1 /************************************************************************
2 Copyright 1988, 1991 by Carnegie Mellon University
6 Permission to use, copy, modify, and distribute this software and its
7 documentation for any purpose and without fee is hereby granted, provided
8 that the above copyright notice appear in all copies and that both that
9 copyright notice and this permission notice appear in supporting
10 documentation, and that the name of Carnegie Mellon University not be used
11 in advertising or publicity pertaining to distribution of the software
12 without specific, written prior permission.
14 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
15 SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
16 IN NO EVENT SHALL CMU BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
17 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
18 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
19 ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
22 $FreeBSD: src/libexec/bootpd/hash.c,v 1.5 1999/08/28 00:09:18 peter Exp $
24 ************************************************************************/
27 * Generalized hash table ADT
29 * Provides multiple, dynamically-allocated, variable-sized hash tables on
30 * various data and keys.
32 * This package attempts to follow some of the coding conventions suggested
33 * by Bob Sidebotham and the AFS Clean Code Committee of the
34 * Information Technology Center at Carnegie Mellon.
38 #include <sys/types.h>
43 /* Yes, memcpy is OK here (no overlapped copies). */
44 #define bcopy(a,b,c) memcpy(b,a,c)
45 #define bzero(p,l) memset(p,0,l)
46 #define bcmp(a,b,c) memcmp(a,b,c)
58 * This can be changed to make internal routines visible to debuggers, etc.
61 #define PRIVATE static
70 PRIVATE void hashi_FreeMembers P((hash_member *, hash_freefp));
77 * Hash table initialization routine.
79 * This routine creates and intializes a hash table of size "tablesize"
80 * entries. Successful calls return a pointer to the hash table (which must
81 * be passed to other hash routines to identify the hash table). Failed
89 register hash_tbl *hashtblptr;
90 register unsigned totalsize;
93 totalsize = sizeof(hash_tbl)
94 + sizeof(hash_member *) * (tablesize - 1);
95 hashtblptr = (hash_tbl *) malloc(totalsize);
97 bzero((char *) hashtblptr, totalsize);
98 hashtblptr->size = tablesize; /* Success! */
99 hashtblptr->bucketnum = 0;
100 hashtblptr->member = (hashtblptr->table)[0];
103 hashtblptr = NULL; /* Disallow zero-length tables */
105 return hashtblptr; /* NULL if failure */
111 * Frees an entire linked list of bucket members (used in the open
112 * hashing scheme). Does nothing if the passed pointer is NULL.
116 hashi_FreeMembers(bucketptr, free_data)
117 hash_member *bucketptr;
118 hash_freefp free_data;
120 hash_member *nextbucket;
122 nextbucket = bucketptr->next;
123 (*free_data) (bucketptr->data);
124 free((char *) bucketptr);
125 bucketptr = nextbucket;
133 * This routine re-initializes the hash table. It frees all the allocated
134 * memory and resets all bucket pointers to NULL.
138 hash_Reset(hashtable, free_data)
140 hash_freefp free_data;
142 hash_member **bucketptr;
145 bucketptr = hashtable->table;
146 for (i = 0; i < hashtable->size; i++) {
147 hashi_FreeMembers(*bucketptr, free_data);
150 hashtable->bucketnum = 0;
151 hashtable->member = (hashtable->table)[0];
157 * Generic hash function to calculate a hash code from the given string.
159 * For each byte of the string, this function left-shifts the value in an
160 * accumulator and then adds the byte into the accumulator. The contents of
161 * the accumulator is returned after the entire string has been processed.
162 * It is assumed that this result will be used as the "hashcode" parameter in
163 * calls to other functions in this package. These functions automatically
164 * adjust the hashcode for the size of each hashtable.
166 * This algorithm probably works best when the hash table size is a prime
169 * Hopefully, this function is better than the previous one which returned
170 * the sum of the squares of all the bytes. I'm still open to other
171 * suggestions for a default hash function. The programmer is more than
172 * welcome to supply his/her own hash function as that is one of the design
173 * features of this package.
177 hash_HashFunction(string, len)
178 unsigned char *string;
179 register unsigned len;
181 register unsigned accum;
184 for (; len > 0; len--) {
186 accum += (unsigned) (*string++ & 0xFF);
194 * Returns TRUE if at least one entry for the given key exists; FALSE
199 hash_Exists(hashtable, hashcode, compare, key)
205 register hash_member *memberptr;
207 memberptr = (hashtable->table)[hashcode % (hashtable->size)];
209 if ((*compare) (key, memberptr->data)) {
210 return TRUE; /* Entry does exist */
212 memberptr = memberptr->next;
214 return FALSE; /* Entry does not exist */
220 * Insert the data item "element" into the hash table using "hashcode"
221 * to determine the bucket number, and "compare" and "key" to determine
224 * If the insertion is successful 0 is returned. If a matching entry
225 * already exists in the given bucket of the hash table, or some other error
226 * occurs, -1 is returned and the insertion is not done.
230 hash_Insert(hashtable, hashcode, compare, key, element)
234 hash_datum *key, *element;
238 hashcode %= hashtable->size;
239 if (hash_Exists(hashtable, hashcode, compare, key)) {
240 return -1; /* At least one entry already exists */
242 temp = (hash_member *) malloc(sizeof(hash_member));
244 return -1; /* malloc failed! */
246 temp->data = element;
247 temp->next = (hashtable->table)[hashcode];
248 (hashtable->table)[hashcode] = temp;
249 return 0; /* Success */
255 * Delete all data elements which match the given key. If at least one
256 * element is found and the deletion is successful, 0 is returned.
257 * If no matching elements can be found in the hash table, -1 is returned.
261 hash_Delete(hashtable, hashcode, compare, key, free_data)
266 hash_freefp free_data;
268 hash_member *memberptr, *tempptr;
269 hash_member *previous = NULL;
273 hashcode %= hashtable->size;
276 * Delete the first member of the list if it matches. Since this moves
277 * the second member into the first position we have to keep doing this
278 * over and over until it no longer matches.
280 memberptr = (hashtable->table)[hashcode];
281 while (memberptr && (*compare) (key, memberptr->data)) {
282 (hashtable->table)[hashcode] = memberptr->next;
284 * Stop hashi_FreeMembers() from deleting the whole list!
286 memberptr->next = NULL;
287 hashi_FreeMembers(memberptr, free_data);
288 memberptr = (hashtable->table)[hashcode];
293 * Now traverse the rest of the list
296 previous = memberptr;
297 memberptr = memberptr->next;
300 if ((*compare) (key, memberptr->data)) {
302 previous->next = memberptr = memberptr->next;
304 * Put the brakes on hashi_FreeMembers(). . . .
306 tempptr->next = NULL;
307 hashi_FreeMembers(tempptr, free_data);
310 previous = memberptr;
311 memberptr = memberptr->next;
320 * Locate and return the data entry associated with the given key.
322 * If the data entry is found, a pointer to it is returned. Otherwise,
327 hash_Lookup(hashtable, hashcode, compare, key)
333 hash_member *memberptr;
335 memberptr = (hashtable->table)[hashcode % (hashtable->size)];
337 if ((*compare) (key, memberptr->data)) {
338 return (memberptr->data);
340 memberptr = memberptr->next;
348 * Return the next available entry in the hashtable for a linear search
352 hash_NextEntry(hashtable)
355 register unsigned bucket;
356 register hash_member *memberptr;
359 * First try to pick up where we left off.
361 memberptr = hashtable->member;
363 hashtable->member = memberptr->next; /* Set up for next call */
364 return memberptr->data; /* Return the data */
367 * We hit the end of a chain, so look through the array of buckets
368 * until we find a new chain (non-empty bucket) or run out of buckets.
370 bucket = hashtable->bucketnum + 1;
371 while ((bucket < hashtable->size) &&
372 !(memberptr = (hashtable->table)[bucket])) {
377 * Check to see if we ran out of buckets.
379 if (bucket >= hashtable->size) {
381 * Reset to top of table for next call.
383 hashtable->bucketnum = 0;
384 hashtable->member = (hashtable->table)[0];
386 * But return end-of-table indication to the caller this time.
391 * Must have found a non-empty bucket.
393 hashtable->bucketnum = bucket;
394 hashtable->member = memberptr->next; /* Set up for next call */
395 return memberptr->data; /* Return the data */
401 * Return the first entry in a hash table for a linear search
405 hash_FirstEntry(hashtable)
408 hashtable->bucketnum = 0;
409 hashtable->member = (hashtable->table)[0];
410 return hash_NextEntry(hashtable);
417 * c-argdecl-indent: 4
418 * c-continued-statement-offset: 4
419 * c-continued-brace-offset: -4