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 */
83 * tdb_close - close and free a tdb.
84 * @tdb: the tdb context returned from tdb_open()
86 * This always succeeds, in that @tdb is unusable after this call. But if
87 * some unexpected error occurred while closing, it will return non-zero
88 * (the only clue as to cause will be via the log attribute).
90 int tdb_close(struct tdb_context *tdb);
93 * struct tdb_data - representation of keys or values.
94 * @dptr: the data pointer
95 * @dsize: the size of the data pointed to by dptr.
97 * This is the "blob" representation of keys and data used by TDB.
99 typedef struct tdb_data {
105 * enum TDB_ERROR - error returns for TDB
111 TDB_SUCCESS = 0, /* No error. */
112 TDB_ERR_CORRUPT = -1, /* We read the db, and it was bogus. */
113 TDB_ERR_IO = -2, /* We couldn't read/write the db. */
114 TDB_ERR_LOCK = -3, /* Locking failed. */
115 TDB_ERR_OOM = -4, /* Out of Memory. */
116 TDB_ERR_EXISTS = -5, /* The key already exists. */
117 TDB_ERR_NOEXIST = -6, /* The key does not exist. */
118 TDB_ERR_EINVAL = -7, /* You're using it wrong. */
119 TDB_ERR_RDONLY = -8, /* The database is read-only. */
120 TDB_ERR_LAST = TDB_ERR_RDONLY
124 * tdb_store - store a key/value pair in a tdb.
125 * @tdb: the tdb context returned from tdb_open()
127 * @dbuf: the data to associate with the key.
128 * @flag: TDB_REPLACE, TDB_INSERT or TDB_MODIFY.
130 * This inserts (or overwrites) a key/value pair in the TDB. If flag
131 * is TDB_REPLACE, it doesn't matter whether the key exists or not;
132 * TDB_INSERT means it must not exist (returns TDB_ERR_EXISTS otherwise),
133 * and TDB_MODIFY means it must exist (returns TDB_ERR_NOEXIST otherwise).
135 * On success, this returns TDB_SUCCESS.
138 * tdb_fetch, tdb_transaction_start, tdb_append, tdb_delete.
140 enum TDB_ERROR tdb_store(struct tdb_context *tdb,
142 struct tdb_data dbuf,
145 /* flags to tdb_store() */
146 #define TDB_REPLACE 1 /* A readability place holder */
147 #define TDB_INSERT 2 /* Don't overwrite an existing entry */
148 #define TDB_MODIFY 3 /* Don't create an existing entry */
151 * tdb_fetch - fetch a value from a tdb.
152 * @tdb: the tdb context returned from tdb_open()
154 * @data: pointer to data.
156 * This looks up a key in the database and sets it in @data.
158 * If it returns TDB_SUCCESS, the key was found: it is your
159 * responsibility to call free() on @data->dptr.
161 * Otherwise, it returns an error (usually, TDB_ERR_NOEXIST) and @data is
164 enum TDB_ERROR tdb_fetch(struct tdb_context *tdb, struct tdb_data key,
165 struct tdb_data *data);
168 * tdb_errorstr - map the tdb error onto a constant readable string
169 * @ecode: the enum TDB_ERROR to map.
171 * This is useful for displaying errors to users.
173 const char *tdb_errorstr(enum TDB_ERROR ecode);
176 * tdb_append - append a value to a key/value pair in a tdb.
177 * @tdb: the tdb context returned from tdb_open()
179 * @dbuf: the data to append.
181 * This is equivalent to fetching a record, reallocating .dptr to add the
182 * data, and writing it back, only it's much more efficient. If the key
183 * doesn't exist, it's equivalent to tdb_store (with an additional hint that
184 * you expect to expand the record in future).
187 * tdb_fetch(), tdb_store()
189 enum TDB_ERROR tdb_append(struct tdb_context *tdb,
190 struct tdb_data key, struct tdb_data dbuf);
193 * tdb_delete - delete a key from a tdb.
194 * @tdb: the tdb context returned from tdb_open()
195 * @key: the key to delete.
