summaryrefslogtreecommitdiff
path: root/lib/tdb/include/tdb.h
blob: a34f089e66dd41acc829340981531145b208ceea (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
#ifndef __TDB_H__
#define __TDB_H__

/* 
   Unix SMB/CIFS implementation.

   trivial database library

   Copyright (C) Andrew Tridgell 1999-2004
   
     ** NOTE! The following LGPL license applies to the tdb
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL
   
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#ifdef  __cplusplus
extern "C" {
#endif

#include <signal.h>

/**
 * @defgroup tdb The tdb API
 *
 * tdb is a Trivial database. In concept, it is very much like GDBM, and BSD's
 * DB except that it allows multiple simultaneous writers and uses locking
 * internally to keep writers from trampling on each other. tdb is also
 * extremely small.
 *
 * @section tdb_interface Interface
 *
 * The interface is very similar to gdbm except for the following:
 *
 * <ul>
 * <li>different open interface. The tdb_open call is more similar to a
 * traditional open()</li>
 * <li>no tdbm_reorganise() function</li>
 * <li>no tdbm_sync() function. No operations are cached in the library
 *     anyway</li>
 * <li>added a tdb_traverse() function for traversing the whole database</li>
 * <li>added transactions support</li>
 * </ul>
 *
 * A general rule for using tdb is that the caller frees any returned TDB_DATA
 * structures. Just call free(p.dptr) to free a TDB_DATA return value called p.
 * This is the same as gdbm.
 *
 * @{
 */

/** Flags to tdb_store() */
#define TDB_REPLACE 1		/** Unused */
#define TDB_INSERT 2 		/** Don't overwrite an existing entry */
#define TDB_MODIFY 3		/** Don't create an existing entry    */

/** Flags for tdb_open() */
#define TDB_DEFAULT 0 /** just a readability place holder */
#define TDB_CLEAR_IF_FIRST 1 /** If this is the first open, wipe the db */
#define TDB_INTERNAL 2 /** Don't store on disk */
#define TDB_NOLOCK   4 /** Don't do any locking */
#define TDB_NOMMAP   8 /** Don't use mmap */
#define TDB_CONVERT 16 /** Convert endian (internal use) */
#define TDB_BIGENDIAN 32 /** Header is big-endian (internal use) */
#define TDB_NOSYNC   64 /** Don't use synchronous transactions */
#define TDB_SEQNUM   128 /** Maintain a sequence number */
#define TDB_VOLATILE   256 /** Activate the per-hashchain freelist, default 5 */
#define TDB_ALLOW_NESTING 512 /** Allow transactions to nest */
#define TDB_DISALLOW_NESTING 1024 /** Disallow transactions to nest */
#define TDB_INCOMPATIBLE_HASH 2048 /** Better hashing: can't be opened by tdb < 1.2.6. */

/** The tdb error codes */
enum TDB_ERROR {TDB_SUCCESS=0, TDB_ERR_CORRUPT, TDB_ERR_IO, TDB_ERR_LOCK, 
		TDB_ERR_OOM, TDB_ERR_EXISTS, TDB_ERR_NOLOCK, TDB_ERR_LOCK_TIMEOUT,
		TDB_ERR_NOEXIST, TDB_ERR_EINVAL, TDB_ERR_RDONLY,
		TDB_ERR_NESTING};

/** Debugging uses one of the following levels */
enum tdb_debug_level {TDB_DEBUG_FATAL = 0, TDB_DEBUG_ERROR, 
		      TDB_DEBUG_WARNING, TDB_DEBUG_TRACE};

/** The tdb data structure */
typedef struct TDB_DATA {
	unsigned char *dptr;
	size_t dsize;
} TDB_DATA;

#ifndef PRINTF_ATTRIBUTE
#if (__GNUC__ >= 3)
/** Use gcc attribute to check printf fns.  a1 is the 1-based index of
 * the parameter containing the format, and a2 the index of the first
 * argument. Note that some gcc 2.x versions don't handle this
 * properly **/
#define PRINTF_ATTRIBUTE(a1, a2) __attribute__ ((format (__printf__, a1, a2)))
#else
#define PRINTF_ATTRIBUTE(a1, a2)
#endif
#endif

