diff -r 3f324ea53152 -r 21840975d541 src/cx/tree.h
--- a/src/cx/tree.h	Wed Feb 14 22:32:13 2024 +0100
+++ b/src/cx/tree.h	Thu Feb 15 21:54:43 2024 +0100
@@ -47,6 +47,8 @@
  * Links a node to a (new) parent.
  *
  * If the node has already a parent, it is unlinked, first.
+ * If the parent has children already, the node is prepended to the list
+ * of all currently existing children.
  *
  * @param parent the parent node
  * @param node the node that shall be linked
@@ -94,22 +96,59 @@
  * contains the given \p data or if one of the children might contain
  * the data.
  *
+ * The function should use the returned integer to indicate how close the
+ * match is, where a negative number means that it does not match at all.
+ *
  * For example if a tree stores file path information, a node that is
  * describing a parent directory of a filename that is searched, shall
- * return 1 to indicate that a child node might contain the searched item.
- * On the other hand, if the node denotes a path that is not a prefix of
- * the searched filename, the function would return -1 to indicate that
- * the search does not need to be continued in that branch.
+ * return a positive number to indicate that a child node might contain the
+ * searched item. On the other hand, if the node denotes a path that is not a
+ * prefix of the searched filename, the function would return -1 to indicate
+ * that * the search does not need to be continued in that branch.
  *
  * @param node the node that is currently investigated
  * @param data the data that is searched for
  *
  * @return 0 if the node contains the data,
- * 1 if one of the children might contain the data,
- * -1 if neither the node, nor the children contains the data
+ * positive if one of the children might contain the data,
+ * negative if neither the node, nor the children contains the data
  */
 typedef int (*cx_tree_search_func)(void const *node, void const* data);
 
+
+/**
+ * Searches for data in a tree.
+ *
+ * When the data cannot be found exactly, the search function might return a
+ * closest result which might be a good starting point for adding a new node
+ * to the tree.
+ *
+ * Depending on the tree structure it is not necessarily guaranteed that the
+ * "closest" match is uniquely defined. This function will search for a node
+ * with the best match according to the \p sfunc (meaning: the return value of
+ * \p sfunc which is closest to zero). If that is also ambiguous, an arbitrary
+ * node matching the criteria is returned.
+ *
+ * @param root the root node
+ * @param data the data to search for
+ * @param sfunc the search function
+ * @param result where the result shall be stored
+ * @param loc_children offset in the node struct for the children linked list
+ * @param loc_next offset in the node struct for the next pointer
+ * @return zero if the node was found exactly, positive if a node was found that
+ * could contain the node (but doesn't right now), negative if the tree does not
+ * contain any node that might be related to the searched data
+ */
+__attribute__((__nonnull__))
+int cx_tree_search(
+        void const *root,
+        void const *data,
+        cx_tree_search_func sfunc,
+        void **result,
+        ptrdiff_t loc_children,
+        ptrdiff_t loc_next
+);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif