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annotate libraries/json/json.c @ 149:5229687c7601

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Removed metatable entries in JSON library module (since they should not be set directly); Added documentation to JSON library
author jbe
date Wed Jul 30 22:56:21 2014 +0200 (2014-07-30)
parents 5354d836e6fb
children 35fb4f92a887
rev   line source
jbe@121 1 #include <lua.h>
jbe@121 2 #include <lauxlib.h>
jbe@122 3 #include <stdlib.h>
jbe@121 4 #include <string.h>
jbe@121 5
jbe@144 6 // maximum number of nested JSON values (objects and arrays):
jbe@142 7 #define JSON_MAXDEPTH 100
jbe@142 8
jbe@144 9 // macros for usage of Lua registry:
jbe@144 10 #define JSON_REGENT char
jbe@145 11 #define JSON_REGPOINTER void *
jbe@145 12 #define json_pushlightref(L, x) (lua_pushlightuserdata((L), &json_reference.x))
jbe@145 13 #define json_regpointer(x) (&json_registry.x)
jbe@145 14 #define json_regfetchpointer(L, x) (lua_pushlightuserdata((L), (x)), lua_rawget((L), LUA_REGISTRYINDEX))
jbe@145 15 #define json_regfetch(L, x) (json_regfetchpointer(L, json_regpointer(x)))
jbe@145 16 #define json_regstore(L, x) (lua_pushlightuserdata(L, json_regpointer(x)), lua_pushvalue(L, -2), lua_rawset(L, LUA_REGISTRYINDEX));
jbe@145 17
jbe@146 18 // generate dummy memory addresses that represent non-modifiable lightuserdata (dummy) objects:
jbe@145 19 static struct {
jbe@146 20 JSON_REGENT nullmark; // magic value to indicate JSON null value in shadow table
jbe@145 21 } json_reference;
jbe@145 22
jbe@138 23
jbe@144 24 // generate dummy memory addresses that represent Lua objects
jbe@145 25 // via lightuserdata keys and LUA_REGISTRYINDEX:
jbe@144 26 static struct {
jbe@145 27 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
jbe@145 28 JSON_REGENT unknownmt; // metatable for tables that may be either JSON objects or JSON arrays
jbe@145 29 JSON_REGENT objectmt; // metatable for JSON objects
jbe@145 30 JSON_REGENT arraymt; // metatable for JSON arrays
jbe@144 31 } json_registry;
jbe@138 32
jbe@145 33 // marks a Lua table as JSON object or JSON array:
jbe@136 34 // (returns its modified argument or a new table if argument is nil)
jbe@145 35 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
jbe@145 36 // check if argument is nil
jbe@136 37 if (lua_isnoneornil(L, 1)) {
jbe@145 38 // create new table at stack position 1:
jbe@136 39 lua_settop(L, 0);
jbe@136 40 lua_newtable(L);
jbe@145 41 // create shadow table (leaving previously created table on stack position 1):
jbe@144 42 json_regfetch(L, shadowtbl);
jbe@136 43 lua_pushvalue(L, 1);
jbe@136 44 lua_newtable(L);
jbe@143 45 lua_rawset(L, -3);
jbe@143 46 } else {
jbe@145 47 // push shadow table on top of stack:
jbe@144 48 json_regfetch(L, shadowtbl);
jbe@143 49 lua_pushvalue(L, 1);
jbe@143 50 lua_rawget(L, -2);
jbe@145 51 // if shadow table does not exist:
jbe@143 52 if (lua_isnil(L, -1)) {
jbe@145 53 // create shadow table and leave it on top of stack:
jbe@143 54 lua_newtable(L);
jbe@143 55 lua_pushvalue(L, 1);
jbe@143 56 lua_pushvalue(L, -2);
jbe@143 57 lua_rawset(L, -5);
jbe@143 58 }
jbe@145 59 // move elements from original table to shadow table (that's expected on top of stack):
jbe@143 60 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@143 61 lua_pushvalue(L, -2);
jbe@143 62 lua_pushnil(L);
jbe@143 63 lua_rawset(L, 1);
jbe@143 64 lua_pushvalue(L, -2);
jbe@143 65 lua_pushvalue(L, -2);
jbe@143 66 lua_rawset(L, -5);
jbe@143 67 }
jbe@136 68 }
jbe@138 69 // discard everything but table to return:
jbe@138 70 lua_settop(L, 1);
jbe@136 71 // set metatable:
jbe@145 72 json_regfetchpointer(L, mt);
jbe@136 73 lua_setmetatable(L, 1);
jbe@138 74 // return table:
jbe@136 75 return 1;
jbe@136 76 }
jbe@136 77
jbe@136 78 // marks a table as JSON object:
jbe@136 79 // (returns its modified argument or a new table if argument is nil)
jbe@136 80 static int json_object(lua_State *L) {
jbe@145 81 return json_mark(L, json_regpointer(objectmt));
jbe@136 82 }
jbe@136 83
jbe@136 84 // marks a table as JSON array:
jbe@136 85 // (returns its modified argument or a new table if argument is nil)
jbe@136 86 static int json_array(lua_State *L) {
jbe@145 87 return json_mark(L, json_regpointer(arraymt));
jbe@136 88 }
jbe@136 89
jbe@145 90 // internal states of JSON parser:
jbe@124 91 #define JSON_STATE_VALUE 0
