qobject/json-parser.c

   1 /*
   2  * JSON Parser
   3  *
   4  * Copyright IBM, Corp. 2009
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  *
  12  */
  13
  14 #include <stdarg.h>
  15
  16 #include "qemu-common.h"
  17 #include "qapi/qmp/qstring.h"
  18 #include "qapi/qmp/qint.h"
  19 #include "qapi/qmp/qdict.h"
  20 #include "qapi/qmp/qlist.h"
  21 #include "qapi/qmp/qfloat.h"
  22 #include "qapi/qmp/qbool.h"
  23 #include "qapi/qmp/json-parser.h"
  24 #include "qapi/qmp/json-lexer.h"
  25 #include "qapi/qmp/qerror.h"
  26
  27 typedef struct JSONParserContext
  28 {
  29     Error *err;
  30     struct {
  31         QObject **buf;
  32         size_t pos;
  33         size_t count;
  34     } tokens;
  35 } JSONParserContext;
  36
  37 #define BUG_ON(cond) assert(!(cond))
  38
  39 /**
  40  * TODO
  41  *
  42  * 0) make errors meaningful again
  43  * 1) add geometry information to tokens
  44  * 3) should we return a parsed size?
  45  * 4) deal with premature EOI
  46  */
  47
  48 static QObject *parse_value(JSONParserContext *ctxt, va_list *ap);
  49
  50 /**
  51  * Token manipulators
  52  *
  53  * tokens are dictionaries that contain a type, a string value, and geometry information
  54  * about a token identified by the lexer.  These are routines that make working with
  55  * these objects a bit easier.
  56  */
  57 static const char *token_get_value(QObject *obj)
  58 {
  59     return qdict_get_str(qobject_to_qdict(obj), "token");
  60 }
  61
  62 static JSONTokenType token_get_type(QObject *obj)
  63 {
  64     return qdict_get_int(qobject_to_qdict(obj), "type");
  65 }
  66
  67 static int token_is_operator(QObject *obj, char op)
  68 {
  69     const char *val;
  70
  71     if (token_get_type(obj) != JSON_OPERATOR) {
  72         return 0;
  73     }
  74
  75     val = token_get_value(obj);
  76
  77     return (val[0] == op) && (val[1] == 0);
  78 }
  79
  80 static int token_is_keyword(QObject *obj, const char *value)
  81 {
  82     if (token_get_type(obj) != JSON_KEYWORD) {
  83         return 0;
  84     }
  85
  86     return strcmp(token_get_value(obj), value) == 0;
  87 }
  88
  89 static int token_is_escape(QObject *obj, const char *value)
  90 {
  91     if (token_get_type(obj) != JSON_ESCAPE) {
  92         return 0;
  93     }
  94
  95     return (strcmp(token_get_value(obj), value) == 0);
  96 }
  97
  98 /**
  99  * Error handler
 100  */
 101 static void GCC_FMT_ATTR(3, 4) parse_error(JSONParserContext *ctxt,
 102                                            QObject *token, const char *msg, ...)
 103 {
 104     va_list ap;
 105     char message[1024];
 106     va_start(ap, msg);
 107     vsnprintf(message, sizeof(message), msg, ap);
 108     va_end(ap);
 109     if (ctxt->err) {
 110         error_free(ctxt->err);
 111         ctxt->err = NULL;
 112     }
 113     error_setg(&ctxt->err, "JSON parse error, %s", message);
 114 }
 115
 116 /**
 117  * String helpers
 118  *
 119  * These helpers are used to unescape strings.
