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>
53 * tdb_open - open a database file
54 * @name: the file name (can be NULL if flags contains TDB_INTERNAL)
55 * @tdb_flags: options for this database
56 * @open_flags: flags argument for tdb's open() call.
57 * @mode: mode argument for tdb's open() call.
58 * @attributes: linked list of extra attributes for this tdb.
60 * This call opens (and potentially creates) a database file.
61 * Multiple processes can have the TDB file open at once.
63 * On failure it will return NULL, and set errno: it may also call
64 * any log attribute found in @attributes.
69 struct tdb_context *tdb_open(const char *name, int tdb_flags,
70 int open_flags, mode_t mode,
71 union tdb_attribute *attributes);
74 /* flags for tdb_open() */
75 #define TDB_DEFAULT 0 /* just a readability place holder */
76 #define TDB_INTERNAL 2 /* don't store on disk */
77 #define TDB_NOLOCK 4 /* don't do any locking */
78 #define TDB_NOMMAP 8 /* don't use mmap */
79 #define TDB_CONVERT 16 /* convert endian */
80 #define TDB_NOSYNC 64 /* don't use synchronous transactions */
81 #define TDB_SEQNUM 128 /* maintain a sequence number */
84 * tdb_close - close and free a tdb.
85 * @tdb: the tdb context returned from tdb_open()
87 * This always succeeds, in that @tdb is unusable after this call. But if
88 * some unexpected error occurred while closing, it will return non-zero
89 * (the only clue as to cause will be via the log attribute).
91 int tdb_close(struct tdb_context *tdb);
94 * struct tdb_data - representation of keys or values.
95 * @dptr: the data pointer
96 * @dsize: the size of the data pointed to by dptr.
98 * This is the "blob" representation of keys and data used by TDB.
100 typedef struct tdb_data {
106 * enum TDB_ERROR - error returns for TDB
112 TDB_SUCCESS = 0, /* No error. */
113 TDB_ERR_CORRUPT = -1, /* We read the db, and it was bogus. */
114 TDB_ERR_IO = -2, /* We couldn't read/write the db. */
115 TDB_ERR_LOCK = -3, /* Locking failed. */
116 TDB_ERR_OOM = -4, /* Out of Memory. */
117 TDB_ERR_EXISTS = -5, /* The key already exists. */
118 TDB_ERR_NOEXIST = -6, /* The key does not exist. */
119 TDB_ERR_EINVAL = -7, /* You're using it wrong. */
120 TDB_ERR_RDONLY = -8, /* The database is read-only. */
121 TDB_ERR_LAST = TDB_ERR_RDONLY
125 * tdb_store - store a key/value pair in a tdb.
126 * @tdb: the tdb context returned from tdb_open()
128 * @dbuf: the data to associate with the key.
129 * @flag: TDB_REPLACE, TDB_INSERT or TDB_MODIFY.
131 * This inserts (or overwrites) a key/value pair in the TDB. If flag
132 * is TDB_REPLACE, it doesn't matter whether the key exists or not;
133 * TDB_INSERT means it must not exist (returns TDB_ERR_EXISTS otherwise),
134 * and TDB_MODIFY means it must exist (returns TDB_ERR_NOEXIST otherwise).
136 * On success, this returns TDB_SUCCESS.
139 * tdb_fetch, tdb_transaction_start, tdb_append, tdb_delete.
141 enum TDB_ERROR tdb_store(struct tdb_context *tdb,
143 struct tdb_data dbuf,
146 /* flags to tdb_store() */
147 #define TDB_REPLACE 1 /* A readability place holder */
148 #define TDB_INSERT 2 /* Don't overwrite an existing entry */
149 #define TDB_MODIFY 3 /* Don't create an existing entry */
152 * tdb_fetch - fetch a value from a tdb.
153 * @tdb: the tdb context returned from tdb_open()
155 * @data: pointer to data.
157 * This looks up a key in the database and sets it in @data.
159 * If it returns TDB_SUCCESS, the key was found: it is your
160 * responsibility to call free() on @data->dptr.
162 * Otherwise, it returns an error (usually, TDB_ERR_NOEXIST) and @data is
165 enum TDB_ERROR tdb_fetch(struct tdb_context *tdb, struct tdb_data key,
166 struct tdb_data *data);
169 * tdb_errorstr - map the tdb error onto a constant readable string
170 * @ecode: the enum TDB_ERROR to map.
172 * This is useful for displaying errors to users.
174 const char *tdb_errorstr(enum TDB_ERROR ecode);
177 * tdb_append - append a value to a key/value pair in a tdb.
