1 /*
2 * Copyright (c) 1988, 1989, 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 1989 by Berkeley Softworks
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Adam de Boor.
9 *
10 * %sccs.include.redist.c%
11 */
12
13 #ifndef lint
14 static char sccsid[] = "@(#)hash.c 8.2 (Berkeley) 04/28/95";
15 #endif /* not lint */
16
17 /* hash.c --
18 *
19 * This module contains routines to manipulate a hash table.
20 * See hash.h for a definition of the structure of the hash
21 * table. Hash tables grow automatically as the amount of
22 * information increases.
23 */
24 #include "sprite.h"
25 #include "make.h"
26 #include "hash.h"
27
28 /*
29 * Forward references to local procedures that are used before they're
30 * defined:
31 */
32
33 static void RebuildTable __P((Hash_Table *));
34
35 /*
36 * The following defines the ratio of # entries to # buckets
37 * at which we rebuild the table to make it larger.
38 */
39
40 #define rebuildLimit 8
41
42 /*
43 *---------------------------------------------------------
44 *
45 * Hash_InitTable --
46 *
47 * This routine just sets up the hash table.
48 *
49 * Results:
50 * None.
51 *
52 * Side Effects:
53 * Memory is allocated for the initial bucket area.
54 *
55 *---------------------------------------------------------
56 */
57
58 void
Hash_InitTable(t,numBuckets)59 Hash_InitTable(t, numBuckets)
60 register Hash_Table *t; /* Structure to use to hold table. */
61 int numBuckets; /* How many buckets to create for starters.
62 * This number is rounded up to a power of
63 * two. If <= 0, a reasonable default is
64 * chosen. The table will grow in size later
65 * as needed. */
66 {
67 register int i;
68 register struct Hash_Entry **hp;
69
70 /*
71 * Round up the size to a power of two.
72 */
73 if (numBuckets <= 0)
74 i = 16;
75 else {
76 for (i = 2; i < numBuckets; i <<= 1)
77 continue;
78 }
79 t->numEntries = 0;
80 t->size = i;
81 t->mask = i - 1;
82 t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
83 while (--i >= 0)
84 *hp++ = NULL;
85 }
86
87 /*
88 *---------------------------------------------------------
89 *
90 * Hash_DeleteTable --
91 *
92 * This routine removes everything from a hash table
93 * and frees up the memory space it occupied (except for
94 * the space in the Hash_Table structure).
95 *
96 * Results:
97 * None.
98 *
99 * Side Effects:
100 * Lots of memory is freed up.
101 *
102 *---------------------------------------------------------
103 */
104
105 void
Hash_DeleteTable(t)106 Hash_DeleteTable(t)
107 Hash_Table *t;
108 {
109 register struct Hash_Entry **hp, *h, *nexth = NULL;
110 register int i;
111
112 for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
113 for (h = *hp++; h != NULL; h = nexth) {
114 nexth = h->next;
115 free((char *)h);
116 }
117 }
118 free((char *)t->bucketPtr);
119
120 /*
121 * Set up the hash table to cause memory faults on any future access
122 * attempts until re-initialization.
123 */
124 t->bucketPtr = NULL;
125 }
126
127 /*
128 *---------------------------------------------------------
129 *
130 * Hash_FindEntry --
131 *
132 * Searches a hash table for an entry corresponding to key.
133 *
134 * Results:
135 * The return value is a pointer to the entry for key,
136 * if key was present in the table. If key was not
137 * present, NULL is returned.
138 *
139 * Side Effects:
140 * None.
141 *
142 *---------------------------------------------------------
143 */
144
145 Hash_Entry *
Hash_FindEntry(t,key)146 Hash_FindEntry(t, key)
147 Hash_Table *t; /* Hash table to search. */
148 char *key; /* A hash key. */
149 {
150 register Hash_Entry *e;
151 register unsigned h;
152 register char *p;
153
154 for (h = 0, p = key; *p;)
155 h = (h << 5) - h + *p++;
156 p = key;
157 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
158 if (e->namehash == h && strcmp(e->name, p) == 0)
159 return (e);
160 return (NULL);
161 }
162
163 /*
164 *---------------------------------------------------------
165 *
166 * Hash_CreateEntry --
167 *
168 * Searches a hash table for an entry corresponding to
169 * key. If no entry is found, then one is created.
170 *
171 * Results:
172 * The return value is a pointer to the entry. If *newPtr
173 * isn't NULL, then *newPtr is filled in with TRUE if a
174 * new entry was created, and FALSE if an entry already existed
175 * with the given key.
176 *
177 * Side Effects:
178 * Memory may be allocated, and the hash buckets may be modified.
179 *---------------------------------------------------------
180 */
181
182 Hash_Entry *
Hash_CreateEntry(t,key,newPtr)183 Hash_CreateEntry(t, key, newPtr)
184 register Hash_Table *t; /* Hash table to search. */
185 char *key; /* A hash key. */
186 Boolean *newPtr; /* Filled in with TRUE if new entry created,
187 * FALSE otherwise. */
188 {
189 register Hash_Entry *e;
190 register unsigned h;
191 register char *p;
192 int keylen;
193 struct Hash_Entry **hp;
194
195 /*
196 * Hash the key. As a side effect, save the length (strlen) of the
197 * key in case we need to create the entry.
