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.
291 * If this fails you must still call tdb_transaction_cancel() to cancel
295 * tdb_transaction_commit()
297 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
300 * tdb_traverse - traverse a TDB
301 * @tdb: the tdb context returned from tdb_open()
302 * @fn: the function to call for every key/value pair (or NULL)
303 * @p: the pointer to hand to @f
305 * This walks the TDB until all they keys have been traversed, or @fn
306 * returns non-zero. If the traverse function or other processes are
307 * changing data or adding or deleting keys, the traverse may be
308 * unreliable: keys may be skipped or (rarely) visited twice.
310 * There is one specific exception: the special case of deleting the
311 * current key does not undermine the reliability of the traversal.
313 * On success, returns the number of keys iterated. On error returns
314 * a negative enum TDB_ERROR value.
316 #define tdb_traverse(tdb, fn, p) \
317 tdb_traverse_(tdb, typesafe_cb_preargs(int, void *, (fn), (p), \
318 struct tdb_context *, \
319 TDB_DATA, TDB_DATA), (p))
321 int64_t tdb_traverse_(struct tdb_context *tdb,
322 int (*fn)(struct tdb_context *,
323 TDB_DATA, TDB_DATA, void *), void *p);
326 * tdb_parse_record - operate directly on data in the database.
327 * @tdb: the tdb context returned from tdb_open()
328 * @key: the key whose record we should hand to @parse
329 * @parse: the function to call for the data
330 * @data: the private pointer to hand to @parse (types must match).
332 * This avoids a copy for many cases, by handing you a pointer into
333 * the memory-mapped database. It also locks the record to prevent
334 * other accesses at the same time.
336 * Do not alter the data handed to parse()!
338 #define tdb_parse_record(tdb, key, parse, data) \
339 tdb_parse_record_((tdb), (key), \
340 typesafe_cb_preargs(enum TDB_ERROR, void *, \
342 TDB_DATA, TDB_DATA), (data))
344 enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
346 enum TDB_ERROR (*parse)(TDB_DATA k,
352 * tdb_get_seqnum - get a database sequence number
353 * @tdb: the tdb context returned from tdb_open()
355 * This returns a sequence number: any change to the database from a
356 * tdb context opened with the TDB_SEQNUM flag will cause that number
357 * to increment. Note that the incrementing is unreliable (it is done
358 * without locking), so this is only useful as an optimization.
360 * For example, you may have a regular database backup routine which
361 * does not operate if the sequence number is unchanged. In the
362 * unlikely event of a failed increment, it will be backed up next
365 * Returns an enum TDB_ERROR (ie. negative) on error.
367 int64_t tdb_get_seqnum(struct tdb_context *tdb);
370 * tdb_firstkey - get the "first" key in a TDB
371 * @tdb: the tdb context returned from tdb_open()
372 * @key: pointer to key.
374 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
375 * open-coded traversal of the database, though it is slightly less efficient
378 * It is your responsibility to free @key->dptr on success.
380 * Returns TDB_ERR_NOEXIST if the database is empty.
382 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
385 * tdb_nextkey - get the "next" key in a TDB
386 * @tdb: the tdb context returned from tdb_open()
387 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
389 * This returns another key in the database; it will free @key.dptr for
392 * Returns TDB_ERR_NOEXIST if there are no more keys.
394 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
397 * tdb_chainlock - lock a record in the TDB
398 * @tdb: the tdb context returned from tdb_open()
399 * @key: the key to lock.
401 * This prevents any access occurring to a group of keys including @key,
402 * even if @key does not exist. This allows primitive atomic updates of
403 * records without using transactions.
405 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
406 * you do any operations on any other keys in the database. This also means
407 * that you cannot hold more than one tdb_chainlock() at a time.
412 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
415 * tdb_chainunlock - unlock a record in the TDB
416 * @tdb: the tdb context returned from tdb_open()
417 * @key: the key to unlock.
419 * The key must have previously been locked by tdb_chainlock().
421 void tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
424 * tdb_chainlock_read - lock a record in the TDB, for reading
425 * @tdb: the tdb context returned from tdb_open()
426 * @key: the key to lock.
