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
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
64 PRIVATE void hashi_FreeMembers(hash_member *, hash_freefp);
70 * Hash table initialization routine.
72 * This routine creates and intializes a hash table of size "tablesize"
73 * entries. Successful calls return a pointer to the hash table (which must
74 * be passed to other hash routines to identify the hash table). Failed
82 register hash_tbl *hashtblptr;
83 register unsigned totalsize;
86 totalsize = sizeof(hash_tbl)
87 + sizeof(hash_member *) * (tablesize - 1);
88 hashtblptr = (hash_tbl *) malloc(totalsize);
90 bzero((char *) hashtblptr, totalsize);
91 hashtblptr->size = tablesize; /* Success! */
92 hashtblptr->bucketnum = 0;
93 hashtblptr->member = (hashtblptr->table)[0];
96 hashtblptr = NULL; /* Disallow zero-length tables */
98 return hashtblptr; /* NULL if failure */
104 * Frees an entire linked list of bucket members (used in the open
105 * hashing scheme). Does nothing if the passed pointer is NULL.
109 hashi_FreeMembers(bucketptr, free_data)
110 hash_member *bucketptr;
111 hash_freefp free_data;
113 hash_member *nextbucket;
115 nextbucket = bucketptr->next;
116 (*free_data) (bucketptr->data);
117 free((char *) bucketptr);
118 bucketptr = nextbucket;
126 * This routine re-initializes the hash table. It frees all the allocated
127 * memory and resets all bucket pointers to NULL.
131 hash_Reset(hashtable, free_data)
133 hash_freefp free_data;
135 hash_member **bucketptr;
138 bucketptr = hashtable->table;
139 for (i = 0; i < hashtable->size; i++) {
140 hashi_FreeMembers(*bucketptr, free_data);
143 hashtable->bucketnum = 0;
144 hashtable->member = (hashtable->table)[0];
150 * Generic hash function to calculate a hash code from the given string.
152 * For each byte of the string, this function left-shifts the value in an
153 * accumulator and then adds the byte into the accumulator. The contents of
154 * the accumulator is returned after the entire string has been processed.
155 * It is assumed that this result will be used as the "hashcode" parameter in
156 * calls to other functions in this package. These functions automatically
157 * adjust the hashcode for the size of each hashtable.
159 * This algorithm probably works best when the hash table size is a prime
162 * Hopefully, this function is better than the previous one which returned
163 * the sum of the squares of all the bytes. I'm still open to other
164 * suggestions for a default hash function. The programmer is more than
165 * welcome to supply his/her own hash function as that is one of the design
166 * features of this package.
170 hash_HashFunction(string, len)
171 unsigned char *string;
172 register unsigned len;
174 register unsigned accum;
177 for (; len > 0; len--) {
179 accum += (unsigned) (*string++ & 0xFF);
187 * Returns TRUE if at least one entry for the given key exists; FALSE
192 hash_Exists(hashtable, hashcode, compare, key)
198 register hash_member *memberptr;
200 memberptr = (hashtable->table)[hashcode % (hashtable->size)];
202 if ((*compare) (key, memberptr->data)) {
203 return TRUE; /* Entry does exist */
205 memberptr = memberptr->next;
207 return FALSE; /* Entry does not exist */
213 * Insert the data item "element" into the hash table using "hashcode"
214 * to determine the bucket number, and "compare" and "key" to determine
217 * If the insertion is successful 0 is returned. If a matching entry
218 * already exists in the given bucket of the hash table, or some other error
219 * occurs, -1 is returned and the insertion is not done.
223 hash_Insert(hashtable, hashcode, compare, key, element)
227 hash_datum *key, *element;
231 hashcode %= hashtable->size;
232 if (hash_Exists(hashtable, hashcode, compare, key)) {
233 return -1; /* At least one entry already exists */
235 temp = (hash_member *) malloc(sizeof(hash_member));
237 return -1; /* malloc failed! */
239 temp->data = element;
240 temp->next = (hashtable->table)[hashcode];
241 (hashtable->table)[hashcode] = temp;
242 return 0; /* Success */
248 * Delete all data elements which match the given key. If at least one
249 * element is found and the deletion is successful, 0 is returned.
250 * If no matching elements can be found in the hash table, -1 is returned.
254 hash_Delete(hashtable, hashcode, compare, key, free_data)
259 hash_freefp free_data;
261 hash_member *memberptr, *tempptr;
262 hash_member *previous = NULL;
266 hashcode %= hashtable->size;
269 * Delete the first member of the list if it matches. Since this moves
270 * the second member into the first position we have to keep doing this
271 * over and over until it no longer matches.
273 memberptr = (hashtable->table)[hashcode];
274 while (memberptr && (*compare) (key, memberptr->data)) {
275 (hashtable->table)[hashcode] = memberptr->next;
277 * Stop hashi_FreeMembers() from deleting the whole list!
279 memberptr->next = NULL;
280 hashi_FreeMembers(memberptr, free_data);
281 memberptr = (hashtable->table)[hashcode];
286 * Now traverse the rest of the list
289 previous = memberptr;
290 memberptr = memberptr->next;
293 if ((*compare) (key, memberptr->data)) {
295 previous->next = memberptr = memberptr->next;
297 * Put the brakes on hashi_FreeMembers(). . . .
299 tempptr->next = NULL;
300 hashi_FreeMembers(tempptr, free_data);
303 previous = memberptr;
304 memberptr = memberptr->next;
313 * Locate and return the data entry associated with the given key.
315 * If the data entry is found, a pointer to it is returned. Otherwise,
320 hash_Lookup(hashtable, hashcode, compare, key)
326 hash_member *memberptr;
328 memberptr = (hashtable->table)[hashcode % (hashtable->size)];
330 if ((*compare) (key, memberptr->data)) {
331 return (memberptr->data);
333 memberptr = memberptr->next;
341 * Return the next available entry in the hashtable for a linear search
345 hash_NextEntry(hashtable)
348 register unsigned bucket;
349 register hash_member *memberptr;
352 * First try to pick up where we left off.
354 memberptr = hashtable->member;
356 hashtable->member = memberptr->next; /* Set up for next call */
357 return memberptr->data; /* Return the data */
360 * We hit the end of a chain, so look through the array of buckets
361 * until we find a new chain (non-empty bucket) or run out of buckets.
363 bucket = hashtable->bucketnum + 1;
364 while ((bucket < hashtable->size) &&
365 !(memberptr = (hashtable->table)[bucket])) {
370 * Check to see if we ran out of buckets.
372 if (bucket >= hashtable->size) {
374 * Reset to top of table for next call.
376 hashtable->bucketnum = 0;
377 hashtable->member = (hashtable->table)[0];
379 * But return end-of-table indication to the caller this time.
384 * Must have found a non-empty bucket.
386 hashtable->bucketnum = bucket;
387 hashtable->member = memberptr->next; /* Set up for next call */
388 return memberptr->data; /* Return the data */
394 * Return the first entry in a hash table for a linear search
398 hash_FirstEntry(hashtable)
401 hashtable->bucketnum = 0;
402 hashtable->member = (hashtable->table)[0];
403 return hash_NextEntry(hashtable);
410 * c-argdecl-indent: 4
411 * c-continued-statement-offset: 4
412 * c-continued-brace-offset: -4