x15/kern/rdxtree.h

/*
 * Copyright (c) 2011-2018 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/>.
 *
 * Upstream site with license notes :
 * http://git.sceen.net/rbraun/librbraun.git/
 *
 *
 * 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 using RCU.
 */

#ifndef KERN_RDXTREE_H
#define KERN_RDXTREE_H

#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#include <kern/init.h>
#include <kern/rcu.h>

typedef uint64_t rdxtree_key_t;

// Radix tree initialization flags.
#define RDXTREE_KEY_ALLOC   0x1   // Enable key allocation.

// Static tree initializer.
#define RDXTREE_INITIALIZER   { 0, NULL }

// Radix tree.
struct rdxtree
{
  uint16_t height;
  uint16_t flags;
  void *root;
};

/*
 * Radix tree iterator.
 *
 * The node member refers to the node containing the current pointer, if any.
 * The key member refers to the current pointer, and is valid if and only if
 * rdxtree_walk() has been called at least once on the iterator.
 */
struct rdxtree_iter
{
  void *node;
  rdxtree_key_t key;
};

// Initialize an iterator.
static inline void
rdxtree_iter_init (struct rdxtree_iter *iter)
{
  iter->node = NULL;
  iter->key = (rdxtree_key_t)-1;
}

int rdxtree_insert_common (struct rdxtree *tree, rdxtree_key_t key,
                           void *ptr, void ***slotp);

int rdxtree_insert_alloc_common (struct rdxtree *tree, void *ptr,
                                 rdxtree_key_t *keyp, void ***slotp);

void* rdxtree_lookup_common (const struct rdxtree *tree, rdxtree_key_t key,
                             bool get_slot);

void* rdxtree_walk (struct rdxtree *tree, struct rdxtree_iter *iter);

// Initialize a tree.
static inline void
rdxtree_init (struct rdxtree *tree, unsigned short flags)
{
  assert ((flags & ~RDXTREE_KEY_ALLOC) == 0);

  tree->height = 0;
  tree->flags = flags;
  tree->root = NULL;
}

/*
 * Insert a pointer in a tree.
 *
 * The ptr parameter must not be NULL.
 */
static inline int
rdxtree_insert (struct rdxtree *tree, rdxtree_key_t 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, rdxtree_key_t 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, rdxtree_key_t *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,
                           rdxtree_key_t *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, rdxtree_key_t key);

/*
 * Look up a pointer in a tree.
 *
 * The matching pointer is returned if successful, NULL otherwise.
 */
static inline void*
rdxtree_lookup (const struct rdxtree *tree, rdxtree_key_t key)
{
  return (rdxtree_lookup_common (tree, key, false));
}

/*
 * Look up a slot in a tree.
 *
 * A slot is a pointer to a stored 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.
 *
 * See rdxtree_replace_slot().
 */
static inline void**
rdxtree_lookup_slot (const struct rdxtree *tree, rdxtree_key_t key)
{
  return (rdxtree_lookup_common (tree, key, true));
}

static inline void*
rdxtree_load_slot (void **slot)
{
  return (rcu_load (slot));
}

/*
 * 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.
 *
 * It is not safe to modify a tree from such a loop.
 */
#define rdxtree_for_each(tree, iter, ptr)   \
  for (rdxtree_iter_init (iter), ptr = rdxtree_walk (tree, iter);   \
       ptr; ptr = rdxtree_walk (tree, iter))

// Return the key of the current pointer from an iterator.
static inline rdxtree_key_t
rdxtree_iter_key (const struct rdxtree_iter *iter)
{
  return (iter->key);
}

/*
 * 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);

/*
 * This init operation provides :
 *  - module fully initialized
 */
INIT_OP_DECLARE (rdxtree_setup);

#endif