Config nodes: added the ability to clear out node values or create empty leaf nodes

Src/Util/NewConfig.cpp

@@ -7,7 +7,7 @@
  *
  * A hierarchical data structure supporting arbitrary nesting. Each node
  * (Config::Node) has a key and either a value or children (in fact, it may
- * have both, but this rarely makes semantic sense and so the config tree 
+ * have both, but this rarely makes semantic sense and so the config tree
  * builders take care not to allow it).
  *
  * Nesting is denoted with the '/' separator. For example:
@@ -20,10 +20,10 @@
  * [1] accesses the value of the node (more on this below). [2] accesses the
  * a child node with key "foo". [3] accesses the value of the child node "foo".
  * [4] accesses child "bar" of child "foo", and so forth.
- * 
+ *
  * Similar to map semantics, the operator [] never fails. If the node does not
  * exist, it creates a dummy "missing" node that is retained as a hidden child.
- * This node will have an empty value, which cannot be accessed, except using 
+ * This node will have an empty value, which cannot be accessed, except using
  * the ValueAsDefault<> method. This scheme exists to simplify lookup code for
  * keys known at compile time, the logic being that any "missing" key should
  * could just as well have been there in the first place, thus making the added
@@ -39,7 +39,7 @@
  *
  * Nodes at the same nesting level (siblings) are strung together in a
  * linked list. Parents also maintain pointers to the first and last of their
- * children (for order-preserving iteration) as well as a map for direct 
+ * children (for order-preserving iteration) as well as a map for direct
  * lookup by key.
  *
  * Keys may be reused at a given level. Key-value pairs will have their order
@@ -80,7 +80,7 @@
  *
  * Conversions as supported but are implemented via serialization and de-
  * serialization using sstream. Most "sane" conversions will work as expected.
- * When a conversion to T is desired, or if the stored value type is not 
+ * When a conversion to T is desired, or if the stored value type is not
  * precisely known, use:
  *
  *    node.ValueAs<T>()
@@ -103,7 +103,7 @@
  *  - Section nodes have their key set to the section name and value empty.
  *    They are the only nodes that can have children (i.e., IsLeaf() == false,
  *    HasChildren() == true).
- *  - Top-level node in the tree is the global section, and its key is 
+ *  - Top-level node in the tree is the global section, and its key is
  *    "Global".
  *  - Only the global section (top-level section) may have child nodes that are
  *    sections. The config tree can therefore only be up to 2 levels deep: the
@@ -133,7 +133,7 @@
  *    [ Section4, , Section5 ]
  *    SettingX = bar
  *
- * In this example, SettingX will be set to "foo" in Section1, Section2, and 
+ * In this example, SettingX will be set to "foo" in Section1, Section2, and
  * Section3. It will be set to "bar" in Section4, Section5, and the "Global"
  * section because of the unnamed element.
  *
@@ -147,6 +147,7 @@
  */
 
 #include "Util/NewConfig.h"
+#include <iostream>
 
 namespace Util
 {
@@ -251,8 +252,36 @@ namespace Util
       return os.str();
     }
 
+    // Adds an empty node (no value and where Empty() will return true)
+    Node &Node::AddEmpty(const std::string &path)
+    {
+      std::vector<std::string> keys = Util::Format(path).Split('/');
+      Node *parent = this;
+      ptr_t node;
+      for (size_t i = 0; i < keys.size(); i++)
+      {
+        bool leaf = i == keys.size() - 1;
+        auto it = parent->m_children.find(keys[i]);
+        if (leaf || it == parent->m_children.end())
+        {
+          // Create node at this level and leave it empty
+          node = std::make_shared<Node>(keys[i]);
+          // Attach node to parent and move down to next nesting level: last
+          // created node is new parent
+          AddChild(*parent, node);
+          parent = node.get();
+        }
+        else
+        {
+          // Descend deeper...
+          parent = it->second.get();
+        }
+      }
+      return *node;
+    }
+
     // Adds a newly-created node (which, among other things, implies no
-    // children) as a child 
+    // children) as a child
     void Node::AddChild(Node &parent, ptr_t &node)
     {
       if (!parent.m_last_child)
@@ -264,7 +293,7 @@ namespace Util
       {
         parent.m_last_child->m_next_sibling = node;
         parent.m_last_child = node;
-      }    
+      }
       parent.m_children[node->m_key] = node;
     }
 
