qobject/qdict.c

   1 /*
   2  * QDict Module
   3  *
   4  * Copyright (C) 2009 Red Hat Inc.
   5  *
   6  * Authors:
   7  *  Luiz Capitulino <lcapitulino@redhat.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 #include "qapi/qmp/qint.h"
  14 #include "qapi/qmp/qfloat.h"
  15 #include "qapi/qmp/qdict.h"
  16 #include "qapi/qmp/qbool.h"
  17 #include "qapi/qmp/qstring.h"
  18 #include "qapi/qmp/qobject.h"
  19 #include "qemu/queue.h"
  20 #include "qemu-common.h"
  21
  22 static void qdict_destroy_obj(QObject *obj);
  23
  24 static const QType qdict_type = {
  25     .code = QTYPE_QDICT,
  26     .destroy = qdict_destroy_obj,
  27 };
  28
  29 /**
  30  * qdict_new(): Create a new QDict
  31  *
  32  * Return strong reference.
  33  */
  34 QDict *qdict_new(void)
  35 {
  36     QDict *qdict;
  37
  38     qdict = g_malloc0(sizeof(*qdict));
  39     QOBJECT_INIT(qdict, &qdict_type);
  40
  41     return qdict;
  42 }
  43
  44 /**
  45  * qobject_to_qdict(): Convert a QObject into a QDict
  46  */
  47 QDict *qobject_to_qdict(const QObject *obj)
  48 {
  49     if (!obj || qobject_type(obj) != QTYPE_QDICT) {
  50         return NULL;
  51     }
  52     return container_of(obj, QDict, base);
  53 }
  54
  55 /**
  56  * tdb_hash(): based on the hash agorithm from gdbm, via tdb
  57  * (from module-init-tools)
  58  */
  59 static unsigned int tdb_hash(const char *name)
  60 {
  61     unsigned value;     /* Used to compute the hash value.  */
  62     unsigned   i;       /* Used to cycle through random values. */
  63
  64     /* Set the initial value from the key size. */
  65     for (value = 0x238F13AF * strlen(name), i=0; name[i]; i++)
  66         value = (value + (((const unsigned char *)name)[i] << (i*5 % 24)));
  67
  68     return (1103515243 * value + 12345);
  69 }
  70
  71 /**
  72  * alloc_entry(): allocate a new QDictEntry
  73  */
  74 static QDictEntry *alloc_entry(const char *key, QObject *value)
  75 {
  76     QDictEntry *entry;
  77
  78     entry = g_malloc0(sizeof(*entry));
  79     entry->key = g_strdup(key);
  80     entry->value = value;
  81
  82     return entry;
  83 }
  84
  85 /**
  86  * qdict_entry_value(): Return qdict entry value
  87  *
  88  * Return weak reference.
  89  */
  90 QObject *qdict_entry_value(const QDictEntry *entry)
  91 {
  92     return entry->value;
  93 }
  94
  95 /**
  96  * qdict_entry_key(): Return qdict entry key
  97  *
  98  * Return a *pointer* to the string, it has to be duplicated before being
  99  * stored.
 100  */
 101 const char *qdict_entry_key(const QDictEntry *entry)
 102 {
 103     return entry->key;
 104 }
 105
 106 /**
 107  * qdict_find(): List lookup function
 108  */
 109 static QDictEntry *qdict_find(const QDict *qdict,
 110                               const char *key, unsigned int bucket)
 111 {
 112     QDictEntry *entry;
 113
 114     QLIST_FOREACH(entry, &qdict->table[bucket], next)
 115         if (!strcmp(entry->key, key))
 116             return entry;
 117
 118     return NULL;
 119 }
 120
 121 /**
 122  * qdict_put_obj(): Put a new QObject into the dictionary
 123  *
 124  * Insert the pair 'key:value' into 'qdict', if 'key' already exists
 125  * its 'value' will be replaced.
 126  *
 127  * This is done by freeing the reference to the stored QObject and
 128  * storing the new one in the same entry.
