Add operations to qlist to allow it to be used as a stack

This makes lists no longer invariant. It's a very useful bit of functionality
though.

To deal with the fact that lists are no longer invariant, introduce a deep
copy mechanism for lists.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

qlist.c

@@ -37,6 +37,23 @@ QList *qlist_new(void)
     return qlist;
 }
 
+static void qlist_copy_elem(QObject *obj, void *opaque)
+{
+    QList *dst = opaque;
+
+    qobject_incref(obj);
+    qlist_append_obj(dst, obj);
+}
+
+QList *qlist_copy(QList *src)
+{
+    QList *dst = qlist_new();
+
+    qlist_iter(src, qlist_copy_elem, dst);
+
+    return dst;
+}
+
 /**
  * qlist_append_obj(): Append an QObject into QList
  *
@@ -67,6 +84,45 @@ void qlist_iter(const QList *qlist,
         iter(entry->value, opaque);
 }
 
+QObject *qlist_pop(QList *qlist)
+{
+    QListEntry *entry;
+    QObject *ret;
+
+    if (qlist == NULL || QTAILQ_EMPTY(&qlist->head)) {
+        return NULL;
+    }
+
+    entry = QTAILQ_FIRST(&qlist->head);
+    QTAILQ_REMOVE(&qlist->head, entry, next);
+
+    ret = entry->value;
+    qemu_free(entry);
+
+    return ret;
+}
+
+QObject *qlist_peek(QList *qlist)
+{
+    QListEntry *entry;
+    QObject *ret;
+
+    if (qlist == NULL || QTAILQ_EMPTY(&qlist->head)) {
+        return NULL;
+    }
+
+    entry = QTAILQ_FIRST(&qlist->head);
+
+    ret = entry->value;
+
+    return ret;
+}
+
+int qlist_empty(const QList *qlist)
+{
+    return QTAILQ_EMPTY(&qlist->head);
+}
+
 /**
  * qobject_to_qlist(): Convert a QObject into a QList
  */

qlist.h

@@ -30,9 +30,13 @@ typedef struct QList {
         qlist_append_obj(qlist, QOBJECT(obj))
 
 QList *qlist_new(void);
+QList *qlist_copy(QList *src);
 void qlist_append_obj(QList *qlist, QObject *obj);
 void qlist_iter(const QList *qlist,
                 void (*iter)(QObject *obj, void *opaque), void *opaque);
+QObject *qlist_pop(QList *qlist);
+QObject *qlist_peek(QList *qlist);
+int qlist_empty(const QList *qlist);
 QList *qobject_to_qlist(const QObject *obj);
 
 #endif /* QLIST_H */