jbe@124 92 #define JSON_STATE_OBJECT_KEY 1
jbe@124 93 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
jbe@124 94 #define JSON_STATE_OBJECT_VALUE 3
jbe@124 95 #define JSON_STATE_OBJECT_SEPARATOR 4
jbe@124 96 #define JSON_STATE_ARRAY_VALUE 5
jbe@124 97 #define JSON_STATE_ARRAY_SEPARATOR 6
jbe@124 98 #define JSON_STATE_END 7
jbe@121 99
jbe@145 100 // special Lua stack indicies for json_import function:
jbe@138 101 #define json_import_objectmt_idx 2
jbe@138 102 #define json_import_arraymt_idx 3
jbe@138 103 #define json_import_shadowtbl_idx 4
jbe@138 104 #define json_import_nullmark_idx 5
jbe@138 105
jbe@136 106 // decodes a JSON document:
jbe@121 107 static int json_import(lua_State *L) {
jbe@136 108 const char *str; // string to parse
jbe@136 109 size_t total; // total length of string to parse
jbe@136 110 size_t pos = 0; // current position in string to parse
jbe@136 111 size_t level = 0; // nested levels of objects/arrays currently being processed
jbe@145 112 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
jbe@136 113 char c; // variable to store a single character to be processed
jbe@145 114 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
jbe@145 115 char *cbuf; // C buffer to decode JSON string values
jbe@136 116 size_t writepos; // write position of decoded strings in C buffer
jbe@147 117 // stack shall contain one function argument:
jbe@138 118 lua_settop(L, 1);
jbe@147 119 // push objectmt onto stack position 2:
jbe@144 120 json_regfetch(L, objectmt);
jbe@147 121 // push arraymt onto stack position 3:
jbe@144 122 json_regfetch(L, arraymt);
jbe@147 123 // push shadowtbl onto stack position 4:
jbe@144 124 json_regfetch(L, shadowtbl);
jbe@147 125 // push nullmark onto stack position 5:
jbe@145 126 json_pushlightref(L, nullmark);
jbe@136 127 // require string as first argument:
jbe@136 128 str = luaL_checklstring(L, 1, &total);
jbe@136 129 // if string contains a NULL byte, this is a syntax error
jbe@136 130 if (strlen(str) != total) goto json_import_syntax_error;
jbe@136 131 // main loop of parser:
jbe@136 132 json_import_loop:
jbe@136 133 // skip whitespace and store next character in variable 'c':
jbe@146 134 while (c = str[pos],
jbe@146 135 c == ' ' ||
jbe@146 136 c == '\f' ||
jbe@146 137 c == '\n' ||
jbe@146 138 c == '\r' ||
jbe@146 139 c == '\t' ||
jbe@146 140 c == '\v'
jbe@146 141 ) pos++;
jbe@136 142 // switch statement to handle certain (single) characters:
jbe@121 143 switch (c) {
jbe@136 144 // handle end of JSON document:
jbe@121 145 case 0:
jbe@136 146 // if end of JSON document was expected, then return top element of stack as result:
jbe@124 147 if (mode == JSON_STATE_END) return 1;
jbe@136 148 // otherwise, the JSON document was malformed:
jbe@121 149 json_import_unexpected_eof:
jbe@121 150 lua_pushnil(L);
jbe@121 151 if (level == 0) lua_pushliteral(L, "Empty string");
jbe@121 152 else lua_pushliteral(L, "Unexpected end of JSON document");
jbe@121 153 return 2;
jbe@136 154 // new JSON object:
jbe@121 155 case '{':
jbe@136 156 // if a JSON object is not expected here, then return an error:
jbe@146 157 if (
jbe@146 158 mode != JSON_STATE_VALUE &&
jbe@146 159 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 160 mode != JSON_STATE_ARRAY_VALUE
jbe@146 161 ) goto json_import_syntax_error;
jbe@136 162 // create JSON object on stack:
jbe@136 163 lua_newtable(L);
jbe@136 164 // set metatable of JSON object:
jbe@138 165 lua_pushvalue(L, json_import_objectmt_idx);
jbe@125 166 lua_setmetatable(L, -2);
jbe@136 167 // create internal shadow table on stack:
jbe@136 168 lua_newtable(L);
jbe@146 169 // register internal shadow table:
jbe@123 170 lua_pushvalue(L, -2);
jbe@123 171 lua_pushvalue(L, -2);
jbe@138 172 lua_rawset(L, json_import_shadowtbl_idx);
jbe@146 173 // expect object key (or end of object) to follow:
jbe@136 174 mode = JSON_STATE_OBJECT_KEY;
jbe@146 175 // jump to common code for opening JSON object and JSON array:
jbe@142 176 goto json_import_open;
jbe@136 177 // new JSON array:
jbe@121 178 case '[':
jbe@136 179 // if a JSON array is not expected here, then return an error:
jbe@146 180 if (
jbe@146 181 mode != JSON_STATE_VALUE &&
jbe@146 182 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 183 mode != JSON_STATE_ARRAY_VALUE
jbe@146 184 ) goto json_import_syntax_error;
jbe@136 185 // create JSON array on stack:
jbe@136 186 lua_newtable(L);
