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annotate libraries/json/json.c @ 161:d476b3c8960d

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Speed up JSON library by better approximation of required buffer length when parsing string values
author jbe
date Thu Jul 31 13:22:35 2014 +0200 (2014-07-31)
parents d5e5e8a9b79a
children 3b8c1e2aef9c
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@154 5 #include <math.h>
jbe@121 6
jbe@144 7 // maximum number of nested JSON values (objects and arrays):
jbe@150 8 // NOTE: The Lua reference states that the stack may typically contain at least
jbe@150 9 // "a few thousand elements". Since every nested level consumes
jbe@150 10 // 3 elements on the Lua stack (the object/array, its shadow table,
jbe@150 11 // a string key or a placeholder), we limit the number of nested levels
jbe@150 12 // to 500. If a stack overflow would still happen in the import function,
jbe@150 13 // this is detected nevertheless and an error is thrown (instead of
jbe@150 14 // returning nil and an error string).
jbe@150 15 #define JSON_MAXDEPTH 500
jbe@142 16
jbe@155 17 // generate dummy memory addresses that represents null values:
jbe@155 18 char json_nullmark;
jbe@155 19 #define json_isnullmark(L, i) (lua_touserdata((L), (i)) == &json_nullmark)
jbe@155 20 #define json_pushnullmark(L) lua_pushlightuserdata((L), &json_nullmark)
jbe@155 21
jbe@144 22 // macros for usage of Lua registry:
jbe@144 23 #define JSON_REGENT char
jbe@145 24 #define JSON_REGPOINTER void *
jbe@145 25 #define json_regpointer(x) (&json_registry.x)
jbe@151 26 #define json_regfetchpointer(L, x) lua_rawgetp((L), LUA_REGISTRYINDEX, (x))
jbe@151 27 #define json_regfetch(L, x) json_regfetchpointer(L, json_regpointer(x))
jbe@151 28 #define json_regstore(L, x) lua_rawsetp(L, LUA_REGISTRYINDEX, json_regpointer(x))
jbe@145 29
jbe@144 30 // generate dummy memory addresses that represent Lua objects
jbe@145 31 // via lightuserdata keys and LUA_REGISTRYINDEX:
jbe@144 32 static struct {
jbe@145 33 JSON_REGENT shadowtbl; // ephemeron table that maps tables to their corresponding shadow table
jbe@145 34 JSON_REGENT objectmt; // metatable for JSON objects
jbe@145 35 JSON_REGENT arraymt; // metatable for JSON arrays
jbe@144 36 } json_registry;
jbe@138 37
jbe@157 38 // returns the string "<JSON null marker>":
jbe@157 39 static int json_nullmark_tostring(lua_State *L) {
jbe@157 40 lua_pushliteral(L, "<JSON null marker>");
jbe@157 41 return 1;
jbe@157 42 }
jbe@157 43
jbe@145 44 // marks a Lua table as JSON object or JSON array:
jbe@136 45 // (returns its modified argument or a new table if argument is nil)
jbe@145 46 static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
jbe@145 47 // check if argument is nil
jbe@136 48 if (lua_isnoneornil(L, 1)) {
jbe@145 49 // create new table at stack position 1:
jbe@136 50 lua_settop(L, 0);
jbe@136 51 lua_newtable(L);
jbe@145 52 // create shadow table (leaving previously created table on stack position 1):
jbe@144 53 json_regfetch(L, shadowtbl);
jbe@136 54 lua_pushvalue(L, 1);
jbe@136 55 lua_newtable(L);
jbe@143 56 lua_rawset(L, -3);
jbe@143 57 } else {
jbe@145 58 // push shadow table on top of stack:
jbe@144 59 json_regfetch(L, shadowtbl);
jbe@143 60 lua_pushvalue(L, 1);
jbe@143 61 lua_rawget(L, -2);
jbe@145 62 // if shadow table does not exist:
jbe@143 63 if (lua_isnil(L, -1)) {
jbe@145 64 // create shadow table and leave it on top of stack:
jbe@143 65 lua_newtable(L);
jbe@143 66 lua_pushvalue(L, 1);
jbe@143 67 lua_pushvalue(L, -2);
jbe@143 68 lua_rawset(L, -5);
jbe@143 69 }
jbe@145 70 // move elements from original table to shadow table (that's expected on top of stack):
jbe@143 71 for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@143 72 lua_pushvalue(L, -2);
jbe@143 73 lua_pushnil(L);
jbe@143 74 lua_rawset(L, 1);
jbe@143 75 lua_pushvalue(L, -2);
jbe@143 76 lua_pushvalue(L, -2);
jbe@143 77 lua_rawset(L, -5);
jbe@143 78 }
jbe@136 79 }
jbe@138 80 // discard everything but table to return:
jbe@138 81 lua_settop(L, 1);
jbe@136 82 // set metatable:
jbe@145 83 json_regfetchpointer(L, mt);
jbe@136 84 lua_setmetatable(L, 1);
jbe@138 85 // return table:
jbe@136 86 return 1;
jbe@136 87 }
jbe@136 88
jbe@136 89 // marks a table as JSON object:
jbe@136 90 // (returns its modified argument or a new table if argument is nil)
jbe@136 91 static int json_object(lua_State *L) {
jbe@145 92 return json_mark(L, json_regpointer(objectmt));
jbe@136 93 }
jbe@136 94
jbe@136 95 // marks a table as JSON array:
jbe@136 96 // (returns its modified argument or a new table if argument is nil)
jbe@136 97 static int json_array(lua_State *L) {
jbe@145 98 return json_mark(L, json_regpointer(arraymt));
jbe@136 99 }
jbe@136 100
jbe@145 101 // internal states of JSON parser:
jbe@124 102 #define JSON_STATE_VALUE 0
jbe@124 103 #define JSON_STATE_OBJECT_KEY 1
jbe@124 104 #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
jbe@124 105 #define JSON_STATE_OBJECT_VALUE 3
jbe@124 106 #define JSON_STATE_OBJECT_SEPARATOR 4
jbe@124 107 #define JSON_STATE_ARRAY_VALUE 5
jbe@124 108 #define JSON_STATE_ARRAY_SEPARATOR 6
jbe@124 109 #define JSON_STATE_END 7
jbe@121 110
jbe@145 111 // special Lua stack indicies for json_import function:
jbe@138 112 #define json_import_objectmt_idx 2
jbe@138 113 #define json_import_arraymt_idx 3
jbe@138 114 #define json_import_shadowtbl_idx 4
jbe@138 115
jbe@136 116 // decodes a JSON document:
jbe@121 117 static int json_import(lua_State *L) {
jbe@136 118 const char *str; // string to parse
jbe@136 119 size_t total; // total length of string to parse
jbe@136 120 size_t pos = 0; // current position in string to parse
jbe@136 121 size_t level = 0; // nested levels of objects/arrays currently being processed
jbe@145 122 int mode = JSON_STATE_VALUE; // state of parser (i.e. "what's expected next?")
jbe@136 123 char c; // variable to store a single character to be processed
jbe@145 124 luaL_Buffer luabuf; // Lua buffer to decode JSON string values
jbe@145 125 char *cbuf; // C buffer to decode JSON string values
jbe@136 126 size_t writepos; // write position of decoded strings in C buffer
jbe@152 127 size_t arraylen; // variable to temporarily store the array length
jbe@147 128 // stack shall contain one function argument:
jbe@138 129 lua_settop(L, 1);
jbe@147 130 // push objectmt onto stack position 2:
jbe@144 131 json_regfetch(L, objectmt);
jbe@147 132 // push arraymt onto stack position 3:
jbe@144 133 json_regfetch(L, arraymt);
jbe@147 134 // push shadowtbl onto stack position 4:
jbe@144 135 json_regfetch(L, shadowtbl);
jbe@136 136 // require string as first argument:
jbe@136 137 str = luaL_checklstring(L, 1, &total);
jbe@136 138 // if string contains a NULL byte, this is a syntax error
jbe@136 139 if (strlen(str) != total) goto json_import_syntax_error;
jbe@136 140 // main loop of parser:
jbe@136 141 json_import_loop:
jbe@136 142 // skip whitespace and store next character in variable 'c':
jbe@146 143 while (c = str[pos],
jbe@146 144 c == ' ' ||
jbe@146 145 c == '\f' ||
jbe@146 146 c == '\n' ||
jbe@146 147 c == '\r' ||
jbe@146 148 c == '\t' ||
jbe@146 149 c == '\v'
jbe@146 150 ) pos++;
jbe@136 151 // switch statement to handle certain (single) characters:
jbe@121 152 switch (c) {
jbe@136 153 // handle end of JSON document:
jbe@121 154 case 0:
jbe@136 155 // if end of JSON document was expected, then return top element of stack as result:
jbe@124 156 if (mode == JSON_STATE_END) return 1;
jbe@136 157 // otherwise, the JSON document was malformed:
jbe@121 158 json_import_unexpected_eof:
jbe@121 159 lua_pushnil(L);
jbe@121 160 if (level == 0) lua_pushliteral(L, "Empty string");
jbe@121 161 else lua_pushliteral(L, "Unexpected end of JSON document");
jbe@121 162 return 2;
jbe@136 163 // new JSON object:
jbe@121 164 case '{':
jbe@136 165 // if a JSON object is not expected here, then return an error:
jbe@146 166 if (
jbe@146 167 mode != JSON_STATE_VALUE &&
jbe@146 168 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 169 mode != JSON_STATE_ARRAY_VALUE
jbe@146 170 ) goto json_import_syntax_error;
jbe@136 171 // create JSON object on stack:
jbe@136 172 lua_newtable(L);
jbe@136 173 // set metatable of JSON object:
jbe@138 174 lua_pushvalue(L, json_import_objectmt_idx);
jbe@125 175 lua_setmetatable(L, -2);
jbe@136 176 // create internal shadow table on stack:
jbe@136 177 lua_newtable(L);
jbe@146 178 // register internal shadow table:
jbe@123 179 lua_pushvalue(L, -2);
jbe@123 180 lua_pushvalue(L, -2);
jbe@138 181 lua_rawset(L, json_import_shadowtbl_idx);
jbe@146 182 // expect object key (or end of object) to follow:
jbe@136 183 mode = JSON_STATE_OBJECT_KEY;
jbe@146 184 // jump to common code for opening JSON object and JSON array:
jbe@142 185 goto json_import_open;
jbe@136 186 // new JSON array:
jbe@121 187 case '[':
jbe@136 188 // if a JSON array is not expected here, then return an error:
jbe@146 189 if (
jbe@146 190 mode != JSON_STATE_VALUE &&
jbe@146 191 mode != JSON_STATE_OBJECT_VALUE &&
jbe@146 192 mode != JSON_STATE_ARRAY_VALUE
jbe@146 193 ) goto json_import_syntax_error;
jbe@136 194 // create JSON array on stack:
jbe@136 195 lua_newtable(L);
jbe@136 196 // set metatable of JSON array:
jbe@138 197 lua_pushvalue(L, json_import_arraymt_idx);
jbe@125 198 lua_setmetatable(L, -2);
jbe@136 199 // create internal shadow table on stack:
jbe@136 200 lua_newtable(L);
jbe@146 201 // register internal shadow table:
jbe@123 202 lua_pushvalue(L, -2);
jbe@123 203 lua_pushvalue(L, -2);
jbe@138 204 lua_rawset(L, json_import_shadowtbl_idx);
jbe@140 205 // add nil as key (needed to keep stack balance) and as magic to detect arrays:
jbe@140 206 lua_pushnil(L);
jbe@146 207 // expect array value (or end of array) to follow:
jbe@142 208 mode = JSON_STATE_ARRAY_VALUE;
jbe@142 209 // continue with common code for opening JSON object and JSON array:
jbe@146 210 // common code for opening JSON object or JSON array:
jbe@142 211 json_import_open:
jbe@142 212 // limit nested levels:
jbe@142 213 if (level >= JSON_MAXDEPTH) {
jbe@142 214 lua_pushnil(L);
jbe@142 215 lua_pushliteral(L, "Too many nested JSON levels");
jbe@142 216 return 2;
jbe@142 217 }
jbe@142 218 // additional buffer overflow protection:
jbe@142 219 if (!lua_checkstack(L, LUA_MINSTACK))
jbe@142 220 return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
jbe@136 221 // increment level:
jbe@121 222 level++;
jbe@142 223 // consume input character:
jbe@142 224 pos++;
jbe@121 225 goto json_import_loop;
jbe@136 226 // end of JSON object:
