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/* -*-c-*-
* This file contains the hashing implementation.
*
* Copyright (C) 1991 Threaded Technologies Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published
* by the Free Software Foundation; either version 1, or any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should receive a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
$Header: /usr/user/dennis_glatting/ObjC/c-runtime/lib/RCS/hash.c,v 0.10 1991/12/10 12:05:28 dennisg Exp dennisg $
$Author: dennisg $
$Date: 1991/12/10 12:05:28 $
$Log: hash.c,v $
* Revision 0.10 1991/12/10 12:05:28 dennisg
* Cleaned up file format for a distribution.
*
* Revision 0.9 1991/12/03 02:01:23 dennisg
* fixed assert macro.
* added memory allocation adjustment macro for hash size allocation.
*
* Revision 0.8 1991/11/24 01:20:02 dennisg
* changed shorts back to ints.
* the efficiency gained didn't out weight the grossness of the code.
*
* Revision 0.7 1991/11/23 22:18:29 dennisg
* deleted hashIndex() and moved it to hash-inline.h
* converted hash_value_for_key () to a inline and moved it to hash-inline.h.
*
* Revision 0.6 1991/11/21 22:27:06 dennisg
* changed hash value calculation.
* func name changed from hashValue () to hashIndex(). the
* func really calculated a index anyway.
* changed hash func impl. essentially it was calculating a hash value
* from a hash value. this is a implementation thing.
*
* Revision 0.5 1991/11/20 23:29:20 dennisg
* converted hashIndex() to a inline.
*
* Revision 0.4 1991/11/19 12:34:41 dennisg
* bug in hash_delete (). It was using void* to obtain nodes to
* pass to hash_remove (). The value passed to hash_removed () is a
* entry from the node structure rather than the node itself. Using
* void* removed compiler checking.
* Modified to implement cache expansion.
*
* Revision 0.3 1991/11/07 23:23:40 dennisg
* implemented hash table expansion as suggested by rms.
*
* Revision 0.2 1991/11/07 22:30:54 dennisg
* added copyleft
*
* Revision 0.1 1991/10/24 00:45:39 dennisg
* Initial check in. Preliminary development stage.
*
*/
#include <hash.h>
#include <hash-inline.h>
#include <ObjC.h>
#include <ObjC-private.h>
#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
/* These two macros determine
when a hash table is full and
by how much it should be
expanded respectively.
These equations are
percentages. */
#define FULLNESS(cache) \
((((cache)->sizeOfHash * 75 ) / 100) <= (cache)->entriesInHash)
#define EXPANSION(cache) \
(((cache)->sizeOfHash * 175 ) / 100 )
#define MEMORY_ALLOCATION_ADJUST(i) \
((i&0x01)?i:(i-1))
Cache_t hash_new (u_int sizeOfHash) {
Cache_t retCache;
assert(sizeOfHash);
/* Memory is allocated on this
machine in even address
chunks. Therefore the
modulus must be odd. */
sizeOfHash = MEMORY_ALLOCATION_ADJUST(sizeOfHash);
/* Allocate the cache
structure. calloc () insures
its initialization for
default values. */
retCache = calloc (1, sizeof (Cache));
assert(retCache);
/* Allocate the array of
buckets for the cache.
calloc () initializes all of
the pointers to NULL. */
retCache->theNodeTable = calloc (sizeOfHash, sizeof (CacheNode_t));
assert(retCache->theNodeTable);
retCache->sizeOfHash = sizeOfHash;
return retCache;
}
void hash_delete (Cache_t theCache) {
CacheNode_t aNode;
/* Purge all key/value pairs
from the table. */
while (aNode = hash_next (theCache, NULL))
hash_remove (theCache, aNode->theKey);
/* Release the array of nodes
and the cache itself. */
free (theCache->theNodeTable);
free (theCache);
}
void hash_add (Cache_t* theCache, void* aKey, void* aValue) {
u_int indx = hashIndex(*theCache, aKey);
CacheNode_t aCacheNode = calloc (1, sizeof (CacheNode));
assert(aCacheNode);
/* Initialize the new node. */
aCacheNode->theKey = aKey;
aCacheNode->theValue = aValue;
aCacheNode->nextNode = (* (*theCache)->theNodeTable)[ indx ];
/* Debugging.
