isnullmark(L, -1)) lua_pushnil(L);
862 // return either looked up value, or nil
863 return 1;
864 }
866 // __newindex metamethod for JSON objects and JSON arrays:
867 static int json_newindex(lua_State *L) {
868 // stack shall contain three function arguments:
869 lua_settop(L, 3);
870 // get corresponding shadow table for first argument:
871 json_regfetch(L, shadowtbl);
872 lua_pushvalue(L, 1);
873 lua_rawget(L, -2);
874 // throw error if no shadow table was found:
875 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
876 // replace first argument with shadow table:
877 lua_replace(L, 1);
878 // reset stack and use second and third argument to write to shadow table:
879 lua_settop(L, 3);
880 lua_rawset(L, 1);
881 // return nothing:
882 return 0;
883 }
885 // function returned as first value by json_pairs function:
886 static int json_pairs_iterfunc(lua_State *L) {
887 // stack shall contain two function arguments:
888 lua_settop(L, 2);
889 // get corresponding shadow table for first argument:
890 json_regfetch(L, shadowtbl);
891 lua_pushvalue(L, 1);
892 lua_rawget(L, -2);
893 // throw error if no shadow table was found:
894 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
895 // get next key value pair from shadow table (using previous key from argument 2)
896 // and return nothing if there is no next pair:
897 lua_pushvalue(L, 2);
898 if (!lua_next(L, -2)) return 0;
899 // replace null-marker with nil:
900 if (json_isnullmark(L, -1)) {
901 lua_pop(L, 1);
902 lua_pushnil(L);
903 }
904 // return key and value (or key and nil, if null-marker was found):
905 return 2;
906 }
908 // returns a triple such that 'for key, value in pairs(obj) do ... end'
909 // iterates through all key value pairs (including JSON null values represented as Lua nil):
910 static int json_pairs(lua_State *L) {
911 // require one argument to function
912 luaL_checkany(L, 1);
913 // return triple of function json_pairs_iterfunc, first argument, and nil:
914 lua_pushcfunction(L, json_pairs_iterfunc);
915 lua_pushvalue(L, 1);
916 lua_pushnil(L);
917 return 3;
918 }
920 // function returned as first value by json_ipairs function:
921 static int json_ipairs_iterfunc(lua_State *L) {
922 lua_Integer idx;
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 // get corresponding shadow table for first argument:
928 json_regfetch(L, shadowtbl);
929 lua_pushvalue(L, 1);
930 lua_rawget(L, -2);
931 // throw error if no shadow table was found:
932 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
933 // do integer lookup in shadow table:
934 lua_rawgeti(L, -1, idx);
935 // return nothing if there was no value:
936 if (lua_isnil(L, -1)) return 0;
937 // return new index and
938 // either the looked up value if it is not equal to the null-marker
939 // or nil instead of null-marker:
940 lua_pushinteger(L, idx);
941 if (json_isnullmark(L, -2)) lua_pushnil(L);
942 else lua_pushvalue(L, -2);
943 return 2;
944 }
946 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
947 // iterates through all values (including JSON null values represented as Lua nil):
948 static int json_ipairs(lua_State *L) {
949 // require one argument to function
950 luaL_checkany(L, 1);
951 // return triple of function json_ipairs_iterfunc, first argument, and zero:
952 lua_pushcfunction(L, json_ipairs_iterfunc);
953 lua_pushvalue(L, 1);
954 lua_pushinteger(L, 0);
955 return 3;
956 }
958 // datatype representing a table key:
959 // (used for sorting)
960 typedef struct {
961 size_t length;
962 const char *data;
963 } json_key_t;
965 // comparation function for table keys to be passed to qsort function:
966 static int json_key_cmp(json_key_t *key1, json_key_t *key2) {
967 size_t pos = 0;
968 unsigned char c1, c2;
969 while (1) {
970 if (key1->length > pos) {
971 if (key2->length > pos) {
972 c1 = key1->data[pos];
973 c2 = key2->data[pos];
974 if (c1 < c2) return -1;
975 else if (c1 > c2) return 1;
976 } else {
977 return 1;
978 }
979 } else {
980 if (key2->length > pos) {
981 return -1;
982 } else {
983 return 0;
984 }
985 }
986 pos++;
987 }
988 }
990 // constants for type detection of ambiguous tables:
991 #define JSON_TABLETYPE_UNKNOWN 0
992 #define JSON_TABLETYPE_OBJECT 1
993 #define JSON_TABLETYPE_ARRAY 2
995 // special Lua stack indicies for json_export_internal function:
996 #define json_export_internal_indentstring_idx 1
997 #define json_export_internal_level_idx 2
998 #define json_export_internal_value_idx 3
999 #define json_export_internal_tmp_idx 4
1001 // encodes a JSON document (passed as third argument)
1002 // optionally using indentation (indentation string passed as first argument)
1003 // for a certain depth level (passed as second argument):
1004 static int json_export_internal(lua_State *L) {
1005 int level; // current depth level
1006 int pretty; // pretty printing on? (i.e. printing with indentation)
1007 int i; // iteration variable for level dependent repetitions:
1008 lua_Number num; // number to encode
1009 const char *str; // string to encode
1010 size_t strlen; // length of string to encode
1011 unsigned char c; // character to encode (unsigned!)
1012 size_t pos = 0; // position in string or position of current key (initialized with zero!)
1013 luaL_Buffer buf; // Lua buffer to create strings
1014 char hexcode[7]; // store for unicode hex escape sequence
1015 // NOTE: 7 bytes due to backslash, character 'u', 4 hex digits, and terminating NULL byte
1016 int tabletype = JSON_TABLETYPE_UNKNOWN; // table type: unknown, JSON object, or JSON array
1017 int anyelement = 0; // set to 1 if at least one array element has been processed
1018 size_t keycount = 0; // number of string keys in object
1019 json_key_t *keybuf = NULL; // temporary buffer to store (and sort) string keys of objects
1020 lua_Integer arrayidx; // index to iterate through arrays
1021 // stack shall contain three function arguments:
1022 lua_settop(L, json_export_internal_value_idx);
1023 // if value to encode is the null-marker, then treat it the same as nil:
1024 if (json_isnullmark(L, json_export_internal_value_idx)) {
1025 lua_pop(L, 1);
1026 lua_pushnil(L);
1027 }
1028 // distinguish between different Lua types:
1029 switch (lua_type(L, json_export_internal_value_idx)) {
1030 // value to encode is nil:
1031 case LUA_TNIL:
1032 // return string "null":
1033 lua_pushliteral(L, "null");
1034 return 1;
1035 // value to encode is of type number:
1036 case LUA_TNUMBER:
1037 // convert value to double precision number:
1038 num = lua_tonumber(L, json_export_internal_value_idx);
1039 // throw error if number is not-a-number:
1040 if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
1041 // throw error if number is positive or negative infinity:
1042 if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
1043 // return Lua's string encoding of the number:
1044 lua_tostring(L, json_export_internal_value_idx);
1045 return 1;
1046 // value to encode is of type boolean:
1047 case LUA_TBOOLEAN:
1048 // return string "true" or "false" according to boolean value:
1049 if (lua_toboolean(L, json_export_internal_value_idx)) {
1050 lua_pushliteral(L, "true");
1051 } else {
1052 lua_pushliteral(L, "false");
1053 }
1054 return 1;
1055 // value to encode is of type string:
1056 case LUA_TSTRING:
1057 // quote, escape and return string:
1058 str = lua_tolstring(L, 3, &strlen);
1059 luaL_buffinit(L, &buf);
1060 luaL_addchar(&buf, '"');
1061 while (pos < strlen) {
1062 c = str[pos++];
1063 if (c == '"') luaL_addstring(&buf, "\\\"");
1064 else if (c == '\\') luaL_addstring(&buf, "\\\\");
1065 else if (c == 127) luaL_addstring(&buf, "\\u007F");
1066 else if (c >= 32) luaL_addchar(&buf, c);
1067 else if (c == '\b') luaL_addstring(&buf, "\\b");
1068 else if (c == '\f') luaL_addstring(&buf, "\\f");
1069 else if (c == '\n') luaL_addstring(&buf, "\\n");
1070 else if (c == '\r') luaL_addstring(&buf, "\\r");
1071 else if (c == '\t') luaL_addstring(&buf, "\\t");
1072 else if (c == '\v') luaL_addstring(&buf, "\\v");
1073 else {
1074 sprintf(hexcode, "\\u%04X", c);
1075 luaL_addstring(&buf, hexcode);
1076 }
1077 }
1078 luaL_addchar(&buf, '"');
1079 luaL_pushresult(&buf);
1080 return 1;
1081 // value to encode is of type table (this includes JSON objects and JSON arrays):
1082 case LUA_TTABLE:
1083 // use table's metatable to try to determine type of table:
1084 if (lua_getmetatable(L, json_export_internal_value_idx)) {
1085 json_regfetch(L, objectmt);
1086 if (lua_rawequal(L, -2, -1)) {
1087 tabletype = JSON_TABLETYPE_OBJECT;
1088 } else {
1089 json_regfetch(L, arraymt);
1090 if (lua_rawequal(L, -3, -1)) {
1091 tabletype = JSON_TABLETYPE_ARRAY;
1092 } else {
1093 return luaL_error(L, "JSON export not possible for tables with nonsupported metatable");
1094 }
1095 }
1096 }
1097 // replace table with its shadow table if existent, and reset stack:
1098 json_regfetch(L, shadowtbl);
1099 lua_pushvalue(L, json_export_internal_value_idx);
1100 lua_rawget(L, -2);
1101 if (!lua_isnil(L, -1)) lua_replace(L, json_export_internal_value_idx);
1102 lua_settop(L, json_export_internal_value_idx);
1103 // check if type of table is still undetermined:
1104 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
1105 // if yes, iterate over all keys:
1106 for (lua_pushnil(L); lua_next(L, json_export_internal_value_idx); lua_pop(L, 1)) {
1107 switch (lua_type(L, -2)) {
1108 case LUA_TSTRING:
1109 // for string keys,
1110 // increase keycount (may avoid another iteration):
1111 keycount++;
1112 // if type of table was unknown, then type of table is a JSON object now:
1113 if (tabletype == JSON_TABLETYPE_UNKNOWN) tabletype = JSON_TABLETYPE_OBJECT;
1114 // if type of table was a JSON array, then the type of table is ambiguous now
1115 // and an error is thrown:
1116 else if (tabletype == JSON_TABLETYPE_ARRAY) goto json_export_tabletype_error;
1117 break;
1118 case LUA_TNUMBER:
1119 // for numeric keys,
1120 // if type of table was unknown, then type of table is a JSON array now:
1121 if (tabletype == JSON_TABLETYPE_UNKNOWN) tabletype = JSON_TABLETYPE_ARRAY;
1122 // if type of table was a JSON object, then the type of table is ambiguous now
1123 // and an error is thrown:
1124 else if (tabletype == JSON_TABLETYPE_OBJECT) goto json_export_tabletype_error;
1125 break;
1126 }
1127 }
1128 }
1129 // set pretty variable to 1 if pretty printing (with indentation) is desired:
1130 pretty = lua_toboolean(L, json_export_internal_indentstring_idx);
1131 // set level variable to corresponding function argument increased by one:
1132 level = lua_tointeger(L, json_export_internal_level_idx) + 1;
1133 // throw error if there are more levels that could be imported by this library:
1134 if (level > JSON_MAXDEPTH) {
1135 return luaL_error(L, "More than %d nested JSON levels", JSON_MAXDEPTH);
1136 }
1137 // distinguish between JSON objects and JSON arrays:
1138 switch (tabletype) {
1139 // JSON object:
1140 case JSON_TABLETYPE_OBJECT:
1141 // calculate count of string keys unless it has been calculated before:
1142 if (!keycount) {
1143 for (lua_pushnil(L); lua_next(L, json_export_internal_value_idx); lua_pop(L, 1)) {
1144 if (lua_type(L, -2) == LUA_TSTRING) keycount++;
1145 }
1146 }
1147 // create a sorted list of all string keys in memory:
1148 if (keycount) {
1149 // allocate memory for string keys:
1150 keybuf = calloc(keycount, sizeof(json_key_t));
1151 // check if memory allocation was successful:
1152 if (!keybuf) {
1153 // in case of memory exhaustion, try to collect garbage:
1154 lua_gc(L, LUA_GCCOLLECT, 0);
1155 // try to allocate memory again:
1156 keybuf = calloc(keycount, sizeof(json_key_t));
1157 // throw error if memory allocation failed again:
1158 if (!keybuf) {
1159 return luaL_error(L, "Memory allocation failed in JSON library");
1160 }
1161 }
1162 // copy all string keys to the C array:
1163 for (lua_pushnil(L); lua_next(L, json_export_internal_value_idx); lua_pop(L, 1)) {
1164 if (lua_type(L, -2) == LUA_TSTRING) {
1165 json_key_t *key = keybuf + (pos++);
1166 key->data = lua_tolstring(L, -2, &key->length);
1167 }
1168 }
1169 // sort C array using quicksort:
1170 qsort(keybuf, keycount, sizeof(json_key_t), (void *)json_key_cmp);
1171 }
1172 // create Lua string buffer:
1173 luaL_buffinit(L, &buf);
1174 // add opening bracket to output buffer:
1175 luaL_addchar(&buf, '{');
1176 // iterate through all (sorted) string keys:
1177 for (pos=0; pos<keycount; pos++) {
1178 json_key_t *key = keybuf + pos;
1179 // add comma to output buffer unless we process the first key:
1180 if (pos) luaL_addchar(&buf, ',');
1181 // handle indentation for pretty results:
1182 if (pretty) {
1183 luaL_addchar(&buf, '\n');
1184 for (i=0; i<level; i++) {
1185 lua_pushvalue(L, json_export_internal_indentstring_idx);
1186 luaL_addvalue(&buf);
1187 }
1188 }
1189 // recursive call to encode key:
1190 lua_pushcfunction(L, json_export_internal);
1191 lua_pushvalue(L, json_export_internal_indentstring_idx);
1192 lua_pushinteger(L, level);
1193 lua_pushlstring(L, key->data, key->length);
1194 if (lua_pcall(L, 3, 1, 0)) {
1195 // free memory of sorted string keys on error:
1196 if (keybuf) free(keybuf);
1197 // rethrow error:
1198 return lua_error(L);
1199 }
1200 // add encoded key to output buffer:
1201 luaL_addvalue(&buf);
1202 // add colon to output buffer:
1203 luaL_addchar(&buf, ':');
1204 // handle indentation for pretty results:
1205 if (pretty) luaL_addchar(&buf, ' ');
1206 // recursive call to encode value:
1207 lua_pushcfunction(L, json_export_internal);
1208 lua_pushvalue(L, json_export_internal_indentstring_idx);
1209 lua_pushinteger(L, level);
1210 lua_pushlstring(L, key->data, key->length);
1211 lua_rawget(L, json_export_internal_value_idx);
1212 if (lua_pcall(L, 3, 1, 0)) {
1213 // free memory of sorted string keys on error:
1214 if (keybuf) free(keybuf);
1215 // rethrow error:
1216 return lua_error(L);
1217 }
1218 // add encoded value to output buffer:
1219 luaL_addvalue(&buf);
1220 }
1221 // decrement level variable for all following statements:
1222 level--;
1223 // free memory of sorted string keys:
1224 if (keybuf) free(keybuf);
1225 // handle indentation for pretty results:
1226 if (pretty && keycount != 0) {
1227 luaL_addchar(&buf, '\n');
1228 for (i=0; i<level; i++) {
1229 lua_pushvalue(L, json_export_internal_indentstring_idx);
1230 luaL_addvalue(&buf);
1231 }
1232 }
1233 // add closing bracket to output buffer:
1234 luaL_addchar(&buf, '}');
1235 // for pretty results, add final newline character if outermost container is processed:
1236 if (pretty && level == 0) luaL_addchar(&buf, '\n');
1237 // convert and return buffer:
1238 luaL_pushresult(&buf);
1239 return 1;
1240 // JSON array:
1241 case JSON_TABLETYPE_ARRAY:
1242 // reserve an extra element on the stack (needed because Lua buffer has unknown size on stack):
1243 lua_settop(L, json_export_internal_tmp_idx);
1244 // create Lua string buffer:
1245 luaL_buffinit(L, &buf);
1246 // add opening bracket to output buffer:
1247 luaL_addchar(&buf, '[');
1248 // iterate through integer keys:
1249 for (arrayidx = 1; ; arrayidx++) {
1250 // get value in array, and break if nil:
1251 lua_rawgeti(L, json_export_internal_value_idx, arrayidx);
1252 if (lua_isnil(L, -1)) {
1253 lua_pop(L, 1);
1254 break;
1255 }
1256 // store value below Lua string buffer on stack (to allow operation on string buffer):
1257 lua_replace(L, json_export_internal_tmp_idx);
1258 //
1259 // add comma to output buffer unless we process the first element:
1260 if (anyelement) luaL_addchar(&buf, ',');
1261 // remember that we processed an element:
1262 anyelement = 1;
1263 // handle indentation for pretty results:
1264 if (pretty) {
1265 luaL_addchar(&buf, '\n');
1266 for (i=0; i<level; i++) {
1267 lua_pushvalue(L, json_export_internal_indentstring_idx);
1268 luaL_addvalue(&buf);
1269 }
1270 }
1271 // recursive call to encode previously stored value:
1272 lua_pushcfunction(L, json_export_internal);
1273 lua_pushvalue(L, json_export_internal_indentstring_idx);
1274 lua_pushinteger(L, level);
1275 lua_pushvalue(L, json_export_internal_tmp_idx);
1276 lua_call(L, 3, 1);
1277 // add encoded value to output buffer:
1278 luaL_addvalue(&buf);
1279 }
1280 // decrement level variable for all following statements:
1281 level--;
1282 // handle indentation for pretty results:
1283 if (pretty && anyelement) {
1284 luaL_addchar(&buf, '\n');
1285 for (i=0; i<level; i++) {
1286 lua_pushvalue(L, json_export_internal_indentstring_idx);
1287 luaL_addvalue(&buf);
1288 }
1289 }
1290 // add closing bracket to output buffer:
1291 luaL_addchar(&buf, ']');
1292 // for pretty results, add final newline character if outermost container is processed:
1293 if (pretty && level == 0) luaL_addchar(&buf, '\n');
1294 // convert and return buffer:
1295 luaL_pushresult(&buf);
1296 return 1;
1297 }
1298 // throw error if table type is unknown:
1299 json_export_tabletype_error:
1300 return luaL_error(L, "JSON export not possible for ambiguous table (cannot decide whether it is an object or array)");
1301 }
1302 // all other datatypes are considered an error:
1303 return luaL_error(L, "JSON export not possible for values of type \"%s\"", lua_typename(L, lua_type(L, json_export_internal_value_idx)));
1304 }
1306 // encodes a JSON document (passed as argument):
1307 static int json_export(lua_State *L) {
1308 // stack shall contain one function argument:
1309 lua_settop(L, 1);
1310 // call json_export_internal function with proper arguments:
1311 lua_pushcfunction(L, json_export_internal);
1312 lua_pushnil(L);
1313 lua_pushinteger(L, 0);
1314 lua_pushvalue(L, 1);
1315 lua_call(L, 3, 1);
1316 // return result:
1317 return 1;
1318 }
1320 // encodes a JSON document (passed as first argument)
1321 // with indentation (indentation string may be passed as second argument):
1322 static int json_pretty(lua_State *L) {
1323 // stack shall contain two function arguments:
1324 lua_settop(L, 2);
1325 // call json_export_internal function with proper arguments:
1326 lua_pushcfunction(L, json_export_internal);
1327 if (lua_isnil(L, 2)) lua_pushliteral(L, " ");
1328 else lua_pushvalue(L, 2);
1329 lua_pushinteger(L, 0);
1330 lua_pushvalue(L, 1);
1331 lua_call(L, 3, 1);
1332 // return result:
1333 return 1;
1334 }
1336 // functions in library module:
1337 static const struct luaL_Reg json_module_functions[] = {
1338 {"object", json_object},
1339 {"array", json_array},
1340 {"import", json_import},
1341 {"export", json_export},
1342 {"pretty", json_pretty},
1343 {"get", json_get},
1344 {"type", json_type},
1345 {"set", json_set},
1346 {NULL, NULL}
1347 };
1349 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
1350 static const struct luaL_Reg json_metatable_functions[] = {
1351 {"__len", json_len},
1352 {"__index", json_index},
1353 {"__newindex", json_newindex},
1354 {"__pairs", json_pairs},
1355 {"__ipairs", json_ipairs},
1356 {"__tostring", json_export},
1357 {NULL, NULL}
1358 };
1360 // metamethods for JSON null marker:
1361 static const struct luaL_Reg json_nullmark_metamethods[] = {
1362 {"__tostring", json_nullmark_tostring},
1363 {NULL, NULL}
1364 };
1366 // initializes json library:
1367 int luaopen_json(lua_State *L) {
1368 // empty stack:
1369 lua_settop(L, 0);
1370 // push library module onto stack position 1:
1371 lua_newtable(L);
1372 // register library functions:
1373 luaL_setfuncs(L, json_module_functions, 0);
1374 // create and store objectmt:
1375 lua_newtable(L);
1376 luaL_setfuncs(L, json_metatable_functions, 0);
1377 json_regstore(L, objectmt);
1378 // create and store arraymt:
1379 lua_newtable(L);
1380 luaL_setfuncs(L, json_metatable_functions, 0);
1381 json_regstore(L, arraymt);
1382 // create and store ephemeron table to store shadow tables for each JSON object/array
1383 // to allow NULL values returned as nil
1384 lua_newtable(L);
1385 lua_newtable(L); // metatable for ephemeron table
1386 lua_pushliteral(L, "__mode");
1387 lua_pushliteral(L, "k");
1388 lua_rawset(L, -3);
1389 lua_setmetatable(L, -2);
1390 json_regstore(L, shadowtbl);
1391 // set metatable of null marker and make it available through library module:
1392 json_pushnullmark(L);
1393 lua_newtable(L);
1394 luaL_setfuncs(L, json_nullmark_metamethods, 0);
1395 lua_setmetatable(L, -2);
1396 lua_setfield(L, 1, "null");
1397 // return library module (that's expected on top of stack):
1398 return 1;
1399 }