qom/object.c

   1 /*
   2  * QEMU Object Model
   3  *
   4  * Copyright IBM, Corp. 2011
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <[email protected]>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10  * See the COPYING file in the top-level directory.
  11  */
  12
  13 #include "qemu/object.h"
  14 #include "qemu-common.h"
  15 #include "qapi/qapi-visit-core.h"
  16 #include "qapi/string-input-visitor.h"
  17 #include "qapi/string-output-visitor.h"
  18
  19 /* TODO: replace QObject with a simpler visitor to avoid a dependency
  20  * of the QOM core on QObject?  */
  21 #include "qemu/qom-qobject.h"
  22 #include "qobject.h"
  23 #include "qbool.h"
  24 #include "qint.h"
  25 #include "qstring.h"
  26
  27 #define MAX_INTERFACES 32
  28
  29 typedef struct InterfaceImpl InterfaceImpl;
  30 typedef struct TypeImpl TypeImpl;
  31
  32 struct InterfaceImpl
  33 {
  34     const char *parent;
  35     void (*interface_initfn)(ObjectClass *class, void *data);
  36     TypeImpl *type;
  37 };
  38
  39 struct TypeImpl
  40 {
  41     const char *name;
  42
  43     size_t class_size;
  44
  45     size_t instance_size;
  46
  47     void (*class_init)(ObjectClass *klass, void *data);
  48     void (*class_finalize)(ObjectClass *klass, void *data);
  49
  50     void *class_data;
  51
  52     void (*instance_init)(Object *obj);
  53     void (*instance_finalize)(Object *obj);
  54
  55     bool abstract;
  56
  57     const char *parent;
  58     TypeImpl *parent_type;
  59
  60     ObjectClass *class;
  61
  62     int num_interfaces;
  63     InterfaceImpl interfaces[MAX_INTERFACES];
  64 };
  65
  66 typedef struct Interface
  67 {
  68     Object parent;
  69     Object *obj;
  70 } Interface;
  71
  72 #define INTERFACE(obj) OBJECT_CHECK(Interface, obj, TYPE_INTERFACE)
  73
  74 static Type type_interface;
  75
  76 static GHashTable *type_table_get(void)
  77 {
  78     static GHashTable *type_table;
  79
  80     if (type_table == NULL) {
  81         type_table = g_hash_table_new(g_str_hash, g_str_equal);
  82     }
  83
  84     return type_table;
  85 }
  86
  87 static void type_table_add(TypeImpl *ti)
  88 {
  89     g_hash_table_insert(type_table_get(), (void *)ti->name, ti);
  90 }
  91
  92 static TypeImpl *type_table_lookup(const char *name)
  93 {
  94     return g_hash_table_lookup(type_table_get(), name);
  95 }
  96
  97 TypeImpl *type_register(const TypeInfo *info)
  98 {
  99     TypeImpl *ti = g_malloc0(sizeof(*ti));
 100
 101     g_assert(info->name != NULL);
 102
 103     if (type_table_lookup(info->name) != NULL) {
 104         fprintf(stderr, "Registering `%s' which already exists\n", info->name);
 105         abort();
 106     }
 107
 108     ti->name = g_strdup(info->name);
 109     ti->parent = g_strdup(info->parent);
 110
 111     ti->class_size = info->class_size;
 112     ti->instance_size = info->instance_size;
 113
 114     ti->class_init = info->class_init;
 115     ti->class_finalize = info->class_finalize;
 116     ti->class_data = info->class_data;
 117
 118     ti->instance_init = info->instance_init;
 119     ti->instance_finalize = info->instance_finalize;
 120
 121     ti->abstract = info->abstract;
 122
 123     if (info->interfaces) {
 124         int i;
 125
 126         for (i = 0; info->interfaces[i].type; i++) {
 127             ti->interfaces[i].parent = info->interfaces[i].type;
 128             ti->interfaces[i].interface_initfn = info->interfaces[i].interface_initfn;
 129             ti->num_interfaces++;
 130         }
 131     }
 132
 133     type_table_add(ti);
 134
 135     return ti;
 136 }
 137
 138 TypeImpl *type_register_static(const TypeInfo *info)
 139 {
 140     return type_register(info);
 141 }
 142
 143 static TypeImpl *type_get_by_name(const char *name)
 144 {
 145     if (name == NULL) {
 146         return NULL;
 147     }
 148
 149     return type_table_lookup(name);
