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. */
44 #include <ccan/compiler/compiler.h>
45 #include <ccan/typesafe_cb/typesafe_cb.h>
51 * tdb_open - open a database file
52 * @name: the file name (can be NULL if flags contains TDB_INTERNAL)
53 * @tdb_flags: options for this database
54 * @open_flags: flags argument for tdb's open() call.
55 * @mode: mode argument for tdb's open() call.
56 * @attributes: linked list of extra attributes for this tdb.
58 * This call opens (and potentially creates) a database file.
59 * Multiple processes can have the TDB file open at once.
61 * On failure it will return NULL, and set errno: it may also call
62 * any log attribute found in @attributes.
67 struct tdb_context *tdb_open(const char *name, int tdb_flags,
68 int open_flags, mode_t mode,
69 union tdb_attribute *attributes);
72 /* flags for tdb_open() */
73 #define TDB_DEFAULT 0 /* just a readability place holder */
74 #define TDB_INTERNAL 2 /* don't store on disk */
75 #define TDB_NOLOCK 4 /* don't do any locking */
76 #define TDB_NOMMAP 8 /* don't use mmap */
77 #define TDB_CONVERT 16 /* convert endian */
78 #define TDB_NOSYNC 64 /* don't use synchronous transactions */
81 * tdb_close - close and free a tdb.
82 * @tdb: the tdb context returned from tdb_open()
84 * This always succeeds, in that @tdb is unusable after this call. But if
85 * some unexpected error occurred while closing, it will return non-zero
86 * (the only clue as to cause will be via the log attribute).
88 int tdb_close(struct tdb_context *tdb);
91 * struct tdb_data - representation of keys or values.
92 * @dptr: the data pointer
93 * @dsize: the size of the data pointed to by dptr.
95 * This is the "blob" representation of keys and data used by TDB.
97 typedef struct tdb_data {
103 * enum TDB_ERROR - error returns for TDB
109 TDB_SUCCESS = 0, /* No error. */
110 TDB_ERR_CORRUPT = -1, /* We read the db, and it was bogus. */
111 TDB_ERR_IO = -2, /* We couldn't read/write the db. */
112 TDB_ERR_LOCK = -3, /* Locking failed. */
113 TDB_ERR_OOM = -4, /* Out of Memory. */
114 TDB_ERR_EXISTS = -5, /* The key already exists. */
115 TDB_ERR_NOEXIST = -6, /* The key does not exist. */
116 TDB_ERR_EINVAL = -7, /* You're using it wrong. */
117 TDB_ERR_RDONLY = -8, /* The database is read-only. */
118 TDB_ERR_LAST = TDB_ERR_RDONLY
122 * tdb_store - store a key/value pair in a tdb.
123 * @tdb: the tdb context returned from tdb_open()
125 * @dbuf: the data to associate with the key.
126 * @flag: TDB_REPLACE, TDB_INSERT or TDB_MODIFY.
128 * This inserts (or overwrites) a key/value pair in the TDB. If flag
129 * is TDB_REPLACE, it doesn't matter whether the key exists or not;
130 * TDB_INSERT means it must not exist (returns TDB_ERR_EXISTS otherwise),
131 * and TDB_MODIFY means it must exist (returns TDB_ERR_NOEXIST otherwise).
133 * On success, this returns TDB_SUCCESS.
136 * tdb_fetch, tdb_transaction_start, tdb_append, tdb_delete.
138 enum TDB_ERROR tdb_store(struct tdb_context *tdb,
140 struct tdb_data dbuf,
143 /* flags to tdb_store() */
144 #define TDB_REPLACE 1 /* A readability place holder */
145 #define TDB_INSERT 2 /* Don't overwrite an existing entry */
146 #define TDB_MODIFY 3 /* Don't create an existing entry */
149 * tdb_fetch - fetch a value from a tdb.
150 * @tdb: the tdb context returned from tdb_open()
152 * @data: pointer to data.
154 * This looks up a key in the database and sets it in @data.
156 * If it returns TDB_SUCCESS, the key was found: it is your
157 * responsibility to call free() on @data->dptr.
159 * Otherwise, it returns an error (usually, TDB_ERR_NOEXIST) and @data is
162 enum TDB_ERROR tdb_fetch(struct tdb_context *tdb, struct tdb_data key,
163 struct tdb_data *data);
166 * tdb_errorstr - map the tdb error onto a constant readable string
167 * @ecode: the enum TDB_ERROR to map.
169 * This is useful for displaying errors to users.
171 const char *tdb_errorstr(enum TDB_ERROR ecode);
174 * tdb_append - append a value to a key/value pair in a tdb.
175 * @tdb: the tdb context returned from tdb_open()
177 * @dbuf: the data to append.
179 * This is equivalent to fetching a record, reallocating .dptr to add the
180 * data, and writing it back, only it's much more efficient. If the key
181 * doesn't exist, it's equivalent to tdb_store (with an additional hint that
182 * you expect to expand the record in future).
185 * tdb_fetch(), tdb_store()
187 enum TDB_ERROR tdb_append(struct tdb_context *tdb,
188 struct tdb_data key, struct tdb_data dbuf);
191 * tdb_delete - delete a key from a tdb.
192 * @tdb: the tdb context returned from tdb_open()
193 * @key: the key to delete.
195 * Returns TDB_SUCCESS on success, or an error (usually TDB_ERR_NOEXIST).
198 * tdb_fetch(), tdb_store()
200 enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
203 * tdb_exists - does a key exist in the database?
204 * @tdb: the tdb context returned from tdb_open()
205 * @key: the key to search for.
207 * Returns true if it exists, or false if it doesn't or any other error.
209 bool tdb_exists(struct tdb_context *tdb, TDB_DATA key);
212 * tdb_transaction_start - start a transaction
213 * @tdb: the tdb context returned from tdb_open()
215 * This begins a series of atomic operations. Other processes will be able
216 * to read the tdb, but not alter it (they will block), nor will they see
217 * any changes until tdb_transaction_commit() is called.
220 * tdb_transaction_cancel, tdb_transaction_commit.
222 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb);
225 * tdb_transaction_cancel - abandon a transaction
226 * @tdb: the tdb context returned from tdb_open()
228 * This aborts a transaction, discarding any changes which were made.
229 * tdb_close() does this implicitly.
231 void tdb_transaction_cancel(struct tdb_context *tdb);
234 * tdb_transaction_commit - commit a transaction
235 * @tdb: the tdb context returned from tdb_open()
237 * This completes a transaction, writing any changes which were made.
239 * fsync() is used to commit the transaction (unless TDB_NOSYNC is set),
240 * making it robust against machine crashes, but very slow compared to
241 * other TDB operations.
243 * A failure can only be caused by unexpected errors (eg. I/O or
244 * memory); this is no point looping on transaction failure.
247 * tdb_transaction_prepare_commit()
249 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
252 * tdb_transaction_prepare_commit - prepare to commit a transaction
253 * @tdb: the tdb context returned from tdb_open()
255 * This ensures we have the resources to commit a transaction (using
256 * tdb_transaction_commit): if this succeeds then a transaction will only
257 * fail if the write() or fsync() calls fail.
260 * tdb_transaction_commit()
262 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
265 * tdb_traverse - traverse a TDB
266 * @tdb: the tdb context returned from tdb_open()
267 * @fn: the function to call for every key/value pair (or NULL)
268 * @p: the pointer to hand to @f
270 * This walks the TDB until all they keys have been traversed, or @fn
271 * returns non-zero. If the traverse function or other processes are
272 * changing data or adding or deleting keys, the traverse may be
273 * unreliable: keys may be skipped or (rarely) visited twice.
275 * There is one specific exception: the special case of deleting the
276 * current key does not undermine the reliability of the traversal.
278 * On success, returns the number of keys iterated. On error returns
279 * a negative enum TDB_ERROR value.
281 #define tdb_traverse(tdb, fn, p) \
282 tdb_traverse_(tdb, typesafe_cb_preargs(int, (fn), (p), \
283 struct tdb_context *, \
284 TDB_DATA, TDB_DATA), (p))
286 int64_t tdb_traverse_(struct tdb_context *tdb,
287 int (*fn)(struct tdb_context *,
288 TDB_DATA, TDB_DATA, void *), void *p);
291 * tdb_parse_record - operate directly on data in the database.
