Annotation of src/usr.bin/make/hash.c, Revision 1.1.1.1
1.1 deraadt 1: /* $NetBSD: hash.c,v 1.5 1995/06/14 15:19:15 christos Exp $ */
2:
3: /*
4: * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
5: * Copyright (c) 1988, 1989 by Adam de Boor
6: * Copyright (c) 1989 by Berkeley Softworks
7: * All rights reserved.
8: *
9: * This code is derived from software contributed to Berkeley by
10: * Adam de Boor.
11: *
12: * Redistribution and use in source and binary forms, with or without
13: * modification, are permitted provided that the following conditions
14: * are met:
15: * 1. Redistributions of source code must retain the above copyright
16: * notice, this list of conditions and the following disclaimer.
17: * 2. Redistributions in binary form must reproduce the above copyright
18: * notice, this list of conditions and the following disclaimer in the
19: * documentation and/or other materials provided with the distribution.
20: * 3. All advertising materials mentioning features or use of this software
21: * must display the following acknowledgement:
22: * This product includes software developed by the University of
23: * California, Berkeley and its contributors.
24: * 4. Neither the name of the University nor the names of its contributors
25: * may be used to endorse or promote products derived from this software
26: * without specific prior written permission.
27: *
28: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38: * SUCH DAMAGE.
39: */
40:
41: #ifndef lint
42: #if 0
43: static char sccsid[] = "@(#)hash.c 5.5 (Berkeley) 12/28/90";
44: #else
45: static char rcsid[] = "$NetBSD: hash.c,v 1.5 1995/06/14 15:19:15 christos Exp $";
46: #endif
47: #endif /* not lint */
48:
49: /* hash.c --
50: *
51: * This module contains routines to manipulate a hash table.
52: * See hash.h for a definition of the structure of the hash
53: * table. Hash tables grow automatically as the amount of
54: * information increases.
55: */
56: #include "sprite.h"
57: #include "make.h"
58: #include "hash.h"
59:
60: /*
61: * Forward references to local procedures that are used before they're
62: * defined:
63: */
64:
65: static void RebuildTable __P((Hash_Table *));
66:
67: /*
68: * The following defines the ratio of # entries to # buckets
69: * at which we rebuild the table to make it larger.
70: */
71:
72: #define rebuildLimit 8
73:
74: /*
75: *---------------------------------------------------------
76: *
77: * Hash_InitTable --
78: *
79: * This routine just sets up the hash table.
80: *
81: * Results:
82: * None.
83: *
84: * Side Effects:
85: * Memory is allocated for the initial bucket area.
86: *
87: *---------------------------------------------------------
88: */
89:
90: void
91: Hash_InitTable(t, numBuckets)
92: register 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
97: * as needed. */
98: {
99: register int i;
100: register struct Hash_Entry **hp;
101:
102: /*
103: * Round up the size to a power of two.
104: */
105: if (numBuckets <= 0)
106: i = 16;
107: else {
108: for (i = 2; i < numBuckets; i <<= 1)
109: continue;
110: }
111: t->numEntries = 0;
112: t->size = i;
113: t->mask = i - 1;
114: t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
115: while (--i >= 0)
116: *hp++ = NULL;
117: }
118:
119: /*
120: *---------------------------------------------------------
121: *
122: * Hash_DeleteTable --
123: *
124: * This routine removes everything from a hash table
125: * and frees up the memory space it occupied (except for
126: * the space in the Hash_Table structure).
127: *
128: * Results:
129: * None.
130: *
131: * Side Effects:
132: * Lots of memory is freed up.
133: *
134: *---------------------------------------------------------
135: */
136:
137: void
138: Hash_DeleteTable(t)
139: Hash_Table *t;
140: {
141: register struct Hash_Entry **hp, *h, *nexth = NULL;
142: register int i;
143:
144: for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
145: for (h = *hp++; h != NULL; h = nexth) {
146: nexth = h->next;
147: free((char *)h);
148: }
149: }
150: free((char *)t->bucketPtr);
151:
152: /*
153: * Set up the hash table to cause memory faults on any future access
154: * attempts until re-initialization.
155: */
156: t->bucketPtr = NULL;
157: }
158:
159: /*
160: *---------------------------------------------------------
161: *
162: * Hash_FindEntry --
163: *
164: * Searches a hash table for an entry corresponding to key.
165: *
166: * Results:
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.
170: *
171: * Side Effects:
172: * None.
173: *
174: *---------------------------------------------------------
175: */
176:
177: Hash_Entry *
178: Hash_FindEntry(t, key)
179: Hash_Table *t; /* Hash table to search. */
180: char *key; /* A hash key. */
181: {
182: register Hash_Entry *e;
183: register unsigned h;
184: register char *p;
185:
186: for (h = 0, p = key; *p;)
187: h = (h << 5) - h + *p++;
188: p = key;
189: for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
190: if (e->namehash == h && strcmp(e->name, p) == 0)
191: return (e);
192: return (NULL);
193: }
194:
195: /*
196: *---------------------------------------------------------
197: *
198: * Hash_CreateEntry --
199: *
200: * Searches a hash table for an entry corresponding to
201: * key. If no entry is found, then one is created.
202: *
203: * Results:
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.
208: *
209: * Side Effects:
210: * Memory may be allocated, and the hash buckets may be modified.
211: *---------------------------------------------------------
212: */
213:
214: Hash_Entry *
215: Hash_CreateEntry(t, key, newPtr)
216: register Hash_Table *t; /* Hash table to search. */
217: char *key; /* A hash key. */
218: Boolean *newPtr; /* Filled in with TRUE if new entry created,
219: * FALSE otherwise. */
220: {
221: register Hash_Entry *e;
222: register unsigned h;
223: register char *p;
224: int keylen;
225: struct Hash_Entry **hp;
226:
227: /*
228: * Hash the key. As a side effect, save the length (strlen) of the
229: * key in case we need to create the entry.