jbe@121 227 case '}':
jbe@136 228 // if end of JSON object is not expected here, then return an error:
jbe@146 229 if (
jbe@146 230 mode != JSON_STATE_OBJECT_KEY &&
jbe@146 231 mode != JSON_STATE_OBJECT_SEPARATOR
jbe@146 232 ) goto json_import_syntax_error;
jbe@136 233 // jump to common code for end of JSON object and JSON array:
jbe@121 234 goto json_import_close;
jbe@136 235 // end of JSON array:
jbe@121 236 case ']':
jbe@136 237 // if end of JSON array is not expected here, then return an error:
jbe@146 238 if (
jbe@146 239 mode != JSON_STATE_ARRAY_VALUE &&
jbe@146 240 mode != JSON_STATE_ARRAY_SEPARATOR
jbe@146 241 ) goto json_import_syntax_error;
jbe@146 242 // pop nil key/magic (that was needed to keep stack balance):
jbe@140 243 lua_pop(L, 1);
jbe@136 244 // continue with common code for end of JSON object and JSON array:
jbe@136 245 // common code for end of JSON object or JSON array:
jbe@121 246 json_import_close:
jbe@136 247 // consume input character:
jbe@121 248 pos++;
jbe@136 249 // pop shadow table:
jbe@136 250 lua_pop(L, 1);
jbe@136 251 // check if nested:
jbe@121 252 if (--level) {
jbe@146 253 // if nested,
jbe@146 254 // check if outer(!) structure is an array or object:
jbe@140 255 if (lua_isnil(L, -2)) {
jbe@136 256 // select array value processing:
jbe@124 257 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 258 } else {
jbe@136 259 // select object value processing:
jbe@124 260 mode = JSON_STATE_OBJECT_VALUE;
jbe@121 261 }
jbe@136 262 // store value in outer structure:
jbe@121 263 goto json_import_process_value;
jbe@121 264 }
jbe@136 265 // if not nested, then expect end of JSON document and continue with loop:
jbe@136 266 mode = JSON_STATE_END;
jbe@121 267 goto json_import_loop;
jbe@136 268 // key terminator:
jbe@121 269 case ':':
jbe@136 270 // if key terminator is not expected here, then return an error:
jbe@124 271 if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
jbe@121 272 goto json_import_syntax_error;
jbe@136 273 // consume input character:
jbe@121 274 pos++;
jbe@146 275 // expect object value to follow:
jbe@124 276 mode = JSON_STATE_OBJECT_VALUE;
jbe@146 277 // continue with loop:
jbe@121 278 goto json_import_loop;
jbe@136 279 // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
jbe@121 280 case ',':
jbe@146 281 // branch according to parser state:
jbe@124 282 if (mode == JSON_STATE_OBJECT_SEPARATOR) {
jbe@146 283 // expect an object key to follow:
jbe@124 284 mode = JSON_STATE_OBJECT_KEY;
jbe@124 285 } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
jbe@146 286 // expect an array value to follow:
jbe@124 287 mode = JSON_STATE_ARRAY_VALUE;
jbe@121 288 } else {
jbe@136 289 // if value terminator is not expected here, then return an error:
jbe@136 290 goto json_import_syntax_error;
jbe@121 291 }
jbe@136 292 // consume input character:
jbe@121 293 pos++;
jbe@136 294 // continue with loop:
jbe@121 295 goto json_import_loop;
jbe@136 296 // string literal:
jbe@121 297 case '"':
jbe@146 298 // consume quote character:
jbe@146 299 pos++;
jbe@161 300 // determine buffer length:
jbe@161 301 writepos = pos;
jbe@161 302 while ((c = str[writepos]) != '"') {
jbe@161 303 // consume one character:
jbe@161 304 writepos++;
jbe@161 305 // handle unexpected end of JSON document:
jbe@161 306 if (c == 0) goto json_import_unexpected_eof;
jbe@161 307 // consume one extra character when encountering an escaped quote:
jbe@161 308 else if (c == '\\' && str[writepos] == '"') writepos++;
jbe@161 309 }
jbe@161 310 writepos -= pos;
jbe@161 311 // check if string is non empty:
jbe@161 312 if (writepos) {
jbe@161 313 // prepare buffer to decode string (with maximum possible length) and set write position to zero:
jbe@161 314 cbuf = luaL_buffinitsize(L, &luabuf, writepos);
jbe@161 315 writepos = 0;
jbe@161 316 // loop through the characters until encountering end quote:
jbe@161 317 while ((c = str[pos++]) != '"') {
jbe@161 318 if (c == 0) {
jbe@161 319 // handle unexpected end of JSON document:
jbe@121 320 goto json_import_unexpected_eof;
jbe@161 321 } else if (c < 32 || c == 127) {
jbe@161 322 // do not allow ASCII control characters:
jbe@161 323 // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
jbe@161 324 // by this parser to allow different encodings than Unicode
jbe@161 325 lua_pushnil(L);
jbe@161 326 lua_pushliteral(L, "Unexpected control character in JSON string");
jbe@161 327 return 2;
jbe@161 328 } else if (c == '\\') {
jbe@161 329 // read next char after backslash escape:
jbe@161 330 c = str[pos++];
jbe@161 331 switch (c) {
jbe@161 332 // unexpected end-of-string:
jbe@161 333 case 0:
jbe@161 334 goto json_import_unexpected_eof;