292 * @tdb: the tdb context returned from tdb_open()
293 * @key: the key whose record we should hand to @parse
294 * @parse: the function to call for the data
295 * @p: the private pointer to hand to @parse (types must match).
297 * This avoids a copy for many cases, by handing you a pointer into
298 * the memory-mapped database. It also locks the record to prevent
299 * other accesses at the same time.
301 * Do not alter the data handed to parse()!
303 #define tdb_parse_record(tdb, key, parse, p) \
304 tdb_parse_record_((tdb), (key), \
305 typesafe_cb_preargs(enum TDB_ERROR, (parse), (p), \
306 TDB_DATA, TDB_DATA), (p))
308 enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb,
310 enum TDB_ERROR (*parse)(TDB_DATA key,
315 * tdb_firstkey - get the "first" key in a TDB
316 * @tdb: the tdb context returned from tdb_open()
317 * @key: pointer to key.
319 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
320 * open-coded traversal of the database, though it is slightly less efficient
323 * It is your responsibility to free @key->dptr on success.
325 * Returns TDB_ERR_NOEXIST if the database is empty.
327 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
330 * tdb_nextkey - get the "next" key in a TDB
331 * @tdb: the tdb context returned from tdb_open()
332 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
334 * This returns another key in the database; it will free @key.dptr for
337 * Returns TDB_ERR_NOEXIST if there are no more keys.
339 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
342 * tdb_chainlock - lock a record in the TDB
343 * @tdb: the tdb context returned from tdb_open()
344 * @key: the key to lock.
346 * This prevents any changes from occurring to a group of keys including @key,
347 * even if @key does not exist. This allows primitive atomic updates of
348 * records without using transactions.
350 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
351 * you do any operations on any other keys in the database. This also means
352 * that you cannot hold more than one tdb_chainlock() at a time.
357 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
360 * tdb_chainunlock - unlock a record in the TDB
361 * @tdb: the tdb context returned from tdb_open()
362 * @key: the key to unlock.
364 enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
367 * tdb_wipe_all - wipe the database clean
368 * @tdb: the tdb context returned from tdb_open()
370 * Completely erase the database. This is faster than iterating through
371 * each key and doing tdb_delete.
373 enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb);
376 * tdb_check - check a TDB for consistency
377 * @tdb: the tdb context returned from tdb_open()
378 * @check: function to check each key/data pair (or NULL)
379 * @private: argument for @check, must match type.
381 * This performs a consistency check of the open database, optionally calling
382 * a check() function on each record so you can do your own data consistency
383 * checks as well. If check() returns an error, that is returned from
386 * Returns TDB_SUCCESS or an error.
388 #define tdb_check(tdb, check, private) \
389 tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, \
390 (check), (private), \
395 enum TDB_ERROR tdb_check_(struct tdb_context *tdb,
396 enum TDB_ERROR (*check)(struct tdb_data key,
397 struct tdb_data data,
402 * enum tdb_summary_flags - flags for tdb_summary.
404 enum tdb_summary_flags {
405 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
409 * tdb_summary - return a string describing the TDB state
410 * @tdb: the tdb context returned from tdb_open()
411 * @flags: flags to control the summary output.
412 * @summary: pointer to string to allocate.
414 * This returns a developer-readable string describing the overall
415 * state of the tdb, such as the percentage used and sizes of records.
416 * It is designed to provide information about the tdb at a glance
417 * without displaying any keys or data in the database.
419 * On success, sets @summary to point to a malloc()'ed nul-terminated
420 * multi-line string. It is your responsibility to free() it.
422 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
423 enum tdb_summary_flags flags,
428 * tdb_get_flags - return the flags for a tdb
429 * @tdb: the tdb context returned from tdb_open()
431 * This returns the flags on the current tdb. Some of these are caused by
432 * the flags argument to tdb_open(), others (such as TDB_CONVERT) are
435 unsigned int tdb_get_flags(struct tdb_context *tdb);
438 * tdb_add_flag - set a flag for a tdb
439 * @tdb: the tdb context returned from tdb_open()
440 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
442 * You can use this to set a flag on the TDB. You cannot set these flags
443 * on a TDB_INTERNAL tdb.