 150 }
 151
 152 static TypeImpl *type_get_parent(TypeImpl *type)
 153 {
 154     if (!type->parent_type && type->parent) {
 155         type->parent_type = type_get_by_name(type->parent);
 156         g_assert(type->parent_type != NULL);
 157     }
 158
 159     return type->parent_type;
 160 }
 161
 162 static bool type_has_parent(TypeImpl *type)
 163 {
 164     return (type->parent != NULL);
 165 }
 166
 167 static size_t type_class_get_size(TypeImpl *ti)
 168 {
 169     if (ti->class_size) {
 170         return ti->class_size;
 171     }
 172
 173     if (type_has_parent(ti)) {
 174         return type_class_get_size(type_get_parent(ti));
 175     }
 176
 177     return sizeof(ObjectClass);
 178 }
 179
 180 static void type_class_interface_init(TypeImpl *ti, InterfaceImpl *iface)
 181 {
 182     TypeInfo info = {
 183         .instance_size = sizeof(Interface),
 184         .parent = iface->parent,
 185         .class_size = sizeof(InterfaceClass),
 186         .class_init = iface->interface_initfn,
 187         .abstract = true,
 188     };
 189     char *name = g_strdup_printf("<%s::%s>", ti->name, iface->parent);
 190
 191     info.name = name;
 192     iface->type = type_register(&info);
 193     g_free(name);
 194 }
 195
 196 static void type_class_init(TypeImpl *ti)
 197 {
 198     size_t class_size = sizeof(ObjectClass);
 199     int i;
 200
 201     if (ti->class) {
 202         return;
 203     }
 204
 205     ti->class_size = type_class_get_size(ti);
 206
 207     ti->class = g_malloc0(ti->class_size);
 208     ti->class->type = ti;
 209
 210     if (type_has_parent(ti)) {
 211         TypeImpl *parent = type_get_parent(ti);
 212
 213         type_class_init(parent);
 214
 215         class_size = parent->class_size;
 216         g_assert(parent->class_size <= ti->class_size);
 217
 218         memcpy((void *)ti->class + sizeof(ObjectClass),
 219                (void *)parent->class + sizeof(ObjectClass),
 220                parent->class_size - sizeof(ObjectClass));
 221     }
 222
 223     memset((void *)ti->class + class_size, 0, ti->class_size - class_size);
 224
 225     for (i = 0; i < ti->num_interfaces; i++) {
 226         type_class_interface_init(ti, &ti->interfaces[i]);
 227     }
 228
 229     if (ti->class_init) {
 230         ti->class_init(ti->class, ti->class_data);
 231     }
 232 }
 233
 234 static void object_interface_init(Object *obj, InterfaceImpl *iface)
 235 {
 236     TypeImpl *ti = iface->type;
 237     Interface *iface_obj;
 238
 239     iface_obj = INTERFACE(object_new(ti->name));
 240     iface_obj->obj = obj;
 241
 242     obj->interfaces = g_slist_prepend(obj->interfaces, iface_obj);
 243 }
 244
 245 static void object_init_with_type(Object *obj, TypeImpl *ti)
 246 {
 247     int i;
 248
 249     if (type_has_parent(ti)) {
 250         object_init_with_type(obj, type_get_parent(ti));
 251     }
 252
 253     for (i = 0; i < ti->num_interfaces; i++) {
 254         object_interface_init(obj, &ti->interfaces[i]);
 255     }
 256
 257     if (ti->instance_init) {
 258         ti->instance_init(obj);
 259     }
 260 }
 261
 262 void object_initialize_with_type(void *data, TypeImpl *type)
 263 {
 264     Object *obj = data;
 265
 266     g_assert(type != NULL);
 267     g_assert(type->instance_size >= sizeof(Object));
 268
 269     type_class_init(type);
 270     g_assert(type->abstract == false);
 271
 272     memset(obj, 0, type->instance_size);
 273     obj->class = type->class;
 274     QTAILQ_INIT(&obj->properties);
 275     object_init_with_type(obj, type);
 276 }
 277
 278 void object_initialize(void *data, const char *typename)
 279 {
 280     TypeImpl *type = type_get_by_name(typename);
 281
 282     object_initialize_with_type(data, type);
 283 }
 284
 285 static void object_property_del_all(Object *obj)
 286 {
 287     while (!QTAILQ_EMPTY(&obj->properties)) {
