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view libraries/json/json.c @ 137:f490b78827d6
More documentation in JSON library; Implement json.isnull(...) through json.type(...) == "null"
| author | jbe |
|---|---|
| date | Mon Jul 28 19:04:32 2014 +0200 (2014-07-28) |
| parents | 3cf5fcf2bd5f |
| children | 8a533f370038 |
line source
1 #include <lua.h>
2 #include <lauxlib.h>
3 #include <stdlib.h>
4 #include <string.h>
6 #define JSON_UPVAL_LIBRARY lua_upvalueindex(1)
7 #define JSON_UPVAL_NULLMARK lua_upvalueindex(2)
8 #define JSON_UPVAL_SHADOWTBL lua_upvalueindex(3)
9 #define JSON_UPVAL_TYPES lua_upvalueindex(4)
10 #define JSON_UPVAL_METATABLE lua_upvalueindex(5)
11 #define JSON_UPVAL_PAIRS_ITERFUNC lua_upvalueindex(6)
12 #define JSON_UPVAL_IPAIRS_ITERFUNC lua_upvalueindex(7)
14 // marks a table as JSON object or JSON array:
15 // (returns its modified argument or a new table if argument is nil)
16 static int json_mark(lua_State *L, const char *marker) {
17 // if argument is nil, then create new table:
18 if (lua_isnoneornil(L, 1)) {
19 lua_settop(L, 0);
20 lua_newtable(L);
21 // skip testing of existing shadow table:
22 goto json_object_create_shadow_table;
23 }
24 lua_pushvalue(L, 1);
25 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
26 if (lua_isnil(L, -1)) {
27 json_object_create_shadow_table:
28 // set shadow table:
29 lua_pushvalue(L, 1);
30 lua_newtable(L);
31 lua_rawset(L, JSON_UPVAL_SHADOWTBL);
32 }
33 // set metatable:
34 lua_pushvalue(L, JSON_UPVAL_METATABLE);
35 lua_setmetatable(L, 1);
36 // mark table as JSON object or as JSON array
37 lua_pushvalue(L, 1);
38 lua_pushstring(L, marker);
39 lua_rawset(L, JSON_UPVAL_TYPES);
40 return 1;
41 }
43 // marks a table as JSON object:
44 // (returns its modified argument or a new table if argument is nil)
45 static int json_object(lua_State *L) {
46 return json_mark(L, "object");
47 }
49 // marks a table as JSON array:
50 // (returns its modified argument or a new table if argument is nil)
51 static int json_array(lua_State *L) {
52 return json_mark(L, "array");
53 }
55 #define JSON_STATE_VALUE 0
56 #define JSON_STATE_OBJECT_KEY 1
57 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
58 #define JSON_STATE_OBJECT_VALUE 3
59 #define JSON_STATE_OBJECT_SEPARATOR 4
60 #define JSON_STATE_ARRAY_VALUE 5
61 #define JSON_STATE_ARRAY_SEPARATOR 6
62 #define JSON_STATE_END 7
64 // decodes a JSON document:
65 static int json_import(lua_State *L) {
66 const char *str; // string to parse
67 size_t total; // total length of string to parse
68 size_t pos = 0; // current position in string to parse
69 size_t level = 0; // nested levels of objects/arrays currently being processed
70 int mode = JSON_STATE_VALUE; // state of parser
71 char c; // variable to store a single character to be processed
72 luaL_Buffer luabuf; // Lua buffer to decode (possibly escaped) strings
73 char *cbuf; // C buffer to decode (possibly escaped) strings
74 size_t writepos; // write position of decoded strings in C buffer
75 // require string as first argument:
76 str = luaL_checklstring(L, 1, &total);
77 // if string contains a NULL byte, this is a syntax error
78 if (strlen(str) != total) goto json_import_syntax_error;
79 // main loop of parser:
80 json_import_loop:
81 // skip whitespace and store next character in variable 'c':
82 while (c = str[pos], c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == '\f') pos++;
