5 TDB version 2: trivial database library
7 Copyright (C) Andrew Tridgell 1999-2004
8 Copyright (C) Rusty Russell 2010-2011
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/>.
34 #include <sys/types.h>
37 /* For sig_atomic_t. */
46 #include <ccan/compiler/compiler.h>
47 #include <ccan/typesafe_cb/typesafe_cb.h>
48 #include <ccan/cast/cast.h>
54 * tdb_open - open a database file
55 * @name: the file name (can be NULL if flags contains TDB_INTERNAL)
56 * @tdb_flags: options for this database
57 * @open_flags: flags argument for tdb's open() call.
58 * @mode: mode argument for tdb's open() call.
59 * @attributes: linked list of extra attributes for this tdb.
61 * This call opens (and potentially creates) a database file.
62 * Multiple processes can have the TDB file open at once.
64 * On failure it will return NULL, and set errno: it may also call
65 * any log attribute found in @attributes.
70 struct tdb_context *tdb_open(const char *name, int tdb_flags,
71 int open_flags, mode_t mode,
72 union tdb_attribute *attributes);
75 /* flags for tdb_open() */
76 #define TDB_DEFAULT 0 /* just a readability place holder */
77 #define TDB_INTERNAL 2 /* don't store on disk */
78 #define TDB_NOLOCK 4 /* don't do any locking */
79 #define TDB_NOMMAP 8 /* don't use mmap */
80 #define TDB_CONVERT 16 /* convert endian */
81 #define TDB_NOSYNC 64 /* don't use synchronous transactions */
82 #define TDB_SEQNUM 128 /* maintain a sequence number */
85 * tdb_close - close and free a tdb.
86 * @tdb: the tdb context returned from tdb_open()
88 * This always succeeds, in that @tdb is unusable after this call. But if
89 * some unexpected error occurred while closing, it will return non-zero
90 * (the only clue as to cause will be via the log attribute).
92 int tdb_close(struct tdb_context *tdb);
95 * struct tdb_data - representation of keys or values.
96 * @dptr: the data pointer
97 * @dsize: the size of the data pointed to by dptr.
99 * This is the "blob" representation of keys and data used by TDB.
101 typedef struct tdb_data {
107 * enum TDB_ERROR - error returns for TDB
113 TDB_SUCCESS = 0, /* No error. */
114 TDB_ERR_CORRUPT = -1, /* We read the db, and it was bogus. */
115 TDB_ERR_IO = -2, /* We couldn't read/write the db. */
116 TDB_ERR_LOCK = -3, /* Locking failed. */
117 TDB_ERR_OOM = -4, /* Out of Memory. */
118 TDB_ERR_EXISTS = -5, /* The key already exists. */
119 TDB_ERR_NOEXIST = -6, /* The key does not exist. */
120 TDB_ERR_EINVAL = -7, /* You're using it wrong. */
121 TDB_ERR_RDONLY = -8, /* The database is read-only. */
122 TDB_ERR_LAST = TDB_ERR_RDONLY
126 * tdb_store - store a key/value pair in a tdb.
127 * @tdb: the tdb context returned from tdb_open()
129 * @dbuf: the data to associate with the key.
130 * @flag: TDB_REPLACE, TDB_INSERT or TDB_MODIFY.
132 * This inserts (or overwrites) a key/value pair in the TDB. If flag
133 * is TDB_REPLACE, it doesn't matter whether the key exists or not;
134 * TDB_INSERT means it must not exist (returns TDB_ERR_EXISTS otherwise),
135 * and TDB_MODIFY means it must exist (returns TDB_ERR_NOEXIST otherwise).
137 * On success, this returns TDB_SUCCESS.
140 * tdb_fetch, tdb_transaction_start, tdb_append, tdb_delete.
142 enum TDB_ERROR tdb_store(struct tdb_context *tdb,
144 struct tdb_data dbuf,
147 /* flags to tdb_store() */
148 #define TDB_REPLACE 1 /* A readability place holder */
149 #define TDB_INSERT 2 /* Don't overwrite an existing entry */
150 #define TDB_MODIFY 3 /* Don't create an existing entry */
153 * tdb_fetch - fetch a value from a tdb.
