481b002cc8
I'm going to fix the JSON parser to recognize null. The obvious representation of JSON null as (QObject *)NULL doesn't work, because the parser already uses it as an error value. Perhaps we should change it to free NULL for null, but that's more than I can do right now. Create a special null QObject instead. The existing QDict, QList, and QString all represent something that is a pointer in C and could therefore be associated with NULL. But right now, all three of these sub-types are always non-null once created, so the new null sentinel object is intentionally unrelated to them. Signed-off-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
123 lines
3.0 KiB
C
123 lines
3.0 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 <stddef.h>
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#include <assert.h>
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typedef enum {
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QTYPE_NONE, /* sentinel value, no QObject has this type code */
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QTYPE_QNULL,
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QTYPE_QINT,
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QTYPE_QSTRING,
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QTYPE_QDICT,
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QTYPE_QLIST,
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QTYPE_QFLOAT,
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QTYPE_QBOOL,
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QTYPE_QERROR,
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QTYPE_MAX,
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} qtype_code;
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struct QObject;
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typedef struct QType {
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qtype_code code;
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void (*destroy)(struct QObject *);
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} QType;
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typedef struct QObject {
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const QType *type;
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size_t refcnt;
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} QObject;
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/* Objects definitions must include this */
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#define QObject_HEAD \
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QObject base
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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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/* Initialize an object to default values */
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#define QOBJECT_INIT(obj, qtype_type) \
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obj->base.refcnt = 1; \
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obj->base.type = qtype_type
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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_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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if (obj && --obj->refcnt == 0) {
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assert(obj->type != NULL);
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assert(obj->type->destroy != NULL);
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obj->type->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_code qobject_type(const QObject *obj)
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{
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assert(obj->type != NULL);
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return obj->type->code;
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}
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extern QObject qnull_;
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static inline QObject *qnull(void)
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{
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qobject_incref(&qnull_);
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return &qnull_;
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}
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#endif /* QOBJECT_H */
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