Fix creating invalid subscription tree on unsubscribe

Unsubscribing paths that didn't exist caused creation of null nodes, which subsequent use of the tree crashed on.

Fix creating invalid subscription tree on unsubscribe
Unsubscribing paths that didn't exist caused creation of null nodes, which subsequent use of the tree crashed on.
Wiebe Cazemier
1 parent 9cbd0be5
Showing 2 changed files with 28 additions and 9 deletions
subscriptionstore.cpp
subscriptionstore.h
@@ -61,6 +61,20 @@ void SubscriptionNode::removeSubscriber(const std::shared_ptr&lt;Session&gt; &amp;subscrib
     }
 }
  
+/**
+ * @brief SubscriptionNode::getChildren gets children or null pointer. Const, so doesn't default-create node for
+ *        non-existing children.
+ * @param subtopic
+ * @return
+ */
+SubscriptionNode *SubscriptionNode::getChildren(const std::string &subtopic) const
+{
+    auto it = children.find(subtopic);
+    if (it != children.end())
+        return it->second.get();
+    return nullptr;
+}
+
  
 SubscriptionStore::SubscriptionStore() :
     root("root"),
@@ -122,26 +136,25 @@ void SubscriptionStore::removeSubscription(std::shared_ptr&lt;Client&gt; &amp;client, cons
     RWLockGuard lock_guard(&subscriptionsRwlock);
     lock_guard.wrlock();
  
-    // TODO: because it's so similar to adding a subscription, make a function to retrieve the deepest node?
+    // This code looks like that for addSubscription(), but it's specifically different in that we don't want to default-create non-existing
+    // nodes. We need to abort when that happens.
     SubscriptionNode *deepestNode = &root;
     for(const std::string &subtopic : subtopics)
     {
-        std::unique_ptr<SubscriptionNode> *selectedChildren = nullptr;
+        SubscriptionNode *selectedChildren = nullptr;
  
         if (subtopic == "#")
-            selectedChildren = &deepestNode->childrenPound;
+            selectedChildren = deepestNode->childrenPound.get();
         else if (subtopic == "+")
-            selectedChildren = &deepestNode->childrenPlus;
+            selectedChildren = deepestNode->childrenPlus.get();
         else
-            selectedChildren = &deepestNode->children[subtopic];
-
-        std::unique_ptr<SubscriptionNode> &node = *selectedChildren;
+            selectedChildren = deepestNode->getChildren(subtopic);
  
-        if (!node)
+        if (!selectedChildren)
         {
             return;
         }
-        deepestNode = node.get();
+        deepestNode = selectedChildren;
     }
  
     assert(deepestNode);
@@ -237,6 +250,10 @@ void SubscriptionStore::publishRecursively(std::vector&lt;std::string&gt;::const_itera
         return;
     }
  
+    // Null nodes in the tree shouldn't happen at this point. It points to bugs elsewhere. However, I don't remember why I check the pointer
+    // inside the if-block above, instead of the start of the method.
+    assert(this_node != nullptr);
+
     if (this_node->children.empty() && !this_node->childrenPlus && !this_node->childrenPound)
         return;
  
@@ -64,6 +64,8 @@ public:
     std::unique_ptr<SubscriptionNode> childrenPlus;
     std::unique_ptr<SubscriptionNode> childrenPound;
  
+    SubscriptionNode *getChildren(const std::string &subtopic) const;
+
     int cleanSubscriptions();
 };