178 * @tdb: the tdb context returned from tdb_open()
180 * @dbuf: the data to append.
182 * This is equivalent to fetching a record, reallocating .dptr to add the
183 * data, and writing it back, only it's much more efficient. If the key
184 * doesn't exist, it's equivalent to tdb_store (with an additional hint that
185 * you expect to expand the record in future).
188 * tdb_fetch(), tdb_store()
190 enum TDB_ERROR tdb_append(struct tdb_context *tdb,
191 struct tdb_data key, struct tdb_data dbuf);
194 * tdb_delete - delete a key from a tdb.
195 * @tdb: the tdb context returned from tdb_open()
196 * @key: the key to delete.
198 * Returns TDB_SUCCESS on success, or an error (usually TDB_ERR_NOEXIST).
201 * tdb_fetch(), tdb_store()
203 enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
206 * tdb_exists - does a key exist in the database?
207 * @tdb: the tdb context returned from tdb_open()
208 * @key: the key to search for.
210 * Returns true if it exists, or false if it doesn't or any other error.
212 bool tdb_exists(struct tdb_context *tdb, TDB_DATA key);
215 * tdb_deq - are struct tdb_data equal?
216 * @a: one struct tdb_data
217 * @b: another struct tdb_data
219 static inline bool tdb_deq(struct tdb_data a, struct tdb_data b)
221 return a.dsize == b.dsize && memcmp(a.dptr, b.dptr, a.dsize) == 0;
225 * tdb_transaction_start - start a transaction
226 * @tdb: the tdb context returned from tdb_open()
228 * This begins a series of atomic operations. Other processes will be able
229 * to read the tdb, but not alter it (they will block), nor will they see
230 * any changes until tdb_transaction_commit() is called.
233 * tdb_transaction_cancel, tdb_transaction_commit.
235 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb);
238 * tdb_transaction_cancel - abandon a transaction
239 * @tdb: the tdb context returned from tdb_open()
241 * This aborts a transaction, discarding any changes which were made.
242 * tdb_close() does this implicitly.
244 void tdb_transaction_cancel(struct tdb_context *tdb);
247 * tdb_transaction_commit - commit a transaction
248 * @tdb: the tdb context returned from tdb_open()
250 * This completes a transaction, writing any changes which were made.
252 * fsync() is used to commit the transaction (unless TDB_NOSYNC is set),
253 * making it robust against machine crashes, but very slow compared to
254 * other TDB operations.
256 * A failure can only be caused by unexpected errors (eg. I/O or
257 * memory); this is no point looping on transaction failure.
260 * tdb_transaction_prepare_commit()
262 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
265 * tdb_transaction_prepare_commit - prepare to commit a transaction
266 * @tdb: the tdb context returned from tdb_open()
268 * This ensures we have the resources to commit a transaction (using
269 * tdb_transaction_commit): if this succeeds then a transaction will only
270 * fail if the write() or fsync() calls fail.
273 * tdb_transaction_commit()
275 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
278 * tdb_traverse - traverse a TDB
279 * @tdb: the tdb context returned from tdb_open()
280 * @fn: the function to call for every key/value pair (or NULL)
281 * @p: the pointer to hand to @f
283 * This walks the TDB until all they keys have been traversed, or @fn
284 * returns non-zero. If the traverse function or other processes are
285 * changing data or adding or deleting keys, the traverse may be
286 * unreliable: keys may be skipped or (rarely) visited twice.
288 * There is one specific exception: the special case of deleting the
289 * current key does not undermine the reliability of the traversal.
291 * On success, returns the number of keys iterated. On error returns
292 * a negative enum TDB_ERROR value.
294 #define tdb_traverse(tdb, fn, p) \
295 tdb_traverse_(tdb, typesafe_cb_preargs(int, (fn), (p), \
296 struct tdb_context *, \
297 TDB_DATA, TDB_DATA), (p))
299 int64_t tdb_traverse_(struct tdb_context *tdb,
300 int (*fn)(struct tdb_context *,
301 TDB_DATA, TDB_DATA, void *), void *p);
304 * tdb_parse_record - operate directly on data in the database.
305 * @tdb: the tdb context returned from tdb_open()
306 * @key: the key whose record we should hand to @parse
307 * @parse: the function to call for the data
308 * @p: the private pointer to hand to @parse (types must match).
310 * This avoids a copy for many cases, by handing you a pointer into
311 * the memory-mapped database. It also locks the record to prevent
312 * other accesses at the same time.
314 * Do not alter the data handed to parse()!
316 #define tdb_parse_record(tdb, key, parse, p) \
317 tdb_parse_record_((tdb), (key), \
318 typesafe_cb_preargs(enum TDB_ERROR, (parse), (p), \
319 TDB_DATA, TDB_DATA), (p))
321 enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
323 enum TDB_ERROR (*parse)(TDB_DATA key,
329 * tdb_get_seqnum - get a database sequence number
330 * @tdb: the tdb context returned from tdb_open()
332 * This returns a sequence number: any change to the database from a
333 * tdb context opened with the TDB_SEQNUM flag will cause that number
334 * to increment. Note that the incrementing is unreliable (it is done
335 * without locking), so this is only useful as an optimization.
337 * For example, you may have a regular database backup routine which
338 * does not operate if the sequence number is unchanged. In the
339 * unlikely event of a failed increment, it will be backed up next
342 * Returns an enum TDB_ERROR (ie. negative) on error.
344 int64_t tdb_get_seqnum(struct tdb_context *tdb);
347 * tdb_firstkey - get the "first" key in a TDB
348 * @tdb: the tdb context returned from tdb_open()
349 * @key: pointer to key.
351 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
352 * open-coded traversal of the database, though it is slightly less efficient
355 * It is your responsibility to free @key->dptr on success.
357 * Returns TDB_ERR_NOEXIST if the database is empty.
359 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
362 * tdb_nextkey - get the "next" key in a TDB
363 * @tdb: the tdb context returned from tdb_open()
364 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
366 * This returns another key in the database; it will free @key.dptr for
369 * Returns TDB_ERR_NOEXIST if there are no more keys.
371 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
374 * tdb_chainlock - lock a record in the TDB
375 * @tdb: the tdb context returned from tdb_open()
376 * @key: the key to lock.
378 * This prevents any changes from occurring to a group of keys including @key,
379 * even if @key does not exist. This allows primitive atomic updates of
380 * records without using transactions.
382 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
383 * you do any operations on any other keys in the database. This also means
384 * that you cannot hold more than one tdb_chainlock() at a time.
389 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
392 * tdb_chainunlock - unlock a record in the TDB
393 * @tdb: the tdb context returned from tdb_open()
394 * @key: the key to unlock.
396 enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
399 * tdb_wipe_all - wipe the database clean
400 * @tdb: the tdb context returned from tdb_open()
402 * Completely erase the database. This is faster than iterating through
403 * each key and doing tdb_delete.
405 enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb);
408 * tdb_check - check a TDB for consistency
409 * @tdb: the tdb context returned from tdb_open()
410 * @check: function to check each key/data pair (or NULL)
411 * @private: argument for @check, must match type.
413 * This performs a consistency check of the open database, optionally calling
414 * a check() function on each record so you can do your own data consistency
415 * checks as well. If check() returns an error, that is returned from
418 * Returns TDB_SUCCESS or an error.
420 #define tdb_check(tdb, check, private) \
421 tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, \
422 (check), (private), \
427 enum TDB_ERROR tdb_check_(struct tdb_context *tdb,
428 enum TDB_ERROR (*check)(struct tdb_data key,
429 struct tdb_data data,
434 * tdb_error - get the last error (not threadsafe)
435 * @tdb: the tdb context returned from tdb_open()
437 * Returns the last error returned by a TDB function.
439 * This makes porting from TDB1 easier, but note that the last error is not
440 * reliable in threaded programs.
442 enum TDB_ERROR tdb_error(struct tdb_context *tdb);
445 * enum tdb_summary_flags - flags for tdb_summary.
447 enum tdb_summary_flags {
448 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
452 * tdb_summary - return a string describing the TDB state
453 * @tdb: the tdb context returned from tdb_open()
454 * @flags: flags to control the summary output.
455 * @summary: pointer to string to allocate.
457 * This returns a developer-readable string describing the overall
458 * state of the tdb, such as the percentage used and sizes of records.
459 * It is designed to provide information about the tdb at a glance
460 * without displaying any keys or data in the database.
462 * On success, sets @summary to point to a malloc()'ed nul-terminated
463 * multi-line string. It is your responsibility to free() it.
465 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
466 enum tdb_summary_flags flags,
471 * tdb_get_flags - return the flags for a tdb
472 * @tdb: the tdb context returned from tdb_open()
474 * This returns the flags on the current tdb. Some of these are caused by
475 * the flags argument to tdb_open(), others (such as TDB_CONVERT) are
478 unsigned int tdb_get_flags(struct tdb_context *tdb);
481 * tdb_add_flag - set a flag for a tdb
482 * @tdb: the tdb context returned from tdb_open()
483 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
485 * You can use this to set a flag on the TDB. You cannot set these flags
486 * on a TDB_INTERNAL tdb.