 288         ObjectProperty *prop = QTAILQ_FIRST(&obj->properties);
 289
 290         QTAILQ_REMOVE(&obj->properties, prop, node);
 291
 292         if (prop->release) {
 293             prop->release(obj, prop->name, prop->opaque);
 294         }
 295
 296         g_free(prop->name);
 297         g_free(prop->type);
 298         g_free(prop);
 299     }
 300 }
 301
 302 static void object_property_del_child(Object *obj, Object *child, Error **errp)
 303 {
 304     ObjectProperty *prop;
 305
 306     QTAILQ_FOREACH(prop, &obj->properties, node) {
 307         if (!strstart(prop->type, "child<", NULL)) {
 308             continue;
 309         }
 310
 311         if (prop->opaque == child) {
 312             object_property_del(obj, prop->name, errp);
 313         }
 314     }
 315 }
 316
 317 void object_unparent(Object *obj)
 318 {
 319     if (obj->parent) {
 320         object_property_del_child(obj->parent, obj, NULL);
 321     }
 322 }
 323
 324 static void object_deinit(Object *obj, TypeImpl *type)
 325 {
 326     if (type->instance_finalize) {
 327         type->instance_finalize(obj);
 328     }
 329
 330     while (obj->interfaces) {
 331         Interface *iface_obj = obj->interfaces->data;
 332         obj->interfaces = g_slist_delete_link(obj->interfaces, obj->interfaces);
 333         object_delete(OBJECT(iface_obj));
 334     }
 335
 336     if (type_has_parent(type)) {
 337         object_deinit(obj, type_get_parent(type));
 338     }
 339
 340     object_unparent(obj);
 341 }
 342
 343 void object_finalize(void *data)
 344 {
 345     Object *obj = data;
 346     TypeImpl *ti = obj->class->type;
 347
 348     object_deinit(obj, ti);
 349     object_property_del_all(obj);
 350
 351     g_assert(obj->ref == 0);
 352 }
 353
 354 Object *object_new_with_type(Type type)
 355 {
 356     Object *obj;
 357
 358     g_assert(type != NULL);
 359
 360     obj = g_malloc(type->instance_size);
 361     object_initialize_with_type(obj, type);
 362     object_ref(obj);
 363
 364     return obj;
 365 }
 366
 367 Object *object_new(const char *typename)
 368 {
 369     TypeImpl *ti = type_get_by_name(typename);
 370
 371     return object_new_with_type(ti);
 372 }
 373
 374 void object_delete(Object *obj)
 375 {
 376     object_unref(obj);
 377     g_assert(obj->ref == 0);
 378     g_free(obj);
 379 }
 380
 381 static bool type_is_ancestor(TypeImpl *type, TypeImpl *target_type)
 382 {
 383     assert(target_type);
 384
 385     /* Check if typename is a direct ancestor of type */
 386     while (type) {
 387         if (type == target_type) {
 388             return true;
 389         }
 390
 391         type = type_get_parent(type);
 392     }
 393
 394     return false;
 395 }
 396
 397 static bool object_is_type(Object *obj, TypeImpl *target_type)
 398 {
 399     return !target_type || type_is_ancestor(obj->class->type, target_type);
 400 }
 401
 402 Object *object_dynamic_cast(Object *obj, const char *typename)
 403 {
 404     TypeImpl *target_type = type_get_by_name(typename);
 405     GSList *i;
 406
 407     /* Check if typename is a direct ancestor.  Special-case TYPE_OBJECT,
 408      * we want to go back from interfaces to the parent.
 409     */
 410     if (target_type && object_is_type(obj, target_type)) {
 411         return obj;
 412     }
 413
 414     /* Check if obj is an interface and its containing object is a direct
 415      * ancestor of typename.  In principle we could do this test at the very
 416      * beginning of object_dynamic_cast, avoiding a second call to
 417      * object_is_type.  However, casting between interfaces is relatively
 418      * rare, and object_is_type(obj, type_interface) would fail almost always.
 419      *
 420      * Perhaps we could add a magic value to the object header for increased
 421      * (run-time) type safety and to speed up tests like this one.  If we ever
 422      * do that we can revisit the order here.