83 // switch statement to handle certain (single) characters:
84 switch (c) {
85 // handle end of JSON document:
86 case 0:
87 // if end of JSON document was expected, then return top element of stack as result:
88 if (mode == JSON_STATE_END) return 1;
89 // otherwise, the JSON document was malformed:
90 json_import_unexpected_eof:
91 lua_pushnil(L);
92 if (level == 0) lua_pushliteral(L, "Empty string");
93 else lua_pushliteral(L, "Unexpected end of JSON document");
94 return 2;
95 // new JSON object:
96 case '{':
97 // if a JSON object is not expected here, then return an error:
98 if (mode != JSON_STATE_VALUE && mode != JSON_STATE_OBJECT_VALUE && mode != JSON_STATE_ARRAY_VALUE)
99 goto json_import_syntax_error;
100 // consume input character:
101 pos++;
102 // create JSON object on stack:
103 lua_newtable(L);
104 // set metatable of JSON object:
105 lua_pushvalue(L, JSON_UPVAL_METATABLE);
106 lua_setmetatable(L, -2);
107 // mark JSON object as JSON object (as opposed to JSON array):
108 lua_pushvalue(L, -1);
109 lua_pushliteral(L, "object");
110 lua_rawset(L, JSON_UPVAL_TYPES);
111 // create internal shadow table on stack:
112 lua_newtable(L);
113 // register internal shadow table:
114 lua_pushvalue(L, -2);
115 lua_pushvalue(L, -2);
116 lua_rawset(L, JSON_UPVAL_SHADOWTBL);
117 // increment level:
118 level++;
119 // expect object key (or end of object) and continue with loop:
120 mode = JSON_STATE_OBJECT_KEY;
121 goto json_import_loop;
122 // new JSON array:
123 case '[':
124 // if a JSON array is not expected here, then return an error:
125 if (mode != JSON_STATE_VALUE && mode != JSON_STATE_OBJECT_VALUE && mode != JSON_STATE_ARRAY_VALUE)
126 goto json_import_syntax_error;
127 // consume input character:
128 pos++;
129 // create JSON array on stack:
130 lua_newtable(L);
131 // set metatable of JSON array:
132 lua_pushvalue(L, JSON_UPVAL_METATABLE);
133 lua_setmetatable(L, -2);
134 // mark JSON array as JSON array (as opposed to JSON object):
135 lua_pushvalue(L, -1);
136 lua_pushliteral(L, "array");
137 lua_rawset(L, JSON_UPVAL_TYPES);
138 // create internal shadow table on stack:
139 lua_newtable(L);
140 // register internal shadow table:
141 lua_pushvalue(L, -2);
142 lua_pushvalue(L, -2);
143 lua_rawset(L, JSON_UPVAL_SHADOWTBL);
144 // increment level:
145 level++;
146 // expect array value (or end of array) and continue with loop:
147 mode = JSON_STATE_ARRAY_VALUE;
148 goto json_import_loop;
149 // end of JSON object:
150 case '}':
151 // if end of JSON object is not expected here, then return an error:
152 if (mode != JSON_STATE_OBJECT_KEY && mode != JSON_STATE_OBJECT_SEPARATOR)
153 goto json_import_syntax_error;
154 // jump to common code for end of JSON object and JSON array:
155 goto json_import_close;
156 // end of JSON array:
157 case ']':
158 // if end of JSON array is not expected here, then return an error:
159 if (mode != JSON_STATE_ARRAY_VALUE && mode != JSON_STATE_ARRAY_SEPARATOR)
160 goto json_import_syntax_error;
161 // continue with common code for end of JSON object and JSON array:
162 // common code for end of JSON object or JSON array:
163 json_import_close:
164 // consume input character:
165 pos++;
166 // pop shadow table:
167 lua_pop(L, 1);
168 // check if nested:
169 if (--level) {
170 // if nested, then check if outer(!) structure is an array or object:
171 lua_pushvalue(L, c == '}' ? -4 : -3);