/** This is the context structure that is returned from a db open. */
typedef struct tdb_context TDB_CONTEXT;

typedef int (*tdb_traverse_func)(struct tdb_context *, TDB_DATA, TDB_DATA, void *);
typedef void (*tdb_log_func)(struct tdb_context *, enum tdb_debug_level, const char *, ...) PRINTF_ATTRIBUTE(3, 4);
typedef unsigned int (*tdb_hash_func)(TDB_DATA *key);

struct tdb_logging_context {
        tdb_log_func log_fn;
        void *log_private;
};

/**
 * @brief Open the database and creating it if necessary.
 *
 * @param[in]  name     The name of the db to open.
 *
 * @param[in]  hash_size The hash size is advisory, use zero for a default
 *                       value.
 *
 * @param[in]  tdb_flags The flags to use to open the db:\n\n
 *                         TDB_CLEAR_IF_FIRST - Clear database if we are the
 *                                              only one with it open\n
 *                         TDB_INTERNAL - Don't use a file, instead store the
 *                                        data in memory. The filename is
 *                                        ignored in this case.\n
 *                         TDB_NOLOCK - Don't do any locking\n
 *                         TDB_NOMMAP - Don't use mmap\n
 *                         TDB_NOSYNC - Don't synchronise transactions to disk\n
 *                         TDB_SEQNUM - Maintain a sequence number\n
 *                         TDB_VOLATILE - activate the per-hashchain freelist,
 *                                        default 5.\n
 *                         TDB_ALLOW_NESTING - Allow transactions to nest.\n
 *                         TDB_DISALLOW_NESTING - Disallow transactions to nest.\n
 *
 * @param[in]  open_flags Flags for the open(2) function.
 *
 * @param[in]  mode     The mode for the open(2) function.
 *
 * @return              A tdb context structure, NULL on error.
 */
struct tdb_context *tdb_open(const char *name, int hash_size, int tdb_flags,
		      int open_flags, mode_t mode);

/**
 * @brief Open the database and creating it if necessary.
 *
 * This is like tdb_open(), but allows you to pass an initial logging and
 * hash function. Be careful when passing a hash function - all users of the
 * database must use the same hash function or you will get data corruption.
 *
 * @param[in]  name     The name of the db to open.
 *
 * @param[in]  hash_size The hash size is advisory, use zero for a default
 *                       value.
 *
 * @param[in]  tdb_flags The flags to use to open the db:\n\n
 *                         TDB_CLEAR_IF_FIRST - Clear database if we are the
 *                                              only one with it open\n
 *                         TDB_INTERNAL - Don't use a file, instead store the
 *                                        data in memory. The filename is
 *                                        ignored in this case.\n
 *                         TDB_NOLOCK - Don't do any locking\n
 *                         TDB_NOMMAP - Don't use mmap\n
 *                         TDB_NOSYNC - Don't synchronise transactions to disk\n
 *                         TDB_SEQNUM - Maintain a sequence number\n
 *                         TDB_VOLATILE - activate the per-hashchain freelist,
 *                                        default 5.\n
 *                         TDB_ALLOW_NESTING - Allow transactions to nest.\n
 *                         TDB_DISALLOW_NESTING - Disallow transactions to nest.\n
 *
 * @param[in]  open_flags Flags for the open(2) function.
 *
 * @param[in]  mode     The mode for the open(2) function.
 *
 * @param[in]  log_ctx  The logging function to use.
 *
 * @param[in]  hash_fn  The hash function you want to use.
 *
 * @return              A tdb context structure, NULL on error.
 *
 * @see tdb_open()
 */
struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
			 int open_flags, mode_t mode,
			 const struct tdb_logging_context *log_ctx,
			 tdb_hash_func hash_fn);

/**
 * @brief Set the maximum number of dead records per hash chain.
 *
 * @param[in]  tdb      The database handle to set the maximum.
 *
 * @param[in]  max_dead The maximum number of dead records per hash chain.
 */
void tdb_set_max_dead(struct tdb_context *tdb, int max_dead);

/**
 * @brief Reopen a tdb.
 *
 * This can be used after a fork to ensure that we have an independent seek
 * pointer from our parent and to re-establish locks.
 *
 * @param[in]  tdb      The database to reopen. It will be free'd on error!
 *
 * @return              0 on success, -1 on error.
 *
 * @note Don't call tdb_error() after this function cause the tdb context will
 *       be freed on error.
 */
int tdb_reopen(struct tdb_context *tdb);

/**
 * @brief Reopen all tdb's
 *
 * If the parent is longlived (ie. a parent daemon architecture), we know it
 * will keep it's active lock on a tdb opened with CLEAR_IF_FIRST. Thus for
 * child processes we don't have to add an active lock. This is essential to
 * improve performance on systems that keep POSIX locks as a non-scalable data
 * structure in the kernel.
 *
 * @param[in]  parent_longlived Wether the parent is longlived or not.
 *
 * @return              0 on success, -1 on error.
 */
int tdb_reopen_all(int parent_longlived);

/**
 * @brief Set a different tdb logging function.
 *
 * @param[in]  tdb      The tdb to set the logging function.
 *
 * @param[in]  log_ctx  The logging function to set.
 */
void tdb_set_logging_function(struct tdb_context *tdb, const struct tdb_logging_context *log_ctx);

/**
 * @brief Get the tdb last error code.
 *
 * @param[in]  tdb      The tdb to get the error code from.
 *
 * @return              A TDB_ERROR code.
 *
 * @see TDB_ERROR
 */
enum TDB_ERROR tdb_error(struct tdb_context *tdb);

/**
 * @brief Get a error string for the last tdb error
 *
 * @param[in]  tdb      The tdb to get the error code from.
 *
 * @return              An error string.
 */
const char *tdb_errorstr(struct tdb_context *tdb);

/**
 * @brief Fetch an entry in the database given a key.
 *
 * The caller must free the resulting data.
 *
 * @param[in]  tdb      The tdb to fetch the key.
 *
 * @param[in]  key      The key to fetch.
 *
 * @return              The key entry found in the database, NULL on error with
 *                      TDB_ERROR set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
TDB_DATA tdb_fetch(struct tdb_context *tdb, TDB_DATA key);

/**
 * @brief Hand a record to a parser function without allocating it.
 *
 * This function is meant as a fast tdb_fetch alternative for large records
 * that are frequently read. The "key" and "data" arguments point directly
 * into the tdb shared memory, they are not aligned at any boundary.
 *
 * @warning The parser is called while tdb holds a lock on the record. DO NOT
 * call other tdb routines from within the parser. Also, for good performance
 * you should make the parser fast to allow parallel operations.
 *
 * @param[in]  tdb      The tdb to parse the record.
 *
 * @param[in]  key      The key to parse.
 *
 * @param[in]  parser   The parser to use to parse the data.
 *
 * @param[in]  private_data A private data pointer which is passed to the parser
 *                          function.
 *
 * @return              -1 if the record was not found. If the record was found,
 *                      the return value of "parser" is passed up to the caller.
 */
int tdb_parse_record(struct tdb_context *tdb, TDB_DATA key,
			      int (*parser)(TDB_DATA key, TDB_DATA data,
					    void *private_data),
			      void *private_data);

/**
 * @brief Delete an entry in the database given a key.
 *
 * @param[in]  tdb      The tdb to delete the key.
 *
 * @param[in]  key      The key to delete.
 *
 * @return              0 on success, -1 if the key doesn't exist.
 */
int tdb_delete(struct tdb_context *tdb, TDB_DATA key);

/**
 * @brief Store an element in the database.
 *
 * This replaces any existing element with the same key.
 *
 * @param[in]  tdb      The tdb to store the entry.
 *
 * @param[in]  key      The key to use to store the entry.
 *
 * @param[in]  dbuf     The data to store under the key.
 *
 * @param[in]  flag     The flags to store the key:\n\n
 *                      TDB_INSERT: Don't overwrite an existing entry.\n
 *                      TDB_MODIFY: Don't create a new entry\n
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag);

/**
 * @brief Append data to an entry.
 *
 * If the entry doesn't exist, it will create a new one.
 *
 * @param[in]  tdb      The database to use.
 *
 * @param[in]  key      The key to append the data.
 *
 * @param[in]  new_dbuf The data to append to the key.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_append(struct tdb_context *tdb, TDB_DATA key, TDB_DATA new_dbuf);

/**
 * @brief Close a database.
 *
 * @param[in]  tdb      The database to close. The context will be free'd.
 *
 * @return              0 for success, -1 on error.
 *
 * @note Don't call tdb_error() after this function cause the tdb context will
 *       be freed on error.
 */
int tdb_close(struct tdb_context *tdb);

/**
 * @brief Find the first entry in the database and return its key.
 *
 * The caller must free the returned data.
 *
 * @param[in]  tdb      The database to use.
 *
 * @return              The first entry of the database, an empty TDB_DATA entry
 *                      if the database is empty.
 */
TDB_DATA tdb_firstkey(struct tdb_context *tdb);

/**
 * @brief Find the next entry in the database, returning its key.
 *
 * The caller must free the returned data.
 *
 * @param[in]  tdb      The database to use.
 *
 * @param[in]  key      The key from which you want the next key.
 *
 * @return              The next entry of the current key, an empty TDB_DATA
 *                      entry if there is no entry.
 */
TDB_DATA tdb_nextkey(struct tdb_context *tdb, TDB_DATA key);

/**
 * @brief Traverse the entire database.
 *
 * While traversing the function fn(tdb, key, data, state) is called on each
 * element. If fn is NULL then it is not called. A non-zero return value from
 * fn() indicates that the traversal should stop. Traversal callbacks may not
 * start transactions.
 *
 * @warning The data buffer given to the callback fn does NOT meet the alignment
 * restrictions malloc gives you.
 *
 * @param[in]  tdb      The database to traverse.
 *
 * @param[in]  fn       The function to call on each entry.
 *
 * @param[in]  private_data The private data which should be passed to the
 *                          traversing function.
 *
 * @return              The record count traversed, -1 on error.
 */
int tdb_traverse(struct tdb_context *tdb, tdb_traverse_func fn, void *private_data);

/**
 * @brief Traverse the entire database.
 *
 * While traversing the database the function fn(tdb, key, data, state) is
 * called on each element, but marking the database read only during the
 * traversal, so any write operations will fail. This allows tdb to use read
 * locks, which increases the parallelism possible during the traversal.
 *
 * @param[in]  tdb      The database to traverse.
 *
 * @param[in]  fn       The function to call on each entry.
 *
 * @param[in]  private_data The private data which should be passed to the
 *                          traversing function.
 *
 * @return              The record count traversed, -1 on error.
 */
int tdb_traverse_read(struct tdb_context *tdb, tdb_traverse_func fn, void *private_data);

/**
 * @brief Check if an entry in the database exists.
 *
 * @note 1 is returned if the key is found and 0 is returned if not found this
 * doesn't match the conventions in the rest of this module, but is compatible
 * with gdbm.
 *
 * @param[in]  tdb      The database to check if the entry exists.
 *
 * @param[in]  key      The key to check if the entry exists.
 *
 * @return              1 if the key is found, 0 if not.
 */
int tdb_exists(struct tdb_context *tdb, TDB_DATA key);

/**
 * @brief Lock entire database with a write lock.
 *
 * @param[in]  tdb      The database to lock.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_lockall(struct tdb_context *tdb);

/**
 * @brief Lock entire database with a write lock.
 *
 * This is the non-blocking call.
 *
 * @param[in]  tdb      The database to lock.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_lockall()
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_lockall_nonblock(struct tdb_context *tdb);

/**
 * @brief Unlock entire database with write lock.
 *
 * @param[in]  tdb      The database to unlock.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_lockall()
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_unlockall(struct tdb_context *tdb);

/**
 * @brief Lock entire database with a read lock.
 *
 * @param[in]  tdb      The database to lock.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_lockall_read(struct tdb_context *tdb);

/**
 * @brief Lock entire database with a read lock.
 *
 * This is the non-blocking call.
 *
 * @param[in]  tdb      The database to lock.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_lockall_read()
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_lockall_read_nonblock(struct tdb_context *tdb);

/**
 * @brief Unlock entire database with read lock.
 *
 * @param[in]  tdb      The database to unlock.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_lockall_read()
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_unlockall_read(struct tdb_context *tdb);

/**
 * @brief Lock entire database with write lock - mark only.
 *
 * @todo Add more details.
 *
 * @param[in]  tdb      The database to mark.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_lockall_mark(struct tdb_context *tdb);

