1 /* $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $ */
4 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
5 * Copyright (c) 1988, 1989 by Adam de Boor
6 * Copyright (c) 1989 by Berkeley Softworks
9 * This code is derived from software contributed to Berkeley by
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
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18 * notice, this list of conditions and the following disclaimer in the
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20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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42 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
44 #include <sys/cdefs.h>
47 static char sccsid[] = "@(#)hash.c 8.1 (Berkeley) 6/6/93";
49 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
54 #include <sys/types.h>
62 * This module contains routines to manipulate a hash table.
63 * See hash.h for a definition of the structure of the hash
64 * table. Hash tables grow automatically as the amount of
65 * information increases.
75 * Forward references to local procedures that are used before they're
79 static void RebuildTable __P((Hash_Table *));
82 * The following defines the ratio of # entries to # buckets
83 * at which we rebuild the table to make it larger.
86 #define rebuildLimit 8
89 *---------------------------------------------------------
93 * This routine just sets up the hash table.
99 * Memory is allocated for the initial bucket area.
101 *---------------------------------------------------------
105 Hash_InitTable(t, numBuckets)
106 register Hash_Table *t; /* Structure to use to hold table. */
107 int numBuckets; /* How many buckets to create for starters.
108 * This number is rounded up to a power of
109 * two. If <= 0, a reasonable default is
110 * chosen. The table will grow in size later
114 register struct Hash_Entry **hp;
117 * Round up the size to a power of two.
122 for (i = 2; i < numBuckets; i <<= 1)
128 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
134 *---------------------------------------------------------
136 * Hash_DeleteTable --
138 * This routine removes everything from a hash table
139 * and frees up the memory space it occupied (except for
140 * the space in the Hash_Table structure).
146 * Lots of memory is freed up.
148 *---------------------------------------------------------
155 register struct Hash_Entry **hp, *h, *nexth = NULL;
158 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
159 for (h = *hp++; h != NULL; h = nexth) {
164 free((char *)t->bucketPtr);
167 * Set up the hash table to cause memory faults on any future access
168 * attempts until re-initialization.
174 *---------------------------------------------------------
178 * Searches a hash table for an entry corresponding to key.
181 * The return value is a pointer to the entry for key,
182 * if key was present in the table. If key was not
183 * present, NULL is returned.
188 *---------------------------------------------------------
192 Hash_FindEntry(t, key)
193 Hash_Table *t; /* Hash table to search. */
194 char *key; /* A hash key. */
196 register Hash_Entry *e;
200 for (h = 0, p = key; *p;)
201 h = (h << 5) - h + *p++;
203 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
204 if (e->namehash == h && strcmp(e->name, p) == 0)
210 *---------------------------------------------------------
212 * Hash_CreateEntry --
214 * Searches a hash table for an entry corresponding to
215 * key. If no entry is found, then one is created.
218 * The return value is a pointer to the entry. If *newPtr
219 * isn't NULL, then *newPtr is filled in with TRUE if a
220 * new entry was created, and FALSE if an entry already existed
221 * with the given key.
224 * Memory may be allocated, and the hash buckets may be modified.
225 *---------------------------------------------------------
229 Hash_CreateEntry(t, key, newPtr)
230 register Hash_Table *t; /* Hash table to search. */
231 char *key; /* A hash key. */
232 Boolean *newPtr; /* Filled in with TRUE if new entry created,
233 * FALSE otherwise. */
235 register Hash_Entry *e;
239 struct Hash_Entry **hp;
242 * Hash the key. As a side effect, save the length (strlen) of the
243 * key in case we need to create the entry.
245 for (h = 0, p = key; *p;)
246 h = (h << 5) - h + *p++;
249 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
250 if (e->namehash == h && strcmp(e->name, p) == 0) {
258 * The desired entry isn't there. Before allocating a new entry,
259 * expand the table if necessary (and this changes the resulting
262 if (t->numEntries >= rebuildLimit * t->size)
264 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
265 hp = &t->bucketPtr[h & t->mask];
268 e->clientData = NULL;
270 (void) strcpy(e->name, p);
279 *---------------------------------------------------------
281 * Hash_DeleteEntry --
283 * Delete the given hash table entry and free memory associated with
290 * Hash chain that entry lives in is modified and memory is freed.
292 *---------------------------------------------------------
296 Hash_DeleteEntry(t, e)
300 register Hash_Entry **hp, *p;
304 for (hp = &t->bucketPtr[e->namehash & t->mask];
305 (p = *hp) != NULL; hp = &p->next) {
313 (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
318 *---------------------------------------------------------
321 * This procedure sets things up for a complete search
322 * of all entries recorded in the hash table.
325 * The return value is the address of the first entry in
326 * the hash table, or NULL if the table is empty.
329 * The information in searchPtr is initialized so that successive
330 * calls to Hash_Next will return successive HashEntry's
333 *---------------------------------------------------------
337 Hash_EnumFirst(t, searchPtr)
338 Hash_Table *t; /* Table to be searched. */
339 register Hash_Search *searchPtr;/* Area in which to keep state
342 searchPtr->tablePtr = t;
343 searchPtr->nextIndex = 0;
344 searchPtr->hashEntryPtr = NULL;
345 return Hash_EnumNext(searchPtr);
349 *---------------------------------------------------------
352 * This procedure returns successive entries in the hash table.
355 * The return value is a pointer to the next HashEntry
356 * in the table, or NULL when the end of the table is
360 * The information in searchPtr is modified to advance to the
363 *---------------------------------------------------------
367 Hash_EnumNext(searchPtr)
368 register Hash_Search *searchPtr; /* Area used to keep state about
371 register Hash_Entry *e;
372 Hash_Table *t = searchPtr->tablePtr;
375 * The hashEntryPtr field points to the most recently returned
376 * entry, or is nil if we are starting up. If not nil, we have
377 * to start at the next one in the chain.
379 e = searchPtr->hashEntryPtr;
383 * If the chain ran out, or if we are starting up, we need to
384 * find the next nonempty chain.
387 if (searchPtr->nextIndex >= t->size)
389 e = t->bucketPtr[searchPtr->nextIndex++];
391 searchPtr->hashEntryPtr = e;
396 *---------------------------------------------------------
399 * This local routine makes a new hash table that
400 * is larger than the old one.
406 * The entire hash table is moved, so any bucket numbers
407 * from the old table are invalid.
409 *---------------------------------------------------------
414 register Hash_Table *t;
416 register Hash_Entry *e, *next = NULL, **hp, **xp;
417 register int i, mask;
418 register Hash_Entry **oldhp;
421 oldhp = t->bucketPtr;
422 oldsize = i = t->size;
425 t->mask = mask = i - 1;
426 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
429 for (hp = oldhp, i = oldsize; --i >= 0;) {
430 for (e = *hp++; e != NULL; e = next) {
432 xp = &t->bucketPtr[e->namehash & mask];