 120  */
 121 static void wchar_to_utf8(uint16_t wchar, char *buffer, size_t buffer_length)
 122 {
 123     if (wchar <= 0x007F) {
 124         BUG_ON(buffer_length < 2);
 125
 126         buffer[0] = wchar & 0x7F;
 127         buffer[1] = 0;
 128     } else if (wchar <= 0x07FF) {
 129         BUG_ON(buffer_length < 3);
 130
 131         buffer[0] = 0xC0 | ((wchar >> 6) & 0x1F);
 132         buffer[1] = 0x80 | (wchar & 0x3F);
 133         buffer[2] = 0;
 134     } else {
 135         BUG_ON(buffer_length < 4);
 136
 137         buffer[0] = 0xE0 | ((wchar >> 12) & 0x0F);
 138         buffer[1] = 0x80 | ((wchar >> 6) & 0x3F);
 139         buffer[2] = 0x80 | (wchar & 0x3F);
 140         buffer[3] = 0;
 141     }
 142 }
 143
 144 static int hex2decimal(char ch)
 145 {
 146     if (ch >= '0' && ch <= '9') {
 147         return (ch - '0');
 148     } else if (ch >= 'a' && ch <= 'f') {
 149         return 10 + (ch - 'a');
 150     } else if (ch >= 'A' && ch <= 'F') {
 151         return 10 + (ch - 'A');
 152     }
 153
 154     return -1;
 155 }
 156
 157 /**
 158  * parse_string(): Parse a json string and return a QObject
 159  *
 160  *  string
 161  *      ""
 162  *      " chars "
 163  *  chars
 164  *      char
 165  *      char chars
 166  *  char
 167  *      any-Unicode-character-
 168  *          except-"-or-\-or-
 169  *          control-character
 170  *      \"
 171  *      \\
 172  *      \/
 173  *      \b
 174  *      \f
 175  *      \n
 176  *      \r
 177  *      \t
 178  *      \u four-hex-digits
 179  */
 180 static QString *qstring_from_escaped_str(JSONParserContext *ctxt, QObject *token)
 181 {
 182     const char *ptr = token_get_value(token);
 183     QString *str;
 184     int double_quote = 1;
 185
 186     if (*ptr == '"') {
 187         double_quote = 1;
 188     } else {
 189         double_quote = 0;
 190     }
 191     ptr++;
 192
 193     str = qstring_new();
 194     while (*ptr &&
 195            ((double_quote && *ptr != '"') || (!double_quote && *ptr != '\''))) {
 196         if (*ptr == '\\') {
 197             ptr++;
 198
 199             switch (*ptr) {
 200             case '"':
 201                 qstring_append(str, "\"");
 202                 ptr++;
 203                 break;
 204             case '\'':
 205                 qstring_append(str, "'");
 206                 ptr++;
 207                 break;
 208             case '\\':
 209                 qstring_append(str, "\\");
 210                 ptr++;
 211                 break;
 212             case '/':
 213                 qstring_append(str, "/");
 214                 ptr++;
 215                 break;
 216             case 'b':
 217                 qstring_append(str, "\b");
 218                 ptr++;
 219                 break;
 220             case 'f':
 221                 qstring_append(str, "\f");
 222                 ptr++;
 223                 break;
 224             case 'n':
 225                 qstring_append(str, "\n");
 226                 ptr++;
 227                 break;
 228             case 'r':
 229                 qstring_append(str, "\r");
 230                 ptr++;
 231                 break;
 232             case 't':
 233                 qstring_append(str, "\t");
 234                 ptr++;
 235                 break;
 236             case 'u': {
 237                 uint16_t unicode_char = 0;
 238                 char utf8_char[4];
 239                 int i = 0;
 240
 241                 ptr++;
 242
 243                 for (i = 0; i < 4; i++) {
 244                     if (qemu_isxdigit(*ptr)) {
 245                         unicode_char |= hex2decimal(*ptr) << ((3 - i) * 4);
 246                     } else {
 247                         parse_error(ctxt, token,
 248                                     "invalid hex escape sequence in string");
 249                         goto out;
 250                     }
 251                     ptr++;
 252                 }
 253
 254                 wchar_to_utf8(unicode_char, utf8_char, sizeof(utf8_char));
 255                 qstring_append(str, utf8_char);
 256             }   break;
 257             default:
 258                 parse_error(ctxt, token, "invalid escape sequence in string");
 259                 goto out;
 260             }
 261         } else {
 262             char dummy[2];
 263
 264             dummy[0] = *ptr++;
 265             dummy[1] = 0;
 266
 267             qstring_append(str, dummy);
 268         }
 269     }
 270
 271     return str;
 272
 273 out:
 274     QDECREF(str);
 275     return NULL;
 276 }
 277
 278 static QObject *parser_context_pop_token(JSONParserContext *ctxt)
 279 {
 280     QObject *token;
 281     g_assert(ctxt->tokens.pos < ctxt->tokens.count);
 282     token = ctxt->tokens.buf[ctxt->tokens.pos];
 283     ctxt->tokens.pos++;
 284     return token;
 285 }
 286
 287 /* Note: parser_context_{peek|pop}_token do not increment the
 288  * token object's refcount. In both cases the references will continue
 289  * to be tracked and cleaned up in parser_context_free(), so do not
 290  * attempt to free the token object.
 291  */
 292 static QObject *parser_context_peek_token(JSONParserContext *ctxt)
 293 {
 294     QObject *token;
 295     g_assert(ctxt->tokens.pos < ctxt->tokens.count);
 296     token = ctxt->tokens.buf[ctxt->tokens.pos];
 297     return token;
 298 }
 299
 300 static JSONParserContext parser_context_save(JSONParserContext *ctxt)
 301 {
 302     JSONParserContext saved_ctxt = {0};
 303     saved_ctxt.tokens.pos = ctxt->tokens.pos;
 304     saved_ctxt.tokens.count = ctxt->tokens.count;
 305     saved_ctxt.tokens.buf = ctxt->tokens.buf;
 306     return saved_ctxt;
 307 }
 308
 309 static void parser_context_restore(JSONParserContext *ctxt,
 310                                    JSONParserContext saved_ctxt)
 311 {
 312     ctxt->tokens.pos = saved_ctxt.tokens.pos;
 313     ctxt->tokens.count = saved_ctxt.tokens.count;
 314     ctxt->tokens.buf = saved_ctxt.tokens.buf;
 315 }
 316
 317 static void tokens_append_from_iter(QObject *obj, void *opaque)
 318 {
 319     JSONParserContext *ctxt = opaque;
 320     g_assert(ctxt->tokens.pos < ctxt->tokens.count);
 321     ctxt->tokens.buf[ctxt->tokens.pos++] = obj;
 322     qobject_incref(obj);
 323 }
 324
 325 static JSONParserContext *parser_context_new(QList *tokens)
 326 {
 327     JSONParserContext *ctxt;
 328     size_t count;
 329
 330     if (!tokens) {
 331         return NULL;
 332     }
 333
 334     count = qlist_size(tokens);
 335     if (count == 0) {
 336         return NULL;
 337     }
 338
 339     ctxt = g_malloc0(sizeof(JSONParserContext));
 340     ctxt->tokens.pos = 0;
 341     ctxt->tokens.count = count;
 342     ctxt->tokens.buf = g_malloc(count * sizeof(QObject *));
 343     qlist_iter(tokens, tokens_append_from_iter, ctxt);
 344     ctxt->tokens.pos = 0;
 345
 346     return ctxt;
 347 }
 348
 349 /* to support error propagation, ctxt->err must be freed separately */
 350 static void parser_context_free(JSONParserContext *ctxt)
 351 {
 352     int i;
 353     if (ctxt) {
 354         for (i = 0; i < ctxt->tokens.count; i++) {
 355             qobject_decref(ctxt->tokens.buf[i]);
 356         }
 357         g_free(ctxt->tokens.buf);
 358         g_free(ctxt);
 359     }
 360 }
 361
 362 /**
 363  * Parsing rules
 364  */
 365 static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
 366 {
 367     QObject *key = NULL, *token = NULL, *value, *peek;
 368     JSONParserContext saved_ctxt = parser_context_save(ctxt);
 369
 370     peek = parser_context_peek_token(ctxt);
 371     if (peek == NULL) {
 372         parse_error(ctxt, NULL, "premature EOI");
 373         goto out;
 374     }
 375
 376     key = parse_value(ctxt, ap);
 377     if (!key || qobject_type(key) != QTYPE_QSTRING) {
 378         parse_error(ctxt, peek, "key is not a string in object");
 379         goto out;
 380     }
 381
 382     token = parser_context_pop_token(ctxt);
 383     if (token == NULL) {
 384         parse_error(ctxt, NULL, "premature EOI");
 385         goto out;
 386     }
 387
 388     if (!token_is_operator(token, ':')) {
 389         parse_error(ctxt, token, "missing : in object pair");
 390         goto out;
 391     }
 392
 393     value = parse_value(ctxt, ap);
 394     if (value == NULL) {
 395         parse_error(ctxt, token, "Missing value in dict");
 396         goto out;
 397     }
 398
 399     qdict_put_obj(dict, qstring_get_str(qobject_to_qstring(key)), value);
 400
 401     qobject_decref(key);
 402
 403     return 0;
 404
 405 out:
 406     parser_context_restore(ctxt, saved_ctxt);
 407     qobject_decref(key);
 408
 409     return -1;
 410 }
 411
 412 static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)
 413 {
 414     QDict *dict = NULL;
 415     QObject *token, *peek;
 416     JSONParserContext saved_ctxt = parser_context_save(ctxt);
 417
 418     token = parser_context_pop_token(ctxt);
 419     if (token == NULL) {
 420         goto out;
 421     }
 422
 423     if (!token_is_operator(token, '{')) {
 424         goto out;
 425     }
 426
 427     dict = qdict_new();
 428
 429     peek = parser_context_peek_token(ctxt);
 430     if (peek == NULL) {
 431         parse_error(ctxt, NULL, "premature EOI");
 432         goto out;
 433     }
 434
 435     if (!token_is_operator(peek, '}')) {
 436         if (parse_pair(ctxt, dict, ap) == -1) {
 437             goto out;
 438         }
 439
 440         token = parser_context_pop_token(ctxt);
 441         if (token == NULL) {
 442             parse_error(ctxt, NULL, "premature EOI");
 443             goto out;
 444         }
 445
 446         while (!token_is_operator(token, '}')) {
 447             if (!token_is_operator(token, ',')) {
 448                 parse_error(ctxt, token, "expected separator in dict");
 449                 goto out;
 450             }
 451
 452             if (parse_pair(ctxt, dict, ap) == -1) {
 453                 goto out;
 454             }
 455
 456             token = parser_context_pop_token(ctxt);
 457             if (token == NULL) {
 458                 parse_error(ctxt, NULL, "premature EOI");
 459                 goto out;
 460             }
 461         }
 462     } else {
 463         (void)parser_context_pop_token(ctxt);
 464     }
 465
 466     return QOBJECT(dict);
 467
 468 out:
 469     parser_context_restore(ctxt, saved_ctxt);
 470     QDECREF(dict);
 471     return NULL;
 472 }
 473
 474 static QObject *parse_array(JSONParserContext *ctxt, va_list *ap)
 475 {
 476     QList *list = NULL;
 477     QObject *token, *peek;
 478     JSONParserContext saved_ctxt = parser_context_save(ctxt);
 479
 480     token = parser_context_pop_token(ctxt);
 481     if (token == NULL) {
 482         goto out;
 483     }
 484
 485     if (!token_is_operator(token, '[')) {
 486         goto out;
 487     }
 488
 489     list = qlist_new();
 490
 491     peek = parser_context_peek_token(ctxt);
 492     if (peek == NULL) {
 493         parse_error(ctxt, NULL, "premature EOI");
 494         goto out;
 495     }
 496
 497     if (!token_is_operator(peek, ']')) {
 498         QObject *obj;
 499
 500         obj = parse_value(ctxt, ap);
 501         if (obj == NULL) {
 502             parse_error(ctxt, token, "expecting value");
 503             goto out;
 504         }
 505
 506         qlist_append_obj(list, obj);
 507
 508         token = parser_context_pop_token(ctxt);
 509         if (token == NULL) {
 510             parse_error(ctxt, NULL, "premature EOI");
 511             goto out;
 512         }
 513
 514         while (!token_is_operator(token, ']')) {
 515             if (!token_is_operator(token, ',')) {
 516                 parse_error(ctxt, token, "expected separator in list");
 517                 goto out;
 518             }
 519
 520             obj = parse_value(ctxt, ap);
 521             if (obj == NULL) {
 522                 parse_error(ctxt, token, "expecting value");
 523                 goto out;
 524             }
 525
 526             qlist_append_obj(list, obj);
 527
 528             token = parser_context_pop_token(ctxt);
 529             if (token == NULL) {
 530                 parse_error(ctxt, NULL, "premature EOI");
 531                 goto out;
 532             }
 533         }
 534     } else {
 535         (void)parser_context_pop_token(ctxt);
 536     }
 537
 538     return QOBJECT(list);
 539
 540 out:
 541     parser_context_restore(ctxt, saved_ctxt);
 542     QDECREF(list);
 543     return NULL;
 544 }
 545
 546 static QObject *parse_keyword(JSONParserContext *ctxt)
 547 {
 548     QObject *token, *ret;
 549     JSONParserContext saved_ctxt = parser_context_save(ctxt);
 550
 551     token = parser_context_pop_token(ctxt);
 552     if (token == NULL) {
 553         goto out;
 554     }
 555
 556     if (token_get_type(token) != JSON_KEYWORD) {
 557         goto out;
 558     }
 559
 560     if (token_is_keyword(token, "true")) {
 561         ret = QOBJECT(qbool_from_int(true));
 562     } else if (token_is_keyword(token, "false")) {
 563         ret = QOBJECT(qbool_from_int(false));
 564     } else if (token_is_keyword(token, "null")) {
 565         ret = qnull();
 566     } else {
 567         parse_error(ctxt, token, "invalid keyword `%s'", token_get_value(token));
 568         goto out;
 569     }
 570
 571     return ret;
 572
 573 out:
 574     parser_context_restore(ctxt, saved_ctxt);
 575
 576     return NULL;
 577 }
 578
 579 static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
 580 {
 581     QObject *token = NULL, *obj;
 582     JSONParserContext saved_ctxt = parser_context_save(ctxt);
 583
 584     if (ap == NULL) {
 585         goto out;
 586     }
 587
 588     token = parser_context_pop_token(ctxt);
 589     if (token == NULL) {
 590         goto out;
 591     }
 592
 593     if (token_is_escape(token, "%p")) {
 594         obj = va_arg(*ap, QObject *);
 595     } else if (token_is_escape(token, "%i")) {
 596         obj = QOBJECT(qbool_from_int(va_arg(*ap, int)));
 597     } else if (token_is_escape(token, "%d")) {
 598         obj = QOBJECT(qint_from_int(va_arg(*ap, int)));
 599     } else if (token_is_escape(token, "%ld")) {
 600         obj = QOBJECT(qint_from_int(va_arg(*ap, long)));
 601     } else if (token_is_escape(token, "%lld") ||
 602                token_is_escape(token, "%I64d")) {
 603         obj = QOBJECT(qint_from_int(va_arg(*ap, long long)));
 604     } else if (token_is_escape(token, "%s")) {
 605         obj = QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
 606     } else if (token_is_escape(token, "%f")) {
 607         obj = QOBJECT(qfloat_from_double(va_arg(*ap, double)));
 608     } else {
 609         goto out;
 610     }
 611
 612     return obj;
 613
 614 out:
 615     parser_context_restore(ctxt, saved_ctxt);
 616
 617     return NULL;
 618 }
 619
 620 static QObject *parse_literal(JSONParserContext *ctxt)
 621 {
 622     QObject *token, *obj;
 623     JSONParserContext saved_ctxt = parser_context_save(ctxt);
 624
 625     token = parser_context_pop_token(ctxt);
 626     if (token == NULL) {
 627         goto out;
 628     }
 629
 630     switch (token_get_type(token)) {
 631     case JSON_STRING:
 632         obj = QOBJECT(qstring_from_escaped_str(ctxt, token));
 633         break;
 634     case JSON_INTEGER: {
 635         /* A possibility exists that this is a whole-valued float where the
 636          * fractional part was left out due to being 0 (.0). It's not a big
 637          * deal to treat these as ints in the parser, so long as users of the
 638          * resulting QObject know to expect a QInt in place of a QFloat in
 639          * cases like these.
 640          *
 641          * However, in some cases these values will overflow/underflow a
 642          * QInt/int64 container, thus we should assume these are to be handled
 643          * as QFloats/doubles rather than silently changing their values.
 644          *
 645          * strtoll() indicates these instances by setting errno to ERANGE
 646          */
 647         int64_t value;
 648
 649         errno = 0; /* strtoll doesn't set errno on success */
 650         value = strtoll(token_get_value(token), NULL, 10);
 651         if (errno != ERANGE) {
 652             obj = QOBJECT(qint_from_int(value));
 653             break;
 654         }
 655         /* fall through to JSON_FLOAT */
 656     }
 657     case JSON_FLOAT:
 658         /* FIXME dependent on locale */
 659         obj = QOBJECT(qfloat_from_double(strtod(token_get_value(token), NULL)));
 660         break;
 661     default:
 662         goto out;
 663     }
 664
 665     return obj;
 666
 667 out:
 668     parser_context_restore(ctxt, saved_ctxt);
 669
 670     return NULL;
 671 }
 672
 673 static QObject *parse_value(JSONParserContext *ctxt, va_list *ap)
 674 {
 675     QObject *obj;
 676
 677     obj = parse_object(ctxt, ap);
 678     if (obj == NULL) {
 679         obj = parse_array(ctxt, ap);
 680     }
 681     if (obj == NULL) {
 682         obj = parse_escape(ctxt, ap);
 683     }
 684     if (obj == NULL) {
 685         obj = parse_keyword(ctxt);
 686     }
 687     if (obj == NULL) {
 688         obj = parse_literal(ctxt);
 689     }
 690
 691     return obj;
 692 }
 693
 694 QObject *json_parser_parse(QList *tokens, va_list *ap)
 695 {
 696     return json_parser_parse_err(tokens, ap, NULL);
 697 }
 698
 699 QObject *json_parser_parse_err(QList *tokens, va_list *ap, Error **errp)
 700 {
 701     JSONParserContext *ctxt = parser_context_new(tokens);
 702     QObject *result;
 703
 704     if (!ctxt) {
 705         return NULL;
 706     }
 707
 708     result = parse_value(ctxt, ap);
 709
 710     error_propagate(errp, ctxt->err);
 711
 712     parser_context_free(ctxt);
 713
 714     return result;
 715 }