@@ -290,7 +319,7 @@ namespace Util
       m_last_child.swap(rhs.m_last_child);
       m_children.swap(rhs.m_children);
      const_cast<std::string *>(&m_key)->swap(*const_cast<std::string *>(&rhs.m_key));
-      m_value.swap(rhs.m_value); 
+      m_value.swap(rhs.m_value);
     }
 
     Node &Node::operator=(const Node &rhs)
@@ -340,5 +369,20 @@ namespace Util
     {
       //std::cout << ">>> Destroyed " << m_key << " (" << this << ")" << std::endl;
     }
+
+    void PrintConfigTree(const Node &config, int indent_level, int tab_stops)
+    {
+      std::fill_n(std::ostream_iterator<char>(std::cout), tab_stops * indent_level, ' ');
+      std::cout << config.Key();
+      if (config.Exists())
+      {
+        std::cout << " = " << config.ValueAs<std::string>();
+      }
+      std::cout << std::endl;
+      for (const Node &child: config)
+      {
+        PrintConfigTree(child, indent_level + 1, tab_stops);
+      }
+    }
   } // Config
 } // Util

Src/Util/NewConfig.h

@@ -36,6 +36,7 @@ namespace Util
 
       void CheckEmptyOrMissing() const;
       const Node &MissingNode(const std::string &key) const;
+      Node &AddEmpty(const std::string &path);
       void AddChild(Node &parent, ptr_t &node);
       void DeepCopy(const Node &that);
       void Swap(Node &rhs);
@@ -168,6 +169,11 @@ namespace Util
         return m_value;
       }
 
+      inline void Clear()
+      {
+        m_value = nullptr;
+      }
+
       inline void SetValue(const std::shared_ptr<GenericValue> &value)
       {
         m_value = value;
@@ -222,32 +228,9 @@ namespace Util
       template <typename T>
       Node &Add(const std::string &path, const T &value)
       {
-        std::vector<std::string> keys = Util::Format(path).Split('/');
-        Node *parent = this;
-        ptr_t node;
-        for (size_t i = 0; i < keys.size(); i++)
-        {
-          bool leaf = i == keys.size() - 1;
-          auto it = parent->m_children.find(keys[i]);
-          if (leaf || it == parent->m_children.end())
-          {
-            // Create node at this level
-            node = std::make_shared<Node>(keys[i]);
-            // The leaf node gets the value
-            if (leaf)
-              node->SetValue(value);
-            // Attach node to parent and move down to next nesting level: last
-            // created node is new parent
-            AddChild(*parent, node);
-            parent = node.get();
-          }
-          else
-          {
-            // Descend deeper...
-            parent = it->second.get();
-          }
-        }
-        return *node;
+        Node &new_leaf_node = AddEmpty(path);
+        new_leaf_node.SetValue(value);
+        return new_leaf_node;
       }
 
       Node &Add(const std::string &path)
@@ -266,6 +249,19 @@ namespace Util
           Add(key, value);
       }
 
+      void SetEmpty(const std::string &key)
+      {
+        Node *node = TryGet(key);
+        if (node)
+        {
+          node->Clear();
+        }
+        else
+        {
+          AddEmpty(key);
+        }
+      }
+
       // True if value is empty (does not exist)
       inline bool Empty() const
       {
@@ -312,6 +308,8 @@ namespace Util
       Node(Node&& that) noexcept;
       ~Node();
     };
+
+    void PrintConfigTree(const Node &config, int indent_level = 0, int tab_stops = 2);
   } // Config
 } // Util