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 #define TDB_NEXT_LOCK_ERR ((tdb_off_t)-1)
32 /* Uses traverse lock: 0 = finish, TDB_NEXT_LOCK_ERR = error,
33 other = record offset */
34 static tdb_off_t tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
35 struct list_struct *rec)
37 int want_next = (tlock->off != 0);
39 /* Lock each chain from the start one. */
40 for (; tlock->hash < tdb->header.hash_size; tlock->hash++) {
41 if (!tlock->off && tlock->hash != 0) {
42 /* this is an optimisation for the common case where
43 the hash chain is empty, which is particularly
44 common for the use of tdb with ldb, where large
45 hashes are used. In that case we spend most of our
46 time in tdb_brlock(), locking empty hash chains.
48 To avoid this, we do an unlocked pre-check to see
49 if the hash chain is empty before starting to look
50 inside it. If it is empty then we can avoid that
51 hash chain. If it isn't empty then we can't believe
52 the value we get back, as we read it without a
53 lock, so instead we get the lock and re-fetch the
56 Notice that not doing this optimisation on the
57 first hash chain is critical. We must guarantee
58 that we have done at least one fcntl lock at the
59 start of a search to guarantee that memory is
60 coherent on SMP systems. If records are added by
61 others during the search then thats OK, and we
62 could possibly miss those with this trick, but we
63 could miss them anyway without this trick, so the
64 semantics don't change.
66 With a non-indexed ldb search this trick gains us a
67 factor of around 80 in speed on a linux 2.6.x
68 system (testing using ldbtest).
70 tdb->methods->next_hash_chain(tdb, &tlock->hash);
71 if (tlock->hash == tdb->header.hash_size) {
76 if (tdb_lock(tdb, tlock->hash, tlock->lock_rw) == -1)
77 return TDB_NEXT_LOCK_ERR;
79 /* No previous record? Start at top of chain. */
81 if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
85 /* Otherwise unlock the previous record. */
86 if (tdb_unlock_record(tdb, tlock->off) != 0)
91 /* We have offset of old record: grab next */
92 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
94 tlock->off = rec->next;
97 /* Iterate through chain */
100 if (tdb_rec_read(tdb, tlock->off, rec) == -1)
103 /* Detect infinite loops. From "Shlomi Yaakobovich" <Shlomi@exanet.com>. */
104 if (tlock->off == rec->next) {
105 tdb->ecode = TDB_ERR_CORRUPT;
106 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
110 if (!TDB_DEAD(rec)) {
111 /* Woohoo: we found one! */
112 if (tdb_lock_record(tdb, tlock->off) != 0)
117 /* Try to clean dead ones from old traverses */
118 current = tlock->off;
119 tlock->off = rec->next;
120 if (!(tdb->read_only || tdb->traverse_read) &&
121 tdb_do_delete(tdb, current, rec) != 0)
124 tdb_unlock(tdb, tlock->hash, tlock->lock_rw);
127 /* We finished iteration without finding anything */
128 return TDB_ERRCODE(TDB_SUCCESS, 0);
132 if (tdb_unlock(tdb, tlock->hash, tlock->lock_rw) != 0)
133 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
134 return TDB_NEXT_LOCK_ERR;
137 /* traverse the entire database - calling fn(tdb, key, data) on each element.
138 return -1 on error or the record count traversed
139 if fn is NULL then it is not called
140 a non-zero return value from fn() indicates that the traversal should stop
142 static int tdb_traverse_internal(struct tdb_context *tdb,
143 tdb_traverse_func fn, void *private_data,
144 struct tdb_traverse_lock *tl)
147 struct list_struct rec;
148 int ret = 0, count = 0;
151 /* This was in the initializaton, above, but the IRIX compiler
152 * did not like it. crh
154 tl->next = tdb->travlocks.next;
156 /* fcntl locks don't stack: beware traverse inside traverse */
157 tdb->travlocks.next = tl;
159 /* tdb_next_lock places locks on the record returned, and its chain */
160 while ((off = tdb_next_lock(tdb, tl, &rec)) != 0) {
161 if (off == TDB_NEXT_LOCK_ERR) {
166 /* now read the full record */
167 key.dptr = tdb_alloc_read(tdb, tl->off + sizeof(rec),
168 rec.key_len + rec.data_len);
171 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0)
173 if (tdb_unlock_record(tdb, tl->off) != 0)
174 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
177 key.dsize = rec.key_len;
178 dbuf.dptr = key.dptr + rec.key_len;
179 dbuf.dsize = rec.data_len;
181 tdb_trace_1rec_retrec(tdb, "traverse", key, dbuf);
183 /* Drop chain lock, call out */
184 if (tdb_unlock(tdb, tl->hash, tl->lock_rw) != 0) {
189 if (fn && fn(tdb, key, dbuf, private_data)) {
190 /* They want us to terminate traversal */
191 tdb_trace_ret(tdb, "tdb_traverse_end", count);
192 if (tdb_unlock_record(tdb, tl->off) != 0) {
193 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_traverse: unlock_record failed!\n"));;
201 tdb_trace(tdb, "tdb_traverse_end");
203 tdb->travlocks.next = tl->next;
212 a write style traverse - temporarily marks the db read only
214 int tdb_traverse_read(struct tdb_context *tdb,
215 tdb_traverse_func fn, void *private_data)
217 struct tdb_traverse_lock tl = { NULL, 0, 0, F_RDLCK };
220 /* we need to get a read lock on the transaction lock here to
221 cope with the lock ordering semantics of solaris10 */
222 if (tdb_transaction_lock(tdb, F_RDLCK)) {
226 tdb->traverse_read++;
227 tdb_trace(tdb, "tdb_traverse_read_start");
228 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
229 tdb->traverse_read--;
231 tdb_transaction_unlock(tdb);
237 a write style traverse - needs to get the transaction lock to
240 WARNING: The data buffer given to the callback fn does NOT meet the
241 alignment restrictions malloc gives you.
