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Luiz Capitulino5a1a2352009-08-28 15:27:04 -03001/*
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
38typedef enum {
39 QTYPE_NONE,
Luiz Capitulino6b8d1ec2009-08-28 15:27:05 -030040 QTYPE_QINT,
Luiz Capitulino66f70482009-08-28 15:27:06 -030041 QTYPE_QSTRING,
Luiz Capitulinofb08dde2009-08-28 15:27:07 -030042 QTYPE_QDICT,
Luiz Capitulinoa6fd08e2009-10-07 13:41:48 -030043 QTYPE_QLIST,
Anthony Liguoriec072ce2009-11-11 10:36:08 -060044 QTYPE_QFLOAT,
Anthony Liguorif7e6b192009-11-11 10:37:39 -060045 QTYPE_QBOOL,
Luiz Capitulino9f9daf92009-11-18 23:05:30 -020046 QTYPE_QERROR,
Luiz Capitulino5a1a2352009-08-28 15:27:04 -030047} qtype_code;
48
49struct QObject;
50
51typedef struct QType {
52 qtype_code code;
53 void (*destroy)(struct QObject *);
54} QType;
55
56typedef 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 */
Anthony Liguoric99ca932009-11-11 10:50:36 -060066#define QOBJECT(obj) (&(obj)->base)
Luiz Capitulino5a1a2352009-08-28 15:27:04 -030067
68/* High-level interface for qobject_incref() */
69#define QINCREF(obj) \
Luiz Capitulino5a1a2352009-08-28 15:27:04 -030070 qobject_incref(QOBJECT(obj))
71
72/* High-level interface for qobject_decref() */
73#define QDECREF(obj) \
Luiz Capitulino5a1a2352009-08-28 15:27:04 -030074 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 */
84static inline void qobject_incref(QObject *obj)
85{
Luiz Capitulinod559ba12009-10-07 13:41:47 -030086 if (obj)
87 obj->refcnt++;
Luiz Capitulino5a1a2352009-08-28 15:27:04 -030088}
89
90/**
91 * qobject_decref(): Decrement QObject's reference count, deallocate
92 * when it reaches zero
93 */
94static inline void qobject_decref(QObject *obj)
95{
Luiz Capitulinod559ba12009-10-07 13:41:47 -030096 if (obj && --obj->refcnt == 0) {
Luiz Capitulino5a1a2352009-08-28 15:27:04 -030097 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 */
106static 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 */