154 * @tdb: the tdb context returned from tdb_open()
156 * @data: pointer to data.
158 * This looks up a key in the database and sets it in @data.
160 * If it returns TDB_SUCCESS, the key was found: it is your
161 * responsibility to call free() on @data->dptr.
163 * Otherwise, it returns an error (usually, TDB_ERR_NOEXIST) and @data is
166 enum TDB_ERROR tdb_fetch(struct tdb_context *tdb, struct tdb_data key,
167 struct tdb_data *data);
170 * tdb_errorstr - map the tdb error onto a constant readable string
171 * @ecode: the enum TDB_ERROR to map.
173 * This is useful for displaying errors to users.
175 const char *tdb_errorstr(enum TDB_ERROR ecode);
178 * tdb_append - append a value to a key/value pair in a tdb.
179 * @tdb: the tdb context returned from tdb_open()
181 * @dbuf: the data to append.
183 * This is equivalent to fetching a record, reallocating .dptr to add the
184 * data, and writing it back, only it's much more efficient. If the key
185 * doesn't exist, it's equivalent to tdb_store (with an additional hint that
186 * you expect to expand the record in future).
189 * tdb_fetch(), tdb_store()
191 enum TDB_ERROR tdb_append(struct tdb_context *tdb,
192 struct tdb_data key, struct tdb_data dbuf);
195 * tdb_delete - delete a key from a tdb.
196 * @tdb: the tdb context returned from tdb_open()
197 * @key: the key to delete.
199 * Returns TDB_SUCCESS on success, or an error (usually TDB_ERR_NOEXIST).
202 * tdb_fetch(), tdb_store()
204 enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
207 * tdb_exists - does a key exist in the database?
208 * @tdb: the tdb context returned from tdb_open()
209 * @key: the key to search for.
211 * Returns true if it exists, or false if it doesn't or any other error.
213 bool tdb_exists(struct tdb_context *tdb, TDB_DATA key);
216 * tdb_deq - are struct tdb_data equal?
217 * @a: one struct tdb_data
218 * @b: another struct tdb_data
220 static inline bool tdb_deq(struct tdb_data a, struct tdb_data b)
222 return a.dsize == b.dsize && memcmp(a.dptr, b.dptr, a.dsize) == 0;
226 * tdb_mkdata - make a struct tdb_data from const data
227 * @p: the constant pointer
230 * As the dptr member of struct tdb_data is not constant, you need to
231 * cast it. This function keeps thost casts in one place, as well as
232 * suppressing the warning some compilers give when casting away a
233 * qualifier (eg. gcc with -Wcast-qual)
235 static inline struct tdb_data tdb_mkdata(const void *p, size_t len)
238 d.dptr = cast_const(void *, p);
244 * tdb_transaction_start - start a transaction
245 * @tdb: the tdb context returned from tdb_open()
247 * This begins a series of atomic operations. Other processes will be able
248 * to read the tdb, but not alter it (they will block), nor will they see
249 * any changes until tdb_transaction_commit() is called.
252 * tdb_transaction_cancel, tdb_transaction_commit.
254 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb);
257 * tdb_transaction_cancel - abandon a transaction
258 * @tdb: the tdb context returned from tdb_open()
260 * This aborts a transaction, discarding any changes which were made.
261 * tdb_close() does this implicitly.
263 void tdb_transaction_cancel(struct tdb_context *tdb);
266 * tdb_transaction_commit - commit a transaction
267 * @tdb: the tdb context returned from tdb_open()
269 * This completes a transaction, writing any changes which were made.
271 * fsync() is used to commit the transaction (unless TDB_NOSYNC is set),
272 * making it robust against machine crashes, but very slow compared to
273 * other TDB operations.
275 * A failure can only be caused by unexpected errors (eg. I/O or
276 * memory); this is no point looping on transaction failure.
279 * tdb_transaction_prepare_commit()
281 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
284 * tdb_transaction_prepare_commit - prepare to commit a transaction
285 * @tdb: the tdb context returned from tdb_open()
287 * This ensures we have the resources to commit a transaction (using
288 * tdb_transaction_commit): if this succeeds then a transaction will only
289 * fail if the write() or fsync() calls fail.
