2 * Bacula hash table routines
4 * htable is a hash table of items (pointers). This code is
5 * adapted and enhanced from code I wrote in 1982 for a
6 * relocatable linker. At that time, the hash table size
7 * was fixed and a primary number, which essentially provides
8 * the randomness. In this program, the hash table can grow when
9 * it gets too full, so the table size here is a binary number. The
10 * hashing is provided using an idea from Tcl where the initial
11 * hash code is "randomized" using a simple calculation from
12 * a random number generator that multiplies by a big number
13 * (I multiply by a prime number, while Tcl did not)
14 * then shifts the result down and does the binary division
15 * by masking. Increasing the size of the hash table is simple.
16 * Just create a new larger table, walk the old table and
17 * re-hash insert each entry into the new table.
20 * Kern Sibbald, July MMIII
26 Bacula® - The Network Backup Solution
28 Copyright (C) 2003-2006 Free Software Foundation Europe e.V.
30 The main author of Bacula is Kern Sibbald, with contributions from
31 many others, a complete list can be found in the file AUTHORS.
32 This program is Free Software; you can redistribute it and/or
33 modify it under the terms of version two of the GNU General Public
34 License as published by the Free Software Foundation and included
37 This program is distributed in the hope that it will be useful, but
38 WITHOUT ANY WARRANTY; without even the implied warranty of
39 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
40 General Public License for more details.
42 You should have received a copy of the GNU General Public License
43 along with this program; if not, write to the Free Software
44 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
47 Bacula® is a registered trademark of John Walker.
48 The licensor of Bacula is the Free Software Foundation Europe
49 (FSFE), Fiduciary Program, Sumatrastrasse 25, 8006 Zürich,
50 Switzerland, email:ftf@fsfeurope.org.
57 /* ===================================================================
62 * Create hash of key, stored in hash then
63 * create and return the pseudo random bucket index
65 void htable::hash_index(char *key)
68 for (char *p=key; *p; p++) {
69 hash += (hash << 3) + (uint32_t)*p;
71 /* Multiply by large prime number, take top bits, mask for remainder */
72 index = ((hash * 1103515249) >> rshift) & mask;
73 Dmsg2(100, "Leave hash_index hash=0x%x index=%d\n", hash, index);
76 htable::htable(void *item, void *link, int tsize)
78 init(item, link, tsize);
81 void htable::init(void *item, void *link, int tsize)
85 for (pwr=0; tsize; pwr++) {
88 loffset = (char *)link - (char *)item;
89 mask = ~((~0)<<pwr); /* 3 bits => table size = 8 */
90 rshift = 30 - pwr; /* start using bits 28, 29, 30 */
91 num_items = 0; /* number of entries in table */
92 buckets = 1<<pwr; /* hash table size -- power of two */
93 max_items = buckets * 4; /* allow average 4 entries per chain */
94 table = (hlink **)malloc(buckets * sizeof(hlink *));
95 memset(table, 0, buckets * sizeof(hlink *));
100 uint32_t htable::size()
106 * Take each hash link and walk down the chain of items
107 * that hash there counting them (i.e. the hits),
108 * then report that number.
109 * Obiously, the more hits in a chain, the more time
110 * it takes to reference them. Empty chains are not so
111 * hot either -- as it means unused or wasted space.
120 printf("\n\nNumItems=%d\nTotal buckets=%d\n", num_items, buckets);
121 printf("Hits/bucket: buckets\n");
122 for (i=0; i < MAX_COUNT; i++) {
125 for (i=0; i<(int)buckets; i++) {
129 p = (hlink *)(p->next);
139 for (i=0; i < MAX_COUNT; i++) {
140 printf("%2d: %d\n",i, hits[i]);
142 printf("max hits in a bucket = %d\n", max);
145 void htable::grow_table()
147 Dmsg1(100, "Grow called old size = %d\n", buckets);
148 /* Setup a bigger table */
149 htable *big = (htable *)malloc(sizeof(htable));
150 big->loffset = loffset;
151 big->mask = mask<<1 | 1;
152 big->rshift = rshift - 1;
154 big->buckets = buckets * 2;
155 big->max_items = big->buckets * 4;
156 big->table = (hlink **)malloc(big->buckets * sizeof(hlink *));
157 memset(big->table, 0, big->buckets * sizeof(hlink *));
160 /* Insert all the items in the new hash table */
161 Dmsg1(100, "Before copy num_items=%d\n", num_items);
163 * We walk through the old smaller tree getting items,
164 * but since we are overwriting the colision links, we must
165 * explicitly save the item->next pointer and walk each
166 * colision chain ourselves. We do use next() for getting
167 * to the next bucket.
169 for (void *item=first(); item; ) {
170 void *ni = ((hlink *)((char *)item+loffset))->next; /* save link overwritten by insert */
171 Dmsg1(100, "Grow insert: %s\n", ((hlink *)((char *)item+loffset))->key);
172 big->insert(((hlink *)((char *)item+loffset))->key, item);
174 item = (void *)((char *)ni-loffset);
180 Dmsg1(100, "After copy new num_items=%d\n", big->num_items);
181 if (num_items != big->num_items) {
182 Dmsg0(000, "****** Big problems num_items mismatch ******\n");
185 memcpy(this, big, sizeof(htable)); /* move everything across */
187 Dmsg0(100, "Exit grow.\n");
190 bool htable::insert(char *key, void *item)
194 return false; /* already exists */
196 sm_check(__FILE__, __LINE__, false);
197 ASSERT(index < buckets);
198 Dmsg2(100, "Insert: hash=0x%x index=%d\n", (unsigned)hash, index);
199 hp = (hlink *)(((char *)item)+loffset);
200 Dmsg4(100, "Insert hp=0x%x index=%d item=0x%x offset=%u\n", (unsigned)hp,
201 index, (unsigned)item, loffset);
202 hp->next = table[index];
206 Dmsg3(100, "Insert hp->next=0x%x hp->hash=0x%x hp->key=%s\n",
207 (unsigned)hp->next, hp->hash, hp->key);
209 if (++num_items >= max_items) {
210 Dmsg2(100, "num_items=%d max_items=%d\n", num_items, max_items);
213 sm_check(__FILE__, __LINE__, false);
214 Dmsg3(100, "Leave insert index=%d num_items=%d key=%s\n", index, num_items, key);
218 void *htable::lookup(char *key)
221 for (hlink *hp=table[index]; hp; hp=(hlink *)hp->next) {
222 // Dmsg2(100, "hp=0x%x key=%s\n", (long)hp, hp->key);
223 if (hash == hp->hash && strcmp(key, hp->key) == 0) {
224 Dmsg1(100, "lookup return %x\n", ((char *)hp)-loffset);
225 return ((char *)hp)-loffset;
233 Dmsg1(100, "Enter next: walkptr=0x%x\n", (unsigned)walkptr);
235 walkptr = (hlink *)(walkptr->next);
237 while (!walkptr && walk_index < buckets) {
238 walkptr = table[walk_index++];
240 Dmsg3(100, "new walkptr=0x%x next=0x%x inx=%d\n", (unsigned)walkptr,
241 (unsigned)(walkptr->next), walk_index-1);
245 Dmsg2(100, "next: rtn 0x%x walk_index=%d\n",
246 (unsigned)(((char *)walkptr)-loffset), walk_index);
247 return ((char *)walkptr)-loffset;
249 Dmsg0(100, "next: return NULL\n");
253 void *htable::first()
255 Dmsg0(100, "Enter first\n");
256 walkptr = table[0]; /* get first bucket */
257 walk_index = 1; /* Point to next index */
258 while (!walkptr && walk_index < buckets) {
259 walkptr = table[walk_index++]; /* go to next bucket */
261 Dmsg3(100, "first new walkptr=0x%x next=0x%x inx=%d\n", (unsigned)walkptr,
262 (unsigned)(walkptr->next), walk_index-1);
266 Dmsg1(100, "Leave first walkptr=0x%x\n", (unsigned)walkptr);
267 return ((char *)walkptr)-loffset;
269 Dmsg0(100, "Leave first walkptr=NULL\n");
273 /* Destroy the table and its contents */
274 void htable::destroy()
286 Dmsg0(100, "Done destroy.\n");
304 MYJCR *save_jcr = NULL, *item;
308 jcrtbl = (htable *)malloc(sizeof(htable));
309 jcrtbl->init(jcr, &jcr->link, NITEMS);
311 Dmsg1(000, "Inserting %d items\n", NITEMS);
312 for (int i=0; i<NITEMS; i++) {
313 sprintf(mkey, "This is htable item %d", i);
314 jcr = (MYJCR *)malloc(sizeof(MYJCR));
315 Dmsg2(100, "link=0x%x jcr=0x%x\n", (unsigned)&jcr->link, (unsigned)jcr);
316 jcr->key = bstrdup(mkey);
318 jcrtbl->insert(jcr->key, jcr);
323 if (!(item = (MYJCR *)jcrtbl->lookup(save_jcr->key))) {
324 printf("Bad news: %s not found.\n", save_jcr->key);
326 printf("Item 10's key is: %s\n", item->key);
330 printf("Walk the hash table:\n");
331 foreach_htable (jcr, jcrtbl) {
332 // printf("htable item = %s\n", jcr->key);
336 printf("Got %d items -- %s\n", count, count==NITEMS?"OK":"***ERROR***");
337 printf("Calling destroy\n");
341 printf("Freed jcrtbl\n");