 129  *
 130  * NOTE: ownership of 'value' is transferred to the QDict
 131  */
 132 void qdict_put_obj(QDict *qdict, const char *key, QObject *value)
 133 {
 134     unsigned int bucket;
 135     QDictEntry *entry;
 136
 137     bucket = tdb_hash(key) % QDICT_BUCKET_MAX;
 138     entry = qdict_find(qdict, key, bucket);
 139     if (entry) {
 140         /* replace key's value */
 141         qobject_decref(entry->value);
 142         entry->value = value;
 143     } else {
 144         /* allocate a new entry */
 145         entry = alloc_entry(key, value);
 146         QLIST_INSERT_HEAD(&qdict->table[bucket], entry, next);
 147         qdict->size++;
 148     }
 149 }
 150
 151 /**
 152  * qdict_get(): Lookup for a given 'key'
 153  *
 154  * Return a weak reference to the QObject associated with 'key' if
 155  * 'key' is present in the dictionary, NULL otherwise.
 156  */
 157 QObject *qdict_get(const QDict *qdict, const char *key)
 158 {
 159     QDictEntry *entry;
 160
 161     entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
 162     return (entry == NULL ? NULL : entry->value);
 163 }
 164
 165 /**
 166  * qdict_haskey(): Check if 'key' exists
 167  *
 168  * Return 1 if 'key' exists in the dict, 0 otherwise
 169  */
 170 int qdict_haskey(const QDict *qdict, const char *key)
 171 {
 172     unsigned int bucket = tdb_hash(key) % QDICT_BUCKET_MAX;
 173     return (qdict_find(qdict, key, bucket) == NULL ? 0 : 1);
 174 }
 175
 176 /**
 177  * qdict_size(): Return the size of the dictionary
 178  */
 179 size_t qdict_size(const QDict *qdict)
 180 {
 181     return qdict->size;
 182 }
 183
 184 /**
 185  * qdict_get_obj(): Get a QObject of a specific type
 186  */
 187 static QObject *qdict_get_obj(const QDict *qdict, const char *key,
 188                               qtype_code type)
 189 {
 190     QObject *obj;
 191
 192     obj = qdict_get(qdict, key);
 193     assert(obj != NULL);
 194     assert(qobject_type(obj) == type);
 195
 196     return obj;
 197 }
 198
 199 /**
 200  * qdict_get_double(): Get an number mapped by 'key'
 201  *
 202  * This function assumes that 'key' exists and it stores a
 203  * QFloat or QInt object.
 204  *
 205  * Return number mapped by 'key'.
 206  */
 207 double qdict_get_double(const QDict *qdict, const char *key)
 208 {
 209     QObject *obj = qdict_get(qdict, key);
 210
 211     assert(obj);
 212     switch (qobject_type(obj)) {
 213     case QTYPE_QFLOAT:
 214         return qfloat_get_double(qobject_to_qfloat(obj));
 215     case QTYPE_QINT:
 216         return qint_get_int(qobject_to_qint(obj));
 217     default:
 218         abort();
 219     }
 220 }
 221
 222 /**
 223  * qdict_get_int(): Get an integer mapped by 'key'
 224  *
 225  * This function assumes that 'key' exists and it stores a
 226  * QInt object.
 227  *
 228  * Return integer mapped by 'key'.
 229  */
 230 int64_t qdict_get_int(const QDict *qdict, const char *key)
 231 {
 232     QObject *obj = qdict_get_obj(qdict, key, QTYPE_QINT);
 233     return qint_get_int(qobject_to_qint(obj));
 234 }
 235
 236 /**
 237  * qdict_get_bool(): Get a bool mapped by 'key'
 238  *
 239  * This function assumes that 'key' exists and it stores a
 240  * QBool object.
 241  *
 242  * Return bool mapped by 'key'.
 243  */
 244 bool qdict_get_bool(const QDict *qdict, const char *key)
 245 {
 246     return qbool_get_bool(qobject_to_qbool(qdict_get(qdict, key)));
 247 }
 248
 249 /**
 250  * qdict_get_qlist(): Get the QList mapped by 'key'
 251  *
 252  * This function assumes that 'key' exists and it stores a
 253  * QList object.