488 void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
491 * tdb_remove_flag - unset a flag for a tdb
492 * @tdb: the tdb context returned from tdb_open()
493 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
495 * You can use this to clear a flag on the TDB. You cannot clear flags
496 * on a TDB_INTERNAL tdb.
498 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
501 * tdb_name - get the name of a tdb
502 * @tdb: the tdb context returned from tdb_open()
504 * This returns a copy of the name string, made at tdb_open() time. If that
505 * argument was NULL (possible for a TDB_INTERNAL db) this will return NULL.
507 * This is mostly useful for logging.
509 const char *tdb_name(const struct tdb_context *tdb);
512 * tdb_fd - get the file descriptor of a tdb
513 * @tdb: the tdb context returned from tdb_open()
515 * This returns the file descriptor for the underlying database file, or -1
518 int tdb_fd(const struct tdb_context *tdb);
521 * enum tdb_attribute_type - descriminator for union tdb_attribute.
523 enum tdb_attribute_type {
524 TDB_ATTRIBUTE_LOG = 0,
525 TDB_ATTRIBUTE_HASH = 1,
526 TDB_ATTRIBUTE_SEED = 2,
527 TDB_ATTRIBUTE_STATS = 3
531 * struct tdb_attribute_base - common fields for all tdb attributes.
533 struct tdb_attribute_base {
534 enum tdb_attribute_type attr;
535 union tdb_attribute *next;
539 * enum tdb_log_level - log levels for tdb_attribute_log
540 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
541 * or internal consistency failures.
542 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
543 * or writing to a read-only database.
544 * @TDB_LOG_WARNING: used for informational messages on issues which
545 * are unusual but handled by TDB internally, such
546 * as a failure to mmap or failure to open /dev/urandom.
555 * struct tdb_attribute_log - log function attribute
557 * This attribute provides a hook for you to log errors.
559 struct tdb_attribute_log {
560 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
561 void (*log_fn)(struct tdb_context *tdb,
562 enum tdb_log_level level,
564 const char *message);
569 * struct tdb_attribute_hash - hash function attribute
571 * This attribute allows you to provide an alternative hash function.
572 * This hash function will be handed keys from the database; it will also
573 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
574 * tdb_open() will fail if the hash value doesn't match the header).
576 * Note that if your hash function gives different results on
577 * different machine endians, your tdb will no longer work across
578 * different architectures!
580 struct tdb_attribute_hash {
581 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
582 uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed,
588 * struct tdb_attribute_seed - hash function seed attribute
590 * The hash function seed is normally taken from /dev/urandom (or equivalent)
591 * but can be set manually here. This is mainly for testing purposes.
593 struct tdb_attribute_seed {
594 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
599 * struct tdb_attribute_stats - tdb operational statistics
601 * This attribute records statistics of various low-level TDB operations.
602 * This can be used to assist performance evaluation.
604 * New fields will be added at the end, hence the "size" argument which
605 * indicates how large your structure is. If your size is larger than
606 * that known about by this version of tdb, the size will be reduced to
607 * the known structure size. Thus you can detect older versions, and
608 * thus know that newer stats will not be updated.
610 struct tdb_attribute_stats {
611 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
612 size_t size; /* = sizeof(struct tdb_attribute_stats) */
614 uint64_t alloc_subhash;
615 uint64_t alloc_chain;
616 uint64_t alloc_bucket_exact;
617 uint64_t alloc_bucket_max;
618 uint64_t alloc_leftover;
619 uint64_t alloc_coalesce_tried;
620 uint64_t alloc_coalesce_lockfail;
621 uint64_t alloc_coalesce_race;
622 uint64_t alloc_coalesce_succeeded;
623 uint64_t alloc_coalesce_num_merged;
625 uint64_t compare_wrong_bucket;
626 uint64_t compare_wrong_offsetbits;
627 uint64_t compare_wrong_keylen;
628 uint64_t compare_wrong_rechash;
629 uint64_t compare_wrong_keycmp;
633 uint64_t lock_lowlevel;
634 uint64_t lock_nonblock;
638 * union tdb_attribute - tdb attributes.
640 * This represents all the known attributes.
643 * struct tdb_attribute_log, struct tdb_attribute_hash,
644 * struct tdb_attribute_seed, struct tdb_attribute_stats.
646 union tdb_attribute {
647 struct tdb_attribute_base base;
648 struct tdb_attribute_log log;
649 struct tdb_attribute_hash hash;
650 struct tdb_attribute_seed seed;
651 struct tdb_attribute_stats stats;