jbe@136 187 // set metatable of JSON array:
jbe@138 188 lua_pushvalue(L, json_import_arraymt_idx);
jbe@125 189 lua_setmetatable(L, -2);
jbe@136 190 // create internal shadow table on stack:
jbe@136 191 lua_newtable(L);
jbe@146 192 // register internal shadow table:
jbe@123 193 lua_pushvalue(L, -2);
jbe@123 194 lua_pushvalue(L, -2);
jbe@138 195 lua_rawset(L, json_import_shadowtbl_idx);
jbe@140 196 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
jbe@140 197 lua_pushnil(L);
jbe@146 198 // expect array value (or end of array) to follow:
jbe@142 199 mode = JSON_STATE_ARRAY_VALUE;
jbe@142 200 // continue with common code for opening JSON object and JSON array:
jbe@146 201 // common code for opening JSON object or JSON array:
jbe@142 202 json_import_open:
jbe@142 203 // limit nested levels:
jbe@142 204 if (level >= JSON_MAXDEPTH) {
jbe@142 205 lua_pushnil(L);
jbe@142 206 lua_pushliteral(L, "Too many nested JSON levels");
jbe@142 207 return 2;
jbe@142 208 }
jbe@142 209 // additional buffer overflow protection:
jbe@142 210 if (!lua_checkstack(L, LUA_MINSTACK))
jbe@142 211 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
jbe@136 212 // increment level:
jbe@121 213 level++;
jbe@142 214 // consume input character:
jbe@142 215 pos++;
jbe@121 216 goto json_import_loop;
jbe@136 217 // end of JSON object:
jbe@121 218 case '}':
jbe@136 219 // if end of JSON object is not expected here, then return an error:
jbe@146 220 if (
jbe@146 221 mode != JSON_STATE_OBJECT_KEY &&
jbe@146 222 mode != JSON_STATE_OBJECT_SEPARATOR
jbe@146 223 ) goto json_import_syntax_error;
jbe@136 224 // jump to common code for end of JSON object and JSON array:
jbe@121 225 goto json_import_close;
jbe@136 226 // end of JSON array:
jbe@121 227 case ']':
jbe@136 228 // if end of JSON array is not expected here, then return an error:
jbe@146 229 if (
jbe@146 230 mode != JSON_STATE_ARRAY_VALUE &&
jbe@146 231 mode != JSON_STATE_ARRAY_SEPARATOR
jbe@146 232 ) goto json_import_syntax_error;
jbe@146 233 // pop nil key/magic (that was needed to keep stack balance):
jbe@140 234 lua_pop(L, 1);
jbe@136 235 // continue with common code for end of JSON object and JSON array:
jbe@136 236 // common code for end of JSON object or JSON array:
jbe@121 237 json_import_close:
jbe@136 238 // consume input character:
jbe@121 239 pos++;
jbe@136 240 // pop shadow table:
jbe@136 241 lua_pop(L, 1);
jbe@136 242 // check if nested:
jbe@121 243 if (--level) {
jbe@146 244 // if nested,
jbe@146 245 // check if outer(!) structure is an array or object:
jbe@140 246 if (lua_isnil(L, -2)) {
jbe@136 247 // select array value processing:
jbe@124 248 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 249 } else {
jbe@136 250 // select object value processing:
jbe@124 251 mode = JSON_STATE_OBJECT_VALUE;
jbe@121 252 }
jbe@136 253 // store value in outer structure:
jbe@121 254 goto json_import_process_value;
jbe@121 255 }
jbe@136 256 // if not nested, then expect end of JSON document and continue with loop:
jbe@136 257 mode = JSON_STATE_END;
jbe@121 258 goto json_import_loop;
jbe@136 259 // key terminator:
jbe@121 260 case ':':
jbe@136 261 // if key terminator is not expected here, then return an error:
jbe@124 262 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
jbe@121 263 goto json_import_syntax_error;
jbe@136 264 // consume input character:
jbe@121 265 pos++;
jbe@146 266 // expect object value to follow:
jbe@124 267 mode = JSON_STATE_OBJECT_VALUE;
jbe@146 268 // continue with loop:
jbe@121 269 goto json_import_loop;
jbe@136 270 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
jbe@121 271 case ',':
jbe@146 272 // branch according to parser state:
jbe@124 273 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
jbe@146 274 // expect an object key to follow:
jbe@124 275 mode = JSON_STATE_OBJECT_KEY;
jbe@124 276 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
jbe@146 277 // expect an array value to follow:
jbe@124 278 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 279 } else {
jbe@136 280 // if value terminator is not expected here, then return an error:
jbe@136 281 goto json_import_syntax_error;
jbe@121 282 }
jbe@136 283 // consume input character:
jbe@121 284 pos++;
jbe@136 285 // continue with loop:
jbe@121 286 goto json_import_loop;
jbe@136 287 // string literal:
jbe@121 288 case '"':
jbe@146 289 // consume quote character:
jbe@146 290 pos++;
