add 2-3 tree header file

src/tree.h

+#ifndef TREE_H
+#define TREE_H
+
+typedef struct _TreeNode {
+	void * data[2];
+	struct _TreeNode * children[3];
+	struct _TreeNode * parent;
+} TreeNode;
+
+typedef struct _Tree {
+	TreeNode headNode;
+	TreeFreeDataFunc * freeFunc;
+	TreeCompareDataFunc * compareFunc;
+} Tree;
+
+typedef enum _TreeIteratorType {
+	PREORDER,
+	INORDER,
+	POSTORDER
+} TreeIteratorType;
+
+typedef struct _TreeIterator {
+	Data * data;
+	/* private data */
+	TreeIteratorType type;
+	TreeNode * currentNode;
+	int pos;
+} TreeIterator;
+
+typedef int TreeCompareDataFunc(void * left, void * right);
+
+typedef int TreeFreeDataFunc(void * data);
+
+Tree * newTree(TreeFreeDataFunc * freeFunc, TreeCompareDataFunc * compareFunc);
+
+void freeTree(Tree * tree);
+
+int insertInTree(Tree * tree, void * data);
+
+int deleteFromTree(Tree * tree, void * needle);
+
+void * findInTree(Tree * tree, void * needle);
+
+TreeIterator * newTreeIterator(Tree * tree, TreeIteratorType type);
+
+/* will return the same pointer passed in on success
+ * if NULL is returned, this indicates the end of tree
+ */
+TreeIterator * nextTreeIterator(TreeIterator * iter);
+
+#endif // TREE_H