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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 1.21 2005/08/04 00:19:04 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.
60 * Forward references to local procedures that are used before they're
63 static void RebuildTable(Hash_Table *);
66 * The following defines the ratio of # entries to # buckets
67 * at which we rebuild the table to make it larger.
70 #define rebuildLimit 8
73 *---------------------------------------------------------
77 * This routine just sets up the hash table.
80 * t Structure to to hold table.
81 * numBuckets How many buckets to create for starters. This
82 * number is rounded up to a power of two. If
83 * <= 0, a reasonable default is chosen. The
84 * table will grow in size later as needed.
90 * Memory is allocated for the initial bucket area.
92 *---------------------------------------------------------
95 Hash_InitTable(Hash_Table *t, int numBuckets)
98 struct Hash_Entry **hp;
101 * Round up the size to a power of two.
106 for (i = 2; i < numBuckets; i <<= 1)
112 t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
118 *---------------------------------------------------------
120 * Hash_DeleteTable --
122 * This routine removes everything from a hash table
123 * and frees up the memory space it occupied (except for
124 * the space in the Hash_Table structure).
130 * Lots of memory is freed up.
132 *---------------------------------------------------------
135 Hash_DeleteTable(Hash_Table *t)
137 struct Hash_Entry **hp, *h, *nexth = NULL;
140 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
141 for (h = *hp++; h != NULL; h = nexth) {
149 * Set up the hash table to cause memory faults on any future access
150 * attempts until re-initialization.
156 *---------------------------------------------------------
160 * Searches a hash table for an entry corresponding to key.
163 * t Hash table to search.
167 * The return value is a pointer to the entry for key,
168 * if key was present in the table. If key was not
169 * present, NULL is returned.
174 *---------------------------------------------------------
177 Hash_FindEntry(const Hash_Table *t, const char *key)
183 for (h = 0, p = key; *p;)
184 h = (h << 5) - h + *p++;
186 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
187 if (e->namehash == h && strcmp(e->name, p) == 0)
193 *---------------------------------------------------------
195 * Hash_CreateEntry --
197 * Searches a hash table for an entry corresponding to
198 * key. If no entry is found, then one is created.
201 * t Hash table to search.
203 * newPtr Filled in with true if new entry created,
207 * The return value is a pointer to the entry. If *newPtr
208 * isn't NULL, then *newPtr is filled in with true if a
209 * new entry was created, and false if an entry already existed
210 * with the given key.
213 * Memory may be allocated, and the hash buckets may be modified.
214 *---------------------------------------------------------
217 Hash_CreateEntry(Hash_Table *t, const char *key, bool *newPtr)
223 struct Hash_Entry **hp;
226 * Hash the key. As a side effect, save the length (strlen) of the
227 * key in case we need to create the entry.
229 for (h = 0, p = key; *p;)
230 h = (h << 5) - h + *p++;
233 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
234 if (e->namehash == h && strcmp(e->name, p) == 0) {
242 * The desired entry isn't there. Before allocating a new entry,
243 * expand the table if necessary (and this changes the resulting
246 if (t->numEntries >= rebuildLimit * t->size)
248 e = emalloc(sizeof(*e) + keylen);
249 hp = &t->bucketPtr[h & t->mask];
252 e->clientData = NULL;
263 *---------------------------------------------------------
265 * Hash_DeleteEntry --
267 * Delete the given hash table entry and free memory associated with
274 * Hash chain that entry lives in is modified and memory is freed.
276 *---------------------------------------------------------
279 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
285 for (hp = &t->bucketPtr[e->namehash & t->mask];
286 (p = *hp) != NULL; hp = &p->next) {
294 write(STDERR_FILENO, "bad call to Hash_DeleteEntry\n", 29);
299 *---------------------------------------------------------
302 * This procedure sets things up for a complete search
303 * of all entries recorded in the hash table.
306 * t Table to be searched.
307 * searchPtr Area in which to keep state about search.
310 * The return value is the address of the first entry in
311 * the hash table, or NULL if the table is empty.
314 * The information in searchPtr is initialized so that successive
315 * calls to Hash_Next will return successive HashEntry's
318 *---------------------------------------------------------
321 Hash_EnumFirst(const Hash_Table *t, Hash_Search *searchPtr)
324 searchPtr->tablePtr = t;
325 searchPtr->nextIndex = 0;
326 searchPtr->hashEntryPtr = NULL;
327 return (Hash_EnumNext(searchPtr));
331 *---------------------------------------------------------
334 * This procedure returns successive entries in the hash table.
337 * searchPtr Area used to keep state about search.
340 * The return value is a pointer to the next HashEntry
341 * in the table, or NULL when the end of the table is
345 * The information in searchPtr is modified to advance to the
348 *---------------------------------------------------------
351 Hash_EnumNext(Hash_Search *searchPtr)
354 const Hash_Table *t = searchPtr->tablePtr;
357 * The hashEntryPtr field points to the most recently returned
358 * entry, or is NULL if we are starting up. If not NULL, we have
359 * to start at the next one in the chain.
361 e = searchPtr->hashEntryPtr;
365 * If the chain ran out, or if we are starting up, we need to
366 * find the next nonempty chain.
369 if (searchPtr->nextIndex >= t->size)
371 e = t->bucketPtr[searchPtr->nextIndex++];
373 searchPtr->hashEntryPtr = e;
378 *---------------------------------------------------------
381 * This local routine makes a new hash table that
382 * is larger than the old one.
388 * The entire hash table is moved, so any bucket numbers
389 * from the old table are invalid.
391 *---------------------------------------------------------
394 RebuildTable(Hash_Table *t)
396 Hash_Entry *e, *next = NULL, **hp, **xp;
401 oldhp = t->bucketPtr;
402 oldsize = i = t->size;
405 t->mask = mask = i - 1;
406 t->bucketPtr = hp = emalloc(sizeof(*hp) * i);
409 for (hp = oldhp, i = oldsize; --i >= 0;) {
410 for (e = *hp++; e != NULL; e = next) {
412 xp = &t->bucketPtr[e->namehash & mask];