134 lines
3.7 KiB
C
134 lines
3.7 KiB
C
/*
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* QEMU Object Model.
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*
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* Based on ideas by Avi Kivity <avi@redhat.com>
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*
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* Copyright (C) 2009, 2015 Red Hat Inc.
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*
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* Authors:
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* Luiz Capitulino <lcapitulino@redhat.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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* QObject Reference Counts Terminology
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* ------------------------------------
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*
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* - Returning references: A function that returns an object may
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* return it as either a weak or a strong reference. If the reference
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* is strong, you are responsible for calling QDECREF() on the reference
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* when you are done.
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*
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* If the reference is weak, the owner of the reference may free it at
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* any time in the future. Before storing the reference anywhere, you
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* should call QINCREF() to make the reference strong.
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*
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* - Transferring ownership: when you transfer ownership of a reference
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* by calling a function, you are no longer responsible for calling
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* QDECREF() when the reference is no longer needed. In other words,
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* when the function returns you must behave as if the reference to the
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* passed object was weak.
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*/
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#ifndef QOBJECT_H
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#define QOBJECT_H
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#include "qapi/qapi-builtin-types.h"
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struct QObject {
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QType type;
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size_t refcnt;
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};
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/* Get the 'base' part of an object */
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#define QOBJECT(obj) (&(obj)->base)
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/* High-level interface for qobject_incref() */
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#define QINCREF(obj) \
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qobject_incref(QOBJECT(obj))
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/* High-level interface for qobject_decref() */
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#define QDECREF(obj) \
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qobject_decref(obj ? QOBJECT(obj) : NULL)
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/* Required for qobject_to() */
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#define QTYPE_CAST_TO_QNull QTYPE_QNULL
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#define QTYPE_CAST_TO_QNum QTYPE_QNUM
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#define QTYPE_CAST_TO_QString QTYPE_QSTRING
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#define QTYPE_CAST_TO_QDict QTYPE_QDICT
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#define QTYPE_CAST_TO_QList QTYPE_QLIST
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#define QTYPE_CAST_TO_QBool QTYPE_QBOOL
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QEMU_BUILD_BUG_MSG(QTYPE__MAX != 7,
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"The QTYPE_CAST_TO_* list needs to be extended");
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#define qobject_to(type, obj) \
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((type *)qobject_check_type(obj, glue(QTYPE_CAST_TO_, type)))
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/* Initialize an object to default values */
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static inline void qobject_init(QObject *obj, QType type)
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{
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assert(QTYPE_NONE < type && type < QTYPE__MAX);
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obj->refcnt = 1;
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obj->type = type;
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}
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/**
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* qobject_incref(): Increment QObject's reference count
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*/
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static inline void qobject_incref(QObject *obj)
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{
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if (obj)
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obj->refcnt++;
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}
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/**
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* qobject_is_equal(): Return whether the two objects are equal.
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*
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* Any of the pointers may be NULL; return true if both are. Always
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* return false if only one is (therefore a QNull object is not
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* considered equal to a NULL pointer).
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*/
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bool qobject_is_equal(const QObject *x, const QObject *y);
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/**
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* qobject_destroy(): Free resources used by the object
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*/
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void qobject_destroy(QObject *obj);
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/**
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* qobject_decref(): Decrement QObject's reference count, deallocate
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* when it reaches zero
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*/
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static inline void qobject_decref(QObject *obj)
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{
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assert(!obj || obj->refcnt);
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if (obj && --obj->refcnt == 0) {
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qobject_destroy(obj);
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}
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}
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/**
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* qobject_type(): Return the QObject's type
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*/
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static inline QType qobject_type(const QObject *obj)
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{
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assert(QTYPE_NONE < obj->type && obj->type < QTYPE__MAX);
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return obj->type;
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}
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/**
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* qobject_check_type(): Helper function for the qobject_to() macro.
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* Return @obj, but only if @obj is not NULL and @type is equal to
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* @obj's type. Return NULL otherwise.
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*/
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static inline QObject *qobject_check_type(const QObject *obj, QType type)
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{
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if (obj && qobject_type(obj) == type) {
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return (QObject *)obj;
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} else {
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return NULL;
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}
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}
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#endif /* QOBJECT_H */
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