230: */
231: for (h = 0, p = key; *p;)
232: h = (h << 5) - h + *p++;
233: keylen = p - key;
234: p = key;
235: for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
236: if (e->namehash == h && strcmp(e->name, p) == 0) {
237: if (newPtr != NULL)
238: *newPtr = FALSE;
239: return (e);
240: }
241: }
242:
243: /*
244: * The desired entry isn't there. Before allocating a new entry,
245: * expand the table if necessary (and this changes the resulting
246: * bucket chain).
247: */
248: if (t->numEntries >= rebuildLimit * t->size)
249: RebuildTable(t);
250: e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
251: hp = &t->bucketPtr[h & t->mask];
252: e->next = *hp;
253: *hp = e;
254: e->clientData = NULL;
255: e->namehash = h;
256: (void) strcpy(e->name, p);
257: t->numEntries++;
258:
259: if (newPtr != NULL)
260: *newPtr = TRUE;
261: return (e);
262: }
263:
264: /*
265: *---------------------------------------------------------
266: *
267: * Hash_DeleteEntry --
268: *
269: * Delete the given hash table entry and free memory associated with
270: * it.
271: *
272: * Results:
273: * None.
274: *
275: * Side Effects:
276: * Hash chain that entry lives in is modified and memory is freed.
277: *
278: *---------------------------------------------------------
279: */
280:
281: void
282: Hash_DeleteEntry(t, e)
283: Hash_Table *t;
284: Hash_Entry *e;
285: {
286: register Hash_Entry **hp, *p;
287:
288: if (e == NULL)
289: return;
290: for (hp = &t->bucketPtr[e->namehash & t->mask];
291: (p = *hp) != NULL; hp = &p->next) {
292: if (p == e) {
293: *hp = p->next;
294: free((char *)p);
295: t->numEntries--;
296: return;
297: }
298: }
299: (void) write(2, "bad call to Hash_DeleteEntry\n", 29);
300: abort();
301: }
302:
303: /*
304: *---------------------------------------------------------
305: *
306: * Hash_EnumFirst --
307: * This procedure sets things up for a complete search
308: * of all entries recorded in the hash table.
309: *
310: * Results:
311: * The return value is the address of the first entry in
312: * the hash table, or NULL if the table is empty.
313: *
314: * Side Effects:
315: * The information in searchPtr is initialized so that successive
316: * calls to Hash_Next will return successive HashEntry's
317: * from the table.
318: *
319: *---------------------------------------------------------
320: */
321:
322: Hash_Entry *
323: Hash_EnumFirst(t, searchPtr)
324: Hash_Table *t; /* Table to be searched. */
325: register Hash_Search *searchPtr;/* Area in which to keep state
326: * about search.*/
327: {
328: searchPtr->tablePtr = t;
329: searchPtr->nextIndex = 0;
330: searchPtr->hashEntryPtr = NULL;
331: return Hash_EnumNext(searchPtr);
332: }
333:
334: /*
335: *---------------------------------------------------------
336: *
337: * Hash_EnumNext --
338: * This procedure returns successive entries in the hash table.
339: *
340: * Results:
341: * The return value is a pointer to the next HashEntry
342: * in the table, or NULL when the end of the table is
343: * reached.
344: *
345: * Side Effects:
346: * The information in searchPtr is modified to advance to the
347: * next entry.
348: *
349: *---------------------------------------------------------
350: */
351:
352: Hash_Entry *
353: Hash_EnumNext(searchPtr)
354: register Hash_Search *searchPtr; /* Area used to keep state about
355: search. */
356: {
357: register Hash_Entry *e;
358: Hash_Table *t = searchPtr->tablePtr;
359:
360: /*
361: * The hashEntryPtr field points to the most recently returned
362: * entry, or is nil if we are starting up. If not nil, we have
363: * to start at the next one in the chain.
364: */
365: e = searchPtr->hashEntryPtr;
366: if (e != NULL)
367: e = e->next;
368: /*
369: * If the chain ran out, or if we are starting up, we need to
370: * find the next nonempty chain.
371: */
372: while (e == NULL) {
373: if (searchPtr->nextIndex >= t->size)
374: return (NULL);
375: e = t->bucketPtr[searchPtr->nextIndex++];
376: }
377: searchPtr->hashEntryPtr = e;
378: return (e);
379: }
380:
381: /*
382: *---------------------------------------------------------
383: *
384: * RebuildTable --
385: * This local routine makes a new hash table that
386: * is larger than the old one.
387: *
388: * Results:
389: * None.
390: *
391: * Side Effects:
392: * The entire hash table is moved, so any bucket numbers
393: * from the old table are invalid.
394: *
395: *---------------------------------------------------------
396: */
397:
398: static void
399: RebuildTable(t)
400: register Hash_Table *t;
401: {
402: register Hash_Entry *e, *next = NULL, **hp, **xp;
403: register int i, mask;
404: register Hash_Entry **oldhp;
405: int oldsize;
406:
407: oldhp = t->bucketPtr;
408: oldsize = i = t->size;
409: i <<= 1;
410: t->size = i;
411: t->mask = mask = i - 1;
412: t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
413: while (--i >= 0)
414: *hp++ = NULL;
415: for (hp = oldhp, i = oldsize; --i >= 0;) {
416: for (e = *hp++; e != NULL; e = next) {
417: next = e->next;
418: xp = &t->bucketPtr[e->namehash & mask];
419: e->next = *xp;
420: *xp = e;
421: }
422: }
423: free((char *)oldhp);
424: }
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