 423      */
 424     if (object_is_type(obj, type_interface)) {
 425         assert(!obj->interfaces);
 426         obj = INTERFACE(obj)->obj;
 427         if (object_is_type(obj, target_type)) {
 428             return obj;
 429         }
 430     }
 431
 432     if (!target_type) {
 433         return obj;
 434     }
 435
 436     /* Check if obj has an interface of typename */
 437     for (i = obj->interfaces; i; i = i->next) {
 438         Interface *iface = i->data;
 439
 440         if (object_is_type(OBJECT(iface), target_type)) {
 441             return OBJECT(iface);
 442         }
 443     }
 444
 445     return NULL;
 446 }
 447
 448
 449 static void register_types(void)
 450 {
 451     static TypeInfo interface_info = {
 452         .name = TYPE_INTERFACE,
 453         .instance_size = sizeof(Interface),
 454         .abstract = true,
 455     };
 456
 457     type_interface = type_register_static(&interface_info);
 458 }
 459
 460 type_init(register_types)
 461
 462 Object *object_dynamic_cast_assert(Object *obj, const char *typename)
 463 {
 464     Object *inst;
 465
 466     inst = object_dynamic_cast(obj, typename);
 467
 468     if (!inst) {
 469         fprintf(stderr, "Object %p is not an instance of type %s\n",
 470                 obj, typename);
 471         abort();
 472     }
 473
 474     return inst;
 475 }
 476
 477 ObjectClass *object_class_dynamic_cast(ObjectClass *class,
 478                                        const char *typename)
 479 {
 480     TypeImpl *target_type = type_get_by_name(typename);
 481     TypeImpl *type = class->type;
 482
 483     while (type) {
 484         if (type == target_type) {
 485             return class;
 486         }
 487
 488         type = type_get_parent(type);
 489     }
 490
 491     return NULL;
 492 }
 493
 494 ObjectClass *object_class_dynamic_cast_assert(ObjectClass *class,
 495                                               const char *typename)
 496 {
 497     ObjectClass *ret = object_class_dynamic_cast(class, typename);
 498
 499     if (!ret) {
 500         fprintf(stderr, "Object %p is not an instance of type %s\n",
 501                 class, typename);
 502         abort();
 503     }
 504
 505     return ret;
 506 }
 507
 508 const char *object_get_typename(Object *obj)
 509 {
 510     return obj->class->type->name;
 511 }
 512
 513 ObjectClass *object_get_class(Object *obj)
 514 {
 515     return obj->class;
 516 }
 517
 518 const char *object_class_get_name(ObjectClass *klass)
 519 {
 520     return klass->type->name;
 521 }
 522
 523 ObjectClass *object_class_by_name(const char *typename)
 524 {
 525     TypeImpl *type = type_get_by_name(typename);
 526
 527     if (!type) {
 528         return NULL;
 529     }
 530
 531     type_class_init(type);
 532
 533     return type->class;
 534 }
 535
 536 typedef struct OCFData
 537 {
 538     void (*fn)(ObjectClass *klass, void *opaque);
 539     const char *implements_type;
 540     bool include_abstract;
 541     void *opaque;
 542 } OCFData;
 543
 544 static void object_class_foreach_tramp(gpointer key, gpointer value,
 545                                        gpointer opaque)
 546 {
 547     OCFData *data = opaque;
 548     TypeImpl *type = value;
 549     ObjectClass *k;
 550
 551     type_class_init(type);
 552     k = type->class;
 553
 554     if (!data->include_abstract && type->abstract) {
 555         return;
 556     }
 557
 558     if (data->implements_type &&
 559         !object_class_dynamic_cast(k, data->implements_type)) {
 560         return;
 561     }
 562
 563     data->fn(k, data->opaque);
 564 }
 565
 566 void object_class_foreach(void (*fn)(ObjectClass *klass, void *opaque),
 567                           const char *implements_type, bool include_abstract,
 568                           void *opaque)
 569 {
 570     OCFData data = { fn, implements_type, include_abstract, opaque };
 571
 572     g_hash_table_foreach(type_table_get(), object_class_foreach_tramp, &data);
 573 }
 574
 575 void object_ref(Object *obj)
 576 {
 577     obj->ref++;
 578 }
 579
 580 void object_unref(Object *obj)
 581 {
 582     g_assert(obj->ref > 0);