Check the list for another
key. */
#ifdef DEBUG
{ CacheNode_t checkHashNode = (* (*theCache)->theNodeTable)[ indx ];
while (checkHashNode) {
assert(checkHashNode->theKey != aKey);
checkHashNode = checkHashNode->nextNode;
}
}
#endif
/* Install the node as the
first element on the list. */
(* (*theCache)->theNodeTable)[ indx ] = aCacheNode;
/* Bump the number of entries
in the cache. */
++ (*theCache)->entriesInHash;
/* Check the hash table's
fullness. We're going
to expand if it is above
the fullness level. */
if (FULLNESS (*theCache)) {
/* The hash table has reached
its fullness level. Time to
expand it.
I'm using a slow method
here but is built on other
primitive functions thereby
increasing its
correctness. */
CacheNode_t aNode = NULL;
Cache_t newCache =
hash_new (MEMORY_ALLOCATION_ADJUST( EXPANSION (*theCache)));
DEBUG_PRINTF (stderr, "Expanding cache %#x from %d to %d\n",
*theCache, (*theCache)->sizeOfHash, newCache->sizeOfHash);
/* Copy the nodes from the
first hash table to the
new one. */
while (aNode = hash_next (*theCache, aNode))
hash_add (&newCache, aNode->theKey, aNode->theValue);
/* Trash the old cache. */
hash_delete (*theCache);
/* Return a pointer to the new
hash table. */
*theCache = newCache;
}
}
void hash_remove (Cache_t theCache, void* aKey) {
u_int indx = hashIndex(theCache, aKey);
CacheNode_t aCacheNode = (*theCache->theNodeTable)[ indx ];
/* We assume there is an entry
in the table. Error if it
is not. */
assert(aCacheNode);
/* Special case. First element
is the key/value pair to be
removed. */
if (aCacheNode->theKey == aKey) {
(*theCache->theNodeTable)[ indx ] = aCacheNode->nextNode;
free (aCacheNode);
} else {
/* Otherwise, find the hash
entry. */
CacheNode_t prevHashNode = aCacheNode;
BOOL removed = NO;
do {
if (aCacheNode->theKey == aKey) {
prevHashNode->nextNode = aCacheNode->nextNode, removed = YES;
free (aCacheNode);
} else
prevHashNode = aCacheNode, aCacheNode = aCacheNode->nextNode;
} while (!removed && aCacheNode);
assert(removed);
}
/* Decrement the number of
entries in the hash table. */
--theCache->entriesInHash;
}
CacheNode_t hash_next (Cache_t theCache, CacheNode_t aCacheNode) {
CacheNode_t theCacheNode = aCacheNode;
/* If the scan is being started
then reset the last node
visitied pointer and bucket
index. */
if (!theCacheNode)
theCache->lastBucket = 0;
/* If there is a node visited
last then check for another
entry in the same bucket;
Otherwise step to the next
bucket. */
if (theCacheNode)
if (theCacheNode->nextNode)
/* There is a node which
follows the last node
returned. Step to that node
and retun it. */
return theCacheNode->nextNode;
else
++theCache->lastBucket;
/* If the list isn't exhausted
then search the buckets for
other nodes. */
if (theCache->lastBucket < theCache->sizeOfHash) {
/* Scan the remainder of the
buckets looking for an entry
at the head of the list.
Return the first item
found. */
while (theCache->lastBucket < theCache->sizeOfHash)
if ((*theCache->theNodeTable)[ theCache->lastBucket ])
return (*theCache->theNodeTable)[ theCache->lastBucket ];
else
++theCache->lastBucket;
/* No further nodes were found
in the hash table. */
return NULL;
} else
return NULL;
}
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