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diff --git a/src/livarot/AVL.h b/src/livarot/AVL.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/** @file
+ * TODO: insert short description here
+ *//*
+ * Authors: see git history
+ *
+ * Copyright (C) 2014 Authors
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+/*
+ *  AVL.h
+ *  nlivarot
+ *
+ *  Created by fred on Mon Jun 16 2003.
+ *
+ */
+
+#ifndef my_avl
+#define my_avl
+
+#include <cstdlib>
+#include "LivarotDefs.h"
+
+/*
+ * base class providing AVL tree functionnality, that is binary balanced tree
+ * there is no Find() function because the class only deal with topological info
+ * subclasses of this class have to implement a Find(), and most certainly to 
+ * override the Insert() function
+ */
+
+class AVLTree
+{
+public:
+    
+    AVLTree *elem[2];
+
+    // left most node (ie, with smallest key) in the subtree of this node
+    AVLTree *Leftmost();
+
+protected:    
+
+    AVLTree *child[2];
+
+    AVLTree();
+    virtual ~AVLTree();
+    
+    // constructor/destructor meant to be called for an array of AVLTree created by malloc
+    void MakeNew();
+    void MakeDelete();
+
+    // insertion of the present node in the tree
+    // insertType is the insertion type (defined in LivarotDefs.h: not_found, found_exact, found_on_left, etc)
+    // insertL is the node in the tree that is immediatly before the current one, NULL is the present node goes to the 
+    // leftmost position. if insertType == found_exact, insertL should be the node with ak key
+    // equal to that of the present node
+    int Insert(AVLTree * &racine, int insertType, AVLTree *insertL,
+               AVLTree * insertR, bool rebalance);
+
+    // called when this node is relocated to a new position in memory, to update pointers to him
+    void Relocate(AVLTree *to);
+
+    // removal of the present element racine is the tree's root; it's a reference because if the
+    // node is the root, removal of the node will change the root
+    // rebalance==true if rebalancing is needed
+    int Remove(AVLTree * &racine, bool rebalance = true);
+
+private:
+
+    AVLTree *parent;
+
+    int balance;
+
+    // insertion gruntwork.
+    int Insert(AVLTree * &racine, int insertType, AVLTree *insertL, AVLTree *insertR);
+
+    // rebalancing functions. both are recursive, but the depth of the trees we'll use should not be a problem
+    // this one is for rebalancing after insertions
+    int RestoreBalances(AVLTree *from, AVLTree * &racine);
+    // this one is for removals
+    int RestoreBalances(int diff, AVLTree * &racine);
+
+    // startNode is the node where the rebalancing starts; rebalancing then moves up the tree to the root
+    // diff is the change in "subtree height", as needed for the rebalancing
+    // racine is the reference to the root, since rebalancing can change it too
+    int Remove(AVLTree * &racine, AVLTree * &startNode, int &diff);
+    
+    void insertOn(Side s, AVLTree *of);
+    void insertBetween(AVLTree *l, AVLTree *r);
+    AVLTree *leaf(AVLTree *from, Side s);
+    AVLTree *leafFromParent(AVLTree *from, Side s);
+};
+
+#endif
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :