hashtab.h

Go to the documentation of this file.

/*
 * 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, <[email protected]>
 */
#ifndef _SS_HASHTAB_H_
#define _SS_HASHTAB_H_

#define HASHTAB_MAX_NODES   0xffffffff

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 */
    u32 (*hash_value)(struct hashtab *h, const void *key);
                    /* hash function */
    int (*keycmp)(struct hashtab *h, const void *key1, const void *key2);
                    /* key comparison function */
};

struct hashtab_info {
    u32 slots_used;
    u32 max_chain_len;
};

/*
 * Creates a new hash table with the specified characteristics.
 *
 * Returns NULL if insufficent space is available or
 * the new hash table otherwise.
 */
struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h, const void *key),
                   int (*keycmp)(struct hashtab *h, const void *key1, const void *key2),
                   u32 size);

/*
 * 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.
 */
int hashtab_insert(struct hashtab *h, void *k, void *d);

/*
 * 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.
 */
void *hashtab_search(struct hashtab *h, const void *k);

/*
 * 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);

/* Fill info with some hash table statistics */
void hashtab_stat(struct hashtab *h, struct hashtab_info *info);

#endif  /* _SS_HASHTAB_H */