 254  *
 255  * Return QList mapped by 'key'.
 256  */
 257 QList *qdict_get_qlist(const QDict *qdict, const char *key)
 258 {
 259     return qobject_to_qlist(qdict_get_obj(qdict, key, QTYPE_QLIST));
 260 }
 261
 262 /**
 263  * qdict_get_qdict(): Get the QDict mapped by 'key'
 264  *
 265  * This function assumes that 'key' exists and it stores a
 266  * QDict object.
 267  *
 268  * Return QDict mapped by 'key'.
 269  */
 270 QDict *qdict_get_qdict(const QDict *qdict, const char *key)
 271 {
 272     return qobject_to_qdict(qdict_get(qdict, key));
 273 }
 274
 275 /**
 276  * qdict_get_str(): Get a pointer to the stored string mapped
 277  * by 'key'
 278  *
 279  * This function assumes that 'key' exists and it stores a
 280  * QString object.
 281  *
 282  * Return pointer to the string mapped by 'key'.
 283  */
 284 const char *qdict_get_str(const QDict *qdict, const char *key)
 285 {
 286     QObject *obj = qdict_get_obj(qdict, key, QTYPE_QSTRING);
 287     return qstring_get_str(qobject_to_qstring(obj));
 288 }
 289
 290 /**
 291  * qdict_get_try_int(): Try to get integer mapped by 'key'
 292  *
 293  * Return integer mapped by 'key', if it is not present in
 294  * the dictionary or if the stored object is not of QInt type
 295  * 'def_value' will be returned.
 296  */
 297 int64_t qdict_get_try_int(const QDict *qdict, const char *key,
 298                           int64_t def_value)
 299 {
 300     QObject *obj;
 301
 302     obj = qdict_get(qdict, key);
 303     if (!obj || qobject_type(obj) != QTYPE_QINT)
 304         return def_value;
 305
 306     return qint_get_int(qobject_to_qint(obj));
 307 }
 308
 309 /**
 310  * qdict_get_try_bool(): Try to get a bool mapped by 'key'
 311  *
 312  * Return bool mapped by 'key', if it is not present in the
 313  * dictionary or if the stored object is not of QBool type
 314  * 'def_value' will be returned.
 315  */
 316 bool qdict_get_try_bool(const QDict *qdict, const char *key, bool def_value)
 317 {
 318     QBool *qbool = qobject_to_qbool(qdict_get(qdict, key));
 319
 320     return qbool ? qbool_get_bool(qbool) : def_value;
 321 }
 322
 323 /**
 324  * qdict_get_try_str(): Try to get a pointer to the stored string
 325  * mapped by 'key'
 326  *
 327  * Return a pointer to the string mapped by 'key', if it is not present
 328  * in the dictionary or if the stored object is not of QString type
 329  * NULL will be returned.
 330  */
 331 const char *qdict_get_try_str(const QDict *qdict, const char *key)
 332 {
 333     QObject *obj;
 334
 335     obj = qdict_get(qdict, key);
 336     if (!obj || qobject_type(obj) != QTYPE_QSTRING)
 337         return NULL;
 338
 339     return qstring_get_str(qobject_to_qstring(obj));
 340 }
 341
 342 /**
 343  * qdict_iter(): Iterate over all the dictionary's stored values.
 344  *
 345  * This function allows the user to provide an iterator, which will be
 346  * called for each stored value in the dictionary.