172 lua_rawget(L, JSON_UPVAL_TYPES);
173 if (lua_tostring(L, -1)[0] == 'a') {
174 // select array value processing:
175 mode = JSON_STATE_ARRAY_VALUE;
176 } else {
177 // select object value processing:
178 mode = JSON_STATE_OBJECT_VALUE;
179 }
180 // pop JSON type from stack (from rawget JSON_UPVAL_TYPES):
181 lua_pop(L, 1);
182 // store value in outer structure:
183 goto json_import_process_value;
184 }
185 // if not nested, then expect end of JSON document and continue with loop:
186 mode = JSON_STATE_END;
187 goto json_import_loop;
188 // key terminator:
189 case ':':
190 // if key terminator is not expected here, then return an error:
191 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
192 goto json_import_syntax_error;
193 // consume input character:
194 pos++;
195 // set state of parser and continue with loop:
196 mode = JSON_STATE_OBJECT_VALUE;
197 goto json_import_loop;
198 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
199 case ',':
200 // change parser state accordingly:
201 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
202 mode = JSON_STATE_OBJECT_KEY;
203 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
204 mode = JSON_STATE_ARRAY_VALUE;
205 } else {
206 // if value terminator is not expected here, then return an error:
207 goto json_import_syntax_error;
208 }
209 // consume input character:
210 pos++;
211 // continue with loop:
212 goto json_import_loop;
213 // string literal:
214 case '"':
215 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
216 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
217 writepos = 0;
218 // consume quote character:
219 pos++;
220 // read next character until encountering end quote:
221 while ((c = str[pos++]) != '"') {
222 if (c == 0) {
223 // handle unexpected end-of-string:
224 goto json_import_unexpected_eof;
225 } else if (c < 32 || c == 127) {
226 // do not allow ASCII control characters:
227 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
228 // by this parser to allow different encodings than Unicode
229 lua_pushnil(L);
230 lua_pushliteral(L, "Unexpected control character in JSON string");
231 return 2;
232 } else if (c == '\\') {
233 // read next char after backslash escape:
234 c = str[pos++];
235 switch (c) {
236 // unexpected end-of-string:
237 case 0:
238 goto json_import_unexpected_eof;
239 // unescaping of quotation mark, slash, and backslash:
240 case '"':
241 case '/':
242 case '\\':
243 cbuf[writepos++] = c;
244 break;
245 // unescaping of backspace:
246 case 'b':
247 cbuf[writepos++] = '\b';
248 break;
249 // unescaping of form-feed:
250 case 'f':
251 cbuf[writepos++] = '\f';
252 break;
253 // unescaping of new-line:
254 case 'n':
255 cbuf[writepos++] = '\n';
256 break;
257 // unescaping of carriage-return:
258 case 'r':
259 cbuf[writepos++] = '\r';
260 break;
261 // unescaping of tabulator:
262 case 't':
263 cbuf[writepos++] = '\t';
264 break;
265 // unescaping of UTF-16 characters
266 case 'u':
267 lua_pushnil(L);
268 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
269 return 2;
270 // unexpected escape sequence:
271 default:
272 lua_pushnil(L);
273 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
274 return 2;
275 }
276 } else {
277 // normal character:
278 cbuf[writepos++] = c;
279 }
280 }
281 // process buffer to Lua string:
282 luaL_pushresultsize(&luabuf, writepos);
283 // continue with processing of decoded string:
284 goto json_import_process_value;
285 }
286 // process values whose type is is not deducible from a single character:
287 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
288 // numbers:
289 char *endptr;
290 double numval;
291 numval = strtod(str+pos, &endptr);
292 if (endptr == str+pos) goto json_import_syntax_error;
293 pos += endptr - (str+pos);
294 lua_pushnumber(L, numval);
295 } else if (!strncmp(str+pos, "true", 4)) {
296 // consume 4 input characters for "true":
297 pos += 4;
298 // put Lua true value on stack:
299 lua_pushboolean(L, 1);
300 } else if (!strncmp(str+pos, "false", 5)) {
301 // consume 5 input characters for "false":
302 pos += 5;
303 // put Lua false value on stack:
304 lua_pushboolean(L, 0);
305 } else if (!strncmp(str+pos, "null", 4)) {
306 // consume 4 input characters for "null":
307 pos += 4;
308 // put special null-marker on stack:
309 lua_pushvalue(L, JSON_UPVAL_NULLMARK);
310 } else {
311 // all other cases are a syntax error:
312 goto json_import_syntax_error;
313 }
314 // process a decoded value or key value pair (expected on top of Lua stack):
315 json_import_process_value:
316 switch (mode) {
317 // an object key has been read:
318 case JSON_STATE_OBJECT_KEY:
319 // if an object key is not a string, then this is a syntax error:
320 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
321 // expect key terminator and continue with loop:
322 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
323 goto json_import_loop;
324 // a key value pair has been read:
325 case JSON_STATE_OBJECT_VALUE:
326 // store key value pair in outer shadow table:
327 lua_rawset(L, -3);
328 // expect value terminator (or end of object) and continue with loop:
329 mode = JSON_STATE_OBJECT_SEPARATOR;
330 goto json_import_loop;
331 // an array value has been read:
332 case JSON_STATE_ARRAY_VALUE:
333 // store value in outer shadow table:
334 lua_rawseti(L, -2, lua_rawlen(L, -2) + 1);
335 // expect value terminator (or end of object) and continue with loop:
336 mode = JSON_STATE_ARRAY_SEPARATOR;
337 goto json_import_loop;
338 // a single value has been read:
339 case JSON_STATE_VALUE:
340 // leave value on top of stack, expect end of JSON document, and continue with loop:
341 mode = JSON_STATE_END;
342 goto json_import_loop;
343 }
344 // syntax error handling (only reachable by goto statement):
345 json_import_syntax_error:
346 lua_pushnil(L);
347 lua_pushliteral(L, "Syntax error in JSON document");
348 return 2;
349 }
351 // gets a value or its type from a JSON document (first argument)
352 // optionally using a path (variable number of keys after first argument):
353 static int json_path(lua_State *L, int type_mode) {
354 int argc;
355 int idx = 2;
356 // store number of arguments:
357 argc = lua_gettop(L);
358 // follow path, starting with first argument as "current value":
359 lua_pushvalue(L, 1);
360 // process each "path key":
361 while (idx <= argc) {
362 // if "current value" is nil, then the path cannot be walked and nil is returned:
363 if (lua_isnil(L, -1)) return 1;
364 // try to get shadow table of "current value":
365 lua_pushvalue(L, -1);
366 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
367 if (lua_isnil(L, -1)) {
368 // if no shadow table is found,
369 // drop nil from stack:
370 lua_pop(L, 1);
371 if (lua_type(L, -1) == LUA_TTABLE) {
372 // if "current value" is a table,
373 // get "next value" using the "path key":
