[libvirt] [PATCH 04/13] Add a generic reference counted virObject type
Daniel P. Berrange
berrange at redhat.com
Wed Jul 11 13:35:44 UTC 2012
From: "Daniel P. Berrange" <berrange at redhat.com>
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 connklass = 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
When creating an instance of an object, one needs simply
pass the virClassPtr eg
virConnectPtr conn = virObjectNew(connklass);
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 at redhat.com>
---
src/Makefile.am | 1 +
src/libvirt_private.syms | 9 ++
src/libvirt_probes.d | 7 ++
src/util/virobject.c | 203 ++++++++++++++++++++++++++++++++++++++++++++++
src/util/virobject.h | 60 ++++++++++++++
5 files changed, 280 insertions(+)
create mode 100644 src/util/virobject.c
create mode 100644 src/util/virobject.h
diff --git a/src/Makefile.am b/src/Makefile.am
index 76d5eb7..2e596d5 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -84,6 +84,7 @@ UTIL_SOURCES = \
util/virauth.c util/virauth.h \
util/virauthconfig.c util/virauthconfig.h \
util/virfile.c util/virfile.h \
+ util/virobject.c util/virobject.h \
util/virnodesuspend.c util/virnodesuspend.h \
util/virpidfile.c util/virpidfile.h \
util/virtypedparam.c util/virtypedparam.h \
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index e22b133..1ff6735 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1492,6 +1492,15 @@ nodeSuspendForDuration;
virNodeSuspendGetTargetMask;
+# virobject.h
+virClassNew;
+virClassName;
+virObjectNew;
+virObjectRef;
+virObjectUnref;
+virObjectIsClass;
+
+
# virpidfile.h
virPidFileAcquire;
virPidFileAcquirePath;
diff --git a/src/libvirt_probes.d b/src/libvirt_probes.d
index 0dac8f3..ceb3caa 100644
--- a/src/libvirt_probes.d
+++ b/src/libvirt_probes.d
@@ -16,6 +16,13 @@ provider libvirt {
probe event_poll_run(int nfds, int timeout);
+ # file: src/util/virobject.c
+ # prefix: object
+ probe object_new(void *obj, const char *klassname);
+ probe object_ref(void *obj);
+ probe object_unref(void *obj);
+ probe object_dispose(void *obj);
+
# file: src/rpc/virnetsocket.c
# prefix: rpc
probe rpc_socket_new(void *sock, int refs, int fd, int errfd, pid_t pid, const char *localAddr, const char *remoteAddr);
diff --git a/src/util/virobject.c b/src/util/virobject.c
new file mode 100644
index 0000000..002196e
--- /dev/null
+++ b/src/util/virobject.c
@@ -0,0 +1,203 @@
+/*
+ * virobject.c: libvirt reference counted object
+ *
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+
+#include <config.h>
+
+#include "virobject.h"
+#include "threads.h"
+#include "memory.h"
+#include "viratomic.h"
+#include "virterror_internal.h"
+#include "logging.h"
+
+#define VIR_FROM_THIS VIR_FROM_NONE
+
+#define virObjectError(code, ...) \
+ virReportErrorHelper(VIR_FROM_THIS, code, __FILE__, \
+ __FUNCTION__, __LINE__, __VA_ARGS__)
+
+static unsigned int magicCounter = 0xCAFE0000;
+
+struct _virClass {
+ unsigned int magic;
+ const char *name;
+ size_t objectSize;
+
+ virObjectDisposeCallback dispose;
+};
+
+
+/**
+ * virClassNew:
+ * @name: the class name
+ * @objectSize: total size of the object struct
+ * @dispose: callback to run to free object fields
+ *
+ * Register a new object class with @name. The @objectSize
+ * should give the total size of the object struct, which
+ * is expected to have a 'virObject object;' field as its
+ * first member. When the last reference on the object is
+ * released, the @dispose callback will be invoked to free
+ * memory of the object fields
+ *
+ * Returns a new class instance
+ */
+virClassPtr virClassNew(const char *name,
+ size_t objectSize,
+ virObjectDisposeCallback dispose)
+{
+ virClassPtr klass;
+
+ if (VIR_ALLOC(klass) < 0)
+ return NULL;
+
+ if (!(klass->name = strdup(name)))
+ goto no_memory;
+ klass->magic = virAtomicIntAdd(&magicCounter, 1);
+ klass->objectSize = objectSize;
+ klass->dispose = dispose;
+
+ return klass;
+
+no_memory:
+ VIR_FREE(klass);
+ virReportOOMError();
+ return NULL;
+}
+
+
+/**
+ * virObjectNew:
+ * @klass: the klass of object to create
+ *
+ * Allocates a new object of type @klass. The returned
+ * object will be an instance of "virObjectPtr", which
+ * can be cast to the struct associated with @klass.
