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/**
* @file hash_table.h
* @author Radek Krejci <rkrejci@cesnet.cz>
* @author Michal Vasko <mvasko@cesnet.cz>
* @brief libyang hash table
*
* Copyright (c) 2015 - 2018 CESNET, z.s.p.o.
*
* This source code is licensed under BSD 3-Clause License (the "License").
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://opensource.org/licenses/BSD-3-Clause
*/
#ifndef LY_HASH_TABLE_H_
#define LY_HASH_TABLE_H_
#include <stdint.h>
#include <pthread.h>
#include "common.h"
#include "dict.h"
/**
* @brief Compute hash from (several) string(s).
*
* Usage:
* - init hash to 0
* - repeatedly call dict_hash_multi(), provide hash from the last call
* - call dict_hash_multi() with key_part = NULL to finish the hash
*/
uint32_t dict_hash_multi(uint32_t hash, const char *key_part, size_t len);
/**
* @brief Callback for checking hash table values equivalence.
*
* @param[in] val1_p Pointer to the first value.
* @param[in] val2_p Pointer to the second value.
* @param[in] mod Whether the operation modifies the hash table (insert or remove) or not (find).
* @param[in] cb_data User callback data.
* @return 0 on non-equal, non-zero on equal.
*/
typedef int (*values_equal_cb)(void *val1_p, void *val2_p, int mod, void *cb_data);
/** when the table is at least this much percent full, it is enlarged (double the size) */
#define LYHT_ENLARGE_PERCENTAGE 75
/** only once the table is this much percent full, enable shrinking */
#define LYHT_FIRST_SHRINK_PERCENTAGE 50
/** when the table is less than this much percent full, it is shrunk (half the size) */
#define LYHT_SHRINK_PERCENTAGE 25
/** never shrink beyond this size */
#define LYHT_MIN_SIZE 8
/**
* @brief Generic hash table record.
*/
struct ht_rec {
uint32_t hash; /* hash of the value */
int32_t hits; /* collision/overflow value count - 1 (a filled entry has 1 hit,
* special value -1 means a deleted record) */
unsigned char val[1]; /* arbitrary-size value */
} _PACKED;
/**
* @brief (Very) generic hash table.
*
* Hash table with open addressing collision resolution and
* linear probing of interval 1 (next free record is used).
* Removal is lazy (removed records are only marked), but
* if possible, they are fully emptied.
*/
struct hash_table {
uint32_t used; /* number of values stored in the hash table (filled records) */
uint32_t size; /* always holds 2^x == size (is power of 2), actually number of records allocated */
values_equal_cb val_equal; /* callback for testing value equivalence */
void *cb_data; /* user data callback arbitrary value */
uint16_t resize; /* 0 - resizing is disabled, *
* 1 - enlarging is enabled, *
* 2 - both shrinking and enlarging is enabled */
uint16_t rec_size; /* real size (in bytes) of one record for accessing recs array */
unsigned char *recs; /* pointer to the hash table itself (array of struct ht_rec) */
};
struct dict_rec {
char *value;
uint32_t refcount;
};
/**
* dictionary to store repeating strings
*/
struct dict_table {
struct hash_table *hash_tab;
pthread_mutex_t lock;
};
/**
* @brief Initiate content (non-zero values) of the dictionary
*
* @param[in] dict Dictionary table to initiate
*/
void lydict_init(struct dict_table *dict);
/**
* @brief Cleanup the dictionary content
*
* @param[in] dict Dictionary table to cleanup
*/
void lydict_clean(struct dict_table *dict);
/**
* @brief Create new hash table.
*
* @param[in] size Starting size of the hash table (capacity of values), must be power of 2.
* @param[in] val_size Size in bytes of value (the stored hashed item).
* @param[in] val_equal Callback for checking value equivalence.
* @param[in] cb_data User data always passed to \p val_equal.
* @param[in] resize Whether to resize the table on too few/too many records taken.
* @return Empty hash table, NULL on error.
*/
struct hash_table *lyht_new(uint32_t size, uint16_t val_size, values_equal_cb val_equal, void *cb_data, int resize);
/**
* @brief Set hash table value equal callback.
*
* @param[in] ht Hash table to modify.
* @param[in] new_val_equal New callback for checking value equivalence.
* @return Previous callback for checking value equivalence.
*/
values_equal_cb lyht_set_cb(struct hash_table *ht, values_equal_cb new_val_equal);
/**
* @brief Set hash table value equal callback user data.
*
* @param[in] ht Hash table to modify.
* @param[in] new_cb_data New data for values callback.
* @return Previous data for values callback.
*/
void *lyht_set_cb_data(struct hash_table *ht, void *new_cb_data);
/**
* @brief Make a duplicate of an existing hash table.
*
* @param[in] orig Original hash table to duplicate.
* @return Duplicated hash table \p orig, NULL on error.
*/
struct hash_table *lyht_dup(const struct hash_table *orig);
/**
* @brief Free a hash table.
*
* @param[in] ht Hash table to be freed.
*/
void lyht_free(struct hash_table *ht);
/**
* @brief Find a value in a hash table.
*
* @param[in] ht Hash table to search in.
* @param[in] val_p Pointer to the value to find.
* @param[in] hash Hash of the stored value.
* @param[out] match_p Pointer to the matching value, optional.
* @return 0 on success, 1 on not found.
*/
int lyht_find(struct hash_table *ht, void *val_p, uint32_t hash, void **match_p);
/**
* @brief Find another equal value in the hash table.
*
* @param[in] ht Hash table to search in.
* @param[in] val_p Pointer to the previously found value in \p ht.
* @param[in] hash Hash of the previously found value.
* @param[out] match_p Pointer to the matching value, optional.
* @return 0 on success, 1 on not found.
*/
int lyht_find_next(struct hash_table *ht, void *val_p, uint32_t hash, void **match_p);
/**
* @brief Insert a value into a hash table.
*
* @param[in] ht Hash table to insert into.
* @param[in] val_p Pointer to the value to insert. Be careful, if the values stored in the hash table
* are pointers, \p val_p must be a pointer to a pointer.
* @param[in] hash Hash of the stored value.
* @param[out] match_p Pointer to the stored value, optional
* @return 0 on success, 1 if already inserted, -1 on error.
*/
int lyht_insert(struct hash_table *ht, void *val_p, uint32_t hash, void **match_p);
/**
* @brief Insert a value into hash table. Same functionality as lyht_insert()
* but allows to specify a temporary val equal callback to be used in case the hash table
* will be resized after successful insertion.
*
* @param[in] ht Hash table to insert into.
* @param[in] val_p Pointer to the value to insert. Be careful, if the values stored in the hash table
* are pointers, \p val_p must be a pointer to a pointer.
* @param[in] hash Hash of the stored value.
* @param[in] resize_val_equal Val equal callback to use for resizing.
* @param[out] match_p Pointer to the stored value, optional
* @return LY_ERR return value (LY_EEXIST if the value is already present).
*/
LY_ERR lyht_insert_with_resize_cb(struct hash_table *ht, void *val_p, uint32_t hash, values_equal_cb resize_val_equal,
void **match_p);
/**
* @brief Remove a value from a hash table.
*
* @param[in] ht Hash table to remove from.
* @param[in] value_p Pointer to value to be removed. Be careful, if the values stored in the hash table
* are pointers, \p value_p must be a pointer to a pointer.
* @param[in] hash Hash of the stored value.
* @return LY_ERR return value (LY_EINVAL if value was not found).
*/
LY_ERR lyht_remove(struct hash_table *ht, void *val_p, uint32_t hash);
#endif /* LY_HASH_TABLE_H_ */