/**
 * @brief Lock entire database with write lock - unmark only.
 *
 * @todo Add more details.
 *
 * @param[in]  tdb      The database to mark.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_lockall_unmark(struct tdb_context *tdb);

/**
 * @brief Get the name of the current tdb file.
 *
 * This is useful for external logging functions.
 *
 * @param[in]  tdb      The database to get the name from.
 *
 * @return              The name of the database.
 */
const char *tdb_name(struct tdb_context *tdb);

/**
 * @brief Get the underlying file descriptor being used by tdb.
 *
 * This is useful for external routines that want to check the device/inode
 * of the fd.
 *
 * @param[in]  tdb      The database to get the fd from.
 *
 * @return              The file descriptor or -1.
 */
int tdb_fd(struct tdb_context *tdb);

/**
 * @brief Get the current logging function.
 *
 * This is useful for external tdb routines that wish to log tdb errors.
 *
 * @param[in]  tdb      The database to get the logging function from.
 *
 * @return              The logging function of the database.
 *
 * @see tdb_get_logging_private()
 */
tdb_log_func tdb_log_fn(struct tdb_context *tdb);

/**
 * @brief Get the private data of the logging function.
 *
 * @param[in]  tdb      The database to get the data from.
 *
 * @return              The private data pointer of the logging function.
 *
 * @see tdb_log_fn()
 */
void *tdb_get_logging_private(struct tdb_context *tdb);

/**
 * @brief Start a transaction.
 *
 * All operations after the transaction start can either be committed with
 * tdb_transaction_commit() or cancelled with tdb_transaction_cancel().
 *
 * If you call tdb_transaction_start() again on the same tdb context while a
 * transaction is in progress, then the same transaction buffer is re-used. The
 * number of tdb_transaction_{commit,cancel} operations must match the number
 * of successful tdb_transaction_start() calls.
 *
 * Note that transactions are by default disk synchronous, and use a recover
 * area in the database to automatically recover the database on the next open
 * if the system crashes during a transaction. You can disable the synchronous
 * transaction recovery setup using the TDB_NOSYNC flag, which will greatly
 * speed up operations at the risk of corrupting your database if the system
 * crashes.
 *
 * Operations made within a transaction are not visible to other users of the
 * database until a successful commit.
 *
 * @param[in]  tdb      The database to start the transaction.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_transaction_start(struct tdb_context *tdb);

/**
 * @brief Start a transaction, non-blocking.
 *
 * @param[in]  tdb      The database to start the transaction.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 * @see tdb_transaction_start()
 */
int tdb_transaction_start_nonblock(struct tdb_context *tdb);

/**
 * @brief Prepare to commit a current transaction, for two-phase commits.
 *
 * Once prepared for commit, the only allowed calls are tdb_transaction_commit()
 * or tdb_transaction_cancel(). Preparing allocates disk space for the pending
 * updates, so a subsequent commit should succeed (barring any hardware
 * failures).
 *
 * @param[in]  tdb      The database to prepare the commit.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_transaction_prepare_commit(struct tdb_context *tdb);

/**
 * @brief Commit a current transaction.
 *
 * This updates the database and releases the current transaction locks.
 *
 * @param[in]  tdb      The database to commit the transaction.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_transaction_commit(struct tdb_context *tdb);

/**
 * @brief Cancel a current transaction.
 *
 * This discards all write and lock operations that have been made since the
 * transaction started.
 *
 * @param[in]  tdb      The tdb to cancel the transaction on.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_transaction_cancel(struct tdb_context *tdb);

/**
 * @brief Get the tdb sequence number.
 *
 * Only makes sense if the writers opened with TDB_SEQNUM set. Note that this
 * sequence number will wrap quite quickly, so it should only be used for a
 * 'has something changed' test, not for code that relies on the count of the
 * number of changes made. If you want a counter then use a tdb record.
 *
 * The aim of this sequence number is to allow for a very lightweight test of a
 * possible tdb change.
 *
 * @param[in]  tdb      The database to get the sequence number from.
 *
 * @return              The sequence number or 0.
 *
 * @see tdb_open()
 * @see tdb_enable_seqnum()
 */
int tdb_get_seqnum(struct tdb_context *tdb);

/**
 * @brief Get the hash size.
 *
 * @param[in]  tdb      The database to get the hash size from.
 *
 * @return              The hash size.
 */
int tdb_hash_size(struct tdb_context *tdb);

/**
 * @brief Get the map size.
 *
 * @param[in]  tdb     The database to get the map size from.
 *
 * @return             The map size.
 */
size_t tdb_map_size(struct tdb_context *tdb);

/**
 * @brief Get the tdb flags set during open.
 *
 * @param[in]  tdb      The database to get the flags form.
 *
 * @return              The flags set to on the database.
 */
int tdb_get_flags(struct tdb_context *tdb);

/**
 * @brief Add flags to the database.
 *
 * @param[in]  tdb      The database to add the flags.
 *
 * @param[in]  flag     The tdb flags to add.
 */
void tdb_add_flags(struct tdb_context *tdb, unsigned flag);

/**
 * @brief Remove flags from the database.
 *
 * @param[in]  tdb      The database to remove the flags.
 *
 * @param[in]  flag     The tdb flags to remove.
 */
void tdb_remove_flags(struct tdb_context *tdb, unsigned flag);

/**
 * @brief Enable sequence number handling on an open tdb.
 *
 * @param[in]  tdb      The database to enable sequence number handling.
 *
 * @see tdb_get_seqnum()
 */
void tdb_enable_seqnum(struct tdb_context *tdb);

/**
 * @brief Increment the tdb sequence number.
 *
 * This only works if the tdb has been opened using the TDB_SEQNUM flag or
 * enabled using tdb_enable_seqnum().
 *
 * @param[in]  tdb      The database to increment the sequence number.
 *
 * @see tdb_enable_seqnum()
 * @see tdb_get_seqnum()
 */
void tdb_increment_seqnum_nonblock(struct tdb_context *tdb);

/**
 * @brief Create a hash of the key.
 *
 * @param[in]  key      The key to hash
 *
 * @return              The hash.
 */
unsigned int tdb_jenkins_hash(TDB_DATA *key);

/**
 * @brief Check the consistency of the database.
 *
 * This check the consistency of the database calling back the check function
 * (if non-NULL) on each record.  If some consistency check fails, or the
 * supplied check function returns -1, tdb_check returns -1, otherwise 0.
 *
 * @note The logging function (if set) will be called with additional
 * information on the corruption found.
 *
 * @param[in]  tdb      The database to check.
 *
 * @param[in]  check    The check function to use.
 *
 * @param[in]  private_data the private data to pass to the check function.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_check(struct tdb_context *tdb,
	      int (*check) (TDB_DATA key, TDB_DATA data, void *private_data),
	      void *private_data);

/**
 * @brief Dump all possible records in a corrupt database.
 *
 * This is the only way to get data out of a database where tdb_check() fails.
 * It will call walk() with anything which looks like a database record; this
 * may well include invalid, incomplete or duplicate records.
 *
 * @param[in]  tdb      The database to check.
 *
 * @param[in]  walk     The walk function to use.
 *
 * @param[in]  private_data the private data to pass to the walk function.
 *
 * @return              0 on success, -1 on error with error code set.
 *
 * @see tdb_error()
 * @see tdb_errorstr()
 */
int tdb_rescue(struct tdb_context *tdb,
	       void (*walk) (TDB_DATA key, TDB_DATA data, void *private_data),
	       void *private_data);

/* @} ******************************************************************/

/* Low level locking functions: use with care */
int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key);
int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key);
int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key);
int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key);
int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key);

void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *sigptr);

/* wipe and repack */
int tdb_wipe_all(struct tdb_context *tdb);
int tdb_repack(struct tdb_context *tdb);

/* Debug functions. Not used in production. */
void tdb_dump_all(struct tdb_context *tdb);
int tdb_printfreelist(struct tdb_context *tdb);
int tdb_validate_freelist(struct tdb_context *tdb, int *pnum_entries);
int tdb_freelist_size(struct tdb_context *tdb);
char *tdb_summary(struct tdb_context *tdb);

extern TDB_DATA tdb_null;

#ifdef  __cplusplus
}
#endif

#endif /* tdb.h */