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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 1.9 1999/09/11 13:08:01 hoek Exp $
41 * $DragonFly: src/usr.bin/make/hash.c,v 1.14 2005/01/06 10:53:00 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.
62 * Forward references to local procedures that are used before they're
65 static void RebuildTable(Hash_Table *);
68 * The following defines the ratio of # entries to # buckets
69 * at which we rebuild the table to make it larger.
72 #define rebuildLimit 8
75 *---------------------------------------------------------
79 * Set up the hash table t with a given number of buckets, or a
80 * reasonable default if the number requested is less than or
81 * equal to zero. Hash tables will grow in size as needed.
88 * Memory is allocated for the initial bucket area.
90 *---------------------------------------------------------
93 Hash_InitTable(Hash_Table *t, int numBuckets)
96 struct Hash_Entry **hp;
99 * Round up the size to a power of two.
104 for (i = 2; i < numBuckets; i <<= 1)
110 t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
116 *---------------------------------------------------------
118 * Hash_DeleteTable --
120 * This routine removes everything from a hash table
121 * and frees up the memory space it occupied (except for
122 * the space in the Hash_Table structure).
128 * Lots of memory is freed up.
130 *---------------------------------------------------------
133 Hash_DeleteTable(Hash_Table *t)
135 struct Hash_Entry **hp, *h, *nexth = NULL;
138 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
139 for (h = *hp++; h != NULL; h = nexth) {
147 * Set up the hash table to cause memory faults on any future access
148 * attempts until re-initialization.
154 *---------------------------------------------------------
158 * Searches a hash table for an entry corresponding to key.
161 * The return value is a pointer to the entry for key,
162 * if key was present in the table. If key was not
163 * present, NULL is returned.
168 *---------------------------------------------------------
171 Hash_FindEntry(const Hash_Table *t, const char *key)
177 for (h = 0, p = key; *p;)
178 h = (h << 5) - h + *p++;
180 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
181 if (e->namehash == h && strcmp(e->name, p) == 0)
187 *---------------------------------------------------------
189 * Hash_CreateEntry --
191 * Searches a hash table for an entry corresponding to
192 * key. If no entry is found, then one is created.
195 * The return value is a pointer to the entry. If *newPtr
196 * isn't NULL, then *newPtr is filled in with TRUE if a
197 * new entry was created, and FALSE if an entry already existed
198 * with the given key.
201 * Memory may be allocated, and the hash buckets may be modified.
202 *---------------------------------------------------------
205 Hash_CreateEntry(Hash_Table *t, const char *key, Boolean *newPtr)
211 struct Hash_Entry **hp;
214 * Hash the key. As a side effect, save the length (strlen) of the
215 * key in case we need to create the entry.
217 for (h = 0, p = key; *p;)
218 h = (h << 5) - h + *p++;
221 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
222 if (e->namehash == h && strcmp(e->name, p) == 0) {
230 * The desired entry isn't there. Before allocating a new entry,
231 * expand the table if necessary (and this changes the resulting
234 if (t->numEntries >= rebuildLimit * t->size)
236 e = emalloc(sizeof(*e) + keylen);
237 hp = &t->bucketPtr[h & t->mask];
240 e->clientData = NULL;
251 *---------------------------------------------------------
253 * Hash_DeleteEntry --
255 * Delete the given hash table entry and free memory associated with
262 * Hash chain that entry lives in is modified and memory is freed.
264 *---------------------------------------------------------
267 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
273 for (hp = &t->bucketPtr[e->namehash & t->mask];
274 (p = *hp) != NULL; hp = &p->next) {
282 write(STDERR_FILENO, "bad call to Hash_DeleteEntry\n", 29);
287 *---------------------------------------------------------
290 * This procedure sets things up for a complete search
291 * of all entries recorded in the hash table.
294 * The return value is the address of the first entry in
295 * the hash table, or NULL if the table is empty.
298 * The information in searchPtr is initialized so that successive
299 * calls to Hash_Next will return successive HashEntry's
302 *---------------------------------------------------------
305 Hash_EnumFirst(const Hash_Table *t, Hash_Search *searchPtr)
308 searchPtr->tablePtr = t;
309 searchPtr->nextIndex = 0;
310 searchPtr->hashEntryPtr = NULL;
311 return (Hash_EnumNext(searchPtr));
315 *---------------------------------------------------------
318 * This procedure returns successive entries in the hash table.
321 * The return value is a pointer to the next HashEntry
322 * in the table, or NULL when the end of the table is
326 * The information in searchPtr is modified to advance to the
329 *---------------------------------------------------------
332 Hash_EnumNext(Hash_Search *searchPtr)
335 const Hash_Table *t = searchPtr->tablePtr;
338 * The hashEntryPtr field points to the most recently returned
339 * entry, or is NULL if we are starting up. If not NULL, we have
340 * to start at the next one in the chain.
342 e = searchPtr->hashEntryPtr;
346 * If the chain ran out, or if we are starting up, we need to
347 * find the next nonempty chain.
350 if (searchPtr->nextIndex >= t->size)
352 e = t->bucketPtr[searchPtr->nextIndex++];
354 searchPtr->hashEntryPtr = e;
359 *---------------------------------------------------------
362 * This local routine makes a new hash table that
363 * is larger than the old one.
369 * The entire hash table is moved, so any bucket numbers
370 * from the old table are invalid.
372 *---------------------------------------------------------
375 RebuildTable(Hash_Table *t)
377 Hash_Entry *e, *next = NULL, **hp, **xp;
382 oldhp = t->bucketPtr;
383 oldsize = i = t->size;
386 t->mask = mask = i - 1;
387 t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
390 for (hp = oldhp, i = oldsize; --i >= 0;) {
391 for (e = *hp++; e != NULL; e = next) {
393 xp = &t->bucketPtr[e->namehash & mask];