1 files changed, 86 insertions, 0 deletions
diff --git a/libnetdata/avl/avl.h b/libnetdata/avl/avl.h
new file mode 100644
index 00000000..595d6ec6
--- /dev/null
+++ b/libnetdata/avl/avl.h
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+
+#ifndef _AVL_H
+#define _AVL_H 1
+
+#include "../libnetdata.h"
+
+/* Maximum AVL tree height. */
+#ifndef AVL_MAX_HEIGHT
+#define AVL_MAX_HEIGHT 92
+#endif
+
+#if defined(AVL_LOCK_WITH_RWLOCK)
+#define AVL_LOCK_INITIALIZER NETDATA_RWLOCK_INITIALIZER
+#else
+#define AVL_LOCK_INITIALIZER NETDATA_RW_SPINLOCK_INITIALIZER
+#endif
+
+/* Data structures */
+
+/* One element of the AVL tree */
+typedef struct avl_element {
+    struct avl_element *avl_link[2];  /* Subtrees. */
+    signed char avl_balance;       /* Balance factor. */
+} avl_t;
+
+typedef struct __attribute__((packed)) avl_element_packed {
+    struct avl_element *avl_link[2];  /* Subtrees. */
+    signed char avl_balance;       /* Balance factor. */
+} avl_t_packed;
+
+/* An AVL tree */
+typedef struct avl_tree_type {
+    avl_t *root;
+    int (*compar)(void *a, void *b);
+} avl_tree_type;
+
+typedef struct avl_tree_lock {
+    avl_tree_type avl_tree;
+
+#if defined(AVL_LOCK_WITH_RWLOCK)
+    netdata_rwlock_t rwlock;
+#else
+    RW_SPINLOCK rwlock;
+#endif
+} avl_tree_lock;
+
+/* Public methods */
+
+/* Insert element a into the AVL tree t
+ * returns the added element a, or a pointer the
+ * element that is equal to a (as returned by t->compar())
+ * a is linked directly to the tree, so it has to
+ * be properly allocated by the caller.
+ */
+avl_t *avl_insert_lock(avl_tree_lock *tree, avl_t *item) NEVERNULL WARNUNUSED;
+avl_t *avl_insert(avl_tree_type *tree, avl_t *item) NEVERNULL WARNUNUSED;
+
+/* Remove an element a from the AVL tree t
+ * returns a pointer to the removed element
+ * or NULL if an element equal to a is not found
+ * (equal as returned by t->compar())
+ */
+avl_t *avl_remove_lock(avl_tree_lock *tree, avl_t *item) WARNUNUSED;
+avl_t *avl_remove(avl_tree_type *tree, avl_t *item) WARNUNUSED;
+
+/* Find the element into the tree that equal to a
+ * (equal as returned by t->compar())
+ * returns NULL is no element is equal to a
+ */
+avl_t *avl_search_lock(avl_tree_lock *tree, avl_t *item);
+avl_t *avl_search(avl_tree_type *tree, avl_t *item);
+
+/* Initialize the avl_tree_lock
+ */
+void avl_init_lock(avl_tree_lock *tree, int (*compar)(void *a, void *b));
+void avl_init(avl_tree_type *tree, int (*compar)(void *a, void *b));
+
+/* Destroy the avl_tree_lock locks
+ */
+void avl_destroy_lock(avl_tree_lock *tree);
+
+int avl_traverse_lock(avl_tree_lock *tree, int (*callback)(void *entry, void *data), void *data);
+int avl_traverse(avl_tree_type *tree, int (*callback)(void *entry, void *data), void *data);
+
+#endif /* avl.h */