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 "qemu/osdep.h"
  15 #include "qemu/cutils.h"
  16 #include "qapi/error.h"
  17 #include "qemu-common.h"
  18 #include "qapi/qmp/types.h"
  19 #include "qapi/qmp/json-parser.h"
  20 #include "qapi/qmp/json-lexer.h"
  21 #include "qapi/qmp/json-streamer.h"
  22
  23 typedef struct JSONParserContext
  24 {
  25     Error *err;
  26     JSONToken *current;
  27     GQueue *buf;
  28 } JSONParserContext;
  29
  30 #define BUG_ON(cond) assert(!(cond))
  31
  32 /**
  33  * TODO
  34  *
  35  * 0) make errors meaningful again
  36  * 1) add geometry information to tokens
  37  * 3) should we return a parsed size?
  38  * 4) deal with premature EOI
  39  */
  40
  41 static QObject *parse_value(JSONParserContext *ctxt, va_list *ap);
  42
  43 /**
  44  * Error handler
  45  */
  46 static void GCC_FMT_ATTR(3, 4) parse_error(JSONParserContext *ctxt,
  47                                            JSONToken *token, const char *msg, ...)
  48 {
  49     va_list ap;
  50     char message[1024];
  51     va_start(ap, msg);
  52     vsnprintf(message, sizeof(message), msg, ap);
  53     va_end(ap);
  54     if (ctxt->err) {
  55         error_free(ctxt->err);
  56         ctxt->err = NULL;
  57     }
  58     error_setg(&ctxt->err, "JSON parse error, %s", message);
  59 }
  60
  61 /**
  62  * String helpers
  63  *
  64  * These helpers are used to unescape strings.
  65  */
  66 static void wchar_to_utf8(uint16_t wchar, char *buffer, size_t buffer_length)
  67 {
  68     if (wchar <= 0x007F) {
  69         BUG_ON(buffer_length < 2);
  70
  71         buffer[0] = wchar & 0x7F;
  72         buffer[1] = 0;
  73     } else if (wchar <= 0x07FF) {
  74         BUG_ON(buffer_length < 3);
  75
  76         buffer[0] = 0xC0 | ((wchar >> 6) & 0x1F);
  77         buffer[1] = 0x80 | (wchar & 0x3F);
  78         buffer[2] = 0;
  79     } else {
  80         BUG_ON(buffer_length < 4);
  81
  82         buffer[0] = 0xE0 | ((wchar >> 12) & 0x0F);
  83         buffer[1] = 0x80 | ((wchar >> 6) & 0x3F);
  84         buffer[2] = 0x80 | (wchar & 0x3F);
  85         buffer[3] = 0;
  86     }
  87 }
  88
  89 static int hex2decimal(char ch)
  90 {
  91     if (ch >= '0' && ch <= '9') {
  92         return (ch - '0');
  93     } else if (ch >= 'a' && ch <= 'f') {
  94         return 10 + (ch - 'a');
  95     } else if (ch >= 'A' && ch <= 'F') {
  96         return 10 + (ch - 'A');
  97     }
  98
  99     return -1;
 100 }
 101
 102 /**
 103  * parse_string(): Parse a json string and return a QObject
 104  *
 105  *  string
 106  *      ""
 107  *      " chars "
 108  *  chars
 109  *      char
 110  *      char chars
 111  *  char
 112  *      any-Unicode-character-
 113  *          except-"-or-\-or-
 114  *          control-character
 115  *      \"
 116  *      \\
 117  *      \/
 118  *      \b
 119  *      \f
 120  *      \n
 121  *      \r
 122  *      \t
 123  *      \u four-hex-digits
 124  */
 125 static QString *qstring_from_escaped_str(JSONParserContext *ctxt,
 126                                          JSONToken *token)
 127 {