jbe@161 335 // unescaping of quotation mark, slash, and backslash:
jbe@161 336 case '"':
jbe@161 337 case '/':
jbe@161 338 case '\\':
jbe@161 339 cbuf[writepos++] = c;
jbe@161 340 break;
jbe@161 341 // unescaping of backspace:
jbe@161 342 case 'b': cbuf[writepos++] = '\b'; break;
jbe@161 343 // unescaping of form-feed:
jbe@161 344 case 'f': cbuf[writepos++] = '\f'; break;
jbe@161 345 // unescaping of new-line:
jbe@161 346 case 'n': cbuf[writepos++] = '\n'; break;
jbe@161 347 // unescaping of carriage-return:
jbe@161 348 case 'r': cbuf[writepos++] = '\r'; break;
jbe@161 349 // unescaping of tabulator:
jbe@161 350 case 't': cbuf[writepos++] = '\t'; break;
jbe@161 351 // unescaping of UTF-16 characters
jbe@161 352 case 'u':
jbe@161 353 lua_pushnil(L);
jbe@161 354 lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet"); // TODO
jbe@161 355 return 2;
jbe@161 356 // unexpected escape sequence:
jbe@161 357 default:
jbe@161 358 lua_pushnil(L);
jbe@161 359 lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
jbe@161 360 return 2;
jbe@161 361 }
jbe@161 362 } else {
jbe@161 363 // normal character:
jbe@121 364 cbuf[writepos++] = c;
jbe@121 365 }
jbe@121 366 }
jbe@161 367 // process buffer to Lua string:
jbe@161 368 luaL_pushresultsize(&luabuf, writepos);
jbe@161 369 } else {
jbe@161 370 // if JSON string is empty,
jbe@161 371 // push empty Lua string:
jbe@161 372 lua_pushliteral(L, "");
jbe@121 373 }
jbe@136 374 // continue with processing of decoded string:
jbe@121 375 goto json_import_process_value;
jbe@121 376 }
jbe@136 377 // process values whose type is is not deducible from a single character:
jbe@136 378 if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
jbe@146 379 // for numbers,
jbe@146 380 // use strtod() call to parse a (double precision) floating point number:
jbe@122 381 char *endptr;
jbe@122 382 double numval;
jbe@122 383 numval = strtod(str+pos, &endptr);
jbe@146 384 // catch parsing errors:
jbe@122 385 if (endptr == str+pos) goto json_import_syntax_error;
jbe@146 386 // consume characters that were parsed:
jbe@122 387 pos += endptr - (str+pos);
jbe@146 388 // push parsed (double precision) floating point number on Lua stack:
jbe@122 389 lua_pushnumber(L, numval);
jbe@122 390 } else if (!strncmp(str+pos, "true", 4)) {
jbe@136 391 // consume 4 input characters for "true":
jbe@121 392 pos += 4;
jbe@147 393 // put Lua true value onto stack:
jbe@136 394 lua_pushboolean(L, 1);
jbe@121 395 } else if (!strncmp(str+pos, "false", 5)) {
jbe@136 396 // consume 5 input characters for "false":
jbe@121 397 pos += 5;
jbe@147 398 // put Lua false value onto stack:
jbe@136 399 lua_pushboolean(L, 0);
jbe@121 400 } else if (!strncmp(str+pos, "null", 4)) {
jbe@136 401 // consume 4 input characters for "null":
jbe@136 402 pos += 4;
jbe@153 403 // different behavor for top-level and sub-levels:
jbe@153 404 if (level) {
jbe@153 405 // if sub-level,
jbe@153 406 // push special null-marker onto stack:
jbe@155 407 json_pushnullmark(L);
jbe@153 408 } else {
jbe@153 409 // if top-level,
jbe@153 410 // push nil onto stack:
jbe@153 411 lua_pushnil(L);
jbe@153 412 }
jbe@121 413 } else {
jbe@136 414 // all other cases are a syntax error:
jbe@121 415 goto json_import_syntax_error;
jbe@121 416 }
jbe@136 417 // process a decoded value or key value pair (expected on top of Lua stack):
jbe@136 418 json_import_process_value:
jbe@121 419 switch (mode) {
jbe@136 420 // an object key has been read:
jbe@124 421 case JSON_STATE_OBJECT_KEY:
jbe@136 422 // if an object key is not a string, then this is a syntax error:
jbe@121 423 if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
jbe@146 424 // expect key terminator to follow:
jbe@124 425 mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
jbe@146 426 // continue with loop:
jbe@121 427 goto json_import_loop;
jbe@136 428 // a key value pair has been read:
jbe@124 429 case JSON_STATE_OBJECT_VALUE:
jbe@136 430 // store key value pair in outer shadow table:
jbe@130 431 lua_rawset(L, -3);
jbe@146 432 // expect value terminator (or end of object) to follow:
jbe@124 433 mode = JSON_STATE_OBJECT_SEPARATOR;
jbe@146 434 // continue with loop:
jbe@121 435 goto json_import_loop;
jbe@136 436 // an array value has been read:
jbe@124 437 case JSON_STATE_ARRAY_VALUE:
jbe@152 438 // get current array length:
jbe@152 439 arraylen = lua_rawlen(L, -3);
jbe@152 440 // throw error if array would exceed INT_MAX elements:
jbe@152 441 // TODO: Lua 5.3 may support more elements
jbe@152 442 if (arraylen >= INT_MAX) {
jbe@152 443 lua_pushnil(L);
jbe@152 444 lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
jbe@152 445 }
