/* SPDX-License-Identifier: GPL-2.0 */
#ifndef BTREE_H
#define BTREE_H
#include <linux/kernel.h>
#include <linux/mempool.h>
/**
* DOC: B+Tree basics
*
* A B+Tree is a data structure for looking up arbitrary (currently allowing
* unsigned long, u32, u64 and 2 * u64) keys into pointers. The data structure
* is described at https://en.wikipedia.org/wiki/B-tree, we currently do not
* use binary search to find the key on lookups.
*
* Each B+Tree consists of a head, that contains bookkeeping information and
* a variable number (starting with zero) nodes. Each node contains the keys
* and pointers to sub-nodes, or, for leaf nodes, the keys and values for the
* tree entries.
*
* Each node in this implementation has the following layout:
* [key1, key2, ..., keyN] [val1, val2, ..., valN]
*
* Each key here is an array of unsigned longs, geo->no_longs in total. The
* number of keys and values (N) is geo->no_pairs.
*/
/**
* struct btree_head - btree head
*
* @node: the first node in the tree
* @mempool: mempool used for node allocations
* @height: current of the tree
*/
struct btree_head {
unsigned long *node;
mempool_t *mempool;
int height;
};
/* btree geometry */
struct btree_geo;
/**
* btree_alloc - allocate function for the mempool
* @gfp_mask: gfp mask for the allocation
* @pool_data: unused
*/
void *btree_alloc(gfp_t gfp_mask, void *pool_data);
/**
* btree_free - free function for the mempool
* @element: the element to free
* @pool_data: unused
*/
void btree_free(void *element, void *pool_data);
/**
* btree_init_mempool - initialise a btree with given mempool
*
* @head: the btree head to initialise
* @mempool: the mempool to use
*
* When this function is used, there is no need to destroy
* the mempool.
*/
void btree_init_mempool(struct btree_head *head, mempool_t *mempool);
/**
* btree_init - initialise a btree
*
* @head: the btree head to initialise
*
* This function allocates the memory pool that the
* btree needs. Returns zero or a negative error code
* (-%ENOMEM) when memory allocation fails.
*
*/
int __must_check btree_init(struct btree_head *head);
/**
* btree_destroy - destroy mempool
*
* @head: the btree head to destroy
*
* This function destroys the internal memory pool, use only
* when using btree_init(), not with btree_init_mempool().
*/
void btree_destroy(struct btree_head *head);
/**
* btree_lookup - look up a key in the btree
*
* @head: the btree to look in
* @geo: the btree geometry
* @key: the key to look up
*
* This function returns the value for the given key, or %NULL.
*/
void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
unsigned long *key);
/**
* btree_insert - insert an entry into the btree
*
* @head: the btree to add to
* @geo: the btree geometry
* @key: the key to add (must not already be present)
* @val: the value to add (must not be %NULL)
* @gfp: allocation flags for node allocations
*
* This function returns 0 if the item could be added, or an
* error code if it failed (may fail due to memory pressure).
*/
int __must_check btree_insert(struct btree_head *head, struct btree_geo *geo,
unsigned long *key, void *val, gfp_t gfp);
/**
* btree_update - update an entry in the btree
*
* @head: the btree to update
* @geo: the btree geometry
* @key: the key to update
* @val: the value to change it to (must not be %NULL)
*
* This function returns 0 if the update was successful, or
* -%ENOENT if the key could not be found.
*/
int btree_update(struct btree_head *head, struct btree_geo *geo,
unsigned long *key, void *val);
/**
* btree_remove - remove an entry from the btree
*
* @head: the btree to update
* @geo: the btree geometry
* @key: the key to remove
*
* This function returns the removed entry, or %NULL if the key
* could not be found.
*/
void *btree_remove(struct btree_head *head, struct btree_geo *geo,
unsigned long *key);
/**
* btree_merge - merge two btrees
*
* @target: the tree that gets all the entries
* @victim: the tree that gets merged into @target
* @geo: the btree geometry
* @gfp: allocation flags
*
* The two trees @target and @victim may not contain the same keys,
* that is a bug and triggers a BUG(). This function returns zero
* if the trees were merged successfully, and may return a failure
* when memory allocation fails, in which case both trees might have
* been partially merged, i.e. some entries have been moved from
* @victim to @target.
*/
int btree_merge(struct btree_head *target, struct btree_head *victim,
struct btree_geo *geo, gfp_t gfp);
/**
* btree_last - get last entry in btree
*
* @head: btree head
* @geo: btree geometry
* @key: last key
*
* Returns the last entry in the btree, and sets @key to the key
* of that entry; returns NULL if the tree is empty, in that case
* key is not changed.
*/
void *btree_last(struct btree_head *head, struct btree_geo *geo,
unsigned long *key);
/**
* btree_get_prev - get previous entry
*
* @head: btree head
* @geo: btree geometry
* @key: pointer to key
*
* The function returns the next item right before the value pointed to by
* @key, and updates @key with its key, or returns %NULL when there is no
* entry with a key smaller than the given key.
*/
void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
unsigned long *key);
/* internal use, use btree_visitor{l,32,64,128} */
size_t btree_visitor(struct btree_head *head, struct btree_geo *geo,
unsigned long opaque,
void (*func)(void *elem, unsigned long opaque,
unsigned long *key, size_t index,
void *func2),
void *func2);
/* internal use, use btree_grim_visitor{l,32,64,128} */
size_t btree_grim_visitor(struct btree_head *head, struct btree_geo *geo,
unsigned long opaque,
void (*func)(void *elem, unsigned long opaque,
unsigned long *key,
size_t index, void *func2),
void *func2);
#include <linux/btree-128.h>
extern struct btree_geo btree_geo32;
#define BTREE_TYPE_SUFFIX l
#define BTREE_TYPE_BITS BITS_PER_LONG
#define BTREE_TYPE_GEO &btree_geo32
#define BTREE_KEYTYPE unsigned long
#include <linux/btree-type.h>
#define btree_for_each_safel(head, key, val) \
for (val = btree_lastl(head, &key); \
val; \
val = btree_get_prevl(head, &key))
#define BTREE_TYPE_SUFFIX 32
#define BTREE_TYPE_BITS 32
#define BTREE_TYPE_GEO &btree_geo32
#define BTREE_KEYTYPE u32
#include <linux/btree-type.h>
#define btree_for_each_safe32(head, key, val) \
for (val = btree_last32(head, &key); \
val; \
val = btree_get_prev32(head, &key))
extern struct btree_geo btree_geo64;
#define BTREE_TYPE_SUFFIX 64
#define BTREE_TYPE_BITS 64
#define BTREE_TYPE_GEO &btree_geo64
#define BTREE_KEYTYPE u64
#include <linux/btree-type.h>
#define btree_for_each_safe64(head, key, val) \
for (val = btree_last64(head, &key); \
val; \
val = btree_get_prev64(head, &key))
#endif
Codebase Browser
linux