first re-commit.

nodes/znode_iterator.h

@@ -0,0 +1,124 @@
+/***************************************************************************
+
+    source::worx xtree
+    Copyright © 2024-2025 c.holzheuer
+    christoph.holzheuer@gmail.com
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+***************************************************************************/
+
+
+#ifndef znode_iterator_H
+#define znode_iterator_H
+
+#include <iterator>
+
+
+
+namespace znode
+{
+  template<class T>
+  struct znode_iterator
+  {
+    using iterator_category = std::forward_iterator_tag;
+    using difference_type   = std::ptrdiff_t;
+    using value_type        = T;
+    using pointer           = T*;  // or also value_type*
+    using reference         = T&;  // or also value_type&
+
+    znode_iterator()
+        : _root{},_node{}
+    {}
+
+    znode_iterator(pointer node)
+        : _root{node},_node{node}
+    {}
+
+    void set_node(pointer node)
+    {
+      _root = node;
+      _node = node;
+    }
+
+    pointer get() // const
+    {
+      return _node;
+    }
+
+    int level() // const
+    {
+      return _level;
+    }
+
+    pointer operator->()
+    {
+      return _node;
+    }
+
+    reference operator*()
+    {
+      return *(operator->());
+    }
+
+    operator bool() const
+    {
+      return _node != nullptr;
+    }
+
+    // Prefix increment
+    znode_iterator& operator++()
+    {
+      if( !_node )
+        return *this;
+
+      // depth first: do we have children?
+      if( _node->has_children() )
+      {
+        _node = _node->first_child().get();
+        _level++;
+        return *this;
+      }
+
+      // no children, so we take siblings
+      pointer tmp = _node->sibling().get();
+      pointer nxt = _node->parent().get();
+
+      while( !tmp && nxt )
+      {
+        tmp = nxt->sibling().get();
+        if( nxt == _root )
+        {
+          //qDebug() << " ouch ";
+          _node = nullptr;
+          return *this;
+        }
+        _level--;
+        nxt = nxt->parent().get();
+      }
+
+      _node = tmp;
+      return *this;
+
+    }
+
+    // Postfix increment
+    znode_iterator operator++(int) { znode_iterator tmp = *this; ++(*this); return tmp; }
+
+    friend bool operator== (const znode_iterator& a, const znode_iterator& b) { return a._node == b._node; };
+    friend bool operator!= (const znode_iterator& a, const znode_iterator& b) { return a._node != b._node; };
+
+  protected:
+
+    pointer _root{};
+    pointer _node{};
+    int     _level{0};
+
+  };
+
+}
+
+#endif // znode_iterator_H