Add support for generic notifier lists

Notifiers are data-less callbacks and a notifier list is a list of registered
notifiers that all are interested in a particular event.

We'll use this in a few patches to implement mouse change notification.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
---
v1 -> v2
 - Do not do memory allocations by placing list nodes in notifier

Makefile.objs

@@ -104,6 +104,7 @@ common-obj-$(CONFIG_VNC_TLS) += vnc-tls.o vnc-auth-vencrypt.o
 common-obj-$(CONFIG_VNC_SASL) += vnc-auth-sasl.o
 common-obj-$(CONFIG_COCOA) += cocoa.o
 common-obj-$(CONFIG_IOTHREAD) += qemu-thread.o
+common-obj-y += notify.o
 
 slirp-obj-y = cksum.o if.o ip_icmp.o ip_input.o ip_output.o
 slirp-obj-y += slirp.o mbuf.o misc.o sbuf.o socket.o tcp_input.o tcp_output.o

notify.c

+/*
+ * Notifier lists
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include "notify.h"
+
+void notifier_list_init(NotifierList *list)
+{
+    QTAILQ_INIT(&list->notifiers);
+}
+
+void notifier_list_add(NotifierList *list, Notifier *notifier)
+{
+    QTAILQ_INSERT_HEAD(&list->notifiers, notifier, node);
+}
+
+void notifier_list_remove(NotifierList *list, Notifier *notifier)
+{
+    QTAILQ_REMOVE(&list->notifiers, notifier, node);
+}
+
+void notifier_list_notify(NotifierList *list)
+{
+    Notifier *notifier, *next;
+
+    QTAILQ_FOREACH_SAFE(notifier, &list->notifiers, node, next) {
+        notifier->notify(notifier);
+    }
+}

notify.h

+/*
+ * Notifier lists
+ *
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef QEMU_NOTIFY_H
+#define QEMU_NOTIFY_H
+
+#include "qemu-queue.h"
+
+typedef struct Notifier Notifier;
+
+struct Notifier
+{
+    void (*notify)(Notifier *notifier);
+    QTAILQ_ENTRY(Notifier) node;
+};
+
+typedef struct NotifierList
+{
+    QTAILQ_HEAD(, Notifier) notifiers;
+} NotifierList;
+
+#define NOTIFIER_LIST_INITIALIZER(head) \
+    { QTAILQ_HEAD_INITIALIZER((head).notifiers) }
+
+void notifier_list_init(NotifierList *list);
+
+void notifier_list_add(NotifierList *list, Notifier *notifier);
+
+void notifier_list_remove(NotifierList *list, Notifier *notifier);
+
+void notifier_list_notify(NotifierList *list);
+
+#endif