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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996, 1997, 1998, 1999
* Sleepycat Software. All rights reserved.
*
* @(#)db_shash.h 11.2 (Sleepycat) 9/23/99
*/
/* Hash Headers */
typedef SH_TAILQ_HEAD(__hash_head) DB_HASHTAB;
/*
* HASHACCESS --
*
* Figure out to which bucket an item belongs and lock that bucket,
* returning the bucket index.
*
* synch: beginning of the array of mutexes that protect the table.
* elt: the item on which we're computing the hash function.
* nelems: the number of buckets in the hash table.
* hash: the hash function that operates on elements of the type of elt
* ndx: the index into the hash/synch array that we're locking.
* fh: the locking file handle.
*/
#define HASHACCESS(synch, elt, nelems, hash, ndx, fh) do { \
ndx = hash(elt) % (nelems); \
MUTEX_LOCK(&synch[ndx], fh); \
} while(0)
/*
* HASHRELEASE --
*
* Release a hash bucket that we have locked.
*
* synch: beginning of the array of mutexes that protect the table.
* ndx: the index into the hash/synch array that we're locking.
* fh: the locking file handle.
*/
#define HASHRELEASE(synch, ndx, fh) do { \
MUTEX_UNLOCK(&synch[ndx]); \
} while(0)
/*
* HASHLOOKUP --
*
* Look up something in a shared memory hash table. The "elt" argument
* should be a key, and cmp_func must know how to compare a key to whatever
* structure it is that appears in the hash table. The comparison function
*
* begin: address of the beginning of the hash table.
* ndx: index into table for this item.
* type: the structure type of the elements that are linked in each bucket.
* field: the name of the field by which the "type" structures are linked.
* elt: the item for which we are searching in the hash table.
* res: the variable into which we'll store the element if we find it.
* cmp: called as: cmp(lookup_elt, table_elt).
*
* If the element is not in the hash table, this macro exits with res set
* to NULL.
*/
#define HASHLOOKUP(begin, ndx, type, field, elt, res, cmp) do { \
DB_HASHTAB *__bucket; \
\
__bucket = &begin[ndx]; \
for (res = SH_TAILQ_FIRST(__bucket, type); \
res != NULL; res = SH_TAILQ_NEXT(res, field, type)) \
if (cmp(elt, res)) \
break; \
} while(0)
/*
* HASHINSERT --
*
* Insert a new entry into the hash table. This assumes that you already
* have the bucket locked and that lookup has failed; don't call it if you
* haven't already called HASHLOOKUP. If you do, you could get duplicate
* entries.
*
* begin: the beginning address of the hash table.
* ndx: the index for this element.
* type: the structure type of the elements that are linked in each bucket.
* field: the name of the field by which the "type" structures are linked.
* elt: the item to be inserted.
*/
#define HASHINSERT(begin, ndx, type, field, elt) do { \
DB_HASHTAB *__bucket; \
\
__bucket = &begin[ndx]; \
SH_TAILQ_INSERT_HEAD(__bucket, elt, field, type); \
} while(0)
/*
* HASHREMOVE_EL --
* Given the object "obj" in the table, remove it.
*
* begin: address of the beginning of the hash table.
* ndx: index into hash table of where this element belongs.
* type: the structure type of the elements that are linked in each bucket.
* field: the name of the field by which the "type" structures are linked.
* obj: the object in the table that we with to delete.
*/
#define HASHREMOVE_EL(begin, ndx, type, field, obj) { \
DB_HASHTAB *__bucket; \
\
__bucket = &begin[ndx]; \
SH_TAILQ_REMOVE(__bucket, obj, field, type); \
}
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