 583     obj->ref--;
 584
 585     /* parent always holds a reference to its children */
 586     if (obj->ref == 0) {
 587         object_finalize(obj);
 588     }
 589 }
 590
 591 void object_property_add(Object *obj, const char *name, const char *type,
 592                          ObjectPropertyAccessor *get,
 593                          ObjectPropertyAccessor *set,
 594                          ObjectPropertyRelease *release,
 595                          void *opaque, Error **errp)
 596 {
 597     ObjectProperty *prop = g_malloc0(sizeof(*prop));
 598
 599     prop->name = g_strdup(name);
 600     prop->type = g_strdup(type);
 601
 602     prop->get = get;
 603     prop->set = set;
 604     prop->release = release;
 605     prop->opaque = opaque;
 606
 607     QTAILQ_INSERT_TAIL(&obj->properties, prop, node);
 608 }
 609
 610 static ObjectProperty *object_property_find(Object *obj, const char *name)
 611 {
 612     ObjectProperty *prop;
 613
 614     QTAILQ_FOREACH(prop, &obj->properties, node) {
 615         if (strcmp(prop->name, name) == 0) {
 616             return prop;
 617         }
 618     }
 619
 620     return NULL;
 621 }
 622
 623 void object_property_del(Object *obj, const char *name, Error **errp)
 624 {
 625     ObjectProperty *prop = object_property_find(obj, name);
 626
 627     QTAILQ_REMOVE(&obj->properties, prop, node);
 628
 629     prop->release(obj, prop->name, prop->opaque);
 630
 631     g_free(prop->name);
 632     g_free(prop->type);
 633     g_free(prop);
 634 }
 635
 636 void object_property_get(Object *obj, Visitor *v, const char *name,
 637                          Error **errp)
 638 {
 639     ObjectProperty *prop = object_property_find(obj, name);
 640
 641     if (prop == NULL) {
 642         error_set(errp, QERR_PROPERTY_NOT_FOUND, "", name);
 643         return;
 644     }
 645
 646     if (!prop->get) {
 647         error_set(errp, QERR_PERMISSION_DENIED);
 648     } else {
 649         prop->get(obj, v, prop->opaque, name, errp);
 650     }
 651 }
 652
 653 void object_property_set(Object *obj, Visitor *v, const char *name,
 654                          Error **errp)
 655 {
 656     ObjectProperty *prop = object_property_find(obj, name);
 657
 658     if (prop == NULL) {
 659         error_set(errp, QERR_PROPERTY_NOT_FOUND, "", name);
 660         return;
 661     }
 662
 663     if (!prop->set) {
 664         error_set(errp, QERR_PERMISSION_DENIED);
 665     } else {
 666         prop->set(obj, v, prop->opaque, name, errp);
 667     }
 668 }
 669
 670 void object_property_set_str(Object *obj, const char *value,
 671                              const char *name, Error **errp)
 672 {
 673     QString *qstr = qstring_from_str(value);
 674     object_property_set_qobject(obj, QOBJECT(qstr), name, errp);
 675
 676     QDECREF(qstr);
 677 }
 678
 679 char *object_property_get_str(Object *obj, const char *name,
 680                               Error **errp)
 681 {
 682     QObject *ret = object_property_get_qobject(obj, name, errp);
 683     QString *qstring;
 684     char *retval;
 685
 686     if (!ret) {
 687         return NULL;
 688     }
 689     qstring = qobject_to_qstring(ret);
 690     if (!qstring) {
 691         error_set(errp, QERR_INVALID_PARAMETER_TYPE, name, "string");
 692         retval = NULL;
 693     } else {
 694         retval = g_strdup(qstring_get_str(qstring));
 695     }
 696
 697     QDECREF(qstring);
 698     return retval;
 699 }
 700
 701 void object_property_set_link(Object *obj, Object *value,
 702                               const char *name, Error **errp)
 703 {
 704     object_property_set_str(obj, object_get_canonical_path(value),
 705                             name, errp);
 706 }
 707
 708 Object *object_property_get_link(Object *obj, const char *name,
 709                                  Error **errp)
 710 {
 711     char *str = object_property_get_str(obj, name, errp);
 712     Object *target = NULL;
 713
 714     if (str && *str) {
 715         target = object_resolve_path(str, NULL);
 716         if (!target) {
 717             error_set(errp, QERR_DEVICE_NOT_FOUND, str);
 718         }