 347  */
 348 void qdict_iter(const QDict *qdict,
 349                 void (*iter)(const char *key, QObject *obj, void *opaque),
 350                 void *opaque)
 351 {
 352     int i;
 353     QDictEntry *entry;
 354
 355     for (i = 0; i < QDICT_BUCKET_MAX; i++) {
 356         QLIST_FOREACH(entry, &qdict->table[i], next)
 357             iter(entry->key, entry->value, opaque);
 358     }
 359 }
 360
 361 static QDictEntry *qdict_next_entry(const QDict *qdict, int first_bucket)
 362 {
 363     int i;
 364
 365     for (i = first_bucket; i < QDICT_BUCKET_MAX; i++) {
 366         if (!QLIST_EMPTY(&qdict->table[i])) {
 367             return QLIST_FIRST(&qdict->table[i]);
 368         }
 369     }
 370
 371     return NULL;
 372 }
 373
 374 /**
 375  * qdict_first(): Return first qdict entry for iteration.
 376  */
 377 const QDictEntry *qdict_first(const QDict *qdict)
 378 {
 379     return qdict_next_entry(qdict, 0);
 380 }
 381
 382 /**
 383  * qdict_next(): Return next qdict entry in an iteration.
 384  */
 385 const QDictEntry *qdict_next(const QDict *qdict, const QDictEntry *entry)
 386 {
 387     QDictEntry *ret;
 388
 389     ret = QLIST_NEXT(entry, next);
 390     if (!ret) {
 391         unsigned int bucket = tdb_hash(entry->key) % QDICT_BUCKET_MAX;
 392         ret = qdict_next_entry(qdict, bucket + 1);
 393     }
 394
 395     return ret;
 396 }
 397
 398 /**
 399  * qdict_clone_shallow(): Clones a given QDict. Its entries are not copied, but
 400  * another reference is added.
 401  */
 402 QDict *qdict_clone_shallow(const QDict *src)
 403 {
 404     QDict *dest;
 405     QDictEntry *entry;
 406     int i;
 407
 408     dest = qdict_new();
 409
 410     for (i = 0; i < QDICT_BUCKET_MAX; i++) {
 411         QLIST_FOREACH(entry, &src->table[i], next) {
 412             qobject_incref(entry->value);
 413             qdict_put_obj(dest, entry->key, entry->value);
 414         }
 415     }
 416
 417     return dest;
 418 }
 419
 420 /**
 421  * qentry_destroy(): Free all the memory allocated by a QDictEntry
 422  */
 423 static void qentry_destroy(QDictEntry *e)
 424 {
 425     assert(e != NULL);
 426     assert(e->key != NULL);
 427     assert(e->value != NULL);
 428
 429     qobject_decref(e->value);
 430     g_free(e->key);
 431     g_free(e);
 432 }
 433
 434 /**
 435  * qdict_del(): Delete a 'key:value' pair from the dictionary
 436  *
 437  * This will destroy all data allocated by this entry.
 438  */
 439 void qdict_del(QDict *qdict, const char *key)
 440 {
 441     QDictEntry *entry;
 442
 443     entry = qdict_find(qdict, key, tdb_hash(key) % QDICT_BUCKET_MAX);
 444     if (entry) {
 445         QLIST_REMOVE(entry, next);
 446         qentry_destroy(entry);
 447         qdict->size--;
 448     }
 449 }
 450
 451 /**
 452  * qdict_destroy_obj(): Free all the memory allocated by a QDict
 453  */
 454 static void qdict_destroy_obj(QObject *obj)
 455 {
 456     int i;
 457     QDict *qdict;
 458
 459     assert(obj != NULL);
 460     qdict = qobject_to_qdict(obj);
 461
 462     for (i = 0; i < QDICT_BUCKET_MAX; i++) {
 463         QDictEntry *entry = QLIST_FIRST(&qdict->table[i]);
 464         while (entry) {
 465             QDictEntry *tmp = QLIST_NEXT(entry, next);
 466             QLIST_REMOVE(entry, next);
 467             qentry_destroy(entry);
 468             entry = tmp;
 469         }
 470     }
 471
 472     g_free(qdict);
 473 }
 474
 475 /**
 476  * qdict_copy_default(): If no entry mapped by 'key' exists in 'dst' yet, the
 477  * value of 'key' in 'src' is copied there (and the refcount increased
 478  * accordingly).
