diff --git a/src/core/ngx_rbtree.h b/src/core/ngx_rbtree.h
new file mode 100644
index 0000000..de6fef9
--- /dev/null
+++ b/src/core/ngx_rbtree.h
@@ -0,0 +1,36 @@
+#ifndef _NGX_RBTREE_H_INCLUDED_
+#define _NGX_RBTREE_H_INCLUDED_
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+
+
+typedef struct ngx_rbtree_s  ngx_rbtree_t;
+
+struct ngx_rbtree_s {
+   ngx_int_t       key;
+   ngx_rbtree_t   *left;
+   ngx_rbtree_t   *right;
+   ngx_rbtree_t   *parent;
+   void           *data;
+};
+
+extern ngx_rbtree_t  sentinel;
+
+
+void ngx_rbtree_insert(ngx_rbtree_t **root, ngx_rbtree_t *node);
+void ngx_rbtree_delete(ngx_rbtree_t **root, ngx_rbtree_t *node);
+
+
+ngx_inline static ngx_rbtree_t *ngx_rbtree_min(ngx_rbtree_t *root)
+{
+   while (root->left != &sentinel) {
+       root = root->left;
+   }
+
+   return root;
+}
+
+
+#endif /* _NGX_RBTREE_H_INCLUDED_ */