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e9666e4455
What's more meta than using qapi to define qapi? :) Convert QType into a full-fledged[*] builtin qapi enum type, so that a subsequent patch can then use it as the discriminator type of qapi alternate types. Fortunately, the judicious use of 'prefix' in the qapi definition avoids churn to the spelling of the enum constants. To avoid circular definitions, we have to flip the order of inclusion between "qobject.h" vs. "qapi-types.h". Back in commit 28770e0, we had the latter include the former, so that we could use 'QObject *' for our implementation of 'any'. But that usage also works with only a forward declaration, whereas the definition of QObject requires QType to be a complete type. [*] The type has to be builtin, rather than declared in qapi/common.json, because we want to use it for alternates even when common.json is not included. But since it is the first builtin enum type, we have to add special cases to qapi-types and qapi-visit to only emit definitions once, even when two qapi files are being compiled into the same binary (the way we already handled builtin list types like 'intList'). We may need to revisit how multiple qapi files share common types, but that's a project for another day. Backports commit 7264f5c50cc1be0f1406e3ebb45aedcca02f603a from qemu
111 lines
2.7 KiB
C
111 lines
2.7 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 <stddef.h>
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#include <assert.h>
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#include "qapi-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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/* 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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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_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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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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