 719     }
 720
 721     g_free(str);
 722     return target;
 723 }
 724
 725 void object_property_set_bool(Object *obj, bool value,
 726                               const char *name, Error **errp)
 727 {
 728     QBool *qbool = qbool_from_int(value);
 729     object_property_set_qobject(obj, QOBJECT(qbool), name, errp);
 730
 731     QDECREF(qbool);
 732 }
 733
 734 bool object_property_get_bool(Object *obj, const char *name,
 735                               Error **errp)
 736 {
 737     QObject *ret = object_property_get_qobject(obj, name, errp);
 738     QBool *qbool;
 739     bool retval;
 740
 741     if (!ret) {
 742         return false;
 743     }
 744     qbool = qobject_to_qbool(ret);
 745     if (!qbool) {
 746         error_set(errp, QERR_INVALID_PARAMETER_TYPE, name, "boolean");
 747         retval = false;
 748     } else {
 749         retval = qbool_get_int(qbool);
 750     }
 751
 752     QDECREF(qbool);
 753     return retval;
 754 }
 755
 756 void object_property_set_int(Object *obj, int64_t value,
 757                              const char *name, Error **errp)
 758 {
 759     QInt *qint = qint_from_int(value);
 760     object_property_set_qobject(obj, QOBJECT(qint), name, errp);
 761
 762     QDECREF(qint);
 763 }
 764
 765 int64_t object_property_get_int(Object *obj, const char *name,
 766                                 Error **errp)
 767 {
 768     QObject *ret = object_property_get_qobject(obj, name, errp);
 769     QInt *qint;
 770     int64_t retval;
 771
 772     if (!ret) {
 773         return -1;
 774     }
 775     qint = qobject_to_qint(ret);
 776     if (!qint) {
 777         error_set(errp, QERR_INVALID_PARAMETER_TYPE, name, "int");
 778         retval = -1;
 779     } else {
 780         retval = qint_get_int(qint);
 781     }
 782
 783     QDECREF(qint);
 784     return retval;
 785 }
 786
 787 void object_property_parse(Object *obj, const char *string,
 788                            const char *name, Error **errp)
 789 {
 790     StringInputVisitor *mi;
 791     mi = string_input_visitor_new(string);
 792     object_property_set(obj, string_input_get_visitor(mi), name, errp);
 793
 794     string_input_visitor_cleanup(mi);
 795 }
 796
 797 char *object_property_print(Object *obj, const char *name,
 798                             Error **errp)
 799 {
 800     StringOutputVisitor *mo;
 801     char *string;
 802
 803     mo = string_output_visitor_new();
 804     object_property_get(obj, string_output_get_visitor(mo), name, NULL);
 805     string = string_output_get_string(mo);
 806     string_output_visitor_cleanup(mo);
 807     return string;
 808 }
 809
 810 const char *object_property_get_type(Object *obj, const char *name, Error **errp)
 811 {
 812     ObjectProperty *prop = object_property_find(obj, name);
 813
 814     if (prop == NULL) {
 815         error_set(errp, QERR_PROPERTY_NOT_FOUND, "", name);
 816         return NULL;
 817     }
 818
 819     return prop->type;
 820 }
 821
 822 Object *object_get_root(void)
 823 {
 824     static Object *root;
 825
 826     if (!root) {
 827         root = object_new("container");
 828     }
 829
 830     return root;
 831 }
 832
 833 static void object_get_child_property(Object *obj, Visitor *v, void *opaque,
 834                                       const char *name, Error **errp)
 835 {
 836     Object *child = opaque;
 837     gchar *path;
 838
 839     path = object_get_canonical_path(child);
 840     visit_type_str(v, &path, name, errp);
 841     g_free(path);
 842 }
 843
 844 static void object_finalize_child_property(Object *obj, const char *name,
 845                                            void *opaque)
 846 {
 847     Object *child = opaque;
 848
 849     object_unref(child);
 850 }
 851
 852 void object_property_add_child(Object *obj, const char *name,
 853                                Object *child, Error **errp)
 854 {
 855     gchar *type;
 856
 857     /* Registering an interface object in the composition tree will mightily
 858      * confuse object_get_canonical_path (which, on the other hand, knows how
 859      * to get the canonical path of an interface object).