 479  */
 480 void qdict_copy_default(QDict *dst, QDict *src, const char *key)
 481 {
 482     QObject *val;
 483
 484     if (qdict_haskey(dst, key)) {
 485         return;
 486     }
 487
 488     val = qdict_get(src, key);
 489     if (val) {
 490         qobject_incref(val);
 491         qdict_put_obj(dst, key, val);
 492     }
 493 }
 494
 495 /**
 496  * qdict_set_default_str(): If no entry mapped by 'key' exists in 'dst' yet, a
 497  * new QString initialised by 'val' is put there.
 498  */
 499 void qdict_set_default_str(QDict *dst, const char *key, const char *val)
 500 {
 501     if (qdict_haskey(dst, key)) {
 502         return;
 503     }
 504
 505     qdict_put(dst, key, qstring_from_str(val));
 506 }
 507
 508 static void qdict_flatten_qdict(QDict *qdict, QDict *target,
 509                                 const char *prefix);
 510
 511 static void qdict_flatten_qlist(QList *qlist, QDict *target, const char *prefix)
 512 {
 513     QObject *value;
 514     const QListEntry *entry;
 515     char *new_key;
 516     int i;
 517
 518     /* This function is never called with prefix == NULL, i.e., it is always
 519      * called from within qdict_flatten_q(list|dict)(). Therefore, it does not
 520      * need to remove list entries during the iteration (the whole list will be
 521      * deleted eventually anyway from qdict_flatten_qdict()). */
 522     assert(prefix);
 523
 524     entry = qlist_first(qlist);
 525
 526     for (i = 0; entry; entry = qlist_next(entry), i++) {
 527         value = qlist_entry_obj(entry);
 528         new_key = g_strdup_printf("%s.%i", prefix, i);
 529
 530         if (qobject_type(value) == QTYPE_QDICT) {
 531             qdict_flatten_qdict(qobject_to_qdict(value), target, new_key);
 532         } else if (qobject_type(value) == QTYPE_QLIST) {
 533             qdict_flatten_qlist(qobject_to_qlist(value), target, new_key);
 534         } else {
 535             /* All other types are moved to the target unchanged. */
 536             qobject_incref(value);
 537             qdict_put_obj(target, new_key, value);
 538         }
 539
 540         g_free(new_key);
 541     }
 542 }
 543
 544 static void qdict_flatten_qdict(QDict *qdict, QDict *target, const char *prefix)
 545 {
 546     QObject *value;
 547     const QDictEntry *entry, *next;
 548     char *new_key;
 549     bool delete;
 550
 551     entry = qdict_first(qdict);
 552
 553     while (entry != NULL) {
 554
 555         next = qdict_next(qdict, entry);
 556         value = qdict_entry_value(entry);
 557         new_key = NULL;
 558         delete = false;
 559
 560         if (prefix) {
 561             new_key = g_strdup_printf("%s.%s", prefix, entry->key);
 562         }
 563
 564         if (qobject_type(value) == QTYPE_QDICT) {
 565             /* Entries of QDicts are processed recursively, the QDict object
 566              * itself disappears. */
 567             qdict_flatten_qdict(qobject_to_qdict(value), target,
 568                                 new_key ? new_key : entry->key);
 569             delete = true;
 570         } else if (qobject_type(value) == QTYPE_QLIST) {
 571             qdict_flatten_qlist(qobject_to_qlist(value), target,
 572                                 new_key ? new_key : entry->key);
 573             delete = true;
 574         } else if (prefix) {
 575             /* All other objects are moved to the target unchanged. */
 576             qobject_incref(value);
 577             qdict_put_obj(target, new_key, value);
 578             delete = true;
 579         }
 580
 581         g_free(new_key);
 582
 583         if (delete) {
 584             qdict_del(qdict, entry->key);
 585
 586             /* Restart loop after modifying the iterated QDict */
 587             entry = qdict_first(qdict);
 588             continue;
 589         }
 590
 591         entry = next;
 592     }
 593 }
 594
 595 /**
 596  * qdict_flatten(): For each nested QDict with key x, all fields with key y
 597  * are moved to this QDict and their key is renamed to "x.y". For each nested
 598  * QList with key x, the field at index y is moved to this QDict with the key
 599  * "x.y" (i.e., the reverse of what qdict_array_split() does).