428 * This prevents any changes from occurring to a group of keys including @key,
429 * even if @key does not exist. This allows primitive atomic updates of
430 * records without using transactions.
432 * You cannot begin a transaction while holding a tdb_chainlock_read(), nor can
433 * you do any operations on any other keys in the database. This also means
434 * that you cannot hold more than one tdb_chainlock()/read() at a time.
439 enum TDB_ERROR tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key);
442 * tdb_chainunlock_read - unlock a record in the TDB for reading
443 * @tdb: the tdb context returned from tdb_open()
444 * @key: the key to unlock.
446 * The key must have previously been locked by tdb_chainlock_read().
448 void tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key);
451 * tdb_lockall - lock the entire TDB
452 * @tdb: the tdb context returned from tdb_open()
454 * You cannot hold a tdb_chainlock while calling this. It nests, so you
455 * must call tdb_unlockall as many times as you call tdb_lockall.
457 enum TDB_ERROR tdb_lockall(struct tdb_context *tdb);
460 * tdb_unlockall - unlock the entire TDB
461 * @tdb: the tdb context returned from tdb_open()
463 void tdb_unlockall(struct tdb_context *tdb);
466 * tdb_lockall_read - lock the entire TDB for reading
467 * @tdb: the tdb context returned from tdb_open()
469 * This prevents others writing to the database, eg. tdb_delete, tdb_store,
470 * tdb_append, but not tdb_fetch.
472 * You cannot hold a tdb_chainlock while calling this. It nests, so you
473 * must call tdb_unlockall_read as many times as you call tdb_lockall_read.
475 enum TDB_ERROR tdb_lockall_read(struct tdb_context *tdb);
478 * tdb_unlockall_read - unlock the entire TDB for reading
479 * @tdb: the tdb context returned from tdb_open()
481 void tdb_unlockall_read(struct tdb_context *tdb);
484 * tdb_wipe_all - wipe the database clean
485 * @tdb: the tdb context returned from tdb_open()
487 * Completely erase the database. This is faster than iterating through
488 * each key and doing tdb_delete.
490 enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb);
493 * tdb_check - check a TDB for consistency
494 * @tdb: the tdb context returned from tdb_open()
495 * @check: function to check each key/data pair (or NULL)
496 * @data: argument for @check, must match type.
498 * This performs a consistency check of the open database, optionally calling
499 * a check() function on each record so you can do your own data consistency
500 * checks as well. If check() returns an error, that is returned from
503 * Returns TDB_SUCCESS or an error.
505 #define tdb_check(tdb, check, data) \
506 tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, void *, \
512 enum TDB_ERROR tdb_check_(struct tdb_context *tdb,
513 enum TDB_ERROR (*check)(struct tdb_data k,
519 * tdb_error - get the last error (not threadsafe)
520 * @tdb: the tdb context returned from tdb_open()
522 * Returns the last error returned by a TDB function.
524 * This makes porting from TDB1 easier, but note that the last error is not
525 * reliable in threaded programs.
527 enum TDB_ERROR tdb_error(struct tdb_context *tdb);
530 * enum tdb_summary_flags - flags for tdb_summary.
532 enum tdb_summary_flags {
533 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
537 * tdb_summary - return a string describing the TDB state
538 * @tdb: the tdb context returned from tdb_open()
539 * @flags: flags to control the summary output.
540 * @summary: pointer to string to allocate.
542 * This returns a developer-readable string describing the overall
543 * state of the tdb, such as the percentage used and sizes of records.
544 * It is designed to provide information about the tdb at a glance
545 * without displaying any keys or data in the database.
547 * On success, sets @summary to point to a malloc()'ed nul-terminated
548 * multi-line string. It is your responsibility to free() it.
550 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
551 enum tdb_summary_flags flags,
556 * tdb_get_flags - return the flags for a tdb
557 * @tdb: the tdb context returned from tdb_open()
559 * This returns the flags on the current tdb. Some of these are caused by
560 * the flags argument to tdb_open(), others (such as TDB_CONVERT) are
563 unsigned int tdb_get_flags(struct tdb_context *tdb);
566 * tdb_add_flag - set a flag for a tdb
567 * @tdb: the tdb context returned from tdb_open()
568 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
570 * You can use this to set a flag on the TDB. You cannot set these flags
571 * on a TDB_INTERNAL tdb.
573 void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
576 * tdb_remove_flag - unset a flag for a tdb
577 * @tdb: the tdb context returned from tdb_open()
578 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
580 * You can use this to clear a flag on the TDB. You cannot clear flags
581 * on a TDB_INTERNAL tdb.
583 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
586 * enum tdb_attribute_type - descriminator for union tdb_attribute.
588 enum tdb_attribute_type {
589 TDB_ATTRIBUTE_LOG = 0,
590 TDB_ATTRIBUTE_HASH = 1,
591 TDB_ATTRIBUTE_SEED = 2,
592 TDB_ATTRIBUTE_STATS = 3,
593 TDB_ATTRIBUTE_OPENHOOK = 4,
594 TDB_ATTRIBUTE_FLOCK = 5
598 * tdb_get_attribute - get an attribute for an existing tdb
599 * @tdb: the tdb context returned from tdb_open()
600 * @attr: the union tdb_attribute to set.
602 * This gets an attribute from a TDB which has previously been set (or
603 * may return the default values). Set @attr.base.attr to the
604 * attribute type you want get.
606 * Currently this does not work for TDB_ATTRIBUTE_OPENHOOK.
608 enum TDB_ERROR tdb_get_attribute(struct tdb_context *tdb,
609 union tdb_attribute *attr);
612 * tdb_set_attribute - set an attribute for an existing tdb
613 * @tdb: the tdb context returned from tdb_open()
614 * @attr: the union tdb_attribute to set.
616 * This sets an attribute on a TDB, overriding any previous attribute
617 * of the same type. It returns TDB_ERR_EINVAL if the attribute is
618 * unknown or invalid.
620 * Note that TDB_ATTRIBUTE_HASH, TDB_ATTRIBUTE_SEED and
621 * TDB_ATTRIBUTE_OPENHOOK cannot currently be set after tdb_open.
623 enum TDB_ERROR tdb_set_attribute(struct tdb_context *tdb,
624 const union tdb_attribute *attr);
627 * tdb_unset_attribute - reset an attribute for an existing tdb
628 * @tdb: the tdb context returned from tdb_open()
629 * @type: the attribute type to unset.
631 * This unsets an attribute on a TDB, returning it to the defaults
632 * (where applicable).
634 * Note that it only makes sense for TDB_ATTRIBUTE_LOG and TDB_ATTRIBUTE_FLOCK
637 void tdb_unset_attribute(struct tdb_context *tdb,
638 enum tdb_attribute_type type);
641 * tdb_name - get the name of a tdb
642 * @tdb: the tdb context returned from tdb_open()
644 * This returns a copy of the name string, made at tdb_open() time. If that
645 * argument was NULL (possible for a TDB_INTERNAL db) this will return NULL.
647 * This is mostly useful for logging.
649 const char *tdb_name(const struct tdb_context *tdb);
652 * tdb_fd - get the file descriptor of a tdb
653 * @tdb: the tdb context returned from tdb_open()
655 * This returns the file descriptor for the underlying database file, or -1
658 int tdb_fd(const struct tdb_context *tdb);
661 * struct tdb_attribute_base - common fields for all tdb attributes.
663 struct tdb_attribute_base {
664 enum tdb_attribute_type attr;
665 union tdb_attribute *next;
669 * enum tdb_log_level - log levels for tdb_attribute_log
670 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
671 * or internal consistency failures.
672 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
673 * or writing to a read-only database.
674 * @TDB_LOG_WARNING: used for informational messages on issues which
675 * are unusual but handled by TDB internally, such
676 * as a failure to mmap or failure to open /dev/urandom.
685 * struct tdb_attribute_log - log function attribute
687 * This attribute provides a hook for you to log errors.
