LXR linux/security/selinux/ss/hashtab.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * A hash table (hashtab) maintains associations between
   4 * key values and datum values.  The type of the key values
   5 * and the type of the datum values is arbitrary.  The
   6 * functions for hash computation and key comparison are
   7 * provided by the creator of the table.
   8 *
   9 * Author : Stephen Smalley, <sds@tycho.nsa.gov>
  10 */
  11#ifndef _SS_HASHTAB_H_
  12#define _SS_HASHTAB_H_
  13
  14#include <linux/types.h>
  15#include <linux/errno.h>
  16#include <linux/sched.h>
  17
  18#define HASHTAB_MAX_NODES       U32_MAX
  19
  20struct hashtab_key_params {
  21        u32 (*hash)(const void *key);   /* hash function */
  22        int (*cmp)(const void *key1, const void *key2);
  23                                        /* key comparison function */
  24};
  25
  26struct hashtab_node {
  27        void *key;
  28        void *datum;
  29        struct hashtab_node *next;
  30};
  31
  32struct hashtab {
  33        struct hashtab_node **htable;   /* hash table */
  34        u32 size;                       /* number of slots in hash table */
  35        u32 nel;                        /* number of elements in hash table */
  36};
  37
  38struct hashtab_info {
  39        u32 slots_used;
  40        u32 max_chain_len;
  41};
  42
  43/*
  44 * Initializes a new hash table with the specified characteristics.
  45 *
  46 * Returns -ENOMEM if insufficient space is available or 0 otherwise.
  47 */
  48int hashtab_init(struct hashtab *h, u32 nel_hint);
  49
  50int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
  51                     void *key, void *datum);
  52
  53/*
  54 * Inserts the specified (key, datum) pair into the specified hash table.
  55 *
  56 * Returns -ENOMEM on memory allocation error,
  57 * -EEXIST if there is already an entry with the same key,
  58 * -EINVAL for general errors or
  59  0 otherwise.
  60 */
  61static inline int hashtab_insert(struct hashtab *h, void *key, void *datum,
  62                                 struct hashtab_key_params key_params)
  63{
  64        u32 hvalue;
  65        struct hashtab_node *prev, *cur;
  66
  67        cond_resched();
  68
  69        if (!h->size || h->nel == HASHTAB_MAX_NODES)
  70                return -EINVAL;
  71
  72        hvalue = key_params.hash(key) & (h->size - 1);
  73        prev = NULL;
  74        cur = h->htable[hvalue];
  75        while (cur) {
  76                int cmp = key_params.cmp(key, cur->key);
  77
  78                if (cmp == 0)
  79                        return -EEXIST;
  80                if (cmp < 0)
  81                        break;
  82                prev = cur;
  83                cur = cur->next;
  84        }
  85
  86        return __hashtab_insert(h, prev ? &prev->next : &h->htable[hvalue],
  87                                key, datum);
  88}
  89
  90/*
  91 * Searches for the entry with the specified key in the hash table.
  92 *
  93 * Returns NULL if no entry has the specified key or
  94 * the datum of the entry otherwise.
  95 */
  96static inline void *hashtab_search(struct hashtab *h, const void *key,
  97                                   struct hashtab_key_params key_params)
  98{
  99        u32 hvalue;
 100        struct hashtab_node *cur;
 101
 102        if (!h->size)
 103                return NULL;
 104
 105        hvalue = key_params.hash(key) & (h->size - 1);
 106        cur = h->htable[hvalue];
 107        while (cur) {
 108                int cmp = key_params.cmp(key, cur->key);
 109
 110                if (cmp == 0)
 111                        return cur->datum;
 112                if (cmp < 0)
 113                        break;
 114                cur = cur->next;
 115        }
 116        return NULL;
 117}
 118
 119/*
 120 * Destroys the specified hash table.
 121 */
 122void hashtab_destroy(struct hashtab *h);
 123
 124/*
 125 * Applies the specified apply function to (key,datum,args)
 126 * for each entry in the specified hash table.
 127 *
 128 * The order in which the function is applied to the entries
 129 * is dependent upon the internal structure of the hash table.
 130 *
 131 * If apply returns a non-zero status, then hashtab_map will cease
 132 * iterating through the hash table and will propagate the error
 133 * return to its caller.
 134 */
 135int hashtab_map(struct hashtab *h,
 136                int (*apply)(void *k, void *d, void *args),
 137                void *args);
 138
 139int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
 140                int (*copy)(struct hashtab_node *new,
 141                        struct hashtab_node *orig, void *args),
 142                int (*destroy)(void *k, void *d, void *args),
 143                void *args);
 144
 145/* Fill info with some hash table statistics */
 146void hashtab_stat(struct hashtab *h, struct hashtab_info *info);
 147
 148#endif  /* _SS_HASHTAB_H */
 149