 600  * This operation is applied recursively for nested QDicts and QLists.
 601  */
 602 void qdict_flatten(QDict *qdict)
 603 {
 604     qdict_flatten_qdict(qdict, qdict, NULL);
 605 }
 606
 607 /* extract all the src QDict entries starting by start into dst */
 608 void qdict_extract_subqdict(QDict *src, QDict **dst, const char *start)
 609
 610 {
 611     const QDictEntry *entry, *next;
 612     const char *p;
 613
 614     *dst = qdict_new();
 615     entry = qdict_first(src);
 616
 617     while (entry != NULL) {
 618         next = qdict_next(src, entry);
 619         if (strstart(entry->key, start, &p)) {
 620             qobject_incref(entry->value);
 621             qdict_put_obj(*dst, p, entry->value);
 622             qdict_del(src, entry->key);
 623         }
 624         entry = next;
 625     }
 626 }
 627
 628 static int qdict_count_prefixed_entries(const QDict *src, const char *start)
 629 {
 630     const QDictEntry *entry;
 631     int count = 0;
 632
 633     for (entry = qdict_first(src); entry; entry = qdict_next(src, entry)) {
 634         if (strstart(entry->key, start, NULL)) {
 635             if (count == INT_MAX) {
 636                 return -ERANGE;
 637             }
 638             count++;
 639         }
 640     }
 641
 642     return count;
 643 }
 644
 645 /**
 646  * qdict_array_split(): This function moves array-like elements of a QDict into
 647  * a new QList. Every entry in the original QDict with a key "%u" or one
 648  * prefixed "%u.", where %u designates an unsigned integer starting at 0 and
 649  * incrementally counting up, will be moved to a new QDict at index %u in the
 650  * output QList with the key prefix removed, if that prefix is "%u.". If the
 651  * whole key is just "%u", the whole QObject will be moved unchanged without
 652  * creating a new QDict. The function terminates when there is no entry in the
 653  * QDict with a prefix directly (incrementally) following the last one; it also
 654  * returns if there are both entries with "%u" and "%u." for the same index %u.
 655  * Example: {"0.a": 42, "0.b": 23, "1.x": 0, "4.y": 1, "o.o": 7, "2": 66}
 656  *      (or {"1.x": 0, "4.y": 1, "0.a": 42, "o.o": 7, "0.b": 23, "2": 66})
 657  *       => [{"a": 42, "b": 23}, {"x": 0}, 66]
 658  *      and {"4.y": 1, "o.o": 7} (remainder of the old QDict)
 659  */
 660 void qdict_array_split(QDict *src, QList **dst)
 661 {
 662     unsigned i;
 663
 664     *dst = qlist_new();
 665
 666     for (i = 0; i < UINT_MAX; i++) {
 667         QObject *subqobj;
 668         bool is_subqdict;
 669         QDict *subqdict;
 670         char indexstr[32], prefix[32];
 671         size_t snprintf_ret;
 672
 673         snprintf_ret = snprintf(indexstr, 32, "%u", i);
 674         assert(snprintf_ret < 32);
 675
 676         subqobj = qdict_get(src, indexstr);
 677
 678         snprintf_ret = snprintf(prefix, 32, "%u.", i);
 679         assert(snprintf_ret < 32);
 680
 681         /* Overflow is the same as positive non-zero results */
 682         is_subqdict = qdict_count_prefixed_entries(src, prefix);
 683
 684         // There may be either a single subordinate object (named "%u") or
 685         // multiple objects (each with a key prefixed "%u."), but not both.