jbe@136 446 // store value in outer shadow table:
jbe@152 447 lua_rawseti(L, -3, arraylen + 1);
jbe@146 448 // expect value terminator (or end of object) to follow:
jbe@124 449 mode = JSON_STATE_ARRAY_SEPARATOR;
jbe@146 450 // continue with loop
jbe@121 451 goto json_import_loop;
jbe@136 452 // a single value has been read:
jbe@124 453 case JSON_STATE_VALUE:
jbe@136 454 // leave value on top of stack, expect end of JSON document, and continue with loop:
jbe@124 455 mode = JSON_STATE_END;
jbe@121 456 goto json_import_loop;
jbe@121 457 }
jbe@146 458 // syntax error handling (reachable by goto statement):
jbe@136 459 json_import_syntax_error:
jbe@121 460 lua_pushnil(L);
jbe@121 461 lua_pushliteral(L, "Syntax error in JSON document");
jbe@121 462 return 2;
jbe@121 463 }
jbe@121 464
jbe@146 465 // special Lua stack indicies for json_path function:
jbe@138 466 #define json_path_shadowtbl_idx 1
jbe@146 467
jbe@146 468 // stack offset of arguments to json_path function:
jbe@155 469 #define json_path_idxshift 1
jbe@138 470
jbe@146 471 // gets a value or its type from a JSON document (passed as first argument)
jbe@147 472 // using a path (passed as variable number of keys after first argument):
jbe@137 473 static int json_path(lua_State *L, int type_mode) {
jbe@146 474 int stacktop; // stack index of top of stack (after shifting)
jbe@146 475 int idx = 2 + json_path_idxshift; // stack index of current argument to process
jbe@148 476 // insert shadowtbl into stack at position 1 (shifting the arguments):
jbe@144 477 json_regfetch(L, shadowtbl);
jbe@138 478 lua_insert(L, 1);
jbe@146 479 // store stack index of top of stack:
jbe@138 480 stacktop = lua_gettop(L);
jbe@146 481 // use first argument as "current value" (stored on top of stack):
jbe@138 482 lua_pushvalue(L, 1 + json_path_idxshift);
jbe@146 483 // process each "path key" (2nd argument and following arguments):
jbe@138 484 while (idx <= stacktop) {
jbe@146 485 // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
jbe@137 486 if (lua_isnil(L, -1)) return 1;
jbe@137 487 // try to get shadow table of "current value":
jbe@130 488 lua_pushvalue(L, -1);
jbe@138 489 lua_rawget(L, json_path_shadowtbl_idx);
jbe@126 490 if (lua_isnil(L, -1)) {
jbe@137 491 // if no shadow table is found,
jbe@130 492 if (lua_type(L, -1) == LUA_TTABLE) {
jbe@146 493 // and if "current value" is a table,
jbe@146 494 // drop nil from stack:
jbe@146 495 lua_pop(L, 1);
jbe@137 496 // get "next value" using the "path key":
jbe@130 497 lua_pushvalue(L, idx++);
jbe@130 498 lua_gettable(L, -2);
jbe@130 499 } else {
jbe@137 500 // if "current value" is not a table,
jbe@146 501 // then the path cannot be walked and nil (already on top of stack) is returned:
jbe@137 502 return 1;
jbe@130 503 }
jbe@130 504 } else {
jbe@137 505 // if a shadow table is found,
jbe@137 506 // set "current value" to its shadow table:
jbe@130 507 lua_replace(L, -2);
jbe@137 508 // get "next value" using the "path key":
jbe@130 509 lua_pushvalue(L, idx++);
jbe@130 510 lua_rawget(L, -2);
jbe@126 511 }
jbe@137 512 // the "next value" replaces the "current value":
jbe@130 513 lua_replace(L, -2);
jbe@126 514 }
jbe@137 515 if (!type_mode) {
jbe@137 516 // if a value (and not its type) was requested,
jbe@137 517 // check if value is the null-marker, and store nil on top of Lua stack in that case:
jbe@155 518 if (json_isnullmark(L, -1)) lua_pushnil(L);
jbe@137 519 } else {
jbe@137 520 // if the type was requested,
jbe@137 521 // check if value is the null-marker:
jbe@155 522 if (json_isnullmark(L, -1)) {
jbe@137 523 // if yes, store string "null" on top of Lua stack:
jbe@130 524 lua_pushliteral(L, "null");
jbe@137 525 } else {
jbe@137 526 // otherwise,
jbe@138 527 // check if metatable indicates "object" or "array":
jbe@138 528 if (lua_getmetatable(L, -1)) {
jbe@144 529 json_regfetch(L, objectmt);
jbe@138 530 if (lua_rawequal(L, -2, -1)) {
jbe@146 531 // if value has metatable for JSON objects,
jbe@138 532 // return string "object":
jbe@138 533 lua_pushliteral(L, "object");
jbe@138 534 return 1;
jbe@138 535 }
jbe@144 536 json_regfetch(L, arraymt);
jbe@138 537 if (lua_rawequal(L, -3, -1)) {
jbe@146 538 // if value has metatable for JSON arrays,
jbe@146 539 // return string "object":
jbe@138 540 lua_pushliteral(L, "array");
jbe@138 541 return 1;
jbe@138 542 }
jbe@146 543 // remove 3 metatables (one of the value, two for comparison) from stack:
jbe@138 544 lua_pop(L, 3);
jbe@138 545 }
jbe@138 546 // otherwise, get the Lua type:
jbe@138 547 lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
jbe@126 548 }
jbe@126 549 }
jbe@137 550 // return the top most value on the Lua stack:
jbe@137 551 return 1;
jbe@130 552 }
