unicorn/qemu/qobject/qobject.c
Marc-André Lureau f4b3c5d0bd
qobject: use a QObjectBase_ struct
By moving the base fields to a QObjectBase_, QObject can be a type
which also has a 'base' field. This allows writing a generic QOBJECT()
macro that will work with any QObject type, including QObject
itself. The container_of() macro ensures that the object to cast has a
QObjectBase_ base field, giving some type safety guarantees. QObject
must have no members but QObjectBase_ base, or else QOBJECT() breaks.

QObjectBase_ is not a typedef and uses a trailing underscore to make
it obvious it is not for normal use and to avoid potential abuse.

Backports commit 3d3eacaeccaab718ea0e2ddaa578bfae9e311c59 from qemu
2018-05-04 10:11:24 -04:00

71 lines
1.7 KiB
C

/*
* QObject
*
* Copyright (C) 2015 Red Hat, Inc.
*
* 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.
*/
#include "qemu-common.h"
#include "qapi/qmp/qbool.h"
#include "qapi/qmp/qnull.h"
#include "qapi/qmp/qnum.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qlist.h"
#include "qapi/qmp/qstring.h"
QEMU_BUILD_BUG_MSG(
offsetof(QNull, base) != 0 ||
offsetof(QNum, base) != 0 ||
offsetof(QString, base) != 0 ||
offsetof(QDict, base) != 0 ||
offsetof(QList, base) != 0 ||
offsetof(QBool, base) != 0,
"base qobject must be at offset 0");
static void (*qdestroy[QTYPE__MAX])(QObject *) = {
NULL, /* No such object exists */
NULL, /* qnull_ is indestructible */
qnum_destroy_obj,
qstring_destroy_obj,
qdict_destroy_obj,
qlist_destroy_obj,
qbool_destroy_obj,
};
void qobject_destroy(QObject *obj)
{
assert(!obj->base.refcnt);
assert(QTYPE_QNULL < obj->base.type && obj->base.type < QTYPE__MAX);
qdestroy[obj->base.type](obj);
}
static bool (*qis_equal[QTYPE__MAX])(const QObject *, const QObject *) = {
NULL, /* No such object exists */
qnull_is_equal,
qnum_is_equal,
qstring_is_equal,
qdict_is_equal,
qlist_is_equal,
qbool_is_equal,
};
bool qobject_is_equal(const QObject *x, const QObject *y)
{
/* We cannot test x == y because an object does not need to be
* equal to itself (e.g. NaN floats are not). */
if (!x && !y) {
return true;
}
if (!x || !y || x->base.type != y->base.type) {
return false;
}
assert(QTYPE_NONE < x->base.type && x->base.type < QTYPE__MAX);
return qis_equal[x->base.type](x, y);
}