2 Unix SMB/CIFS implementation.
4 trivial database library
6 Copyright (C) Andrew Tridgell 1999-2005
7 Copyright (C) Paul `Rusty' Russell 2000
8 Copyright (C) Jeremy Allison 2000-2003
10 ** NOTE! The following LGPL license applies to the tdb
11 ** library. This does NOT imply that all of Samba is released
14 This library is free software; you can redistribute it and/or
15 modify it under the terms of the GNU Lesser General Public
16 License as published by the Free Software Foundation; either
17 version 3 of the License, or (at your option) any later version.
19 This library is distributed in the hope that it will be useful,
20 but WITHOUT ANY WARRANTY; without even the implied warranty of
21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
22 Lesser General Public License for more details.
24 You should have received a copy of the GNU Lesser General Public
25 License along with this library; if not, see <http://www.gnu.org/licenses/>.
28 #include "tdb_private.h"
30 /* Uses traverse lock: 0 = finish, -1 = error, other = record offset */
31 static int tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
32 struct list_struct *rec)
34 int want_next = (tlock->off != 0);
36 /* Lock each chain from the start one. */
37 for (; tlock->hash < tdb->header.hash_size; tlock->hash++) {
38 if (!tlock->off && tlock->hash != 0) {
39 /* this is an optimisation for the common case where
40 the hash chain is empty, which is particularly
41 common for the use of tdb with ldb, where large
42 hashes are used. In that case we spend most of our
43 time in tdb_brlock(), locking empty hash chains.
45 To avoid this, we do an unlocked pre-check to see
46 if the hash chain is empty before starting to look
47 inside it. If it is empty then we can avoid that
48 hash chain. If it isn't empty then we can't believe
49 the value we get back, as we read it without a
50 lock, so instead we get the lock and re-fetch the
53 Notice that not doing this optimisation on the
54 first hash chain is critical. We must guarantee
55 that we have done at least one fcntl lock at the
56 start of a search to guarantee that memory is
57 coherent on SMP systems. If records are added by
58 others during the search then thats OK, and we
59 could possibly miss those with this trick, but we
60 could miss them anyway without this trick, so the
61 semantics don't change.
63 With a non-indexed ldb search this trick gains us a
64 factor of around 80 in speed on a linux 2.6.x
65 system (testing using ldbtest).
67 tdb->methods->next_hash_chain(tdb, &tlock->hash);
68 if (tlock->hash == tdb->header.hash_size) {
73 if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
76 /* No previous record? Start at top of chain. */
78 if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
82 /* Otherwise unlock the previous record. */
83 if (tdb_unlock_record(tdb, tlock->off) != 0)
88 /* We have offset of old record: grab next */
89 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
91 tlock->off = rec->next;
94 /* Iterate through chain */
97 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
100 /* Detect infinite loops. From "Shlomi Yaakobovich" <Shlomi@exanet.com>. */
101 if (tlock->off == rec->next) {
102 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
106 if (!TDB_DEAD(rec)) {
107 /* Woohoo: we found one! */
108 if (tdb_lock_record(tdb, tlock->off) != 0)
113 /* Try to clean dead ones from old traverses */
114 current = tlock->off;
115 tlock->off = rec->next;
116 if (!(tdb->read_only || tdb->traverse_read) &&
117 tdb_do_delete(tdb, current, rec) != 0)
120 tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
123 /* We finished iteration without finding anything */
124 return TDB_ERRCODE(TDB_SUCCESS, 0);
128 if (tdb_unlock(tdb, tlock->hash, tlock->lock_rw) != 0)
129 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
133 /* traverse the entire database - calling fn(tdb, key, data) on each element.