jbe@130 553
jbe@147 554 // gets a value from a JSON document (passed as first argument)
jbe@147 555 // using a path (passed as variable number of keys after first argument):
jbe@130 556 static int json_get(lua_State *L) {
jbe@137 557 return json_path(L, 0);
jbe@130 558 }
jbe@130 559
jbe@147 560 // gets a value's type from a JSON document (passed as first argument)
jbe@147 561 // using a path (variable number of keys after first argument):
jbe@130 562 static int json_type(lua_State *L) {
jbe@137 563 return json_path(L, 1);
jbe@130 564 }
jbe@130 565
jbe@147 566 // returns the length of a JSON array (or zero for a table without numeric keys):
jbe@130 567 static int json_len(lua_State *L) {
jbe@147 568 // stack shall contain one function argument:
jbe@130 569 lua_settop(L, 1);
jbe@148 570 // try to get corresponding shadow table for first argument:
jbe@144 571 json_regfetch(L, shadowtbl);
jbe@130 572 lua_pushvalue(L, 1);
jbe@138 573 lua_rawget(L, -2);
jbe@147 574 // if shadow table does not exist, return length of argument, else length of shadow table:
jbe@147 575 lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
jbe@123 576 return 1;
jbe@123 577 }
jbe@123 578
jbe@130 579 static int json_index(lua_State *L) {
jbe@148 580 // stack shall contain two function arguments:
jbe@130 581 lua_settop(L, 2);
jbe@155 582 // get corresponding shadow table for first argument:
jbe@144 583 json_regfetch(L, shadowtbl);
jbe@130 584 lua_pushvalue(L, 1);
jbe@155 585 lua_rawget(L, -2);
jbe@148 586 // throw error if no shadow table was found:
jbe@139 587 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 588 // use key passed as second argument to lookup value in shadow table:
jbe@130 589 lua_pushvalue(L, 2);
jbe@130 590 lua_rawget(L, -2);
jbe@148 591 // if value is null-marker, then push nil onto stack:
jbe@155 592 if (json_isnullmark(L, -1)) lua_pushnil(L);
jbe@148 593 // return either looked up value, or nil
jbe@127 594 return 1;
jbe@127 595 }
jbe@127 596
jbe@130 597 static int json_newindex(lua_State *L) {
jbe@148 598 // stack shall contain three function arguments:
jbe@130 599 lua_settop(L, 3);
jbe@148 600 // get corresponding shadow table for first argument:
jbe@144 601 json_regfetch(L, shadowtbl);
jbe@123 602 lua_pushvalue(L, 1);
jbe@143 603 lua_rawget(L, -2);
jbe@148 604 // throw error if no shadow table was found:
jbe@130 605 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148 606 // replace first argument with shadow table:
jbe@130 607 lua_replace(L, 1);
jbe@148 608 // reset stack and use second and third argument to write to shadow table:
jbe@139 609 lua_settop(L, 3);
jbe@130 610 lua_rawset(L, 1);
jbe@148 611 // return nothing:
jbe@148 612 return 0;
jbe@121 613 }
jbe@121 614
jbe@135 615 static int json_pairs_iterfunc(lua_State *L) {
jbe@149 616 // stack shall contain two function arguments:
jbe@135 617 lua_settop(L, 2);
jbe@155 618 // get corresponding shadow table for first argument:
jbe@144 619 json_regfetch(L, shadowtbl);
jbe@135 620 lua_pushvalue(L, 1);
jbe@155 621 lua_rawget(L, -2);
jbe@149 622 // throw error if no shadow table was found:
jbe@135 623 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 624 // get next key value pair from shadow table (using previous key from argument 2)
jbe@149 625 // and return nothing if there is no next pair:
jbe@135 626 lua_pushvalue(L, 2);
jbe@135 627 if (!lua_next(L, -2)) return 0;
jbe@149 628 // replace null-marker with nil:
jbe@155 629 if (json_isnullmark(L, -1)) {
jbe@135 630 lua_pop(L, 1);
jbe@135 631 lua_pushnil(L);
jbe@135 632 }
jbe@149 633 // return key and value (or key and nil, if null-marker was found):
jbe@135 634 return 2;
jbe@135 635 }
jbe@135 636
jbe@149 637 // returns a triple such that 'for key, value in pairs(obj) do ... end'
jbe@149 638 // iterates through all key value pairs (including JSON null keys represented as Lua nil):
jbe@135 639 static int json_pairs(lua_State *L) {
jbe@149 640 // return triple of function json_pairs_iterfunc, first argument, and nil:
jbe@139 641 lua_pushcfunction(L, json_pairs_iterfunc);
jbe@135 642 lua_pushvalue(L, 1);
jbe@135 643 lua_pushnil(L);
jbe@135 644 return 3;
jbe@135 645 }
jbe@135 646
jbe@134 647 static int json_ipairs_iterfunc(lua_State *L) {
jbe@152 648 lua_Integer idx;
jbe@149 649 // stack shall contain two function arguments:
jbe@134 650 lua_settop(L, 2);
jbe@149 651 // calculate new index by incrementing second argument:
jbe@134 652 idx = lua_tointeger(L, 2) + 1;
jbe@149 653 // get corresponding shadow table for first argument:
jbe@155 654 json_regfetch(L, shadowtbl);
jbe@134 655 lua_pushvalue(L, 1);
jbe@155 656 lua_rawget(L, -2);
jbe@149 657 // throw error if no shadow table was found:
jbe@134 658 if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149 659 // do integer lookup in shadow table:
jbe@134 660 lua_rawgeti(L, -1, idx);
jbe@149 661 // return nothing if there was no value:
jbe@134 662 if (lua_isnil(L, -1)) return 0;
jbe@149 663 // return new index and
jbe@149 664 // either the looked up value if it is not equal to the null-marker
jbe@149 665 // or nil instead of null-marker:
jbe@134 666 lua_pushinteger(L, idx);
jbe@155 667 if (json_isnullmark(L, -2)) lua_pushnil(L);
jbe@134 668 else lua_pushvalue(L, -2);
jbe@134 669 return 2;
jbe@134 670 }
jbe@134 671
jbe@149 672 // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
jbe@149 673 // iterates through all values (including JSON null represented as Lua nil):
jbe@134 674 static int json_ipairs(lua_State *L) {
jbe@149 675 // return triple of function json_ipairs_iterfunc, first argument, and zero:
jbe@139 676 lua_pushcfunction(L, json_ipairs_iterfunc);
jbe@134 677 lua_pushvalue(L, 1);
jbe@134 678 lua_pushinteger(L, 0);
jbe@134 679 return 3;
jbe@134 680 }
jbe@134 681
jbe@154 682 #define JSON_TABLETYPE_UNKNOWN 0
jbe@154 683 #define JSON_TABLETYPE_OBJECT 1
jbe@154 684 #define JSON_TABLETYPE_ARRAY 2
jbe@154 685
jbe@154 686 static int json_export(lua_State *L) {
jbe@154 687 lua_Number num;
jbe@154 688 const char *str;
jbe@154 689 unsigned char c;
jbe@154 690 size_t strlen;
jbe@154 691 size_t pos = 0;
jbe@154 692 luaL_Buffer buf;
jbe@154 693 char hexcode[7]; // backslash, character 'u', 4 hex digits, and terminating NULL byte
jbe@154 694 int luatype;
jbe@154 695 int tabletype = JSON_TABLETYPE_UNKNOWN;
jbe@154 696 int needsep = 0;
jbe@154 697 lua_Integer idx;
jbe@154 698 lua_settop(L, 1);
jbe@157 699 if (json_isnullmark(L, 1)) {
jbe@157 700 lua_pushnil(L);
jbe@157 701 lua_replace(L, 1);
jbe@157 702 }
jbe@154 703 switch (lua_type(L, 1)) {
jbe@154 704 case LUA_TNIL:
jbe@154 705 lua_pushliteral(L, "null");
jbe@154 706 return 1;
jbe@154 707 case LUA_TNUMBER:
jbe@154 708 num = lua_tonumber(L, 1);
jbe@154 709 if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
jbe@154 710 if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
jbe@154 711 lua_tostring(L, 1);
jbe@154 712 return 1;
jbe@154 713 case LUA_TBOOLEAN:
jbe@154 714 if (lua_toboolean(L, 1)) lua_pushliteral(L, "true");
jbe@154 715 else lua_pushliteral(L, "false");
jbe@154 716 return 1;
jbe@154 717 case LUA_TSTRING:
jbe@154 718 str = lua_tolstring(L, 1, &strlen);
jbe@154 719 luaL_buffinit(L, &buf);
jbe@154 720 luaL_addchar(&buf, '"');
jbe@154 721 while (pos < strlen) {
jbe@154 722 c = str[pos++];
jbe@154 723 if (c == '"') luaL_addstring(&buf, "\\\"");
jbe@154 724 else if (c == '\\') luaL_addstring(&buf, "\\\\");
jbe@154 725 else if (c == 127) luaL_addstring(&buf, "\\u007F");
jbe@154 726 else if (c >= 32) luaL_addchar(&buf, c);
jbe@154 727 else if (c == '\b') luaL_addstring(&buf, "\\b");
jbe@154 728 else if (c == '\f') luaL_addstring(&buf, "\\f");
jbe@154 729 else if (c == '\n') luaL_addstring(&buf, "\\n");
jbe@154 730 else if (c == '\r') luaL_addstring(&buf, "\\r");
jbe@154 731 else if (c == '\t') luaL_addstring(&buf, "\\t");
jbe@154 732 else if (c == '\v') luaL_addstring(&buf, "\\v");
jbe@154 733 else {
jbe@154 734 sprintf(hexcode, "\\u%04X", c);
jbe@154 735 luaL_addstring(&buf, hexcode);
jbe@154 736 }
jbe@154 737 }
jbe@154 738 luaL_addchar(&buf, '"');
jbe@154 739 luaL_pushresult(&buf);
jbe@154 740 return 1;
jbe@154 741 case LUA_TTABLE:
jbe@154 742 if (lua_getmetatable(L, 1)) {
jbe@154 743 json_regfetch(L, objectmt);
jbe@154 744 if (lua_rawequal(L, -2, -1)) {
jbe@154 745 tabletype = JSON_TABLETYPE_OBJECT;
jbe@154 746 } else {
jbe@154 747 json_regfetch(L, arraymt);
jbe@154 748 if (lua_rawequal(L, -3, -1)) tabletype = JSON_TABLETYPE_ARRAY;
jbe@154 749 }
jbe@154 750 }
jbe@154 751 json_regfetch(L, shadowtbl);
jbe@154 752 lua_pushvalue(L, 1);
jbe@154 753 lua_rawget(L, -2);
jbe@154 754 if (!lua_isnil(L, -1)) lua_replace(L, 1);
jbe@154 755 lua_settop(L, 1);
jbe@154 756 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
jbe@154 757 for (lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@154 758 luatype = lua_type(L, -2);
jbe@154 759 if (tabletype == JSON_TABLETYPE_UNKNOWN) {
jbe@154 760 if (luatype == LUA_TSTRING) tabletype = JSON_TABLETYPE_OBJECT;
jbe@154 761 else if (luatype == LUA_TNUMBER) tabletype = JSON_TABLETYPE_ARRAY;
jbe@154 762 } else if (
jbe@154 763 (tabletype == JSON_TABLETYPE_OBJECT && luatype == LUA_TNUMBER) ||
jbe@154 764 (tabletype == JSON_TABLETYPE_ARRAY && luatype == LUA_TSTRING)
jbe@154 765 ) {
jbe@154 766 goto json_export_tabletype_error;
jbe@154 767 }
jbe@154 768 }
jbe@154 769 }