689 struct tdb_attribute_log {
690 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
691 void (*fn)(struct tdb_context *tdb,
692 enum tdb_log_level level,
699 * struct tdb_attribute_hash - hash function attribute
701 * This attribute allows you to provide an alternative hash function.
702 * This hash function will be handed keys from the database; it will also
703 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
704 * tdb_open() will fail if the hash value doesn't match the header).
706 * Note that if your hash function gives different results on
707 * different machine endians, your tdb will no longer work across
708 * different architectures!
710 struct tdb_attribute_hash {
711 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
712 uint64_t (*fn)(const void *key, size_t len, uint64_t seed,
718 * struct tdb_attribute_seed - hash function seed attribute
720 * The hash function seed is normally taken from /dev/urandom (or equivalent)
721 * but can be set manually here. This is mainly for testing purposes.
723 struct tdb_attribute_seed {
724 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
729 * struct tdb_attribute_stats - tdb operational statistics
731 * This attribute records statistics of various low-level TDB operations.
732 * This can be used to assist performance evaluation. This is only
733 * useful for tdb_get_attribute().
735 * New fields will be added at the end, hence the "size" argument which
736 * indicates how large your structure is: it must be filled in before
737 * calling tdb_get_attribute(), which will overwrite it with the size
740 struct tdb_attribute_stats {
741 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
742 size_t size; /* = sizeof(struct tdb_attribute_stats) */
744 uint64_t alloc_subhash;
745 uint64_t alloc_chain;
746 uint64_t alloc_bucket_exact;
747 uint64_t alloc_bucket_max;
748 uint64_t alloc_leftover;
749 uint64_t alloc_coalesce_tried;
750 uint64_t alloc_coalesce_lockfail;
751 uint64_t alloc_coalesce_race;
752 uint64_t alloc_coalesce_succeeded;
753 uint64_t alloc_coalesce_num_merged;
755 uint64_t compare_wrong_bucket;
756 uint64_t compare_wrong_offsetbits;
757 uint64_t compare_wrong_keylen;
758 uint64_t compare_wrong_rechash;
759 uint64_t compare_wrong_keycmp;
763 uint64_t lock_lowlevel;
764 uint64_t lock_nonblock;
768 * struct tdb_attribute_openhook - tdb special effects hook for open
770 * This attribute contains a function to call once we have the OPEN_LOCK
771 * for the tdb, but before we've examined its contents. If this succeeds,
772 * the tdb will be populated if it's then zero-length.
774 * This is a hack to allow support for TDB1-style TDB_CLEAR_IF_FIRST
777 struct tdb_attribute_openhook {
778 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_OPENHOOK */
779 enum TDB_ERROR (*fn)(int fd, void *data);
784 * struct tdb_attribute_flock - tdb special effects hook for file locking
786 * This attribute contains function to call to place locks on a file; it can
787 * be used to support non-blocking operations or lock proxying.
789 * They should return 0 on success, -1 on failure and set errno.
791 * An error will be logged on error if errno is neither EAGAIN nor EINTR
792 * (normally it would only return EAGAIN if waitflag is false, and
793 * loop internally on EINTR).
795 struct tdb_attribute_flock {
796 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_FLOCK */
797 int (*lock)(int fd,int rw, off_t off, off_t len, bool waitflag, void *);
798 int (*unlock)(int fd, int rw, off_t off, off_t len, void *);
803 * union tdb_attribute - tdb attributes.
805 * This represents all the known attributes.
808 * struct tdb_attribute_log, struct tdb_attribute_hash,
809 * struct tdb_attribute_seed, struct tdb_attribute_stats,
810 * struct tdb_attribute_openhook, struct tdb_attribute_flock.
812 union tdb_attribute {
813 struct tdb_attribute_base base;
814 struct tdb_attribute_log log;
815 struct tdb_attribute_hash hash;
816 struct tdb_attribute_seed seed;
817 struct tdb_attribute_stats stats;
818 struct tdb_attribute_openhook openhook;
819 struct tdb_attribute_flock flock;