445 void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
448 * tdb_remove_flag - unset a flag for a tdb
449 * @tdb: the tdb context returned from tdb_open()
450 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
452 * You can use this to clear a flag on the TDB. You cannot clear flags
453 * on a TDB_INTERNAL tdb.
455 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
458 * enum tdb_attribute_type - descriminator for union tdb_attribute.
460 enum tdb_attribute_type {
461 TDB_ATTRIBUTE_LOG = 0,
462 TDB_ATTRIBUTE_HASH = 1,
463 TDB_ATTRIBUTE_SEED = 2,
464 TDB_ATTRIBUTE_STATS = 3
468 * struct tdb_attribute_base - common fields for all tdb attributes.
470 struct tdb_attribute_base {
471 enum tdb_attribute_type attr;
472 union tdb_attribute *next;
476 * enum tdb_log_level - log levels for tdb_attribute_log
477 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
478 * or internal consistency failures.
479 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
480 * or writing to a read-only database.
481 * @TDB_LOG_WARNING: used for informational messages on issues which
482 * are unusual but handled by TDB internally, such
483 * as a failure to mmap or failure to open /dev/urandom.
492 * struct tdb_attribute_log - log function attribute
494 * This attribute provides a hook for you to log errors.
496 struct tdb_attribute_log {
497 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
498 void (*log_fn)(struct tdb_context *tdb,
499 enum tdb_log_level level,
501 const char *message);
506 * struct tdb_attribute_hash - hash function attribute
508 * This attribute allows you to provide an alternative hash function.
509 * This hash function will be handed keys from the database; it will also
510 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
511 * tdb_open() will fail if the hash value doesn't match the header).
513 * Note that if your hash function gives different results on
514 * different machine endians, your tdb will no longer work across
515 * different architectures!
517 struct tdb_attribute_hash {
518 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
519 uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed,
525 * struct tdb_attribute_seed - hash function seed attribute
527 * The hash function seed is normally taken from /dev/urandom (or equivalent)
528 * but can be set manually here. This is mainly for testing purposes.
530 struct tdb_attribute_seed {
531 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
536 * struct tdb_attribute_stats - tdb operational statistics
538 * This attribute records statistics of various low-level TDB operations.
539 * This can be used to assist performance evaluation.
541 * New fields will be added at the end, hence the "size" argument which
542 * indicates how large your structure is. If your size is larger than
543 * that known about by this version of tdb, the size will be reduced to
544 * the known structure size. Thus you can detect older versions, and
545 * thus know that newer stats will not be updated.
547 struct tdb_attribute_stats {
548 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
549 size_t size; /* = sizeof(struct tdb_attribute_stats) */
551 uint64_t alloc_subhash;
552 uint64_t alloc_chain;
553 uint64_t alloc_bucket_exact;
554 uint64_t alloc_bucket_max;
555 uint64_t alloc_leftover;
556 uint64_t alloc_coalesce_tried;
557 uint64_t alloc_coalesce_lockfail;
558 uint64_t alloc_coalesce_race;
559 uint64_t alloc_coalesce_succeeded;
560 uint64_t alloc_coalesce_num_merged;
562 uint64_t compare_wrong_bucket;
563 uint64_t compare_wrong_offsetbits;
564 uint64_t compare_wrong_keylen;
565 uint64_t compare_wrong_rechash;
566 uint64_t compare_wrong_keycmp;
570 uint64_t lock_lowlevel;
571 uint64_t lock_nonblock;
575 * union tdb_attribute - tdb attributes.
577 * This represents all the known attributes.
580 * struct tdb_attribute_log, struct tdb_attribute_hash,
581 * struct tdb_attribute_seed, struct tdb_attribute_stats.
583 union tdb_attribute {
584 struct tdb_attribute_base base;
585 struct tdb_attribute_log log;
586 struct tdb_attribute_hash hash;
587 struct tdb_attribute_seed seed;
588 struct tdb_attribute_stats stats;
592 * tdb_null - a convenient value for errors.
594 extern struct tdb_data tdb_null;