jbe@154 770 switch (tabletype) {
jbe@154 771 case JSON_TABLETYPE_OBJECT:
jbe@154 772 lua_settop(L, 3);
jbe@154 773 luaL_buffinit(L, &buf);
jbe@154 774 luaL_addchar(&buf, '{');
jbe@154 775 for (lua_pushnil(L); lua_next(L, 1); ) {
jbe@154 776 if (lua_type(L, -2) == LUA_TSTRING) {
jbe@154 777 lua_replace(L, 3);
jbe@154 778 lua_replace(L, 2);
jbe@154 779 if (needsep) luaL_addchar(&buf, ',');
jbe@154 780 else needsep = 1;
jbe@154 781 lua_pushcfunction(L, json_export);
jbe@154 782 lua_pushvalue(L, 2);
jbe@154 783 lua_call(L, 1, 1);
jbe@154 784 luaL_addvalue(&buf);
jbe@154 785 luaL_addchar(&buf, ':');
jbe@155 786 if (json_isnullmark(L, 3)) {
jbe@154 787 luaL_addstring(&buf, "null");
jbe@154 788 } else {
jbe@154 789 lua_pushcfunction(L, json_export);
jbe@154 790 lua_pushvalue(L, 3);
jbe@154 791 lua_call(L, 1, 1);
jbe@154 792 luaL_addvalue(&buf);
jbe@154 793 }
jbe@154 794 lua_pushvalue(L, 2);
jbe@154 795 } else {
jbe@154 796 lua_pop(L, 1);
jbe@154 797 }
jbe@154 798 }
jbe@154 799 luaL_addchar(&buf, '}');
jbe@154 800 luaL_pushresult(&buf);
jbe@154 801 return 1;
jbe@154 802 case JSON_TABLETYPE_ARRAY:
jbe@154 803 lua_settop(L, 2);
jbe@154 804 luaL_buffinit(L, &buf);
jbe@154 805 luaL_addchar(&buf, '[');
jbe@154 806 for (idx = 1; ; idx++) {
jbe@154 807 lua_rawgeti(L, 1, idx);
jbe@154 808 if (lua_isnil(L, -1)) {
jbe@154 809 lua_pop(L, 1);
jbe@154 810 break;
jbe@154 811 }
jbe@154 812 lua_replace(L, 2);
jbe@154 813 if (needsep) luaL_addchar(&buf, ',');
jbe@154 814 else needsep = 1;
jbe@154 815 lua_pushcfunction(L, json_export);
jbe@154 816 lua_pushvalue(L, 2);
jbe@154 817 lua_call(L, 1, 1);
jbe@154 818 luaL_addvalue(&buf);
jbe@154 819 }
jbe@154 820 luaL_addchar(&buf, ']');
jbe@154 821 luaL_pushresult(&buf);
jbe@154 822 return 1;
jbe@154 823 }
jbe@154 824 json_export_tabletype_error:
jbe@154 825 return luaL_error(L, "JSON export not possible for ambiguous table (cannot decide whether it is an object or array)");
jbe@154 826 }
jbe@154 827 return luaL_error(L, "JSON export not possible for values of type \"%s\"", lua_typename(L, lua_type(L, 1)));
jbe@154 828 }
jbe@154 829
jbe@149 830 // functions in library module:
jbe@121 831 static const struct luaL_Reg json_module_functions[] = {
jbe@133 832 {"object", json_object},
jbe@133 833 {"array", json_array},
jbe@121 834 {"import", json_import},
jbe@154 835 {"export", json_export},
jbe@130 836 {"get", json_get},
jbe@127 837 {"type", json_type},
jbe@121 838 {NULL, NULL}
jbe@121 839 };
jbe@121 840
jbe@149 841 // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
jbe@126 842 static const struct luaL_Reg json_metatable_functions[] = {
jbe@130 843 {"__len", json_len},
jbe@130 844 {"__index", json_index},
jbe@130 845 {"__newindex", json_newindex},
jbe@135 846 {"__pairs", json_pairs},
jbe@134 847 {"__ipairs", json_ipairs},
jbe@160 848 {"__tostring", json_export},
jbe@126 849 {NULL, NULL}
jbe@126 850 };
jbe@126 851
jbe@157 852 // metamethods for JSON null marker:
jbe@157 853 static const struct luaL_Reg json_nullmark_metamethods[] = {
jbe@157 854 {"__tostring", json_nullmark_tostring},
jbe@157 855 {NULL, NULL}
jbe@157 856 };
jbe@157 857
jbe@149 858 // initializes json library:
jbe@121 859 int luaopen_json(lua_State *L) {
jbe@149 860 // empty stack:
jbe@126 861 lua_settop(L, 0);
jbe@149 862 // push library module onto stack position 1:
jbe@149 863 lua_newtable(L);
jbe@149 864 // register library functions:
jbe@149 865 luaL_setfuncs(L, json_module_functions, 0);
jbe@149 866 // create and store objectmt:
jbe@138 867 lua_newtable(L);
jbe@138 868 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 869 json_regstore(L, objectmt);
jbe@149 870 // create and store arraymt:
jbe@138 871 lua_newtable(L);
jbe@138 872 luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144 873 json_regstore(L, arraymt);
jbe@149 874 // create and store ephemeron table to store shadow tables for each JSON object/array
jbe@149 875 // to allow NULL values returned as nil
jbe@149 876 lua_newtable(L);
jbe@138 877 lua_newtable(L); // metatable for ephemeron table
jbe@121 878 lua_pushliteral(L, "__mode");
jbe@121 879 lua_pushliteral(L, "k");
jbe@138 880 lua_rawset(L, -3);
jbe@138 881 lua_setmetatable(L, -2);
jbe@144 882 json_regstore(L, shadowtbl);
jbe@157 883 // set metatable of null marker and make it available through library module:
jbe@157 884 json_pushnullmark(L);
jbe@157 885 lua_newtable(L);
jbe@157 886 luaL_setfuncs(L, json_nullmark_metamethods, 0);
jbe@157 887 lua_setmetatable(L, -2);
jbe@157 888 lua_setfield(L, 1, "null");
jbe@157 889 // return library module (that's expected on top of stack):
jbe@121 890 return 1;
jbe@121 891 }

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