1 /*
2 * QEMU Object Model.
3 *
4 * Based on ideas by Avi Kivity <avi@redhat.com>
5 *
6 * Copyright (C) 2009 Red Hat Inc.
7 *
8 * Authors:
9 * Luiz Capitulino <lcapitulino@redhat.com>
10 *
11 * This work is licensed under the terms of the GNU GPL, version 2. See
12 * the COPYING file in the top-level directory.
13 *
14 * QObject Reference Counts Terminology
15 * ------------------------------------
16 *
17 * - Returning references: A function that returns an object may
18 * return it as either a weak or a strong reference. If the reference
19 * is strong, you are responsible for calling QDECREF() on the reference
20 * when you are done.
21 *
22 * If the reference is weak, the owner of the reference may free it at
23 * any time in the future. Before storing the reference anywhere, you
24 * should call QINCREF() to make the reference strong.
25 *
26 * - Transferring ownership: when you transfer ownership of a reference
27 * by calling a function, you are no longer responsible for calling
28 * QDECREF() when the reference is no longer needed. In other words,
29 * when the function returns you must behave as if the reference to the
30 * passed object was weak.
31 */
32 #ifndef QOBJECT_H
33 #define QOBJECT_H
34
35 #include <stddef.h>
36 #include <assert.h>
37
38 typedef enum {
39 QTYPE_NONE,
40 QTYPE_QINT,
41 QTYPE_QSTRING,
42 QTYPE_QDICT,
43 QTYPE_QLIST,
44 QTYPE_QFLOAT,
45 QTYPE_QBOOL,
46 QTYPE_QERROR,
47 } qtype_code;
48
49 struct QObject;
50
51 typedef struct QType {
52 qtype_code code;
53 void (*destroy)(struct QObject *);
54 } QType;
55
56 typedef struct QObject {
57 const QType *type;
58 size_t refcnt;
59 } QObject;
60
61 /* Objects definitions must include this */
62 #define QObject_HEAD \
63 QObject base
64
65 /* Get the 'base' part of an object */
66 #define QOBJECT(obj) (&(obj)->base)
67
68 /* High-level interface for qobject_incref() */
69 #define QINCREF(obj) \
70 qobject_incref(QOBJECT(obj))
71
72 /* High-level interface for qobject_decref() */
73 #define QDECREF(obj) \
74 qobject_decref(QOBJECT(obj))
75
76 /* Initialize an object to default values */
77 #define QOBJECT_INIT(obj, qtype_type) \
78 obj->base.refcnt = 1; \
79 obj->base.type = qtype_type
80
81 /**
82 * qobject_incref(): Increment QObject's reference count
83 */
qobject_incref(QObject * obj)84 static inline void qobject_incref(QObject *obj)
85 {
86 if (obj)
87 obj->refcnt++;
88 }
89
90 /**
91 * qobject_decref(): Decrement QObject's reference count, deallocate
92 * when it reaches zero
93 */
qobject_decref(QObject * obj)94 static inline void qobject_decref(QObject *obj)
95 {
96 if (obj && --obj->refcnt == 0) {
97 assert(obj->type != NULL);
98 assert(obj->type->destroy != NULL);
99 obj->type->destroy(obj);
100 }
101 }
102
103 /**
104 * qobject_type(): Return the QObject's type
105 */
qobject_type(const QObject * obj)106 static inline qtype_code qobject_type(const QObject *obj)
107 {
108 assert(obj->type != NULL);
109 return obj->type->code;
110 }
111
112 #endif /* QOBJECT_H */
113