 128     const char *ptr = token->str;
 129     QString *str;
 130     int double_quote = 1;
 131
 132     if (*ptr == '"') {
 133         double_quote = 1;
 134     } else {
 135         double_quote = 0;
 136     }
 137     ptr++;
 138
 139     str = qstring_new();
 140     while (*ptr &&
 141            ((double_quote && *ptr != '"') || (!double_quote && *ptr != '\''))) {
 142         if (*ptr == '\\') {
 143             ptr++;
 144
 145             switch (*ptr) {
 146             case '"':
 147                 qstring_append(str, "\"");
 148                 ptr++;
 149                 break;
 150             case '\'':
 151                 qstring_append(str, "'");
 152                 ptr++;
 153                 break;
 154             case '\\':
 155                 qstring_append(str, "\\");
 156                 ptr++;
 157                 break;
 158             case '/':
 159                 qstring_append(str, "/");
 160                 ptr++;
 161                 break;
 162             case 'b':
 163                 qstring_append(str, "\b");
 164                 ptr++;
 165                 break;
 166             case 'f':
 167                 qstring_append(str, "\f");
 168                 ptr++;
 169                 break;
 170             case 'n':
 171                 qstring_append(str, "\n");
 172                 ptr++;
 173                 break;
 174             case 'r':
 175                 qstring_append(str, "\r");
 176                 ptr++;
 177                 break;
 178             case 't':
 179                 qstring_append(str, "\t");
 180                 ptr++;
 181                 break;
 182             case 'u': {
 183                 uint16_t unicode_char = 0;
 184                 char utf8_char[4];
 185                 int i = 0;
 186
 187                 ptr++;
 188
 189                 for (i = 0; i < 4; i++) {
 190                     if (qemu_isxdigit(*ptr)) {
 191                         unicode_char |= hex2decimal(*ptr) << ((3 - i) * 4);
 192                     } else {
 193                         parse_error(ctxt, token,
 194                                     "invalid hex escape sequence in string");
 195                         goto out;
 196                     }
 197                     ptr++;
 198                 }
 199
 200                 wchar_to_utf8(unicode_char, utf8_char, sizeof(utf8_char));
 201                 qstring_append(str, utf8_char);
 202             }   break;
 203             default:
 204                 parse_error(ctxt, token, "invalid escape sequence in string");
 205                 goto out;
 206             }
 207         } else {
 208             char dummy[2];
 209
 210             dummy[0] = *ptr++;
 211             dummy[1] = 0;
 212
 213             qstring_append(str, dummy);
 214         }
 215     }
 216
 217     return str;
 218
 219 out:
 220     QDECREF(str);
 221     return NULL;
 222 }
 223
 224 /* Note: the token object returned by parser_context_peek_token or
 225  * parser_context_pop_token is deleted as soon as parser_context_pop_token
 226  * is called again.
