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https://gitlab.com/libvirt/libvirt.git
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Add a generic reference counted virObject type
This introduces a fairly basic reference counted virObject type and an associated virClass type, that use atomic operations for ref counting. In a global initializer (recommended to be invoked using the virOnceInit API), a virClass type must be allocated for each object type. This requires a class name, a "dispose" callback which will be invoked to free memory associated with the object's fields, and the size in bytes of the object struct. eg, virClassPtr connclass = virClassNew("virConnect", sizeof(virConnect), virConnectDispose); The struct for the object, must include 'virObject' as its first member eg struct _virConnect { virObject object; virURIPtr uri; }; The 'dispose' callback is only responsible for freeing fields in the object, not the object itself. eg a suitable impl for the above struct would be void virConnectDispose(void *obj) { virConnectPtr conn = obj; virURIFree(conn->uri); } There is no need to reset fields to 'NULL' or '0' in the dispose callback, since the entire object will be memset to 0, and the klass pointer & magic integer fields will be poisoned with 0xDEADBEEF before being free()d When creating an instance of an object, one needs simply pass the virClassPtr eg virConnectPtr conn = virObjectNew(connclass); if (!conn) return NULL; conn->uri = virURIParse("foo:///bar") Object references can be manipulated with virObjectRef(conn) virObjectUnref(conn) The latter returns a true value, if the object has been freed (ie its ref count hit zero) Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
parent
b0e478986f
commit
784a99f794
2
cfg.mk
2
cfg.mk
@ -171,6 +171,8 @@ useless_free_options = \
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--name=virNetworkObjFree \
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--name=virNetworkObjFree \
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--name=virNodeDeviceDefFree \
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--name=virNodeDeviceDefFree \
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--name=virNodeDeviceObjFree \
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--name=virNodeDeviceObjFree \
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--name=virObjectUnref \
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--name=virObjectFreeCallback \
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--name=virSecretDefFree \
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--name=virSecretDefFree \
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--name=virStorageEncryptionFree \
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--name=virStorageEncryptionFree \
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--name=virStorageEncryptionSecretFree \
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--name=virStorageEncryptionSecretFree \
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@ -85,6 +85,7 @@ UTIL_SOURCES = \
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util/virauthconfig.c util/virauthconfig.h \
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util/virauthconfig.c util/virauthconfig.h \
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util/virfile.c util/virfile.h \
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util/virfile.c util/virfile.h \
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util/virnodesuspend.c util/virnodesuspend.h \
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util/virnodesuspend.c util/virnodesuspend.h \
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util/virobject.c util/virobject.h \
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util/virpidfile.c util/virpidfile.h \
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util/virpidfile.c util/virpidfile.h \
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util/virtypedparam.c util/virtypedparam.h \
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util/virtypedparam.c util/virtypedparam.h \
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util/xml.c util/xml.h \
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util/xml.c util/xml.h \
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@ -1644,6 +1644,16 @@ nodeSuspendForDuration;
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virNodeSuspendGetTargetMask;
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virNodeSuspendGetTargetMask;
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# virobject.h
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virClassName;
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virClassNew;
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virObjectFreeCallback;
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virObjectIsClass;
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virObjectNew;
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virObjectRef;
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virObjectUnref;
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# virpidfile.h
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# virpidfile.h
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virPidFileAcquire;
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virPidFileAcquire;
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virPidFileAcquirePath;
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virPidFileAcquirePath;
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@ -16,6 +16,13 @@ provider libvirt {
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probe event_poll_run(int nfds, int timeout);
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probe event_poll_run(int nfds, int timeout);
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# file: src/util/virobject.c
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# prefix: object
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probe object_new(void *obj, const char *klassname);
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probe object_ref(void *obj);
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probe object_unref(void *obj);
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probe object_dispose(void *obj);
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# file: src/rpc/virnetsocket.c
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# file: src/rpc/virnetsocket.c
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# prefix: rpc
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# prefix: rpc
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probe rpc_socket_new(void *sock, int refs, int fd, int errfd, pid_t pid, const char *localAddr, const char *remoteAddr);
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probe rpc_socket_new(void *sock, int refs, int fd, int errfd, pid_t pid, const char *localAddr, const char *remoteAddr);
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214
src/util/virobject.c
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214
src/util/virobject.c
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@ -0,0 +1,214 @@
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/*
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* virobject.c: libvirt reference counted object
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*
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* Copyright (C) 2012 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; If not, see
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* <http://www.gnu.org/licenses/>.
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*
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*/
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#include <config.h>
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#include "virobject.h"
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#include "threads.h"
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#include "memory.h"
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#include "viratomic.h"
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#include "virterror_internal.h"
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#include "logging.h"
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#define VIR_FROM_THIS VIR_FROM_NONE
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static unsigned int magicCounter = 0xCAFE0000;
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struct _virClass {
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unsigned int magic;
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const char *name;
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size_t objectSize;
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virObjectDisposeCallback dispose;
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};
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/**
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* virClassNew:
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* @name: the class name
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* @objectSize: total size of the object struct
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* @dispose: callback to run to free object fields
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*
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* Register a new object class with @name. The @objectSize
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* should give the total size of the object struct, which
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* is expected to have a 'virObject object;' field as its
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* first member. When the last reference on the object is
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* released, the @dispose callback will be invoked to free
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* memory of the object fields
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*
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* Returns a new class instance
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*/
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virClassPtr virClassNew(const char *name,
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size_t objectSize,
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virObjectDisposeCallback dispose)
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{
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virClassPtr klass;
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if (VIR_ALLOC(klass) < 0)
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goto no_memory;
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if (!(klass->name = strdup(name)))
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goto no_memory;
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klass->magic = virAtomicIntInc(&magicCounter);
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klass->objectSize = objectSize;
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klass->dispose = dispose;
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return klass;
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no_memory:
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VIR_FREE(klass);
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virReportOOMError();
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return NULL;
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}
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/**
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* virObjectNew:
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* @klass: the klass of object to create
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*
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* Allocates a new object of type @klass. The returned
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* object will be an instance of "virObjectPtr", which
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* can be cast to the struct associated with @klass.
