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. */
42 #include <ccan/compiler/compiler.h>
43 #include <ccan/typesafe_cb/typesafe_cb.h>
49 * tdb_open - open a database file
50 * @name: the file name (can be NULL if flags contains TDB_INTERNAL)
51 * @tdb_flags: options for this database
52 * @open_flags: flags argument for tdb's open() call.
53 * @mode: mode argument for tdb's open() call.
54 * @attributes: linked list of extra attributes for this tdb.
56 * This call opens (and potentially creates) a database file.
57 * Multiple processes can have the TDB file open at once.
59 * On failure it will return NULL, and set errno: it may also call
60 * any log attribute found in @attributes.
65 struct tdb_context *tdb_open(const char *name, int tdb_flags,
66 int open_flags, mode_t mode,
67 union tdb_attribute *attributes);
70 /* flags for tdb_open() */
71 #define TDB_DEFAULT 0 /* just a readability place holder */
72 #define TDB_INTERNAL 2 /* don't store on disk */
73 #define TDB_NOLOCK 4 /* don't do any locking */
74 #define TDB_NOMMAP 8 /* don't use mmap */
75 #define TDB_CONVERT 16 /* convert endian */
76 #define TDB_NOSYNC 64 /* don't use synchronous transactions */
79 * tdb_close - close and free a tdb.
80 * @tdb: the tdb context returned from tdb_open()
82 * This always succeeds, in that @tdb is unusable after this call. But if
83 * some unexpected error occurred while closing, it will return non-zero
84 * (the only clue as to cause will be via the log attribute).
86 int tdb_close(struct tdb_context *tdb);
89 * struct tdb_data - representation of keys or values.
90 * @dptr: the data pointer
91 * @dsize: the size of the data pointed to by dptr.
93 * This is the "blob" representation of keys and data used by TDB.
95 typedef struct tdb_data {
101 * enum TDB_ERROR - error returns for TDB
107 TDB_SUCCESS = 0, /* No error. */
108 TDB_ERR_CORRUPT = -1, /* We read the db, and it was bogus. */
109 TDB_ERR_IO = -2, /* We couldn't read/write the db. */
110 TDB_ERR_LOCK = -3, /* Locking failed. */
111 TDB_ERR_OOM = -4, /* Out of Memory. */
112 TDB_ERR_EXISTS = -5, /* The key already exists. */
113 TDB_ERR_NOEXIST = -6, /* The key does not exist. */
114 TDB_ERR_EINVAL = -7, /* You're using it wrong. */
115 TDB_ERR_RDONLY = -8, /* The database is read-only. */
116 TDB_ERR_LAST = TDB_ERR_RDONLY
120 * tdb_store - store a key/value pair in a tdb.
121 * @tdb: the tdb context returned from tdb_open()
123 * @dbuf: the data to associate with the key.
124 * @flag: TDB_REPLACE, TDB_INSERT or TDB_MODIFY.
126 * This inserts (or overwrites) a key/value pair in the TDB. If flag
127 * is TDB_REPLACE, it doesn't matter whether the key exists or not;
128 * TDB_INSERT means it must not exist (returns TDB_ERR_EXISTS otherwise),
129 * and TDB_MODIFY means it must exist (returns TDB_ERR_NOEXIST otherwise).
131 * On success, this returns TDB_SUCCESS.
134 * tdb_fetch, tdb_transaction_start, tdb_append, tdb_delete.
136 enum TDB_ERROR tdb_store(struct tdb_context *tdb,
138 struct tdb_data dbuf,
141 /* flags to tdb_store() */
142 #define TDB_REPLACE 1 /* A readability place holder */
143 #define TDB_INSERT 2 /* Don't overwrite an existing entry */
144 #define TDB_MODIFY 3 /* Don't create an existing entry */
147 * tdb_fetch - fetch a value from a tdb.
148 * @tdb: the tdb context returned from tdb_open()
150 * @data: pointer to data.
152 * This looks up a key in the database and sets it in @data.
154 * If it returns TDB_SUCCESS, the key was found: it is your
155 * responsibility to call free() on @data->dptr.
157 * Otherwise, it returns an error (usually, TDB_ERR_NOEXIST) and @data is
160 enum TDB_ERROR tdb_fetch(struct tdb_context *tdb, struct tdb_data key,
161 struct tdb_data *data);
164 * tdb_errorstr - map the tdb error onto a constant readable string
165 * @ecode: the enum TDB_ERROR to map.