jbe@136 291 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
jbe@121 292 cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
jbe@121 293 writepos = 0;
jbe@146 294 // loop through the characters until encountering end quote:
jbe@121 295 while ((c = str[pos++]) != '"') {
jbe@121 296 if (c == 0) {
jbe@146 297 // handle unexpected end of JSON document:
jbe@121 298 goto json_import_unexpected_eof;
jbe@121 299 } else if (c < 32 || c == 127) {
jbe@136 300 // do not allow ASCII control characters:
jbe@136 301 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
jbe@136 302 // by this parser to allow different encodings than Unicode
jbe@121 303 lua_pushnil(L);
jbe@121 304 lua_pushliteral(L, "Unexpected control character in JSON string");
jbe@121 305 return 2;
jbe@121 306 } else if (c == '\\') {
jbe@136 307 // read next char after backslash escape:
jbe@121 308 c = str[pos++];
jbe@121 309 switch (c) {
jbe@136 310 // unexpected end-of-string:
jbe@121 311 case 0:
jbe@121 312 goto json_import_unexpected_eof;
jbe@136 313 // unescaping of quotation mark, slash, and backslash:
jbe@121 314 case '"':
jbe@121 315 case '/':
jbe@121 316 case '\\':
jbe@121 317 cbuf[writepos++] = c;
jbe@121 318 break;
jbe@136 319 // unescaping of backspace:
jbe@146 320 case 'b': cbuf[writepos++] = '\b'; break;
jbe@136 321 // unescaping of form-feed:
jbe@146 322 case 'f': cbuf[writepos++] = '\f'; break;
jbe@136 323 // unescaping of new-line:
jbe@146 324 case 'n': cbuf[writepos++] = '\n'; break;
jbe@136 325 // unescaping of carriage-return:
jbe@146 326 case 'r': cbuf[writepos++] = '\r'; break;
jbe@136 327 // unescaping of tabulator:
jbe@146 328 case 't': cbuf[writepos++] = '\t'; break;
jbe@136 329 // unescaping of UTF-16 characters
jbe@121 330 case 'u':
jbe@121 331 lua_pushnil(L);
jbe@121 332 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
jbe@121 333 return 2;
jbe@136 334 // unexpected escape sequence:
jbe@121 335 default:
jbe@121 336 lua_pushnil(L);
jbe@121 337 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
jbe@121 338 return 2;
jbe@121 339 }
jbe@121 340 } else {
jbe@136 341 // normal character:
jbe@121 342 cbuf[writepos++] = c;
jbe@121 343 }
jbe@121 344 }
jbe@136 345 // process buffer to Lua string:
jbe@121 346 luaL_pushresultsize(&luabuf, writepos);
jbe@136 347 // continue with processing of decoded string:
jbe@121 348 goto json_import_process_value;
jbe@121 349 }
jbe@136 350 // process values whose type is is not deducible from a single character:
jbe@136 351 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
jbe@146 352 // for numbers,
jbe@146 353 // use strtod() call to parse a (double precision) floating point number:
jbe@122 354 char *endptr;
jbe@122 355 double numval;
jbe@122 356 numval = strtod(str+pos, &endptr);
jbe@146 357 // catch parsing errors:
jbe@122 358 if (endptr == str+pos) goto json_import_syntax_error;
jbe@146 359 // consume characters that were parsed:
jbe@122 360 pos += endptr - (str+pos);
jbe@146 361 // push parsed (double precision) floating point number on Lua stack:
jbe@122 362 lua_pushnumber(L, numval);
jbe@122 363 } else if (!strncmp(str+pos, "true", 4)) {
jbe@136 364 // consume 4 input characters for "true":
jbe@121 365 pos += 4;
jbe@147 366 // put Lua true value onto stack:
jbe@136 367 lua_pushboolean(L, 1);
jbe@121 368 } else if (!strncmp(str+pos, "false", 5)) {
jbe@136 369 // consume 5 input characters for "false":
jbe@121 370 pos += 5;
jbe@147 371 // put Lua false value onto stack:
jbe@136 372 lua_pushboolean(L, 0);
jbe@121 373 } else if (!strncmp(str+pos, "null", 4)) {
jbe@136 374 // consume 4 input characters for "null":
jbe@136 375 pos += 4;
jbe@147 376 // put special null-marker onto stack:
jbe@138 377 lua_pushvalue(L, json_import_nullmark_idx);
jbe@121 378 } else {
jbe@136 379 // all other cases are a syntax error:
jbe@121 380 goto json_import_syntax_error;
jbe@121 381 }
jbe@136 382 // process a decoded value or key value pair (expected on top of Lua stack):
jbe@136 383 json_import_process_value:
jbe@121 384 switch (mode) {
jbe@136 385 // an object key has been read:
jbe@124 386 case JSON_STATE_OBJECT_KEY:
jbe@136 387 // if an object key is not a string, then this is a syntax error:
jbe@121 388 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
jbe@146 389 // expect key terminator to follow:
jbe@124 390 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
