2 * Copyright (c) 1988, 1989, 1990, 1993
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4 * Copyright (c) 1988, 1989 by Adam de Boor
5 * Copyright (c) 1989 by Berkeley Softworks
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39 * @(#)hash.c 8.1 (Berkeley) 6/6/93
40 * $FreeBSD: src/usr.bin/make/hash.c,v 1.24 2005/02/01 10:50:35 harti Exp $
41 * $DragonFly: src/usr.bin/make/hash.c,v 1.16 2005/02/15 01:01:18 okumoto Exp $
46 * This module contains routines to manipulate a hash table.
47 * See hash.h for a definition of the structure of the hash
48 * table. Hash tables grow automatically as the amount of
49 * information increases.
61 * Forward references to local procedures that are used before they're
64 static void RebuildTable(Hash_Table *);
67 * The following defines the ratio of # entries to # buckets
68 * at which we rebuild the table to make it larger.
71 #define rebuildLimit 8
74 *---------------------------------------------------------
78 * Set up the hash table t with a given number of buckets, or a
79 * reasonable default if the number requested is less than or
80 * equal to zero. Hash tables will grow in size as needed.
87 * Memory is allocated for the initial bucket area.
89 *---------------------------------------------------------
92 Hash_InitTable(Hash_Table *t, int numBuckets)
95 struct Hash_Entry **hp;
98 * Round up the size to a power of two.
103 for (i = 2; i < numBuckets; i <<= 1)
109 t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
115 *---------------------------------------------------------
117 * Hash_DeleteTable --
119 * This routine removes everything from a hash table
120 * and frees up the memory space it occupied (except for
121 * the space in the Hash_Table structure).
127 * Lots of memory is freed up.
129 *---------------------------------------------------------
132 Hash_DeleteTable(Hash_Table *t)
134 struct Hash_Entry **hp, *h, *nexth = NULL;
137 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
138 for (h = *hp++; h != NULL; h = nexth) {
146 * Set up the hash table to cause memory faults on any future access
147 * attempts until re-initialization.
153 *---------------------------------------------------------
157 * Searches a hash table for an entry corresponding to key.
160 * The return value is a pointer to the entry for key,
161 * if key was present in the table. If key was not
162 * present, NULL is returned.
167 *---------------------------------------------------------
170 Hash_FindEntry(const Hash_Table *t, const char *key)
176 for (h = 0, p = key; *p;)
177 h = (h << 5) - h + *p++;
179 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
180 if (e->namehash == h && strcmp(e->name, p) == 0)
186 *---------------------------------------------------------
188 * Hash_CreateEntry --
190 * Searches a hash table for an entry corresponding to
191 * key. If no entry is found, then one is created.
194 * The return value is a pointer to the entry. If *newPtr
195 * isn't NULL, then *newPtr is filled in with TRUE if a
196 * new entry was created, and FALSE if an entry already existed
197 * with the given key.
200 * Memory may be allocated, and the hash buckets may be modified.
201 *---------------------------------------------------------
204 Hash_CreateEntry(Hash_Table *t, const char *key, Boolean *newPtr)
210 struct Hash_Entry **hp;
213 * Hash the key. As a side effect, save the length (strlen) of the
214 * key in case we need to create the entry.
216 for (h = 0, p = key; *p;)
217 h = (h << 5) - h + *p++;
220 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
221 if (e->namehash == h && strcmp(e->name, p) == 0) {
229 * The desired entry isn't there. Before allocating a new entry,
230 * expand the table if necessary (and this changes the resulting
233 if (t->numEntries >= rebuildLimit * t->size)
235 e = emalloc(sizeof(*e) + keylen);
236 hp = &t->bucketPtr[h & t->mask];
239 e->clientData = NULL;
250 *---------------------------------------------------------
252 * Hash_DeleteEntry --
254 * Delete the given hash table entry and free memory associated with
261 * Hash chain that entry lives in is modified and memory is freed.
263 *---------------------------------------------------------
266 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
272 for (hp = &t->bucketPtr[e->namehash & t->mask];
273 (p = *hp) != NULL; hp = &p->next) {
281 write(STDERR_FILENO, "bad call to Hash_DeleteEntry\n", 29);
286 *---------------------------------------------------------
289 * This procedure sets things up for a complete search
290 * of all entries recorded in the hash table.
293 * The return value is the address of the first entry in
294 * the hash table, or NULL if the table is empty.
297 * The information in searchPtr is initialized so that successive
298 * calls to Hash_Next will return successive HashEntry's
301 *---------------------------------------------------------
304 Hash_EnumFirst(const Hash_Table *t, Hash_Search *searchPtr)
307 searchPtr->tablePtr = t;
308 searchPtr->nextIndex = 0;
309 searchPtr->hashEntryPtr = NULL;
310 return (Hash_EnumNext(searchPtr));
314 *---------------------------------------------------------
317 * This procedure returns successive entries in the hash table.
320 * The return value is a pointer to the next HashEntry
321 * in the table, or NULL when the end of the table is
325 * The information in searchPtr is modified to advance to the
328 *---------------------------------------------------------
331 Hash_EnumNext(Hash_Search *searchPtr)
334 const Hash_Table *t = searchPtr->tablePtr;
337 * The hashEntryPtr field points to the most recently returned
338 * entry, or is NULL if we are starting up. If not NULL, we have
339 * to start at the next one in the chain.
341 e = searchPtr->hashEntryPtr;
345 * If the chain ran out, or if we are starting up, we need to
346 * find the next nonempty chain.
349 if (searchPtr->nextIndex >= t->size)
351 e = t->bucketPtr[searchPtr->nextIndex++];
353 searchPtr->hashEntryPtr = e;
358 *---------------------------------------------------------
361 * This local routine makes a new hash table that
362 * is larger than the old one.
368 * The entire hash table is moved, so any bucket numbers
369 * from the old table are invalid.
371 *---------------------------------------------------------
374 RebuildTable(Hash_Table *t)
376 Hash_Entry *e, *next = NULL, **hp, **xp;
381 oldhp = t->bucketPtr;
382 oldsize = i = t->size;
385 t->mask = mask = i - 1;
386 t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
389 for (hp = oldhp, i = oldsize; --i >= 0;) {
390 for (e = *hp++; e != NULL; e = next) {
392 xp = &t->bucketPtr[e->namehash & mask];