167 * This is useful for displaying errors to users.
169 const char *tdb_errorstr(enum TDB_ERROR ecode);
172 * tdb_append - append a value to a key/value pair in a tdb.
173 * @tdb: the tdb context returned from tdb_open()
175 * @dbuf: the data to append.
177 * This is equivalent to fetching a record, reallocating .dptr to add the
178 * data, and writing it back, only it's much more efficient. If the key
179 * doesn't exist, it's equivalent to tdb_store (with an additional hint that
180 * you expect to expand the record in future).
183 * tdb_fetch(), tdb_store()
185 enum TDB_ERROR tdb_append(struct tdb_context *tdb,
186 struct tdb_data key, struct tdb_data dbuf);
189 * tdb_delete - delete a key from a tdb.
190 * @tdb: the tdb context returned from tdb_open()
191 * @key: the key to delete.
193 * Returns TDB_SUCCESS on success, or an error (usually TDB_ERR_NOEXIST).
196 * tdb_fetch(), tdb_store()
198 enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
201 * tdb_transaction_start - start a transaction
202 * @tdb: the tdb context returned from tdb_open()
204 * This begins a series of atomic operations. Other processes will be able
205 * to read the tdb, but not alter it (they will block), nor will they see
206 * any changes until tdb_transaction_commit() is called.
209 * tdb_transaction_cancel, tdb_transaction_commit.
211 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb);
214 * tdb_transaction_cancel - abandon a transaction
215 * @tdb: the tdb context returned from tdb_open()
217 * This aborts a transaction, discarding any changes which were made.
218 * tdb_close() does this implicitly.
220 void tdb_transaction_cancel(struct tdb_context *tdb);
223 * tdb_transaction_commit - commit a transaction
224 * @tdb: the tdb context returned from tdb_open()
226 * This completes a transaction, writing any changes which were made.
228 * fsync() is used to commit the transaction (unless TDB_NOSYNC is set),
229 * making it robust against machine crashes, but very slow compared to
230 * other TDB operations.
232 * A failure can only be caused by unexpected errors (eg. I/O or
233 * memory); this is no point looping on transaction failure.
236 * tdb_transaction_prepare_commit()
238 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
241 * tdb_transaction_prepare_commit - prepare to commit a transaction
242 * @tdb: the tdb context returned from tdb_open()
244 * This ensures we have the resources to commit a transaction (using
245 * tdb_transaction_commit): if this succeeds then a transaction will only
246 * fail if the write() or fsync() calls fail.
249 * tdb_transaction_commit()
251 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
254 * tdb_traverse - traverse a TDB
255 * @tdb: the tdb context returned from tdb_open()
256 * @fn: the function to call for every key/value pair (or NULL)
257 * @p: the pointer to hand to @f
259 * This walks the TDB until all they keys have been traversed, or @fn
260 * returns non-zero. If the traverse function or other processes are
261 * changing data or adding or deleting keys, the traverse may be
262 * unreliable: keys may be skipped or (rarely) visited twice.
264 * There is one specific exception: the special case of deleting the
265 * current key does not undermine the reliability of the traversal.
267 * On success, returns the number of keys iterated. On error returns
268 * a negative enum TDB_ERROR value.
270 #define tdb_traverse(tdb, fn, p) \
271 tdb_traverse_(tdb, typesafe_cb_preargs(int, (fn), (p), \
272 struct tdb_context *, \
273 TDB_DATA, TDB_DATA), (p))
275 int64_t tdb_traverse_(struct tdb_context *tdb,
276 int (*fn)(struct tdb_context *,
277 TDB_DATA, TDB_DATA, void *), void *p);
280 * tdb_firstkey - get the "first" key in a TDB
281 * @tdb: the tdb context returned from tdb_open()
282 * @key: pointer to key.
284 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
285 * open-coded traversal of the database, though it is slightly less efficient
288 * It is your responsibility to free @key->dptr on success.
290 * Returns TDB_ERR_NOEXIST if the database is empty.
292 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
295 * tdb_nextkey - get the "next" key in a TDB
296 * @tdb: the tdb context returned from tdb_open()
297 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
299 * This returns another key in the database; it will free @key.dptr for
302 * Returns TDB_ERR_NOEXIST if there are no more keys.
304 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
307 * tdb_chainlock - lock a record in the TDB
308 * @tdb: the tdb context returned from tdb_open()
309 * @key: the key to lock.