jbe@146 391 // continue with loop:
jbe@121 392 goto json_import_loop;
jbe@136 393 // a key value pair has been read:
jbe@124 394 case JSON_STATE_OBJECT_VALUE:
jbe@136 395 // store key value pair in outer shadow table:
jbe@130 396 lua_rawset(L, -3);
jbe@146 397 // expect value terminator (or end of object) to follow:
jbe@124 398 mode = JSON_STATE_OBJECT_SEPARATOR;
jbe@146 399 // continue with loop:
jbe@121 400 goto json_import_loop;
jbe@136 401 // an array value has been read:
jbe@124 402 case JSON_STATE_ARRAY_VALUE:
jbe@136 403 // store value in outer shadow table:
jbe@140 404 lua_rawseti(L, -3, lua_rawlen(L, -3) + 1);
jbe@146 405 // expect value terminator (or end of object) to follow:
jbe@124 406 mode = JSON_STATE_ARRAY_SEPARATOR;
jbe@146 407 // continue with loop
jbe@121 408 goto json_import_loop;
jbe@136 409 // a single value has been read:
jbe@124 410 case JSON_STATE_VALUE:
jbe@136 411 // leave value on top of stack, expect end of JSON document, and continue with loop:
jbe@124 412 mode = JSON_STATE_END;
jbe@121 413 goto json_import_loop;
jbe@121 414 }
jbe@146 415 // syntax error handling (reachable by goto statement):
jbe@136 416 json_import_syntax_error:
jbe@121 417 lua_pushnil(L);
jbe@121 418 lua_pushliteral(L, "Syntax error in JSON document");
jbe@121 419 return 2;
jbe@121 420 }
jbe@121 421
jbe@146 422 // special Lua stack indicies for json_path function:
jbe@138 423 #define json_path_shadowtbl_idx 1
jbe@138 424 #define json_path_nullmark_idx 2
jbe@146 425
jbe@146 426 // stack offset of arguments to json_path function:
jbe@138 427 #define json_path_idxshift 2
jbe@138 428
jbe@146 429 // gets a value or its type from a JSON document (passed as first argument)
jbe@147 430 // using a path (passed as variable number of keys after first argument):
jbe@137 431 static int json_path(lua_State *L, int type_mode) {
jbe@146 432 int stacktop; // stack index of top of stack (after shifting)
jbe@146 433 int idx = 2 + json_path_idxshift; // stack index of current argument to process
jbe@148 434 // insert shadowtbl into stack at position 1 (shifting the arguments):
jbe@144 435 json_regfetch(L, shadowtbl);
jbe@138 436 lua_insert(L, 1);
jbe@148 437 // insert nullmark into stack at position 2 (shifting the arguments):
jbe@145 438 json_pushlightref(L, nullmark);
jbe@138 439 lua_insert(L, 2);
jbe@146 440 // store stack index of top of stack:
jbe@138 441 stacktop = lua_gettop(L);
jbe@146 442 // use first argument as "current value" (stored on top of stack):
jbe@138 443 lua_pushvalue(L, 1 + json_path_idxshift);
jbe@146 444 // process each "path key" (2nd argument and following arguments):
jbe@138 445 while (idx <= stacktop) {
jbe@146 446 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
jbe@137 447 if (lua_isnil(L, -1)) return 1;
jbe@137 448 // try to get shadow table of "current value":
jbe@130 449 lua_pushvalue(L, -1);
jbe@138 450 lua_rawget(L, json_path_shadowtbl_idx);
jbe@126 451 if (lua_isnil(L, -1)) {
jbe@137 452 // if no shadow table is found,
jbe@130 453 if (lua_type(L, -1) == LUA_TTABLE) {
jbe@146 454 // and if "current value" is a table,
jbe@146 455 // drop nil from stack:
jbe@146 456 lua_pop(L, 1);
jbe@137 457 // get "next value" using the "path key":
jbe@130 458 lua_pushvalue(L, idx++);
jbe@130 459 lua_gettable(L, -2);
jbe@130 460 } else {
jbe@137 461 // if "current value" is not a table,
jbe@146 462 // then the path cannot be walked and nil (already on top of stack) is returned:
jbe@137 463 return 1;
jbe@130 464 }
jbe@130 465 } else {
jbe@137 466 // if a shadow table is found,
jbe@137 467 // set "current value" to its shadow table:
jbe@130 468 lua_replace(L, -2);
jbe@137 469 // get "next value" using the "path key":
jbe@130 470 lua_pushvalue(L, idx++);
jbe@130 471 lua_rawget(L, -2);
jbe@126 472 }
jbe@137 473 // the "next value" replaces the "current value":
jbe@130 474 lua_replace(L, -2);
jbe@126 475 }
jbe@137 476 if (!type_mode) {
jbe@137 477 // if a value (and not its type) was requested,
jbe@137 478 // check if value is the null-marker, and store nil on top of Lua stack in that case:
jbe@138 479 if (lua_rawequal(L, -1, json_path_nullmark_idx)) lua_pushnil(L);
jbe@137 480 } else {
jbe@137 481 // if the type was requested,
jbe@137 482 // check if value is the null-marker:
jbe@138 483 if (lua_rawequal(L, -1, json_path_nullmark_idx)) {
jbe@137 484 // if yes, store string "null" on top of Lua stack:
jbe@130 485 lua_pushliteral(L, "null");
jbe@137 486 } else {
jbe@137 487 // otherwise,
jbe@138 488 // check if metatable indicates "object" or "array":
jbe@138 489 if (lua_getmetatable(L, -1)) {
jbe@144 490 json_regfetch(L, objectmt);
jbe@138 491 if (lua_rawequal(L, -2, -1)) {
jbe@146 492 // if value has metatable for JSON objects,
jbe@138 493 // return string "object":
jbe@138 494 lua_pushliteral(L, "object");
jbe@138 495 return 1;
jbe@138 496 }
jbe@144 497 json_regfetch(L, arraymt);
jbe@138 498 if (lua_rawequal(L, -3, -1)) {
jbe@146 499 // if value has metatable for JSON arrays,
jbe@146 500 // return string "object":
jbe@138 501 lua_pushliteral(L, "array");
jbe@138 502 return 1;
jbe@138 503 }
jbe@146 504 // remove 3 metatables (one of the value, two for comparison) from stack:
jbe@138 505 lua_pop(L, 3);
jbe@138 506 }
jbe@138 507 // otherwise, get the Lua type:
jbe@138 508 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
jbe@126 509 }
jbe@126 510 }
jbe@137 511 // return the top most value on the Lua stack:
jbe@137 512 return 1;
jbe@130 513 }
jbe@130 514
jbe@147 515 // gets a value from a JSON document (passed as first argument)
jbe@147 516 // using a path (passed as variable number of keys after first argument):
jbe@130 517 static int json_get(lua_State *L) {
jbe@137 518 return json_path(L, 0);
jbe@130 519 }
jbe@130 520
jbe@147 521 // gets a value's type from a JSON document (passed as first argument)
jbe@147 522 // using a path (variable number of keys after first argument):
jbe@130 523 static int json_type(lua_State *L) {
jbe@137 524 return json_path(L, 1);
jbe@130 525 }
jbe@130 526
jbe@147 527 // checks if a value in a JSON document (first argument) is
jbe@147 528 // explicitly set to null:
jbe@130 529 static int json_isnull(lua_State *L) {
jbe@137 530 const char *jsontype;
jbe@147 531 // call json_type function with variable arguments:
jbe@138 532 lua_pushcfunction(L, json_type);
jbe@137 533 lua_insert(L, 1);
jbe@137 534 lua_call(L, lua_gettop(L) - 1, 1);
jbe@147 535 // return true if result equals to string "null", otherwise return false:
jbe@137 536 jsontype = lua_tostring(L, -1);
jbe@137 537 if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
jbe@137 538 else lua_pushboolean(L, 0);
jbe@137 539 return 1;
jbe@130 540 }
jbe@130 541
jbe@146 542 // special Lua stack indicies for json_setnull function:
jbe@138 543 #define json_setnull_unknownmt_idx 3
jbe@138 544 #define json_setnull_objectmt_idx 4
jbe@138 545 #define json_setnull_arraymt_idx 5
jbe@138 546 #define json_setnull_shadowtbl_idx 6
jbe@138 547
jbe@147 548 // sets a value in a JSON object or JSON array explicitly to null:
jbe@147 549 // NOTE: JSON null is different than absence of a key
jbe@131 550 static int json_setnull(lua_State *L) {
jbe@147 551 // stack shall contain two function arguments:
jbe@131 552 lua_settop(L, 2);
jbe@148 553 // push unknownmt onto stack position 3:
jbe@144 554 json_regfetch(L, unknownmt);
jbe@148 555 // push objectmt onto stack position 4:
jbe@144 556 json_regfetch(L, objectmt);
jbe@148 557 // push arraymt onto stack position 5:
jbe@144 558 json_regfetch(L, arraymt);
jbe@148 559 // push shadowtbl onto stack position 6:
jbe@144 560 json_regfetch(L, shadowtbl);
jbe@147 561 // set metatable if necessary (leaves unknown number of elements on stack):
jbe@138 562 if (
jbe@147 563 !lua_getmetatable(L, 1) || (
jbe@147 564 !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
jbe@147 565 !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
jbe@147 566 !lua_rawequal(L, -1, json_setnull_arraymt_idx)
jbe@147 567 )
jbe@138 568 ) {
jbe@138 569 lua_pushvalue(L, json_setnull_unknownmt_idx);
jbe@138 570 lua_setmetatable(L, 1);
jbe@138 571 }
jbe@147 572 // try to get shadow table:
jbe@131 573 lua_pushvalue(L, 1);
jbe@138 574 lua_rawget(L, json_setnull_shadowtbl_idx);
jbe@131 575 if (lua_isnil(L, -1)) {
jbe@147 576 // if no shadow table is found,
jbe@147 577 // create new shadow table (and leave it on top of stack):
jbe@131 578 lua_newtable(L);
jbe@147 579 // register shadow table:
jbe@131 580 lua_pushvalue(L, 1);
jbe@131 581 lua_pushvalue(L, -2);
jbe@138 582 lua_rawset(L, json_setnull_shadowtbl_idx);
jbe@131 583 }
jbe@147 584 // push key (second argument) and null-marker after shadow table onto stack:
jbe@131 585 lua_pushvalue(L, 2);
jbe@145 586 json_pushlightref(L, nullmark);