 860      */
 861     assert(!object_is_type(obj, type_interface));
 862
 863     type = g_strdup_printf("child<%s>", object_get_typename(OBJECT(child)));
 864
 865     object_property_add(obj, name, type, object_get_child_property,
 866                         NULL, object_finalize_child_property, child, errp);
 867
 868     object_ref(child);
 869     g_assert(child->parent == NULL);
 870     child->parent = obj;
 871
 872     g_free(type);
 873 }
 874
 875 static void object_get_link_property(Object *obj, Visitor *v, void *opaque,
 876                                      const char *name, Error **errp)
 877 {
 878     Object **child = opaque;
 879     gchar *path;
 880
 881     if (*child) {
 882         path = object_get_canonical_path(*child);
 883         visit_type_str(v, &path, name, errp);
 884         g_free(path);
 885     } else {
 886         path = (gchar *)"";
 887         visit_type_str(v, &path, name, errp);
 888     }
 889 }
 890
 891 static void object_set_link_property(Object *obj, Visitor *v, void *opaque,
 892                                      const char *name, Error **errp)
 893 {
 894     Object **child = opaque;
 895     Object *old_target;
 896     bool ambiguous = false;
 897     const char *type;
 898     char *path;
 899     gchar *target_type;
 900
 901     type = object_property_get_type(obj, name, NULL);
 902
 903     visit_type_str(v, &path, name, errp);
 904
 905     old_target = *child;
 906     *child = NULL;
 907
 908     if (strcmp(path, "") != 0) {
 909         Object *target;
 910
 911         /* Go from link<FOO> to FOO.  */
 912         target_type = g_strndup(&type[5], strlen(type) - 6);
 913         target = object_resolve_path_type(path, target_type, &ambiguous);
 914
 915         if (ambiguous) {
 916             error_set(errp, QERR_AMBIGUOUS_PATH, path);
 917         } else if (target) {
 918             object_ref(target);
 919             *child = target;
 920         } else {
 921             target = object_resolve_path(path, &ambiguous);
 922             if (target || ambiguous) {
 923                 error_set(errp, QERR_INVALID_PARAMETER_TYPE, name, target_type);
 924             } else {
 925                 error_set(errp, QERR_DEVICE_NOT_FOUND, path);
 926             }
 927         }
 928         g_free(target_type);
 929     }
 930
 931     g_free(path);
 932
 933     if (old_target != NULL) {
 934         object_unref(old_target);
 935     }
 936 }
 937
 938 void object_property_add_link(Object *obj, const char *name,
 939                               const char *type, Object **child,
 940                               Error **errp)
 941 {
 942     gchar *full_type;
 943
 944     full_type = g_strdup_printf("link<%s>", type);
 945
 946     object_property_add(obj, name, full_type,
 947                         object_get_link_property,
 948                         object_set_link_property,
 949                         NULL, child, errp);
 950
 951     g_free(full_type);
 952 }
 953
 954 gchar *object_get_canonical_path(Object *obj)
 955 {
 956     Object *root = object_get_root();
 957     char *newpath = NULL, *path = NULL;
 958
 959     if (object_is_type(obj, type_interface)) {
 960         obj = INTERFACE(obj)->obj;
 961     }
 962
 963     while (obj != root) {
 964         ObjectProperty *prop = NULL;
 965
 966         g_assert(obj->parent != NULL);
 967
 968         QTAILQ_FOREACH(prop, &obj->parent->properties, node) {
 969             if (!strstart(prop->type, "child<", NULL)) {
 970                 continue;
 971             }
 972
 973             if (prop->opaque == obj) {
 974                 if (path) {
 975                     newpath = g_strdup_printf("%s/%s", prop->name, path);
 976                     g_free(path);
 977                     path = newpath;
 978                 } else {
 979                     path = g_strdup(prop->name);
 980                 }
 981                 break;
 982             }
 983         }
 984
 985         g_assert(prop != NULL);
 986
 987         obj = obj->parent;
 988     }
 989
 990     newpath = g_strdup_printf("/%s", path);
 991     g_free(path);
 992
 993     return newpath;
 994 }
 995
 996 static Object *object_resolve_abs_path(Object *parent,
 997                                           gchar **parts,
 998                                           const char *typename,
 999                                           int index)
1000 {
1001     ObjectProperty *prop;
1002     Object *child;
1003
1004     if (parts[index] == NULL) {
1005         return object_dynamic_cast(parent, typename);
1006     }
1007
1008     if (strcmp(parts[index], "") == 0) {
1009         return object_resolve_abs_path(parent, parts, typename, index + 1);
