1 /*
2  * A hash table (hashtab) maintains associations between
3  * key values and datum values.  The type of the key values
4  * and the type of the datum values is arbitrary.  The
5  * functions for hash computation and key comparison are
6  * provided by the creator of the table.
7  *
8  * Author : Stephen Smalley, <sds@epoch.ncsc.mil>
9  */
10 #ifndef _SS_HASHTAB_H_
11 #define _SS_HASHTAB_H_
12 
13 #define HASHTAB_MAX_NODES    0xffffffff
14 
15 struct hashtab_node {
16     void *key;
17     void *datum;
18     struct hashtab_node *next;
19 };
20 
21 struct hashtab {
22     struct hashtab_node **htable;    /* hash table */
23     u32 size;            /* number of slots in hash table */
24     u32 nel;            /* number of elements in hash table */
25     u32 (*hash_value)(struct hashtab *h, const void *key);
26                     /* hash function */
27     int (*keycmp)(struct hashtab *h, const void *key1, const void *key2);
28                     /* key comparison function */
29 };
30 
31 struct hashtab_info {
32     u32 slots_used;
33     u32 max_chain_len;
34 };
35 
36 /*
37  * Creates a new hash table with the specified characteristics.
38  *
39  * Returns NULL if insufficent space is available or
40  * the new hash table otherwise.
41  */
42 struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h,
43 						 const void *key),
44             int (*keycmp)(struct hashtab *h, const void *key1,
45 			  const void *key2), u32 size);
46 
47 /*
48  * Inserts the specified (key, datum) pair into the specified hash table.
49  *
50  * Returns -ENOMEM on memory allocation error,
51  * -EEXIST if there is already an entry with the same key,
52  * -EINVAL for general errors or
53  * 0 otherwise.
54  */
55 int hashtab_insert(struct hashtab *h, void *k, void *d);
56 
57 /*
58  * Searches for the entry with the specified key in the hash table.
59  *
60  * Returns NULL if no entry has the specified key or
61  * the datum of the entry otherwise.
62  */
63 void *hashtab_search(struct hashtab *h, const void *k);
64 
65 /*
66  * Destroys the specified hash table.
67  */
68 void hashtab_destroy(struct hashtab *h);
69 
70 /*
71  * Applies the specified apply function to (key,datum,args)
72  * for each entry in the specified hash table.
73  *
74  * The order in which the function is applied to the entries
75  * is dependent upon the internal structure of the hash table.
76  *
77  * If apply returns a non-zero status, then hashtab_map will cease
78  * iterating through the hash table and will propagate the error
79  * return to its caller.
80  */
81 int hashtab_map(struct hashtab *h,
82                         int (*apply)(void *k, void *d, void *args), void *args);
83 
84 /* Fill info with some hash table statistics */
85 void hashtab_stat(struct hashtab *h, struct hashtab_info *info);
86 
87 #endif    /* _SS_HASHTAB_H */
88