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*
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* The initial reference count of the object will be 1.
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*
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* Returns the new object
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*/
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void *virObjectNew(virClassPtr klass)
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{
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virObjectPtr obj = NULL;
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char *somebytes;
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if (VIR_ALLOC_N(somebytes, klass->objectSize) < 0) {
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virReportOOMError();
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return NULL;
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}
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obj = (virObjectPtr)somebytes;
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obj->magic = klass->magic;
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obj->klass = klass;
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virAtomicIntSet(&obj->refs, 1);
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PROBE(OBJECT_NEW, "obj=%p classname=%s", obj, obj->klass->name);
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return obj;
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}
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/**
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* virObjectUnref:
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* @anyobj: any instance of virObjectPtr
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*
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* Decrement the reference count on @anyobj and if
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* it hits zero, runs the "dispose" callback associated
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* with the object class and frees @anyobj.
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*
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* Returns true if the remaining reference count is
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* non-zero, false if the object was disposed of
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*/
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bool virObjectUnref(void *anyobj)
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{
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virObjectPtr obj = anyobj;
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if (!obj)
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return false;
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bool lastRef = virAtomicIntDecAndTest(&obj->refs);
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PROBE(OBJECT_UNREF, "obj=%p", obj);
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if (lastRef) {
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PROBE(OBJECT_DISPOSE, "obj=%p", obj);
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if (obj->klass->dispose)
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obj->klass->dispose(obj);
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/* Clear & poison object */
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memset(obj, 0, obj->klass->objectSize);
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obj->magic = 0xDEADBEEF;
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obj->klass = (void*)0xDEADBEEF;
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VIR_FREE(obj);
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}
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return !lastRef;
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}
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/**
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* virObjectRef:
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* @anyobj: any instance of virObjectPtr
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*
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* Increment the reference count on @anyobj and return
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* the same pointer
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*
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* Returns @anyobj
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*/
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void *virObjectRef(void *anyobj)
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{
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virObjectPtr obj = anyobj;
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if (!obj)
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return NULL;
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virAtomicIntInc(&obj->refs);
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PROBE(OBJECT_REF, "obj=%p", obj);
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return anyobj;
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}
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/**
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* virObjectIsClass:
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* @anyobj: any instance of virObjectPtr
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* @klass: the class to check
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*
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* Checks whether @anyobj is an instance of
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* @klass
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*
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* Returns true if @anyobj is an instance of @klass
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*/
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bool virObjectIsClass(void *anyobj,
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virClassPtr klass)
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{
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virObjectPtr obj = anyobj;
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return obj != NULL && (obj->magic == klass->magic) && (obj->klass == klass);
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}
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/**
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* virClassName:
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* @klass: the object class
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*
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* Returns the name of @klass
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*/
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const char *virClassName(virClassPtr klass)
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{
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return klass->name;
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}
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/**
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* virObjectFreeCallback:
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* @opaque: a pointer to a virObject instance
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*
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* Provides identical functionality to virObjectUnref,
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* but with the signature matching the virFreeCallback
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* typedef.
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*/
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void virObjectFreeCallback(void *opaque)
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{
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virObjectUnref(opaque);
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}
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60
src/util/virobject.h
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60
src/util/virobject.h
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@ -0,0 +1,60 @@
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/*
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* virobject.h: libvirt reference counted object
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*
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* Copyright (C) 2012 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; If not, see
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* <http://www.gnu.org/licenses/>.
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*
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*/
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#ifndef __VIR_OBJECT_H__
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# define __VIR_OBJECT_H__
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# include "internal.h"
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typedef struct _virClass virClass;
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typedef virClass *virClassPtr;
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typedef struct _virObject virObject;
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typedef virObject *virObjectPtr;
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typedef void (*virObjectDisposeCallback)(void *obj);
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struct _virObject {
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unsigned int magic;
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int refs;
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virClassPtr klass;
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};
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virClassPtr virClassNew(const char *name,
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size_t objectSize,
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virObjectDisposeCallback dispose)
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ATTRIBUTE_NONNULL(1);
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const char *virClassName(virClassPtr klass)
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ATTRIBUTE_NONNULL(1);
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void *virObjectNew(virClassPtr klass)
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ATTRIBUTE_NONNULL(1);
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bool virObjectUnref(void *obj);
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void *virObjectRef(void *obj);
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bool virObjectIsClass(void *obj,
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virClassPtr klass)
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ATTRIBUTE_NONNULL(2);
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void virObjectFreeCallback(void *opaque);
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#endif /* __VIR_OBJECT_H */
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