1010     }
1011
1012     prop = object_property_find(parent, parts[index]);
1013     if (prop == NULL) {
1014         return NULL;
1015     }
1016
1017     child = NULL;
1018     if (strstart(prop->type, "link<", NULL)) {
1019         Object **pchild = prop->opaque;
1020         if (*pchild) {
1021             child = *pchild;
1022         }
1023     } else if (strstart(prop->type, "child<", NULL)) {
1024         child = prop->opaque;
1025     }
1026
1027     if (!child) {
1028         return NULL;
1029     }
1030
1031     return object_resolve_abs_path(child, parts, typename, index + 1);
1032 }
1033
1034 static Object *object_resolve_partial_path(Object *parent,
1035                                               gchar **parts,
1036                                               const char *typename,
1037                                               bool *ambiguous)
1038 {
1039     Object *obj;
1040     ObjectProperty *prop;
1041
1042     obj = object_resolve_abs_path(parent, parts, typename, 0);
1043
1044     QTAILQ_FOREACH(prop, &parent->properties, node) {
1045         Object *found;
1046
1047         if (!strstart(prop->type, "child<", NULL)) {
1048             continue;
1049         }
1050
1051         found = object_resolve_partial_path(prop->opaque, parts,
1052                                             typename, ambiguous);
1053         if (found) {
1054             if (obj) {
1055                 if (ambiguous) {
1056                     *ambiguous = true;
1057                 }
1058                 return NULL;
1059             }
1060             obj = found;
1061         }
1062
1063         if (ambiguous && *ambiguous) {
1064             return NULL;
1065         }
1066     }
1067
1068     return obj;
1069 }
1070
1071 Object *object_resolve_path_type(const char *path, const char *typename,
1072                                  bool *ambiguous)
1073 {
1074     bool partial_path = true;
1075     Object *obj;
1076     gchar **parts;
1077
1078     parts = g_strsplit(path, "/", 0);
1079     if (parts == NULL || parts[0] == NULL) {
1080         g_strfreev(parts);
1081         return object_get_root();
1082     }
1083
1084     if (strcmp(parts[0], "") == 0) {
1085         partial_path = false;
1086     }
1087
1088     if (partial_path) {
1089         if (ambiguous) {
1090             *ambiguous = false;
1091         }
1092         obj = object_resolve_partial_path(object_get_root(), parts,
1093                                           typename, ambiguous);
1094     } else {
1095         obj = object_resolve_abs_path(object_get_root(), parts, typename, 1);
1096     }
1097
1098     g_strfreev(parts);
1099
1100     return obj;
1101 }
1102
1103 Object *object_resolve_path(const char *path, bool *ambiguous)
1104 {
1105     return object_resolve_path_type(path, TYPE_OBJECT, ambiguous);
1106 }
1107
1108 typedef struct StringProperty
1109 {
1110     char *(*get)(Object *, Error **);
1111     void (*set)(Object *, const char *, Error **);
1112 } StringProperty;
1113
1114 static void property_get_str(Object *obj, Visitor *v, void *opaque,
1115                              const char *name, Error **errp)
1116 {
1117     StringProperty *prop = opaque;
1118     char *value;
1119
1120     value = prop->get(obj, errp);
1121     if (value) {
1122         visit_type_str(v, &value, name, errp);
1123         g_free(value);
1124     }
1125 }
1126
1127 static void property_set_str(Object *obj, Visitor *v, void *opaque,
1128                              const char *name, Error **errp)
1129 {
1130     StringProperty *prop = opaque;
1131     char *value;
1132     Error *local_err = NULL;
1133
1134     visit_type_str(v, &value, name, &local_err);
1135     if (local_err) {
1136         error_propagate(errp, local_err);
1137         return;
1138     }
1139
1140     prop->set(obj, value, errp);
1141     g_free(value);
1142 }
1143
1144 static void property_release_str(Object *obj, const char *name,
1145                                  void *opaque)
1146 {
1147     StringProperty *prop = opaque;
1148     g_free(prop);
1149 }
1150
1151 void object_property_add_str(Object *obj, const char *name,
1152                            char *(*get)(Object *, Error **),
1153                            void (*set)(Object *, const char *, Error **),
1154                            Error **errp)
1155 {
1156     StringProperty *prop = g_malloc0(sizeof(*prop));
1157
1158     prop->get = get;
1159     prop->set = set;
1160
1161     object_property_add(obj, name, "string",
1162                         get ? property_get_str : NULL,
1163                         set ? property_set_str : NULL,
1164                         property_release_str,
1165                         prop, errp);
1166 }