1 /*-
2  * See the file LICENSE for redistribution information.
3  *
4  * Copyright (c) 1996, 1997, 1998
5  *	Sleepycat Software.  All rights reserved.
6  *
7  *	@(#)db_shash.h	10.3 (Sleepycat) 4/10/98
8  */
9 
10 /* Hash Headers */
11 typedef	SH_TAILQ_HEAD(hash_head) DB_HASHTAB;
12 
13 /*
14  * HASHLOOKUP --
15  *
16  * Look up something in a shared memory hash table.  The "elt" argument
17  * should be a key, and cmp_func must know how to compare a key to whatever
18  * structure it is that appears in the hash table.  The comparison function
19  * cmp_func is called as: cmp_func(lookup_elt, table_elt);
20  * begin: address of the beginning of the hash table.
21  * type: the structure type of the elements that are linked in each bucket.
22  * field: the name of the field by which the "type" structures are linked.
23  * elt: the item for which we are searching in the hash table.
24  * result: the variable into which we'll store the element if we find it.
25  * nelems: the number of buckets in the hash table.
26  * hash_func: the hash function that operates on elements of the type of elt
27  * cmp_func: compare elements of the type of elt with those in the table (of
28  *	type "type").
29  *
30  * If the element is not in the hash table, this macro exits with result
31  * set to NULL.
32  */
33 #define	HASHLOOKUP(begin, type, field, elt, r, n, hash, cmp) do {	\
34 	DB_HASHTAB *__bucket;						\
35 	u_int32_t __ndx;						\
36 									\
37 	__ndx = hash(elt) % (n);					\
38 	__bucket = &begin[__ndx];					\
39 	for (r = SH_TAILQ_FIRST(__bucket, type);			\
40 	    r != NULL; r = SH_TAILQ_NEXT(r, field, type))		\
41 		if (cmp(elt, r))					\
42 			break;						\
43 } while(0)
44 
45 /*
46  * HASHINSERT --
47  *
48  * Insert a new entry into the hash table.  This assumes that lookup has
49  * failed; don't call it if you haven't already called HASHLOOKUP.
50  * begin: the beginning address of the hash table.
51  * type: the structure type of the elements that are linked in each bucket.
52  * field: the name of the field by which the "type" structures are linked.
53  * elt: the item to be inserted.
54  * nelems: the number of buckets in the hash table.
55  * hash_func: the hash function that operates on elements of the type of elt
56  */
57 #define	HASHINSERT(begin, type, field, elt, n, hash) do {		\
58 	u_int32_t __ndx;						\
59 	DB_HASHTAB *__bucket;						\
60 									\
61 	__ndx = hash(elt) % (n);					\
62 	__bucket = &begin[__ndx];					\
63 	SH_TAILQ_INSERT_HEAD(__bucket, elt, field, type);		\
64 } while(0)
65 
66 /*
67  * HASHREMOVE --
68  *	Remove the entry with a key == elt.
69  * begin: address of the beginning of the hash table.
70  * type: the structure type of the elements that are linked in each bucket.
71  * field: the name of the field by which the "type" structures are linked.
72  * elt: the item to be deleted.
73  * nelems: the number of buckets in the hash table.
74  * hash_func: the hash function that operates on elements of the type of elt
75  * cmp_func: compare elements of the type of elt with those in the table (of
76  *	type "type").
77  */
78 #define	HASHREMOVE(begin, type, field, elt, n, hash, cmp) {		\
79 	u_int32_t __ndx;						\
80 	DB_HASHTAB *__bucket;						\
81 	SH_TAILQ_ENTRY *__entp;						\
82 									\
83 	__ndx = hash(elt) % (n);					\
84 	__bucket = &begin[__ndx];					\
85 	HASHLOOKUP(begin, type, field, elt, __entp, n, hash, cmp);	\
86 	SH_TAILQ_REMOVE(__bucket, __entp, field, type);			\
87 }
88 
89 /*
90  * HASHREMOVE_EL --
91  *	Given the object "obj" in the table, remove it.
92  * begin: address of the beginning of the hash table.
93  * type: the structure type of the elements that are linked in each bucket.
94  * field: the name of the field by which the "type" structures are linked.
95  * obj: the object in the table that we with to delete.
96  * nelems: the number of buckets in the hash table.
97  * hash_func: the hash function that operates on elements of the type of elt
98  */
99 #define	HASHREMOVE_EL(begin, type, field, obj, n, hash) {		\
100 	u_int32_t __ndx;						\
101 	DB_HASHTAB *__bucket;						\
102 									\
103 	__ndx = hash(obj) % (n);					\
104 	__bucket = &begin[__ndx];					\
105 	SH_TAILQ_REMOVE(__bucket, obj, field, type);			\
106 }
107