jbe@147 587 // store key and null-marker in shadow table:
jbe@131 588 lua_rawset(L, -3);
jbe@147 589 // return nothing:
jbe@131 590 return 0;
jbe@131 591 }
jbe@131 592
jbe@147 593 // returns the length of a JSON array (or zero for a table without numeric keys):
jbe@130 594 static int json_len(lua_State *L) {
jbe@147 595 // stack shall contain one function argument:
jbe@130 596 lua_settop(L, 1);
jbe@148 597 // try to get corresponding shadow table for first argument:
jbe@144 598 json_regfetch(L, shadowtbl);
jbe@130 599 lua_pushvalue(L, 1);
jbe@138 600 lua_rawget(L, -2);
jbe@147 601 // if shadow table does not exist, return length of argument, else length of shadow table:
jbe@147 602 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
jbe@123 603 return 1;
jbe@123 604 }
jbe@123 605
jbe@146 606 // special Lua stack indicies for json_index function:
jbe@141 607 #define json_index_nullmark_idx 3
jbe@141 608 #define json_index_shadowtbl_idx 4
jbe@141 609
jbe@130 610 static int json_index(lua_State *L) {
jbe@148 611 // stack shall contain two function arguments:
jbe@130 612 lua_settop(L, 2);
jbe@148 613 // push nullmark onto stack position 3:
jbe@148 614 json_pushlightref(L, nullmark);
jbe@148 615 // push shadowtbl onto stack position 4:
jbe@144 616 json_regfetch(L, shadowtbl);
jbe@148 617 // get corresponding shadow table for first argument:
jbe@130 618 lua_pushvalue(L, 1);
jbe@141 619 lua_rawget(L, json_index_shadowtbl_idx);
jbe@148 620 // throw error if no shadow table was found:
jbe@139 621 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 622 // use key passed as second argument to lookup value in shadow table:
jbe@130 623 lua_pushvalue(L, 2);
jbe@130 624 lua_rawget(L, -2);
jbe@148 625 // if value is null-marker, then push nil onto stack:
jbe@141 626 if (lua_rawequal(L, -1, json_index_nullmark_idx)) lua_pushnil(L);
jbe@148 627 // return either looked up value, or nil
jbe@127 628 return 1;
jbe@127 629 }
jbe@127 630
jbe@130 631 static int json_newindex(lua_State *L) {
jbe@148 632 // stack shall contain three function arguments:
jbe@130 633 lua_settop(L, 3);
jbe@148 634 // get corresponding shadow table for first argument:
jbe@144 635 json_regfetch(L, shadowtbl);
jbe@123 636 lua_pushvalue(L, 1);
jbe@143 637 lua_rawget(L, -2);
jbe@148 638 // throw error if no shadow table was found:
jbe@130 639 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 640 // replace first argument with shadow table:
jbe@130 641 lua_replace(L, 1);
jbe@148 642 // reset stack and use second and third argument to write to shadow table:
jbe@139 643 lua_settop(L, 3);
jbe@130 644 lua_rawset(L, 1);
jbe@148 645 // return nothing:
jbe@148 646 return 0;
jbe@121 647 }
jbe@121 648
jbe@146 649 // special Lua stack indicies for json_pairs_iterfunc function:
jbe@139 650 #define json_pairs_iterfunc_nullmark_idx 3
jbe@139 651 #define json_pairs_iterfunc_shadowtbl_idx 4
jbe@139 652
jbe@135 653 static int json_pairs_iterfunc(lua_State *L) {
jbe@149 654 // stack shall contain two function arguments:
jbe@135 655 lua_settop(L, 2);
jbe@149 656 // push nullmark onto stack position 3:
jbe@149 657 json_pushlightref(L, nullmark);
jbe@149 658 // push shadowtbl onto stack position 4:
jbe@144 659 json_regfetch(L, shadowtbl);
jbe@149 660 // get corresponding shadow table for first argument:
jbe@135 661 lua_pushvalue(L, 1);
jbe@139 662 lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
jbe@149 663 // throw error if no shadow table was found:
jbe@135 664 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 665 // get next key value pair from shadow table (using previous key from argument 2)
jbe@149 666 // and return nothing if there is no next pair:
jbe@135 667 lua_pushvalue(L, 2);
jbe@135 668 if (!lua_next(L, -2)) return 0;
jbe@149 669 // replace null-marker with nil:
jbe@139 670 if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
jbe@135 671 lua_pop(L, 1);
jbe@135 672 lua_pushnil(L);
jbe@135 673 }
jbe@149 674 // return key and value (or key and nil, if null-marker was found):
jbe@135 675 return 2;
jbe@135 676 }
jbe@135 677
jbe@149 678 // returns a triple such that 'for key, value in pairs(obj) do ... end'
jbe@149 679 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
jbe@135 680 static int json_pairs(lua_State *L) {
jbe@149 681 // return triple of function json_pairs_iterfunc, first argument, and nil:
jbe@139 682 lua_pushcfunction(L, json_pairs_iterfunc);
jbe@135 683 lua_pushvalue(L, 1);
jbe@135 684 lua_pushnil(L);
jbe@135 685 return 3;
jbe@135 686 }
jbe@135 687
jbe@146 688 // special Lua stack indicies for json_ipairs_iterfunc function:
jbe@139 689 #define json_ipairs_iterfunc_nullmark_idx 3
jbe@139 690 #define json_ipairs_iterfunc_shadowtbl_idx 4
jbe@139 691
jbe@134 692 static int json_ipairs_iterfunc(lua_State *L) {
jbe@134 693 int idx;
jbe@149 694 // stack shall contain two function arguments:
jbe@134 695 lua_settop(L, 2);
jbe@149 696 // push nullmark onto stack position 3:
jbe@149 697 json_pushlightref(L, nullmark);
jbe@149 698 // push shadowtbl onto stack position 4:
jbe@144 699 json_regfetch(L, shadowtbl);
jbe@149 700 // calculate new index by incrementing second argument:
jbe@134 701 idx = lua_tointeger(L, 2) + 1;
jbe@149 702 // get corresponding shadow table for first argument:
jbe@134 703 lua_pushvalue(L, 1);
jbe@139 704 lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
jbe@149 705 // throw error if no shadow table was found:
jbe@134 706 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 707 // do integer lookup in shadow table:
jbe@134 708 lua_rawgeti(L, -1, idx);
jbe@149 709 // return nothing if there was no value:
jbe@134 710 if (lua_isnil(L, -1)) return 0;
jbe@149 711 // return new index and
jbe@149 712 // either the looked up value if it is not equal to the null-marker
jbe@149 713 // or nil instead of null-marker:
jbe@134 714 lua_pushinteger(L, idx);
jbe@139 715 if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
jbe@134 716 else lua_pushvalue(L, -2);
jbe@134 717 return 2;
jbe@134 718 }
jbe@134 719
jbe@149 720 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
jbe@149 721 // iterates through all values (including JSON null represented as Lua nil):
jbe@134 722 static int json_ipairs(lua_State *L) {
jbe@149 723 // return triple of function json_ipairs_iterfunc, first argument, and zero:
jbe@139 724 lua_pushcfunction(L, json_ipairs_iterfunc);
jbe@134 725 lua_pushvalue(L, 1);
jbe@134 726 lua_pushinteger(L, 0);
jbe@134 727 return 3;
jbe@134 728 }
jbe@134 729
jbe@149 730 // functions in library module:
jbe@121 731 static const struct luaL_Reg json_module_functions[] = {
jbe@133 732 {"object", json_object},
jbe@133 733 {"array", json_array},
jbe@121 734 {"import", json_import},
jbe@130 735 {"get", json_get},
jbe@127 736 {"type", json_type},
jbe@123 737 {"isnull", json_isnull},
jbe@131 738 {"setnull", json_setnull},
jbe@121 739 {NULL, NULL}
jbe@121 740 };
jbe@121 741
jbe@149 742 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
jbe@126 743 static const struct luaL_Reg json_metatable_functions[] = {
jbe@130 744 {"__len", json_len},
jbe@130 745 {"__index", json_index},
jbe@130 746 {"__newindex", json_newindex},
jbe@135 747 {"__pairs", json_pairs},
jbe@134 748 {"__ipairs", json_ipairs},
jbe@126 749 {NULL, NULL}
jbe@126 750 };
jbe@126 751
jbe@149 752 // initializes json library:
jbe@121 753 int luaopen_json(lua_State *L) {
jbe@149 754 // empty stack:
jbe@126 755 lua_settop(L, 0);
jbe@149 756 // push library module onto stack position 1:
jbe@149 757 lua_newtable(L);
jbe@149 758 // register library functions:
jbe@149 759 luaL_setfuncs(L, json_module_functions, 0);
jbe@149 760 // create and store unknownmt:
jbe@138 761 lua_newtable(L);
jbe@138 762 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 763 json_regstore(L, unknownmt);
jbe@149 764 // create and store objectmt:
jbe@138 765 lua_newtable(L);
jbe@138 766 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 767 json_regstore(L, objectmt);
jbe@149 768 // create and store arraymt:
jbe@138 769 lua_newtable(L);
jbe@138 770 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 771 json_regstore(L, arraymt);
jbe@149 772 // create and store ephemeron table to store shadow tables for each JSON object/array
jbe@149 773 // to allow NULL values returned as nil
jbe@149 774 lua_newtable(L);
jbe@138 775 lua_newtable(L); // metatable for ephemeron table
jbe@121 776 lua_pushliteral(L, "__mode");
jbe@121 777 lua_pushliteral(L, "k");
jbe@138 778 lua_rawset(L, -3);
jbe@138 779 lua_setmetatable(L, -2);
jbe@144 780 json_regstore(L, shadowtbl);
jbe@149 781 // return library module stored on lowest stack position:
jbe@138 782 lua_settop(L, 1);
jbe@121 783 return 1;
jbe@121 784 }

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