374 lua_pushvalue(L, idx++);
375 lua_gettable(L, -2);
376 } else {
377 // if "current value" is not a table,
378 // then the path cannot be walked and nil is returned:
379 lua_pushnil(L);
380 return 1;
381 }
382 } else {
383 // if a shadow table is found,
384 // set "current value" to its shadow table:
385 lua_replace(L, -2);
386 // get "next value" using the "path key":
387 lua_pushvalue(L, idx++);
388 lua_rawget(L, -2);
389 }
390 // the "next value" replaces the "current value":
391 lua_replace(L, -2);
392 }
393 if (!type_mode) {
394 // if a value (and not its type) was requested,
395 // check if value is the null-marker, and store nil on top of Lua stack in that case:
396 if (lua_rawequal(L, -1, JSON_UPVAL_NULLMARK)) lua_pushnil(L);
397 } else {
398 // if the type was requested,
399 // check if value is the null-marker:
400 if (lua_rawequal(L, -1, JSON_UPVAL_NULLMARK)) {
401 // if yes, store string "null" on top of Lua stack:
402 lua_pushliteral(L, "null");
403 } else {
404 // otherwise,
405 // try to read type ("object" or "array") from internal type table:
406 lua_pushvalue(L, -1);
407 lua_rawget(L, JSON_UPVAL_TYPES);
408 // if no entry is found in the internal type table, get the Lua type:
409 if (lua_isnil(L, -1)) lua_pushstring(L, lua_typename(L, lua_type(L, -2)));
410 }
411 }
412 // return the top most value on the Lua stack:
413 return 1;
414 }
416 // gets a value from a JSON document (first argument)
417 // optionally using a path (variable number of keys after first argument):
418 static int json_get(lua_State *L) {
419 return json_path(L, 0);
420 }
422 // gets a value's type from a JSON document (first argument)
423 // optionally using a path (variable number of keys after first argument):
424 static int json_type(lua_State *L) {
425 return json_path(L, 1);
426 }
428 // checks if a value in a JSON document (first argument) is null:
429 static int json_isnull(lua_State *L) {
430 const char *jsontype;
431 lua_getfield(L, JSON_UPVAL_LIBRARY, "type");
432 lua_insert(L, 1);
433 lua_call(L, lua_gettop(L) - 1, 1);
434 jsontype = lua_tostring(L, -1);
435 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
436 else lua_pushboolean(L, 0);
437 return 1;
438 }
440 static int json_setnull(lua_State *L) {
441 lua_settop(L, 2);
442 lua_pushvalue(L, JSON_UPVAL_METATABLE);
443 lua_setmetatable(L, 1);
444 lua_pushvalue(L, 1);
445 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
446 if (lua_isnil(L, -1)) {
447 lua_newtable(L);
448 lua_pushvalue(L, 1);
449 lua_pushvalue(L, -2);
450 lua_rawset(L, JSON_UPVAL_SHADOWTBL);
451 }
452 lua_pushvalue(L, 2);
453 lua_pushvalue(L, JSON_UPVAL_NULLMARK);
454 lua_rawset(L, -3);
455 return 0;
456 }
458 static int json_len(lua_State *L) {
459 lua_settop(L, 1);
460 lua_pushvalue(L, 1);
461 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
462 if (lua_isnil(L, -1)) lua_pop(L, 1);
463 lua_pushinteger(L, lua_rawlen(L, -1));
464 return 1;
465 }
467 static int json_index(lua_State *L) {
468 lua_settop(L, 2);
469 lua_pushvalue(L, 1);
470 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
471 if (lua_isnil(L, -1)) return 1;
472 lua_pushvalue(L, 2);
473 lua_rawget(L, -2);
474 if (lua_rawequal(L, -1, JSON_UPVAL_NULLMARK)) lua_pushnil(L);
475 return 1;
476 }
478 static int json_newindex(lua_State *L) {
479 lua_settop(L, 3);
480 lua_pushvalue(L, 1);
481 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