+ *
+ * The initial reference count of the object will be 1.
+ *
+ * Returns the new object
+ */
+void *virObjectNew(virClassPtr klass)
+{
+ virObjectPtr obj = NULL;
+ char *somebytes;
+
+ if (VIR_ALLOC_N(somebytes, klass->objectSize) < 0) {
+ virReportOOMError();
+ return NULL;
+ }
+ obj = (void*)somebytes;
+
+ obj->magic = klass->magic;
+ obj->klass = klass;
+ virAtomicIntSet(&obj->refs, 1);
+
+ PROBE(OBJECT_NEW, "obj=%p classname=%s", obj, obj->klass->name);
+
+ return obj;
+}
+
+
+/**
+ * virObjectUnref:
+ * @anyobj: any instance of virObjectPtr
+ *
+ * Decrement the reference count on @anyobj and if
+ * it hits zero, runs the "dispose" callback associated
+ * with the object class.
+ *
+ * Returns true if the remaining reference count is
+ * non-zero, false if the object was disposed of
+ */
+bool virObjectUnref(void *anyobj)
+{
+ virObjectPtr obj = anyobj;
+
+ if (!obj)
+ return false;
+
+ bool lastRef = virAtomicIntDecAndTest(&obj->refs);
+ PROBE(OBJECT_UNREF, "obj=%p", obj);
+ if (lastRef) {
+ PROBE(OBJECT_DISPOSE, "obj=%p", obj);
+ obj->klass->dispose(obj);
+
+ /* Clear & poison object */
+ memset(obj, 0, obj->klass->objectSize);
+ obj->magic = 0xDEADBEEF;
+ obj->klass = (void*)0xDEADBEEF;
+ VIR_FREE(obj);
+ }
+
+ return !lastRef;
+}
+
+
+/**
+ * virObjectRef:
+ * @anyobj: any instance of virObjectPtr
+ *
+ * Increment the reference count on @anyobj and return
+ * the same pointer
+ *
+ * Returns @anyobj
+ */
+void *virObjectRef(void *anyobj)
+{
+ virObjectPtr obj = anyobj;
+
+ if (!obj)
+ return NULL;
+ virAtomicIntInc(&obj->refs);
+ PROBE(OBJECT_REF, "obj=%p", obj);
+ return anyobj;
+}
+
+
+/**
+ * virObjectIsClass:
+ * @anyobj: any instance of virObjectPtr
+ * @klass: the class to check
+ *
+ * Checks whether @anyobj is an instance of
+ * @klass
+ *
+ * Returns true if @anyobj is an instance of @klass
+ */
+bool virObjectIsClass(void *anyobj,
+ virClassPtr klass)
+{
+ virObjectPtr obj = anyobj;
+ return obj != NULL && (obj->magic == klass->magic) && (obj->klass == klass);
+}
+
+
+/**
+ * virClassName:
+ * @klass: the object class
+ *
+ * Returns the name of @klass
+ */
+const char *virClassName(virClassPtr klass)
+{
+ return klass->name;
+}
diff --git a/src/util/virobject.h b/src/util/virobject.h
new file mode 100644
index 0000000..235fb24
--- /dev/null
+++ b/src/util/virobject.h
@@ -0,0 +1,60 @@
+/*
+ * virobject.h: libvirt reference counted object
+ *
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+
+#ifndef __VIR_OBJECT_H__
+# define __VIR_OBJECT_H__
+
+# include "internal.h"
+
+typedef struct _virClass virClass;
+typedef virClass *virClassPtr;
+
+typedef struct _virObject virObject;
+typedef virObject *virObjectPtr;
+
+typedef void (*virObjectDisposeCallback)(void *obj);
+
+struct _virObject {
+ unsigned int magic;
+ virClassPtr klass;
+ int refs;
+};
+
+virClassPtr virClassNew(const char *name,
+ size_t objectSize,
+ virObjectDisposeCallback dispose)
+ ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(3);
+
+const char *virClassName(virClassPtr klass)
+ ATTRIBUTE_NONNULL(1);
+
+void *virObjectNew(virClassPtr klass)
+ ATTRIBUTE_NONNULL(1);
+bool virObjectUnref(void *obj)
+ ATTRIBUTE_NONNULL(1);
+void *virObjectRef(void *obj)
+ ATTRIBUTE_NONNULL(1);
+
+bool virObjectIsClass(void *obj,
+ virClassPtr klass)
+ ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
+
+#endif /* __VIR_OBJECT_H */
--
1.7.10.2
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