2 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
3 * Copyright (c) 1988, 1989 by Adam de Boor
4 * Copyright (c) 1989 by Berkeley Softworks
7 * This code is derived from software contributed to Berkeley by
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38 * $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $
41 #include <sys/types.h>
50 * This module contains routines to manipulate a hash table.
51 * See hash.h for a definition of the structure of the hash
52 * table. Hash tables grow automatically as the amount of
53 * information increases.
62 * Forward references to local procedures that are used before they're
66 static void RebuildTable(Hash_Table *);
69 * The following defines the ratio of # entries to # buckets
70 * at which we rebuild the table to make it larger.
73 #define rebuildLimit 8
76 *---------------------------------------------------------
80 * This routine just sets up the hash table.
86 * Memory is allocated for the initial bucket area.
88 *---------------------------------------------------------
92 * Hash_Table *t; Structure to use to hold table.
93 * int numBuckets; How many buckets to create for starters.
94 * This number is rounded up to a power of
95 * two. If <= 0, a reasonable default is
96 * chosen. The table will grow in size later
100 Hash_InitTable(Hash_Table *t, int numBuckets)
103 struct Hash_Entry **hp;
106 * Round up the size to a power of two.
111 for (i = 2; i < numBuckets; i <<= 1)
117 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
123 *---------------------------------------------------------
125 * Hash_DeleteTable --
127 * This routine removes everything from a hash table
128 * and frees up the memory space it occupied (except for
129 * the space in the Hash_Table structure).
135 * Lots of memory is freed up.
137 *---------------------------------------------------------
141 Hash_DeleteTable(Hash_Table *t)
143 struct Hash_Entry **hp, *h, *nexth = NULL;
146 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
147 for (h = *hp++; h != NULL; h = nexth) {
152 free((char *)t->bucketPtr);
155 * Set up the hash table to cause memory faults on any future access
156 * attempts until re-initialization.
162 *---------------------------------------------------------
166 * Searches a hash table for an entry corresponding to key.
169 * The return value is a pointer to the entry for key,
170 * if key was present in the table. If key was not
171 * present, NULL is returned.
176 *---------------------------------------------------------
180 Hash_FindEntry(Hash_Table *t, char *key)
186 for (h = 0, p = key; *p;)
187 h = (h << 5) - h + *p++;
189 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
190 if (e->namehash == h && strcmp(e->name, p) == 0)
196 *---------------------------------------------------------
198 * Hash_CreateEntry --
200 * Searches a hash table for an entry corresponding to
201 * key. If no entry is found, then one is created.
204 * The return value is a pointer to the entry. If *newPtr
205 * isn't NULL, then *newPtr is filled in with TRUE if a
206 * new entry was created, and FALSE if an entry already existed
207 * with the given key.
210 * Memory may be allocated, and the hash buckets may be modified.
211 *---------------------------------------------------------
215 Hash_CreateEntry(Hash_Table *t, char *key, Boolean *newPtr)
221 struct Hash_Entry **hp;
224 * Hash the key. As a side effect, save the length (strlen) of the
225 * key in case we need to create the entry.
227 for (h = 0, p = key; *p;)
228 h = (h << 5) - h + *p++;
231 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
232 if (e->namehash == h && strcmp(e->name, p) == 0) {
240 * The desired entry isn't there. Before allocating a new entry,
241 * expand the table if necessary (and this changes the resulting
244 if (t->numEntries >= rebuildLimit * t->size)
246 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
247 hp = &t->bucketPtr[h & t->mask];
250 e->clientData = NULL;
261 *---------------------------------------------------------
263 * Hash_DeleteEntry --
265 * Delete the given hash table entry and free memory associated with
272 * Hash chain that entry lives in is modified and memory is freed.
274 *---------------------------------------------------------
278 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
284 for (hp = &t->bucketPtr[e->namehash & t->mask];
285 (p = *hp) != NULL; hp = &p->next) {
293 write(2, "bad call to Hash_DeleteEntry\n", 29);
298 *---------------------------------------------------------
301 * This procedure sets things up for a complete search
302 * of all entries recorded in the hash table.
305 * The return value is the address of the first entry in
306 * the hash table, or NULL if the table is empty.
309 * The information in searchPtr is initialized so that successive
310 * calls to Hash_Next will return successive HashEntry's
313 *---------------------------------------------------------
317 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
319 searchPtr->tablePtr = t;
320 searchPtr->nextIndex = 0;
321 searchPtr->hashEntryPtr = NULL;
322 return Hash_EnumNext(searchPtr);
326 *---------------------------------------------------------
329 * This procedure returns successive entries in the hash table.
332 * The return value is a pointer to the next HashEntry
333 * in the table, or NULL when the end of the table is
337 * The information in searchPtr is modified to advance to the
340 *---------------------------------------------------------
344 Hash_EnumNext(Hash_Search *searchPtr)
347 Hash_Table *t = searchPtr->tablePtr;
350 * The hashEntryPtr field points to the most recently returned
351 * entry, or is nil if we are starting up. If not nil, we have
352 * to start at the next one in the chain.
354 e = searchPtr->hashEntryPtr;
358 * If the chain ran out, or if we are starting up, we need to
359 * find the next nonempty chain.
362 if (searchPtr->nextIndex >= t->size)
364 e = t->bucketPtr[searchPtr->nextIndex++];
366 searchPtr->hashEntryPtr = e;
371 *---------------------------------------------------------
374 * This local routine makes a new hash table that
375 * is larger than the old one.
381 * The entire hash table is moved, so any bucket numbers
382 * from the old table are invalid.
384 *---------------------------------------------------------
388 RebuildTable(Hash_Table *t)
390 Hash_Entry *e, *next = NULL, **hp, **xp;
395 oldhp = t->bucketPtr;
396 oldsize = i = t->size;
399 t->mask = mask = i - 1;
400 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
403 for (hp = oldhp, i = oldsize; --i >= 0;) {
404 for (e = *hp++; e != NULL; e = next) {
406 xp = &t->bucketPtr[e->namehash & mask];