482 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
483 lua_replace(L, 1);
484 lua_rawset(L, 1);
485 return 1;
486 }
488 static int json_pairs_iterfunc(lua_State *L) {
489 lua_settop(L, 2);
490 lua_pushvalue(L, 1);
491 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
492 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
493 lua_pushvalue(L, 2);
494 if (!lua_next(L, -2)) return 0;
495 if (lua_rawequal(L, -1, JSON_UPVAL_NULLMARK)) {
496 lua_pop(L, 1);
497 lua_pushnil(L);
498 }
499 return 2;
500 }
502 static int json_pairs(lua_State *L) {
503 lua_pushvalue(L, JSON_UPVAL_PAIRS_ITERFUNC);
504 lua_pushvalue(L, 1);
505 lua_pushnil(L);
506 return 3;
507 }
509 static int json_ipairs_iterfunc(lua_State *L) {
510 int idx;
511 lua_settop(L, 2);
512 idx = lua_tointeger(L, 2) + 1;
513 lua_pushvalue(L, 1);
514 lua_rawget(L, JSON_UPVAL_SHADOWTBL);
515 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
516 lua_rawgeti(L, -1, idx);
517 if (lua_isnil(L, -1)) return 0;
518 lua_pushinteger(L, idx);
519 if (lua_rawequal(L, -2, JSON_UPVAL_NULLMARK)) lua_pushnil(L);
520 else lua_pushvalue(L, -2);
521 return 2;
522 }
524 static int json_ipairs(lua_State *L) {
525 lua_pushvalue(L, JSON_UPVAL_IPAIRS_ITERFUNC);
526 lua_pushvalue(L, 1);
527 lua_pushinteger(L, 0);
528 return 3;
529 }
531 static const struct luaL_Reg json_module_functions[] = {
532 {"object", json_object},
533 {"array", json_array},
534 {"import", json_import},
535 {"get", json_get},
536 {"type", json_type},
537 {"isnull", json_isnull},
538 {"setnull", json_setnull},
539 {NULL, NULL}
540 };
542 static const struct luaL_Reg json_metatable_functions[] = {
543 {"__len", json_len},
544 {"__index", json_index},
545 {"__newindex", json_newindex},
546 {"__pairs", json_pairs},
547 {"__ipairs", json_ipairs},
548 {NULL, NULL}
549 };
551 int luaopen_json(lua_State *L) {
552 lua_settop(L, 0);
553 lua_newtable(L); // 1: library table on stack position
554 lua_pushvalue(L, 1); // 2: copy of library table
555 lua_newtable(L); // 3: table used as JSON NULL value in internal shadow tables
556 lua_newtable(L); // 4: ephemeron table to store shadow tables for each JSON object/array to allow NULL values returned as nil
557 lua_newtable(L); // 5: ephemeron table to store the type of the JSON object/array
558 lua_newtable(L); // 6: metatable for ephemeron tables
559 lua_pushliteral(L, "__mode");
560 lua_pushliteral(L, "k");
561 lua_rawset(L, 6);
562 lua_pushvalue(L, 6); // 7: cloned metatable reference
563 lua_setmetatable(L, 4);
564 lua_setmetatable(L, 5);
565 lua_newtable(L); // 6: metatable for JSON objects and JSON arrays
566 lua_pushvalue(L, 2);
567 lua_pushvalue(L, 3);
568 lua_pushvalue(L, 4);
569 lua_pushvalue(L, 5);
570 lua_pushvalue(L, 6);
571 lua_pushcclosure(L, json_pairs_iterfunc, 5); // 7: iteration function for pairs
572 lua_pushvalue(L, 2);
573 lua_pushvalue(L, 3);
574 lua_pushvalue(L, 4);
575 lua_pushvalue(L, 5);
576 lua_pushvalue(L, 6);
577 lua_pushcclosure(L, json_ipairs_iterfunc, 5); // 8: iteration function for ipairs
578 lua_pushvalue(L, 6);
579 lua_pushvalue(L, 2);
580 lua_pushvalue(L, 3);
581 lua_pushvalue(L, 4);
582 lua_pushvalue(L, 5);
583 lua_pushvalue(L, 6);
584 lua_pushvalue(L, 7);
585 lua_pushvalue(L, 8);
586 luaL_setfuncs(L, json_metatable_functions, 7);
587 lua_setfield(L, 1, "metatable");
588 luaL_setfuncs(L, json_module_functions, 7);
589 return 1;
590 }