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/*
* QEMU Object Model.
*
* Based on ideas by Avi Kivity <avi@redhat.com>
*
* Copyright (C) 2009, 2015 Red Hat Inc.
*
* Authors:
* Luiz Capitulino <lcapitulino@redhat.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB 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, /* sentinel value, no QObject has this type code */
QTYPE_QNULL,
QTYPE_QINT,
QTYPE_QSTRING,
QTYPE_QDICT,
QTYPE_QLIST,
QTYPE_QFLOAT,
QTYPE_QBOOL,
QTYPE_MAX,
} QType;
typedef struct QObject {
QType type;
size_t refcnt;
} QObject;
/* 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(obj ? QOBJECT(obj) : NULL)
/* Initialize an object to default values */
static inline void qobject_init(QObject *obj, QType type)
{
assert(QTYPE_NONE < type && type < QTYPE_MAX);
obj->refcnt = 1;
obj->type = type;
}
/**
* qobject_incref(): Increment QObject's reference count
*/
static inline void qobject_incref(QObject *obj)
{
if (obj)
obj->refcnt++;
}
/**
* qobject_destroy(): Free resources used by the object
*/
void qobject_destroy(QObject *obj);
/**
* qobject_decref(): Decrement QObject's reference count, deallocate
* when it reaches zero
*/
static inline void qobject_decref(QObject *obj)
{
assert(!obj || obj->refcnt);
if (obj && --obj->refcnt == 0) {
qobject_destroy(obj);
}
}
/**
* qobject_type(): Return the QObject's type
*/
static inline QType qobject_type(const QObject *obj)
{
assert(QTYPE_NONE < obj->type && obj->type < QTYPE_MAX);
return obj->type;
}
extern QObject qnull_;
static inline QObject *qnull(void)
{
qobject_incref(&qnull_);
return &qnull_;
}
#endif /* QOBJECT_H */
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