134 return -1 on error or the record count traversed
135 if fn is NULL then it is not called
136 a non-zero return value from fn() indicates that the traversal should stop
138 static int tdb_traverse_internal(struct tdb_context *tdb,
139 tdb_traverse_func fn, void *private_data,
140 struct tdb_traverse_lock *tl)
143 struct list_struct rec;
146 /* This was in the initializaton, above, but the IRIX compiler
147 * did not like it. crh
149 tl->next = tdb->travlocks.next;
151 /* fcntl locks don't stack: beware traverse inside traverse */
152 tdb->travlocks.next = tl;
154 /* tdb_next_lock places locks on the record returned, and its chain */
155 while ((ret = tdb_next_lock(tdb, tl, &rec)) > 0) {
157 /* now read the full record */
158 key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
159 rec.key_len + rec.data_len);
162 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
164 if (tdb_unlock_record(tdb, tl->off) != 0)
165 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
168 key.dsize = rec.key_len;
169 dbuf.dptr = key.dptr + rec.key_len;
170 dbuf.dsize = rec.data_len;
172 /* Drop chain lock, call out */
173 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
178 if (fn && fn(tdb, key, dbuf, private_data)) {
179 /* They want us to terminate traversal */
181 if (tdb_unlock_record(tdb, tl->off) != 0) {
182 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
191 tdb->travlocks.next = tl->next;
200 a write style traverse - temporarily marks the db read only
202 int tdb_traverse_read(struct tdb_context *tdb,
203 tdb_traverse_func fn, void *private_data)
205 struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
207 bool in_transaction = (tdb->transaction != NULL);
209 /* we need to get a read lock on the transaction lock here to
210 cope with the lock ordering semantics of solaris10 */
211 if (!in_transaction) {
212 if (tdb_transaction_lock(tdb, F_RDLCK)) {
217 tdb->traverse_read++;
218 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
219 tdb->traverse_read--;
221 if (!in_transaction) {
222 tdb_transaction_unlock(tdb);
229 a write style traverse - needs to get the transaction lock to
232 WARNING: The data buffer given to the callback fn does NOT meet the
233 alignment restrictions malloc gives you.
235 int tdb_traverse(struct tdb_context *tdb,
236 tdb_traverse_func fn, void *private_data)
238 struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
240 bool in_transaction = (tdb->transaction != NULL);
242 if (tdb->read_only || tdb->traverse_read) {
243 return tdb_traverse_read(tdb, fn, private_data);
246 if (!in_transaction) {
247 if (tdb_transaction_lock(tdb, F_WRLCK)) {
252 tdb->traverse_write++;
253 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
254 tdb->traverse_write--;
256 if (!in_transaction) {
257 tdb_transaction_unlock(tdb);
264 /* find the first entry in the database and return its key */
265 TDB_DATA tdb_firstkey(struct tdb_context *tdb)
268 struct list_struct rec;
270 /* release any old lock */
271 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
273 tdb->travlocks.off = tdb->travlocks.hash = 0;
274 tdb->travlocks.lock_rw = F_RDLCK;
276 /* Grab first record: locks chain and returned record. */
277 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) <= 0)
279 /* now read the key */
280 key.dsize = rec.key_len;
281 key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
283 /* Unlock the hash chain of the record we just read. */
284 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
285 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
289 /* find the next entry in the database, returning its key */
290 TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
293 TDB_DATA key = tdb_null;
294 struct list_struct rec;
295 unsigned char *k = NULL;
297 /* Is locked key the old key? If so, traverse will be reliable. */
298 if (tdb->travlocks.off) {
299 if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
301 if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
302 || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
304 || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
305 /* No, it wasn't: unlock it and start from scratch */
306 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
310 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
314 tdb->travlocks.off = 0;
320 if (!tdb->travlocks.off) {
321 /* No previous element: do normal find, and lock record */
322 tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
323 if (!tdb->travlocks.off)
325 tdb->travlocks.hash = BUCKET(rec.full_hash);
326 if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
327 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
331 oldhash = tdb->travlocks.hash;
333 /* Grab next record: locks chain and returned record,
334 unlocks old record */
335 if (tdb_next_lock(tdb, &tdb->travlocks, &rec) > 0) {
336 key.dsize = rec.key_len;
337 key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
339 /* Unlock the chain of this new record */
340 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
341 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
343 /* Unlock the chain of old record */
344 if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
345 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));