197 * Returns TDB_SUCCESS on success, or an error (usually TDB_ERR_NOEXIST).
200 * tdb_fetch(), tdb_store()
202 enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
205 * tdb_exists - does a key exist in the database?
206 * @tdb: the tdb context returned from tdb_open()
207 * @key: the key to search for.
209 * Returns true if it exists, or false if it doesn't or any other error.
211 bool tdb_exists(struct tdb_context *tdb, TDB_DATA key);
214 * tdb_deq - are struct tdb_data equal?
215 * @a: one struct tdb_data
216 * @b: another struct tdb_data
218 static inline bool tdb_deq(struct tdb_data a, struct tdb_data b)
220 return a.dsize == b.dsize && memcmp(a.dptr, b.dptr, a.dsize) == 0;
224 * tdb_transaction_start - start a transaction
225 * @tdb: the tdb context returned from tdb_open()
227 * This begins a series of atomic operations. Other processes will be able
228 * to read the tdb, but not alter it (they will block), nor will they see
229 * any changes until tdb_transaction_commit() is called.
232 * tdb_transaction_cancel, tdb_transaction_commit.
234 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb);
237 * tdb_transaction_cancel - abandon a transaction
238 * @tdb: the tdb context returned from tdb_open()
240 * This aborts a transaction, discarding any changes which were made.
241 * tdb_close() does this implicitly.
243 void tdb_transaction_cancel(struct tdb_context *tdb);
246 * tdb_transaction_commit - commit a transaction
247 * @tdb: the tdb context returned from tdb_open()
249 * This completes a transaction, writing any changes which were made.
251 * fsync() is used to commit the transaction (unless TDB_NOSYNC is set),
252 * making it robust against machine crashes, but very slow compared to
253 * other TDB operations.
255 * A failure can only be caused by unexpected errors (eg. I/O or
256 * memory); this is no point looping on transaction failure.
259 * tdb_transaction_prepare_commit()
261 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
264 * tdb_transaction_prepare_commit - prepare to commit a transaction
265 * @tdb: the tdb context returned from tdb_open()
267 * This ensures we have the resources to commit a transaction (using
268 * tdb_transaction_commit): if this succeeds then a transaction will only
269 * fail if the write() or fsync() calls fail.
272 * tdb_transaction_commit()
274 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
277 * tdb_traverse - traverse a TDB
278 * @tdb: the tdb context returned from tdb_open()
279 * @fn: the function to call for every key/value pair (or NULL)
280 * @p: the pointer to hand to @f
282 * This walks the TDB until all they keys have been traversed, or @fn
283 * returns non-zero. If the traverse function or other processes are
284 * changing data or adding or deleting keys, the traverse may be
285 * unreliable: keys may be skipped or (rarely) visited twice.
287 * There is one specific exception: the special case of deleting the
288 * current key does not undermine the reliability of the traversal.
290 * On success, returns the number of keys iterated. On error returns
291 * a negative enum TDB_ERROR value.
293 #define tdb_traverse(tdb, fn, p) \
294 tdb_traverse_(tdb, typesafe_cb_preargs(int, (fn), (p), \
295 struct tdb_context *, \
296 TDB_DATA, TDB_DATA), (p))
298 int64_t tdb_traverse_(struct tdb_context *tdb,
299 int (*fn)(struct tdb_context *,
300 TDB_DATA, TDB_DATA, void *), void *p);
303 * tdb_parse_record - operate directly on data in the database.
304 * @tdb: the tdb context returned from tdb_open()
305 * @key: the key whose record we should hand to @parse
306 * @parse: the function to call for the data
307 * @p: the private pointer to hand to @parse (types must match).
309 * This avoids a copy for many cases, by handing you a pointer into
310 * the memory-mapped database. It also locks the record to prevent
311 * other accesses at the same time.
313 * Do not alter the data handed to parse()!
