4d2d5c41a9
I expect the 'null' type to be useful mostly for members of alternate types. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
109 lines
2.6 KiB
C
109 lines
2.6 KiB
C
/*
|
|
* 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 "qapi-types.h"
|
|
|
|
struct QObject {
|
|
QType type;
|
|
size_t refcnt;
|
|
};
|
|
|
|
/* 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;
|
|
}
|
|
|
|
struct QNull {
|
|
QObject base;
|
|
};
|
|
|
|
extern QNull qnull_;
|
|
|
|
static inline QNull *qnull(void)
|
|
{
|
|
QINCREF(&qnull_);
|
|
return &qnull_;
|
|
}
|
|
|
|
#endif /* QOBJECT_H */
|