198 */
199 for (h = 0, p = key; *p;)
200 h = (h << 5) - h + *p++;
201 keylen = p - key;
202 p = key;
203 for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
204 if (e->namehash == h && strcmp(e->name, p) == 0) {
205 if (newPtr != NULL)
206 *newPtr = FALSE;
207 return (e);
208 }
209 }
210
211 /*
212 * The desired entry isn't there. Before allocating a new entry,
213 * expand the table if necessary (and this changes the resulting
214 * bucket chain).
215 */
216 if (t->numEntries >= rebuildLimit * t->size)
217 RebuildTable(t);
218 e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
219 hp = &t->bucketPtr[h & t->mask];
220 e->next = *hp;
221 *hp = e;
222 e->clientData = NULL;
223 e->namehash = h;
224 (void) strcpy(e->name, p);
225 t->numEntries++;
226
227 if (newPtr != NULL)
228 *newPtr = TRUE;
229 return (e);
230 }
231
232 /*
233 *---------------------------------------------------------
234 *
235 * Hash_DeleteEntry --
236 *
237 * Delete the given hash table entry and free memory associated with
238 * it.
239 *
240 * Results:
241 * None.
242 *
243 * Side Effects:
244 * Hash chain that entry lives in is modified and memory is freed.
245 *
246 *---------------------------------------------------------
247 */
248
249 void
Hash_DeleteEntry(t,e)250 Hash_DeleteEntry(t, e)
251 Hash_Table *t;
252 Hash_Entry *e;
253 {
254 register Hash_Entry **hp, *p;
255
256 if (e == NULL)
257 return;
258 for (hp = &t->bucketPtr[e->namehash & t->mask];
259 (p = *hp) != NULL; hp = &p->next) {
260 if (p == e) {
261 *hp = p->next;
262 free((char *)p);
263 t->numEntries--;
264 return;
265 }
266 }
267 (void) write(2, "bad call to Hash_DeleteEntry\n", 29);
268 abort();
269 }
270
271 /*
272 *---------------------------------------------------------
273 *
274 * Hash_EnumFirst --
275 * This procedure sets things up for a complete search
276 * of all entries recorded in the hash table.
277 *
278 * Results:
279 * The return value is the address of the first entry in
280 * the hash table, or NULL if the table is empty.
281 *
282 * Side Effects:
283 * The information in searchPtr is initialized so that successive
284 * calls to Hash_Next will return successive HashEntry's
285 * from the table.
286 *
287 *---------------------------------------------------------
288 */
289
290 Hash_Entry *
Hash_EnumFirst(t,searchPtr)291 Hash_EnumFirst(t, searchPtr)
292 Hash_Table *t; /* Table to be searched. */
293 register Hash_Search *searchPtr;/* Area in which to keep state
294 * about search.*/
295 {
296 searchPtr->tablePtr = t;
297 searchPtr->nextIndex = 0;
298 searchPtr->hashEntryPtr = NULL;
299 return Hash_EnumNext(searchPtr);
300 }
301
302 /*
303 *---------------------------------------------------------
304 *
305 * Hash_EnumNext --
306 * This procedure returns successive entries in the hash table.
307 *
308 * Results:
309 * The return value is a pointer to the next HashEntry
310 * in the table, or NULL when the end of the table is
311 * reached.
312 *
313 * Side Effects:
314 * The information in searchPtr is modified to advance to the
315 * next entry.
316 *
317 *---------------------------------------------------------
318 */
319
320 Hash_Entry *
Hash_EnumNext(searchPtr)321 Hash_EnumNext(searchPtr)
322 register Hash_Search *searchPtr; /* Area used to keep state about
323 search. */
324 {
325 register Hash_Entry *e;
326 Hash_Table *t = searchPtr->tablePtr;
327
328 /*
329 * The hashEntryPtr field points to the most recently returned
330 * entry, or is nil if we are starting up. If not nil, we have
331 * to start at the next one in the chain.
332 */
333 e = searchPtr->hashEntryPtr;
334 if (e != NULL)
335 e = e->next;
336 /*
337 * If the chain ran out, or if we are starting up, we need to
338 * find the next nonempty chain.
339 */
340 while (e == NULL) {
341 if (searchPtr->nextIndex >= t->size)
342 return (NULL);
343 e = t->bucketPtr[searchPtr->nextIndex++];
344 }
345 searchPtr->hashEntryPtr = e;
346 return (e);
347 }
348
349 /*
350 *---------------------------------------------------------
351 *
352 * RebuildTable --
353 * This local routine makes a new hash table that
354 * is larger than the old one.
355 *
356 * Results:
357 * None.
358 *
359 * Side Effects:
360 * The entire hash table is moved, so any bucket numbers
361 * from the old table are invalid.
362 *
363 *---------------------------------------------------------
364 */
365
366 static void
RebuildTable(t)367 RebuildTable(t)
368 register Hash_Table *t;
369 {
370 register Hash_Entry *e, *next = NULL, **hp, **xp;
371 register int i, mask;
372 register Hash_Entry **oldhp;
373 int oldsize;
374
375 oldhp = t->bucketPtr;
376 oldsize = i = t->size;
377 i <<= 1;
378 t->size = i;
379 t->mask = mask = i - 1;
380 t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
381 while (--i >= 0)
382 *hp++ = NULL;
383 for (hp = oldhp, i = oldsize; --i >= 0;) {
384 for (e = *hp++; e != NULL; e = next) {
385 next = e->next;
386 xp = &t->bucketPtr[e->namehash & mask];
387 e->next = *xp;
388 *xp = e;
389 }
390 }
391 free((char *)oldhp);
392 }
393