315 #define tdb_parse_record(tdb, key, parse, p) \
316 tdb_parse_record_((tdb), (key), \
317 typesafe_cb_preargs(enum TDB_ERROR, (parse), (p), \
318 TDB_DATA, TDB_DATA), (p))
320 enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
322 enum TDB_ERROR (*parse)(TDB_DATA key,
327 * tdb_firstkey - get the "first" key in a TDB
328 * @tdb: the tdb context returned from tdb_open()
329 * @key: pointer to key.
331 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
332 * open-coded traversal of the database, though it is slightly less efficient
335 * It is your responsibility to free @key->dptr on success.
337 * Returns TDB_ERR_NOEXIST if the database is empty.
339 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
342 * tdb_nextkey - get the "next" key in a TDB
343 * @tdb: the tdb context returned from tdb_open()
344 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
346 * This returns another key in the database; it will free @key.dptr for
349 * Returns TDB_ERR_NOEXIST if there are no more keys.
351 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
354 * tdb_chainlock - lock a record in the TDB
355 * @tdb: the tdb context returned from tdb_open()
356 * @key: the key to lock.
358 * This prevents any changes from occurring to a group of keys including @key,
359 * even if @key does not exist. This allows primitive atomic updates of
360 * records without using transactions.
362 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
363 * you do any operations on any other keys in the database. This also means
364 * that you cannot hold more than one tdb_chainlock() at a time.
369 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
372 * tdb_chainunlock - unlock a record in the TDB
373 * @tdb: the tdb context returned from tdb_open()
374 * @key: the key to unlock.
376 enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
379 * tdb_wipe_all - wipe the database clean
380 * @tdb: the tdb context returned from tdb_open()
382 * Completely erase the database. This is faster than iterating through
383 * each key and doing tdb_delete.
385 enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb);
388 * tdb_check - check a TDB for consistency
389 * @tdb: the tdb context returned from tdb_open()
390 * @check: function to check each key/data pair (or NULL)
391 * @private: argument for @check, must match type.
393 * This performs a consistency check of the open database, optionally calling
394 * a check() function on each record so you can do your own data consistency
395 * checks as well. If check() returns an error, that is returned from
398 * Returns TDB_SUCCESS or an error.
400 #define tdb_check(tdb, check, private) \
401 tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, \
402 (check), (private), \
407 enum TDB_ERROR tdb_check_(struct tdb_context *tdb,
408 enum TDB_ERROR (*check)(struct tdb_data key,
409 struct tdb_data data,
414 * enum tdb_summary_flags - flags for tdb_summary.
416 enum tdb_summary_flags {
417 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
421 * tdb_summary - return a string describing the TDB state
422 * @tdb: the tdb context returned from tdb_open()
423 * @flags: flags to control the summary output.
424 * @summary: pointer to string to allocate.
426 * This returns a developer-readable string describing the overall
427 * state of the tdb, such as the percentage used and sizes of records.
428 * It is designed to provide information about the tdb at a glance
429 * without displaying any keys or data in the database.
431 * On success, sets @summary to point to a malloc()'ed nul-terminated
432 * multi-line string. It is your responsibility to free() it.
434 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
435 enum tdb_summary_flags flags,
440 * tdb_get_flags - return the flags for a tdb
441 * @tdb: the tdb context returned from tdb_open()
443 * This returns the flags on the current tdb. Some of these are caused by
444 * the flags argument to tdb_open(), others (such as TDB_CONVERT) are
447 unsigned int tdb_get_flags(struct tdb_context *tdb);
450 * tdb_add_flag - set a flag for a tdb
451 * @tdb: the tdb context returned from tdb_open()
452 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
454 * You can use this to set a flag on the TDB. You cannot set these flags
455 * on a TDB_INTERNAL tdb.
457 void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
460 * tdb_remove_flag - unset a flag for a tdb
461 * @tdb: the tdb context returned from tdb_open()
462 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
464 * You can use this to clear a flag on the TDB. You cannot clear flags
465 * on a TDB_INTERNAL tdb.
467 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
470 * tdb_name - get the name of a tdb
471 * @tdb: the tdb context returned from tdb_open()
473 * This returns a copy of the name string, made at tdb_open() time. If that
474 * argument was NULL (possible for a TDB_INTERNAL db) this will return NULL.
