/* SPDX-License-Identifier: GPL-2.0 */
/*
 * A hash table (hashtab) maintains associations between
 * key values and datum values.  The type of the key values
 * and the type of the datum values is arbitrary.  The
 * functions for hash computation and key comparison are
 * provided by the creator of the table.
 *
 * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
 */

#ifndef _SS_HASHTAB_H_
#define _SS_HASHTAB_H_

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/sched.h>

#define HASHTAB_MAX_NODES U32_MAX

struct hashtab_key_params {
        u32 (*hash)(const void *key); /* hash func */
        int (*cmp)(const void *key1, const void *key2); /* comparison func */
};

struct hashtab_node {
        void *key;
        void *datum;
        struct hashtab_node *next;
};

struct hashtab {
        struct hashtab_node **htable; /* hash table */
        u32 size; /* number of slots in hash table */
        u32 nel; /* number of elements in hash table */
};

struct hashtab_info {
        u32 slots_used;
        u32 max_chain_len;
        u64 chain2_len_sum;
};

/*
 * Initializes a new hash table with the specified characteristics.
 *
 * Returns -ENOMEM if insufficient space is available or 0 otherwise.
 */
int hashtab_init(struct hashtab *h, u32 nel_hint);

int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst, void *key,
                     void *datum);

/*
 * Inserts the specified (key, datum) pair into the specified hash table.
 *
 * Returns -ENOMEM on memory allocation error,
 * -EEXIST if there is already an entry with the same key,
 * -EINVAL for general errors or
  0 otherwise.
 */
static inline int hashtab_insert(struct hashtab *h, void *key, void *datum,
                                 struct hashtab_key_params key_params)
{
        u32 hvalue;
        struct hashtab_node *prev, *cur;

        cond_resched();

        if (!h->size || h->nel == HASHTAB_MAX_NODES)
                return -EINVAL;

        hvalue = key_params.hash(key) & (h->size - 1);
        prev = NULL;
        cur = h->htable[hvalue];
        while (cur) {
                int cmp = key_params.cmp(key, cur->key);

                if (cmp == 0)
                        return -EEXIST;
                if (cmp < 0)
                        break;
                prev = cur;
                cur = cur->next;
        }

        return __hashtab_insert(h, prev ? &prev->next : &h->htable[hvalue], key,
                                datum);
}

/*
 * Searches for the entry with the specified key in the hash table.
 *
 * Returns NULL if no entry has the specified key or
 * the datum of the entry otherwise.
 */
static inline void *hashtab_search(struct hashtab *h, const void *key,
                                   struct hashtab_key_params key_params)
{
        u32 hvalue;
        struct hashtab_node *cur;

        if (!h->size)
                return NULL;

        hvalue = key_params.hash(key) & (h->size - 1);
        cur = h->htable[hvalue];
        while (cur) {
                int cmp = key_params.cmp(key, cur->key);

                if (cmp == 0)
                        return cur->datum;
                if (cmp < 0)
                        break;
                cur = cur->next;
        }
        return NULL;
}

/*
 * Destroys the specified hash table.
 */
void hashtab_destroy(struct hashtab *h);

/*
 * Applies the specified apply function to (key,datum,args)
 * for each entry in the specified hash table.
 *
 * The order in which the function is applied to the entries
 * is dependent upon the internal structure of the hash table.
 *
 * If apply returns a non-zero status, then hashtab_map will cease
 * iterating through the hash table and will propagate the error
 * return to its caller.
 */
int hashtab_map(struct hashtab *h, int (*apply)(void *k, void *d, void *args),
                void *args);

int hashtab_duplicate(struct hashtab *new, const struct hashtab *orig,
                      int (*copy)(struct hashtab_node *new,
                                  const struct hashtab_node *orig, void *args),
                      int (*destroy)(void *k, void *d, void *args), void *args);

#ifdef CONFIG_SECURITY_SELINUX_DEBUG
/* Fill info with some hash table statistics */
void hashtab_stat(struct hashtab *h, struct hashtab_info *info);
#else
static inline void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
{
        return;
}
#endif

#endif /* _SS_HASHTAB_H */