 686         if (!subqobj == !is_subqdict) {
 687             break;
 688         }
 689
 690         if (is_subqdict) {
 691             qdict_extract_subqdict(src, &subqdict, prefix);
 692             assert(qdict_size(subqdict) > 0);
 693         } else {
 694             qobject_incref(subqobj);
 695             qdict_del(src, indexstr);
 696         }
 697
 698         qlist_append_obj(*dst, subqobj ?: QOBJECT(subqdict));
 699     }
 700 }
 701
 702 /**
 703  * qdict_array_entries(): Returns the number of direct array entries if the
 704  * sub-QDict of src specified by the prefix in subqdict (or src itself for
 705  * prefix == "") is valid as an array, i.e. the length of the created list if
 706  * the sub-QDict would become empty after calling qdict_array_split() on it. If
 707  * the array is not valid, -EINVAL is returned.
 708  */
 709 int qdict_array_entries(QDict *src, const char *subqdict)
 710 {
 711     const QDictEntry *entry;
 712     unsigned i;
 713     unsigned entries = 0;
 714     size_t subqdict_len = strlen(subqdict);
 715
 716     assert(!subqdict_len || subqdict[subqdict_len - 1] == '.');
 717
 718     /* qdict_array_split() loops until UINT_MAX, but as we want to return
 719      * negative errors, we only have a signed return value here. Any additional
 720      * entries will lead to -EINVAL. */
 721     for (i = 0; i < INT_MAX; i++) {
 722         QObject *subqobj;
 723         int subqdict_entries;
 724         size_t slen = 32 + subqdict_len;
 725         char indexstr[slen], prefix[slen];
 726         size_t snprintf_ret;
 727
 728         snprintf_ret = snprintf(indexstr, slen, "%s%u", subqdict, i);
 729         assert(snprintf_ret < slen);
 730
 731         subqobj = qdict_get(src, indexstr);
 732
 733         snprintf_ret = snprintf(prefix, slen, "%s%u.", subqdict, i);
 734         assert(snprintf_ret < slen);
 735
 736         subqdict_entries = qdict_count_prefixed_entries(src, prefix);
 737         if (subqdict_entries < 0) {
 738             return subqdict_entries;
 739         }
 740
 741         /* There may be either a single subordinate object (named "%u") or
 742          * multiple objects (each with a key prefixed "%u."), but not both. */
 743         if (subqobj && subqdict_entries) {
 744             return -EINVAL;
 745         } else if (!subqobj && !subqdict_entries) {
 746             break;
 747         }
 748
 749         entries += subqdict_entries ? subqdict_entries : 1;
 750     }
 751
 752     /* Consider everything handled that isn't part of the given sub-QDict */
 753     for (entry = qdict_first(src); entry; entry = qdict_next(src, entry)) {
 754         if (!strstart(qdict_entry_key(entry), subqdict, NULL)) {
 755             entries++;
 756         }
 757     }
 758
 759     /* Anything left in the sub-QDict that wasn't handled? */
 760     if (qdict_size(src) != entries) {
 761         return -EINVAL;
 762     }
 763
 764     return i;
 765 }
 766
 767 /**
 768  * qdict_join(): Absorb the src QDict into the dest QDict, that is, move all
 769  * elements from src to dest.
 770  *
 771  * If an element from src has a key already present in dest, it will not be
 772  * moved unless overwrite is true.
 773  *
 774  * If overwrite is true, the conflicting values in dest will be discarded and
 775  * replaced by the corresponding values from src.
 776  *
 777  * Therefore, with overwrite being true, the src QDict will always be empty when
 778  * this function returns. If overwrite is false, the src QDict will be empty
 779  * iff there were no conflicts.
 780  */
 781 void qdict_join(QDict *dest, QDict *src, bool overwrite)
 782 {
 783     const QDictEntry *entry, *next;
 784
 785     entry = qdict_first(src);
 786     while (entry) {
 787         next = qdict_next(src, entry);
 788
 789         if (overwrite || !qdict_haskey(dest, entry->key)) {
 790             qobject_incref(entry->value);
 791             qdict_put_obj(dest, entry->key, entry->value);
 792             qdict_del(src, entry->key);
 793         }
 794
 795         entry = next;
 796     }
 797 }