476 * This is mostly useful for logging.
478 const char *tdb_name(const struct tdb_context *tdb);
481 * tdb_fd - get the file descriptor of a tdb
482 * @tdb: the tdb context returned from tdb_open()
484 * This returns the file descriptor for the underlying database file, or -1
487 int tdb_fd(const struct tdb_context *tdb);
490 * enum tdb_attribute_type - descriminator for union tdb_attribute.
492 enum tdb_attribute_type {
493 TDB_ATTRIBUTE_LOG = 0,
494 TDB_ATTRIBUTE_HASH = 1,
495 TDB_ATTRIBUTE_SEED = 2,
496 TDB_ATTRIBUTE_STATS = 3
500 * struct tdb_attribute_base - common fields for all tdb attributes.
502 struct tdb_attribute_base {
503 enum tdb_attribute_type attr;
504 union tdb_attribute *next;
508 * enum tdb_log_level - log levels for tdb_attribute_log
509 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
510 * or internal consistency failures.
511 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
512 * or writing to a read-only database.
513 * @TDB_LOG_WARNING: used for informational messages on issues which
514 * are unusual but handled by TDB internally, such
515 * as a failure to mmap or failure to open /dev/urandom.
524 * struct tdb_attribute_log - log function attribute
526 * This attribute provides a hook for you to log errors.
528 struct tdb_attribute_log {
529 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
530 void (*log_fn)(struct tdb_context *tdb,
531 enum tdb_log_level level,
533 const char *message);
538 * struct tdb_attribute_hash - hash function attribute
540 * This attribute allows you to provide an alternative hash function.
541 * This hash function will be handed keys from the database; it will also
542 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
543 * tdb_open() will fail if the hash value doesn't match the header).
545 * Note that if your hash function gives different results on
546 * different machine endians, your tdb will no longer work across
547 * different architectures!
549 struct tdb_attribute_hash {
550 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
551 uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed,
557 * struct tdb_attribute_seed - hash function seed attribute
559 * The hash function seed is normally taken from /dev/urandom (or equivalent)
560 * but can be set manually here. This is mainly for testing purposes.
562 struct tdb_attribute_seed {
563 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
568 * struct tdb_attribute_stats - tdb operational statistics
570 * This attribute records statistics of various low-level TDB operations.
571 * This can be used to assist performance evaluation.
573 * New fields will be added at the end, hence the "size" argument which
574 * indicates how large your structure is. If your size is larger than
575 * that known about by this version of tdb, the size will be reduced to
576 * the known structure size. Thus you can detect older versions, and
577 * thus know that newer stats will not be updated.
579 struct tdb_attribute_stats {
580 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
581 size_t size; /* = sizeof(struct tdb_attribute_stats) */
583 uint64_t alloc_subhash;
584 uint64_t alloc_chain;
585 uint64_t alloc_bucket_exact;
586 uint64_t alloc_bucket_max;
587 uint64_t alloc_leftover;
588 uint64_t alloc_coalesce_tried;
589 uint64_t alloc_coalesce_lockfail;
590 uint64_t alloc_coalesce_race;
591 uint64_t alloc_coalesce_succeeded;
592 uint64_t alloc_coalesce_num_merged;
594 uint64_t compare_wrong_bucket;
595 uint64_t compare_wrong_offsetbits;
596 uint64_t compare_wrong_keylen;
597 uint64_t compare_wrong_rechash;
598 uint64_t compare_wrong_keycmp;
602 uint64_t lock_lowlevel;
603 uint64_t lock_nonblock;
607 * union tdb_attribute - tdb attributes.
609 * This represents all the known attributes.
612 * struct tdb_attribute_log, struct tdb_attribute_hash,
613 * struct tdb_attribute_seed, struct tdb_attribute_stats.
615 union tdb_attribute {
616 struct tdb_attribute_base base;
617 struct tdb_attribute_log log;
618 struct tdb_attribute_hash hash;
619 struct tdb_attribute_seed seed;
620 struct tdb_attribute_stats stats;