243 int tdb_traverse(struct tdb_context *tdb,
244 tdb_traverse_func fn, void *private_data)
246 struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
249 if (tdb->read_only || tdb->traverse_read) {
250 return tdb_traverse_read(tdb, fn, private_data);
253 if (tdb_transaction_lock(tdb, F_WRLCK)) {
257 tdb->traverse_write++;
258 tdb_trace(tdb, "tdb_traverse_start");
259 ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
260 tdb->traverse_write--;
262 tdb_transaction_unlock(tdb);
268 /* find the first entry in the database and return its key */
269 TDB_DATA tdb_firstkey(struct tdb_context *tdb)
272 struct list_struct rec;
275 /* release any old lock */
276 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0)
278 tdb->travlocks.off = tdb->travlocks.hash = 0;
279 tdb->travlocks.lock_rw = F_RDLCK;
281 /* Grab first record: locks chain and returned record. */
282 off = tdb_next_lock(tdb, &tdb->travlocks, &rec);
283 if (off == 0 || off == TDB_NEXT_LOCK_ERR) {
284 tdb_trace_retrec(tdb, "tdb_firstkey", tdb_null);
287 /* now read the key */
288 key.dsize = rec.key_len;
289 key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
291 tdb_trace_retrec(tdb, "tdb_firstkey", key);
293 /* Unlock the hash chain of the record we just read. */
294 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
295 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
299 /* find the next entry in the database, returning its key */
300 TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA oldkey)
303 TDB_DATA key = tdb_null;
304 struct list_struct rec;
305 unsigned char *k = NULL;
308 /* Is locked key the old key? If so, traverse will be reliable. */
309 if (tdb->travlocks.off) {
310 if (tdb_lock(tdb,tdb->travlocks.hash,tdb->travlocks.lock_rw))
312 if (tdb_rec_read(tdb, tdb->travlocks.off, &rec) == -1
313 || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
315 || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
316 /* No, it wasn't: unlock it and start from scratch */
317 if (tdb_unlock_record(tdb, tdb->travlocks.off) != 0) {
318 tdb_trace_1rec_retrec(tdb, "tdb_nextkey",
323 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0) {
327 tdb->travlocks.off = 0;
333 if (!tdb->travlocks.off) {
334 /* No previous element: do normal find, and lock record */
335 tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), tdb->travlocks.lock_rw, &rec);
336 if (!tdb->travlocks.off) {
337 tdb_trace_1rec_retrec(tdb, "tdb_nextkey", oldkey, tdb_null);
340 tdb->travlocks.hash = BUCKET(rec.full_hash);
341 if (tdb_lock_record(tdb, tdb->travlocks.off) != 0) {
342 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
346 oldhash = tdb->travlocks.hash;
348 /* Grab next record: locks chain and returned record,
349 unlocks old record */
350 off = tdb_next_lock(tdb, &tdb->travlocks, &rec);
351 if (off != TDB_NEXT_LOCK_ERR && off != 0) {
352 key.dsize = rec.key_len;
353 key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
355 /* Unlock the chain of this new record */
356 if (tdb_unlock(tdb, tdb->travlocks.hash, tdb->travlocks.lock_rw) != 0)
357 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
359 /* Unlock the chain of old record */
360 if (tdb_unlock(tdb, BUCKET(oldhash), tdb->travlocks.lock_rw) != 0)
361 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
362 tdb_trace_1rec_retrec(tdb, "tdb_nextkey", oldkey, key);