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diff --git a/kern/rdxtree.h b/kern/rdxtree.h
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+/*
+ * Copyright (c) 2011, 2013 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *
+ * Radix tree.
+ *
+ * In addition to the standard insertion operation, this implementation can
+ * allocate keys for the caller at insertion time. It also allows lookups to
+ * occur concurrently with updates through the use of lockless synchronization
+ * (see the llsync module).
+ */
+
+#ifndef _KERN_RDXTREE_H
+#define _KERN_RDXTREE_H
+
+#include <kern/stddef.h>
+#include <kern/rdxtree_i.h>
+
+/*
+ * Radix tree.
+ */
+struct rdxtree;
+
+/*
+ * Radix tree iterator.
+ */
+struct rdxtree_iter;
+
+/*
+ * Static tree initializer.
+ */
+#define RDXTREE_INITIALIZER { 0, NULL }
+
+/*
+ * Initialize a tree.
+ */
+static inline void
+rdxtree_init(struct rdxtree *tree)
+{
+    tree->height = 0;
+    tree->root = NULL;
+}
+
+/*
+ * Insert a pointer in a tree.
+ *
+ * The ptr parameter must not be null.
+ */
+static inline int
+rdxtree_insert(struct rdxtree *tree, unsigned long key, void *ptr)
+{
+    return rdxtree_insert_common(tree, key, ptr, NULL);
+}
+
+/*
+ * Insert a pointer in a tree and obtain its slot.
+ *
+ * The ptr and slotp parameters must not be null. If successful, the slot of
+ * the newly inserted pointer is stored at the address pointed to by the slotp
+ * parameter.
+ */
+static inline int
+rdxtree_insert_slot(struct rdxtree *tree, unsigned long key, void *ptr,
+                    void ***slotp)
+{
+    return rdxtree_insert_common(tree, key, ptr, slotp);
+}
+
+/*
+ * Insert a pointer in a tree, for which a new key is allocated.
+ *
+ * The ptr and keyp parameters must not be null. The newly allocated key is
+ * stored at the address pointed to by the keyp parameter.
+ */
+static inline int
+rdxtree_insert_alloc(struct rdxtree *tree, void *ptr, unsigned long *keyp)
+{
+    return rdxtree_insert_alloc_common(tree, ptr, keyp, NULL);
+}
+
+/*
+ * Insert a pointer in a tree, for which a new key is allocated, and obtain
+ * its slot.
+ *
+ * The ptr, keyp and slotp parameters must not be null. The newly allocated
+ * key is stored at the address pointed to by the keyp parameter while the
+ * slot of the inserted pointer is stored at the address pointed to by the
+ * slotp parameter.
+ */
+static inline int
+rdxtree_insert_alloc_slot(struct rdxtree *tree, void *ptr,
+                          unsigned long *keyp, void ***slotp)
+{
+    return rdxtree_insert_alloc_common(tree, ptr, keyp, slotp);
+}
+
+/*
+ * Remove a pointer from a tree.
+ *
+ * The matching pointer is returned if successful, null otherwise.
+ */
+void * rdxtree_remove(struct rdxtree *tree, unsigned long key);
+
+/*
+ * Look up a pointer in a tree.
+ *
+ * The matching pointer is returned if successful, null otherwise.
+ *
+ * This function can safely proceed while the tree is being concurrently
+ * updated through the use of lockless synchronization.
+ */
+static inline void *
+rdxtree_lookup(struct rdxtree *tree, unsigned long key)
+{
+    return rdxtree_lookup_common(tree, key, 0);
+}
+
+/*
+ * Look up a slot in a tree.
+ *
+ * A slot is a pointer to a contained pointer in a tree. It can be used as
+ * a placeholder for fast replacements to avoid multiple lookups on the same
+ * key.
+ *
+ * A slot for the matching pointer is returned if successful, null otherwise.
+ *
+ * Unlike rdxtree_lookup(), the caller must synchronize access to the tree,
+ * because otherwise, the slot might be made invalid by concurrent updates.
+ *
+ * See rdxtree_replace_slot().
+ */
+static inline void **
+rdxtree_lookup_slot(struct rdxtree *tree, unsigned long key)
+{
+    return rdxtree_lookup_common(tree, key, 1);
+}
+
+/*
+ * Replace a pointer in a tree.
+ *
+ * The ptr parameter must not be null. The previous pointer is returned.
+ *
+ * See rdxtree_lookup_slot().
+ */
+void * rdxtree_replace_slot(void **slot, void *ptr);
+
+/*
+ * Forge a loop to process all pointers of a tree.
+ */
+#define rdxtree_for_each(tree, iter, ptr)                           \
+for (rdxtree_iter_init(iter), ptr = rdxtree_iter_next(tree, iter);  \
+     ptr != NULL;                                                   \
+     ptr = rdxtree_iter_next(tree, iter))
+
+/*
+ * Remove all pointers from a tree.
+ *
+ * The common way to destroy a tree and its pointers is to loop over all
+ * the pointers using rdxtree_for_each(), freeing them, then call this
+ * function.
+ */
+void rdxtree_remove_all(struct rdxtree *tree);
+
+/*
+ * Initialize the rdxtree module.
+ */
+void rdxtree_setup(void);
+
+#endif /* _KERN_RDXTREE_H */