292 * tdb_transaction_commit()
294 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
297 * tdb_traverse - traverse a TDB
298 * @tdb: the tdb context returned from tdb_open()
299 * @fn: the function to call for every key/value pair (or NULL)
300 * @p: the pointer to hand to @f
302 * This walks the TDB until all they keys have been traversed, or @fn
303 * returns non-zero. If the traverse function or other processes are
304 * changing data or adding or deleting keys, the traverse may be
305 * unreliable: keys may be skipped or (rarely) visited twice.
307 * There is one specific exception: the special case of deleting the
308 * current key does not undermine the reliability of the traversal.
310 * On success, returns the number of keys iterated. On error returns
311 * a negative enum TDB_ERROR value.
313 #define tdb_traverse(tdb, fn, p) \
314 tdb_traverse_(tdb, typesafe_cb_preargs(int, void *, (fn), (p), \
315 struct tdb_context *, \
316 TDB_DATA, TDB_DATA), (p))
318 int64_t tdb_traverse_(struct tdb_context *tdb,
319 int (*fn)(struct tdb_context *,
320 TDB_DATA, TDB_DATA, void *), void *p);
323 * tdb_parse_record - operate directly on data in the database.
324 * @tdb: the tdb context returned from tdb_open()
325 * @key: the key whose record we should hand to @parse
326 * @parse: the function to call for the data
327 * @p: the private pointer to hand to @parse (types must match).
329 * This avoids a copy for many cases, by handing you a pointer into
330 * the memory-mapped database. It also locks the record to prevent
331 * other accesses at the same time.
333 * Do not alter the data handed to parse()!
335 #define tdb_parse_record(tdb, key, parse, p) \
336 tdb_parse_record_((tdb), (key), \
337 typesafe_cb_preargs(enum TDB_ERROR, void *, \
339 TDB_DATA, TDB_DATA), (p))
341 enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
343 enum TDB_ERROR (*parse)(TDB_DATA key,
349 * tdb_get_seqnum - get a database sequence number
350 * @tdb: the tdb context returned from tdb_open()
352 * This returns a sequence number: any change to the database from a
353 * tdb context opened with the TDB_SEQNUM flag will cause that number
354 * to increment. Note that the incrementing is unreliable (it is done
355 * without locking), so this is only useful as an optimization.
357 * For example, you may have a regular database backup routine which
358 * does not operate if the sequence number is unchanged. In the
359 * unlikely event of a failed increment, it will be backed up next
362 * Returns an enum TDB_ERROR (ie. negative) on error.
364 int64_t tdb_get_seqnum(struct tdb_context *tdb);
367 * tdb_firstkey - get the "first" key in a TDB
368 * @tdb: the tdb context returned from tdb_open()
369 * @key: pointer to key.
371 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
372 * open-coded traversal of the database, though it is slightly less efficient
375 * It is your responsibility to free @key->dptr on success.
377 * Returns TDB_ERR_NOEXIST if the database is empty.
379 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
382 * tdb_nextkey - get the "next" key in a TDB
383 * @tdb: the tdb context returned from tdb_open()
384 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
386 * This returns another key in the database; it will free @key.dptr for
389 * Returns TDB_ERR_NOEXIST if there are no more keys.
391 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
394 * tdb_chainlock - lock a record in the TDB
395 * @tdb: the tdb context returned from tdb_open()
396 * @key: the key to lock.
398 * This prevents any changes from occurring to a group of keys including @key,
399 * even if @key does not exist. This allows primitive atomic updates of
400 * records without using transactions.
402 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
403 * you do any operations on any other keys in the database. This also means
404 * that you cannot hold more than one tdb_chainlock() at a time.
409 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
412 * tdb_chainunlock - unlock a record in the TDB
413 * @tdb: the tdb context returned from tdb_open()
414 * @key: the key to unlock.
416 * The key must have previously been locked by tdb_chainlock().
418 void tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
421 * tdb_lockall - lock the entire TDB
422 * @tdb: the tdb context returned from tdb_open()
424 * You cannot hold a tdb_chainlock while calling this. It nests, so you
425 * must call tdb_unlockall as many times as you call tdb_lockall.
427 enum TDB_ERROR tdb_lockall(struct tdb_context *tdb);
430 * tdb_unlockall - unlock the entire TDB
431 * @tdb: the tdb context returned from tdb_open()
433 void tdb_unlockall(struct tdb_context *tdb);
436 * tdb_lockall_read - lock the entire TDB for reading
437 * @tdb: the tdb context returned from tdb_open()
439 * This prevents others writing to the database, eg. tdb_delete, tdb_store,
440 * tdb_append, but not tdb_fetch.
442 * You cannot hold a tdb_chainlock while calling this. It nests, so you
443 * must call tdb_unlockall_read as many times as you call tdb_lockall_read.
445 enum TDB_ERROR tdb_lockall_read(struct tdb_context *tdb);
448 * tdb_unlockall_read - unlock the entire TDB for reading
449 * @tdb: the tdb context returned from tdb_open()
451 void tdb_unlockall_read(struct tdb_context *tdb);
454 * tdb_wipe_all - wipe the database clean
455 * @tdb: the tdb context returned from tdb_open()
457 * Completely erase the database. This is faster than iterating through
458 * each key and doing tdb_delete.
460 enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb);
463 * tdb_check - check a TDB for consistency
464 * @tdb: the tdb context returned from tdb_open()
465 * @check: function to check each key/data pair (or NULL)
466 * @private_data: argument for @check, must match type.
468 * This performs a consistency check of the open database, optionally calling
469 * a check() function on each record so you can do your own data consistency
470 * checks as well. If check() returns an error, that is returned from
473 * Returns TDB_SUCCESS or an error.
475 #define tdb_check(tdb, check, private_data) \
476 tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, void *, \
477 (check), (private_data), \
482 enum TDB_ERROR tdb_check_(struct tdb_context *tdb,
483 enum TDB_ERROR (*check)(struct tdb_data key,
484 struct tdb_data data,
489 * tdb_error - get the last error (not threadsafe)
490 * @tdb: the tdb context returned from tdb_open()
492 * Returns the last error returned by a TDB function.
494 * This makes porting from TDB1 easier, but note that the last error is not
495 * reliable in threaded programs.
497 enum TDB_ERROR tdb_error(struct tdb_context *tdb);
500 * enum tdb_summary_flags - flags for tdb_summary.
502 enum tdb_summary_flags {
503 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
507 * tdb_summary - return a string describing the TDB state
508 * @tdb: the tdb context returned from tdb_open()
509 * @flags: flags to control the summary output.
510 * @summary: pointer to string to allocate.
512 * This returns a developer-readable string describing the overall
513 * state of the tdb, such as the percentage used and sizes of records.
514 * It is designed to provide information about the tdb at a glance
515 * without displaying any keys or data in the database.
517 * On success, sets @summary to point to a malloc()'ed nul-terminated
518 * multi-line string. It is your responsibility to free() it.
520 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
521 enum tdb_summary_flags flags,
526 * tdb_get_flags - return the flags for a tdb
527 * @tdb: the tdb context returned from tdb_open()
529 * This returns the flags on the current tdb. Some of these are caused by
530 * the flags argument to tdb_open(), others (such as TDB_CONVERT) are
533 unsigned int tdb_get_flags(struct tdb_context *tdb);
536 * tdb_add_flag - set a flag for a tdb
537 * @tdb: the tdb context returned from tdb_open()
538 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
540 * You can use this to set a flag on the TDB. You cannot set these flags
541 * on a TDB_INTERNAL tdb.
543 void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
546 * tdb_remove_flag - unset a flag for a tdb
547 * @tdb: the tdb context returned from tdb_open()
548 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
550 * You can use this to clear a flag on the TDB. You cannot clear flags
551 * on a TDB_INTERNAL tdb.
553 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
556 * tdb_name - get the name of a tdb
557 * @tdb: the tdb context returned from tdb_open()
559 * This returns a copy of the name string, made at tdb_open() time. If that
560 * argument was NULL (possible for a TDB_INTERNAL db) this will return NULL.
562 * This is mostly useful for logging.
564 const char *tdb_name(const struct tdb_context *tdb);
567 * tdb_fd - get the file descriptor of a tdb
568 * @tdb: the tdb context returned from tdb_open()
570 * This returns the file descriptor for the underlying database file, or -1
573 int tdb_fd(const struct tdb_context *tdb);
576 * enum tdb_attribute_type - descriminator for union tdb_attribute.
578 enum tdb_attribute_type {
579 TDB_ATTRIBUTE_LOG = 0,
580 TDB_ATTRIBUTE_HASH = 1,
581 TDB_ATTRIBUTE_SEED = 2,
582 TDB_ATTRIBUTE_STATS = 3
586 * struct tdb_attribute_base - common fields for all tdb attributes.
588 struct tdb_attribute_base {
589 enum tdb_attribute_type attr;
590 union tdb_attribute *next;
594 * enum tdb_log_level - log levels for tdb_attribute_log
595 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
596 * or internal consistency failures.
597 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
598 * or writing to a read-only database.
599 * @TDB_LOG_WARNING: used for informational messages on issues which
600 * are unusual but handled by TDB internally, such
601 * as a failure to mmap or failure to open /dev/urandom.
610 * struct tdb_attribute_log - log function attribute
612 * This attribute provides a hook for you to log errors.
614 struct tdb_attribute_log {
615 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
616 void (*log_fn)(struct tdb_context *tdb,
617 enum tdb_log_level level,
619 const char *message);
624 * struct tdb_attribute_hash - hash function attribute
626 * This attribute allows you to provide an alternative hash function.
627 * This hash function will be handed keys from the database; it will also
628 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
629 * tdb_open() will fail if the hash value doesn't match the header).
631 * Note that if your hash function gives different results on
632 * different machine endians, your tdb will no longer work across
633 * different architectures!
635 struct tdb_attribute_hash {
636 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
637 uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed,
643 * struct tdb_attribute_seed - hash function seed attribute
645 * The hash function seed is normally taken from /dev/urandom (or equivalent)
646 * but can be set manually here. This is mainly for testing purposes.
648 struct tdb_attribute_seed {
649 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
654 * struct tdb_attribute_stats - tdb operational statistics
656 * This attribute records statistics of various low-level TDB operations.
657 * This can be used to assist performance evaluation.
659 * New fields will be added at the end, hence the "size" argument which
660 * indicates how large your structure is. If your size is larger than
661 * that known about by this version of tdb, the size will be reduced to
662 * the known structure size. Thus you can detect older versions, and
663 * thus know that newer stats will not be updated.
665 struct tdb_attribute_stats {
666 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
667 size_t size; /* = sizeof(struct tdb_attribute_stats) */
669 uint64_t alloc_subhash;
670 uint64_t alloc_chain;
671 uint64_t alloc_bucket_exact;
672 uint64_t alloc_bucket_max;
673 uint64_t alloc_leftover;
674 uint64_t alloc_coalesce_tried;
675 uint64_t alloc_coalesce_lockfail;
676 uint64_t alloc_coalesce_race;
677 uint64_t alloc_coalesce_succeeded;
678 uint64_t alloc_coalesce_num_merged;
680 uint64_t compare_wrong_bucket;
681 uint64_t compare_wrong_offsetbits;
682 uint64_t compare_wrong_keylen;
683 uint64_t compare_wrong_rechash;
684 uint64_t compare_wrong_keycmp;
688 uint64_t lock_lowlevel;
689 uint64_t lock_nonblock;
693 * union tdb_attribute - tdb attributes.
695 * This represents all the known attributes.
698 * struct tdb_attribute_log, struct tdb_attribute_hash,
699 * struct tdb_attribute_seed, struct tdb_attribute_stats.
701 union tdb_attribute {
702 struct tdb_attribute_base base;
703 struct tdb_attribute_log log;
704 struct tdb_attribute_hash hash;
705 struct tdb_attribute_seed seed;
706 struct tdb_attribute_stats stats;