/* * QEMU Object Model. * * Based on ideas by Avi Kivity <avi@redhat.com> * * Copyright (C) 2009 Red Hat Inc. * * Authors: * Luiz Capitulino <lcapitulino@redhat.com> * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. * * QObject Reference Counts Terminology * ------------------------------------ * * - Returning references: A function that returns an object may * return it as either a weak or a strong reference. If the reference * is strong, you are responsible for calling QDECREF() on the reference * when you are done. * * If the reference is weak, the owner of the reference may free it at * any time in the future. Before storing the reference anywhere, you * should call QINCREF() to make the reference strong. * * - Transferring ownership: when you transfer ownership of a reference * by calling a function, you are no longer responsible for calling * QDECREF() when the reference is no longer needed. In other words, * when the function returns you must behave as if the reference to the * passed object was weak. */ #ifndef QOBJECT_H #define QOBJECT_H #include <stddef.h> #include <assert.h> typedef enum { QTYPE_NONE, QTYPE_QINT, QTYPE_QSTRING, QTYPE_QDICT, QTYPE_QLIST, } qtype_code; struct QObject; typedef struct QType { qtype_code code; void (*destroy)(struct QObject *); } QType; typedef struct QObject { const QType *type; size_t refcnt; } QObject; /* Objects definitions must include this */ #define QObject_HEAD \ QObject base /* Get the 'base' part of an object */ #define QOBJECT(obj) (&obj->base) /* High-level interface for qobject_incref() */ #define QINCREF(obj) \ qobject_incref(QOBJECT(obj)) /* High-level interface for qobject_decref() */ #define QDECREF(obj) \ qobject_decref(QOBJECT(obj)) /* Initialize an object to default values */ #define QOBJECT_INIT(obj, qtype_type) \ obj->base.refcnt = 1; \ obj->base.type = qtype_type /** * qobject_incref(): Increment QObject's reference count */ static inline void qobject_incref(QObject *obj) { if (obj) obj->refcnt++; } /** * qobject_decref(): Decrement QObject's reference count, deallocate * when it reaches zero */ static inline void qobject_decref(QObject *obj) { if (obj && --obj->refcnt == 0) { assert(obj->type != NULL); assert(obj->type->destroy != NULL); obj->type->destroy(obj); } } /** * qobject_type(): Return the QObject's type */ static inline qtype_code qobject_type(const QObject *obj) { assert(obj->type != NULL); return obj->type->code; } #endif /* QOBJECT_H */