virdomainmomentobjlist: introduce virDomainMomentIsAncestor

This new helper will allow us to check if we are able to delete external
snapshot after user did revert to non-leaf snapshot.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

src/conf/virdomainmomentobjlist.c

@@ -582,3 +582,20 @@ virDomainMomentFindLeaf(virDomainMomentObjList *list)
         return moment;
     return NULL;
 }
+
+
+/* Check if @moment is descendant of @ancestor. */
+bool
+virDomainMomentIsAncestor(virDomainMomentObj *moment,
+                          virDomainMomentObj *ancestor)
+{
+    if (moment == ancestor)
+        return false;
+
+    for (moment = moment->parent; moment; moment = moment->parent) {
+        if (moment == ancestor)
+            return true;
+    }
+
+    return false;
+}

src/conf/virdomainmomentobjlist.h

@@ -157,3 +157,7 @@ virDomainMomentCheckCycles(virDomainMomentObjList *list,
 
 virDomainMomentObj *
 virDomainMomentFindLeaf(virDomainMomentObjList *list);
+
+bool
+virDomainMomentIsAncestor(virDomainMomentObj *moment,
+                          virDomainMomentObj *ancestor);

src/libvirt_private.syms

@@ -1221,6 +1221,7 @@ virDomainMomentDropChildren;
 virDomainMomentDropParent;
 virDomainMomentForEachChild;
 virDomainMomentForEachDescendant;
+virDomainMomentIsAncestor;
 virDomainMomentMoveChildren;
 virDomainMomentObjFree;
 virDomainMomentObjNew;