 227  */
 228 static JSONToken *parser_context_pop_token(JSONParserContext *ctxt)
 229 {
 230     g_free(ctxt->current);
 231     assert(!g_queue_is_empty(ctxt->buf));
 232     ctxt->current = g_queue_pop_head(ctxt->buf);
 233     return ctxt->current;
 234 }
 235
 236 static JSONToken *parser_context_peek_token(JSONParserContext *ctxt)
 237 {
 238     assert(!g_queue_is_empty(ctxt->buf));
 239     return g_queue_peek_head(ctxt->buf);
 240 }
 241
 242 static JSONParserContext *parser_context_new(GQueue *tokens)
 243 {
 244     JSONParserContext *ctxt;
 245
 246     if (!tokens) {
 247         return NULL;
 248     }
 249
 250     ctxt = g_malloc0(sizeof(JSONParserContext));
 251     ctxt->buf = tokens;
 252
 253     return ctxt;
 254 }
 255
 256 /* to support error propagation, ctxt->err must be freed separately */
 257 static void parser_context_free(JSONParserContext *ctxt)
 258 {
 259     if (ctxt) {
 260         while (!g_queue_is_empty(ctxt->buf)) {
 261             parser_context_pop_token(ctxt);
 262         }
 263         g_free(ctxt->current);
 264         g_queue_free(ctxt->buf);
 265         g_free(ctxt);
 266     }
 267 }
 268
 269 /**
 270  * Parsing rules
 271  */
 272 static int parse_pair(JSONParserContext *ctxt, QDict *dict, va_list *ap)
 273 {
 274     QObject *key = NULL, *value;
 275     JSONToken *peek, *token;
 276
 277     peek = parser_context_peek_token(ctxt);
 278     if (peek == NULL) {
 279         parse_error(ctxt, NULL, "premature EOI");
 280         goto out;
 281     }
 282
 283     key = parse_value(ctxt, ap);
 284     if (!key || qobject_type(key) != QTYPE_QSTRING) {
 285         parse_error(ctxt, peek, "key is not a string in object");
 286         goto out;
 287     }
 288
 289     token = parser_context_pop_token(ctxt);
 290     if (token == NULL) {
 291         parse_error(ctxt, NULL, "premature EOI");
 292         goto out;
 293     }
 294
 295     if (token->type != JSON_COLON) {
 296         parse_error(ctxt, token, "missing : in object pair");
 297         goto out;
 298     }
 299
 300     value = parse_value(ctxt, ap);
 301     if (value == NULL) {
 302         parse_error(ctxt, token, "Missing value in dict");
 303         goto out;
 304     }
 305
 306     qdict_put_obj(dict, qstring_get_str(qobject_to_qstring(key)), value);
 307
 308     qobject_decref(key);
 309
 310     return 0;
 311
 312 out:
 313     qobject_decref(key);
 314
 315     return -1;
 316 }
 317
 318 static QObject *parse_object(JSONParserContext *ctxt, va_list *ap)
 319 {
 320     QDict *dict = NULL;
 321     JSONToken *token, *peek;
 322
 323     token = parser_context_pop_token(ctxt);
 324     assert(token && token->type == JSON_LCURLY);
 325
 326     dict = qdict_new();
 327
 328     peek = parser_context_peek_token(ctxt);
 329     if (peek == NULL) {
 330         parse_error(ctxt, NULL, "premature EOI");
 331         goto out;
 332     }
 333
 334     if (peek->type != JSON_RCURLY) {
 335         if (parse_pair(ctxt, dict, ap) == -1) {
 336             goto out;
 337         }
 338
 339         token = parser_context_pop_token(ctxt);
 340         if (token == NULL) {
 341             parse_error(ctxt, NULL, "premature EOI");
 342             goto out;
 343         }
 344
 345         while (token->type != JSON_RCURLY) {
 346             if (token->type != JSON_COMMA) {
 347                 parse_error(ctxt, token, "expected separator in dict");
 348                 goto out;
 349             }
 350
 351             if (parse_pair(ctxt, dict, ap) == -1) {
 352                 goto out;
 353             }
 354
 355             token = parser_context_pop_token(ctxt);
 356             if (token == NULL) {
 357                 parse_error(ctxt, NULL, "premature EOI");
 358                 goto out;
 359             }
 360         }
 361     } else {
 362         (void)parser_context_pop_token(ctxt);
 363     }
 364
 365     return QOBJECT(dict);
 366
 367 out:
 368     QDECREF(dict);
 369     return NULL;
 370 }
 371
 372 static QObject *parse_array(JSONParserContext *ctxt, va_list *ap)
 373 {
 374     QList *list = NULL;
 375     JSONToken *token, *peek;
 376
 377     token = parser_context_pop_token(ctxt);
 378     assert(token && token->type == JSON_LSQUARE);
 379
 380     list = qlist_new();
 381
 382     peek = parser_context_peek_token(ctxt);
 383     if (peek == NULL) {
 384         parse_error(ctxt, NULL, "premature EOI");
 385         goto out;
 386     }
 387
 388     if (peek->type != JSON_RSQUARE) {
 389         QObject *obj;
 390
 391         obj = parse_value(ctxt, ap);
 392         if (obj == NULL) {
 393             parse_error(ctxt, token, "expecting value");
 394             goto out;
 395         }
 396
 397         qlist_append_obj(list, obj);
 398
 399         token = parser_context_pop_token(ctxt);
 400         if (token == NULL) {
 401             parse_error(ctxt, NULL, "premature EOI");
 402             goto out;
 403         }
 404
 405         while (token->type != JSON_RSQUARE) {
 406             if (token->type != JSON_COMMA) {
 407                 parse_error(ctxt, token, "expected separator in list");
 408                 goto out;
 409             }
 410
 411             obj = parse_value(ctxt, ap);
 412             if (obj == NULL) {
 413                 parse_error(ctxt, token, "expecting value");
 414                 goto out;
 415             }
 416
 417             qlist_append_obj(list, obj);
 418
 419             token = parser_context_pop_token(ctxt);
 420             if (token == NULL) {
 421                 parse_error(ctxt, NULL, "premature EOI");
 422                 goto out;
 423             }
 424         }
 425     } else {
 426         (void)parser_context_pop_token(ctxt);
 427     }
 428
 429     return QOBJECT(list);
 430
 431 out:
 432     QDECREF(list);
 433     return NULL;
 434 }
 435
 436 static QObject *parse_keyword(JSONParserContext *ctxt)
 437 {
 438     JSONToken *token;
 439
 440     token = parser_context_pop_token(ctxt);
 441     assert(token && token->type == JSON_KEYWORD);
 442
 443     if (!strcmp(token->str, "true")) {
 444         return QOBJECT(qbool_from_bool(true));
 445     } else if (!strcmp(token->str, "false")) {
 446         return QOBJECT(qbool_from_bool(false));
 447     } else if (!strcmp(token->str, "null")) {
 448         return qnull();
 449     }
 450     parse_error(ctxt, token, "invalid keyword '%s'", token->str);
 451     return NULL;
 452 }
 453
 454 static QObject *parse_escape(JSONParserContext *ctxt, va_list *ap)
 455 {
 456     JSONToken *token;
 457
 458     if (ap == NULL) {
 459         return NULL;
 460     }
 461
 462     token = parser_context_pop_token(ctxt);
 463     assert(token && token->type == JSON_ESCAPE);
 464
 465     if (!strcmp(token->str, "%p")) {
 466         return va_arg(*ap, QObject *);
 467     } else if (!strcmp(token->str, "%i")) {
 468         return QOBJECT(qbool_from_bool(va_arg(*ap, int)));
 469     } else if (!strcmp(token->str, "%d")) {
 470         return QOBJECT(qnum_from_int(va_arg(*ap, int)));
 471     } else if (!strcmp(token->str, "%ld")) {
 472         return QOBJECT(qnum_from_int(va_arg(*ap, long)));
 473     } else if (!strcmp(token->str, "%lld") ||
 474                !strcmp(token->str, "%I64d")) {
 475         return QOBJECT(qnum_from_int(va_arg(*ap, long long)));
 476     } else if (!strcmp(token->str, "%u")) {
 477         return QOBJECT(qnum_from_uint(va_arg(*ap, unsigned int)));
 478     } else if (!strcmp(token->str, "%lu")) {
 479         return QOBJECT(qnum_from_uint(va_arg(*ap, unsigned long)));
 480     } else if (!strcmp(token->str, "%llu") ||
 481                !strcmp(token->str, "%I64u")) {
 482         return QOBJECT(qnum_from_uint(va_arg(*ap, unsigned long long)));
 483     } else if (!strcmp(token->str, "%s")) {
 484         return QOBJECT(qstring_from_str(va_arg(*ap, const char *)));
 485     } else if (!strcmp(token->str, "%f")) {
 486         return QOBJECT(qnum_from_double(va_arg(*ap, double)));
 487     }
 488     return NULL;
 489 }
 490
 491 static QObject *parse_literal(JSONParserContext *ctxt)
 492 {
 493     JSONToken *token;
 494
 495     token = parser_context_pop_token(ctxt);
 496     assert(token);
 497
 498     switch (token->type) {
 499     case JSON_STRING:
 500         return QOBJECT(qstring_from_escaped_str(ctxt, token));
 501     case JSON_INTEGER: {
 502         /*
 503          * Represent JSON_INTEGER as QNUM_I64 if possible, else as
 504          * QNUM_U64, else as QNUM_DOUBLE.  Note that qemu_strtoi64()
 505          * and qemu_strtou64() fail with ERANGE when it's not
 506          * possible.
 507          *
 508          * qnum_get_int() will then work for any signed 64-bit
 509          * JSON_INTEGER, qnum_get_uint() for any unsigned 64-bit
 510          * integer, and qnum_get_double() both for any JSON_INTEGER
 511          * and any JSON_FLOAT (with precision loss for integers beyond
 512          * 53 bits)
 513          */
 514         int ret;
 515         int64_t value;
 516         uint64_t uvalue;
 517
 518         ret = qemu_strtoi64(token->str, NULL, 10, &value);
 519         if (!ret) {
 520             return QOBJECT(qnum_from_int(value));
 521         }
 522         assert(ret == -ERANGE);
 523
 524         if (token->str[0] != '-') {
 525             ret = qemu_strtou64(token->str, NULL, 10, &uvalue);
 526             if (!ret) {
 527                 return QOBJECT(qnum_from_uint(uvalue));
 528             }
 529             assert(ret == -ERANGE);
 530         }
 531         /* fall through to JSON_FLOAT */
 532     }
 533     case JSON_FLOAT:
 534         /* FIXME dependent on locale; a pervasive issue in QEMU */
 535         /* FIXME our lexer matches RFC 7159 in forbidding Inf or NaN,
 536          * but those might be useful extensions beyond JSON */
 537         return QOBJECT(qnum_from_double(strtod(token->str, NULL)));
 538     default:
 539         abort();
 540     }
 541 }
 542
 543 static QObject *parse_value(JSONParserContext *ctxt, va_list *ap)
 544 {
 545     JSONToken *token;
 546
 547     token = parser_context_peek_token(ctxt);
 548     if (token == NULL) {
 549         parse_error(ctxt, NULL, "premature EOI");
 550         return NULL;
 551     }
 552
 553     switch (token->type) {
 554     case JSON_LCURLY:
 555         return parse_object(ctxt, ap);
 556     case JSON_LSQUARE:
 557         return parse_array(ctxt, ap);
 558     case JSON_ESCAPE:
 559         return parse_escape(ctxt, ap);
 560     case JSON_INTEGER:
 561     case JSON_FLOAT:
 562     case JSON_STRING:
 563         return parse_literal(ctxt);
 564     case JSON_KEYWORD:
 565         return parse_keyword(ctxt);
 566     default:
 567         parse_error(ctxt, token, "expecting value");
 568         return NULL;
 569     }
 570 }
 571
 572 QObject *json_parser_parse(GQueue *tokens, va_list *ap)
 573 {
 574     return json_parser_parse_err(tokens, ap, NULL);
 575 }
 576
 577 QObject *json_parser_parse_err(GQueue *tokens, va_list *ap, Error **errp)
 578 {
 579     JSONParserContext *ctxt = parser_context_new(tokens);
 580     QObject *result;
 581
 582     if (!ctxt) {
 583         return NULL;
 584     }
 585
 586     result = parse_value(ctxt, ap);
 587
 588     error_propagate(errp, ctxt->err);
 589
 590     parser_context_free(ctxt);
 591
 592     return result;
 593 }