311 * This prevents any changes from occurring to a group of keys including @key,
312 * even if @key does not exist. This allows primitive atomic updates of
313 * records without using transactions.
315 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
316 * you do any operations on any other keys in the database. This also means
317 * that you cannot hold more than one tdb_chainlock() at a time.
322 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
325 * tdb_chainunlock - unlock a record in the TDB
326 * @tdb: the tdb context returned from tdb_open()
327 * @key: the key to unlock.
329 enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
332 * tdb_check - check a TDB for consistency
333 * @tdb: the tdb context returned from tdb_open()
334 * @check: function to check each key/data pair (or NULL)
335 * @private: argument for @check, must match type.
337 * This performs a consistency check of the open database, optionally calling
338 * a check() function on each record so you can do your own data consistency
339 * checks as well. If check() returns an error, that is returned from
342 * Returns TDB_SUCCESS or an error.
344 #define tdb_check(tdb, check, private) \
345 tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, \
346 (check), (private), \
351 enum TDB_ERROR tdb_check_(struct tdb_context *tdb,
352 enum TDB_ERROR (*check)(struct tdb_data key,
353 struct tdb_data data,
358 * enum tdb_summary_flags - flags for tdb_summary.
360 enum tdb_summary_flags {
361 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
365 * tdb_summary - return a string describing the TDB state
366 * @tdb: the tdb context returned from tdb_open()
367 * @flags: flags to control the summary output.
368 * @summary: pointer to string to allocate.
370 * This returns a developer-readable string describing the overall
371 * state of the tdb, such as the percentage used and sizes of records.
372 * It is designed to provide information about the tdb at a glance
373 * without displaying any keys or data in the database.
375 * On success, sets @summary to point to a malloc()'ed nul-terminated
376 * multi-line string. It is your responsibility to free() it.
378 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
379 enum tdb_summary_flags flags,
384 * tdb_get_flags - return the flags for a tdb
385 * @tdb: the tdb context returned from tdb_open()
387 * This returns the flags on the current tdb. Some of these are caused by
388 * the flags argument to tdb_open(), others (such as TDB_CONVERT) are
391 unsigned int tdb_get_flags(struct tdb_context *tdb);
394 * tdb_add_flag - set a flag for a tdb
395 * @tdb: the tdb context returned from tdb_open()
396 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
398 * You can use this to set a flag on the TDB. You cannot set these flags
399 * on a TDB_INTERNAL tdb.
401 void tdb_add_flag(struct tdb_context *tdb, unsigned flag);
404 * tdb_remove_flag - unset a flag for a tdb
405 * @tdb: the tdb context returned from tdb_open()
406 * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC.
408 * You can use this to clear a flag on the TDB. You cannot clear flags
409 * on a TDB_INTERNAL tdb.
411 void tdb_remove_flag(struct tdb_context *tdb, unsigned flag);
414 * enum tdb_attribute_type - descriminator for union tdb_attribute.
416 enum tdb_attribute_type {
417 TDB_ATTRIBUTE_LOG = 0,
418 TDB_ATTRIBUTE_HASH = 1,
419 TDB_ATTRIBUTE_SEED = 2,
420 TDB_ATTRIBUTE_STATS = 3
424 * struct tdb_attribute_base - common fields for all tdb attributes.
426 struct tdb_attribute_base {
427 enum tdb_attribute_type attr;
428 union tdb_attribute *next;
432 * enum tdb_log_level - log levels for tdb_attribute_log
433 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
434 * or internal consistency failures.
435 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
436 * or writing to a read-only database.
437 * @TDB_LOG_WARNING: used for informational messages on issues which
438 * are unusual but handled by TDB internally, such
439 * as a failure to mmap or failure to open /dev/urandom.
448 * struct tdb_attribute_log - log function attribute
450 * This attribute provides a hook for you to log errors.
452 struct tdb_attribute_log {
453 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
454 void (*log_fn)(struct tdb_context *tdb,
455 enum tdb_log_level level,
457 const char *message);
462 * struct tdb_attribute_hash - hash function attribute
464 * This attribute allows you to provide an alternative hash function.
465 * This hash function will be handed keys from the database; it will also
466 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
467 * tdb_open() will fail if the hash value doesn't match the header).
469 * Note that if your hash function gives different results on
470 * different machine endians, your tdb will no longer work across
471 * different architectures!
473 struct tdb_attribute_hash {
474 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
475 uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed,
481 * struct tdb_attribute_seed - hash function seed attribute
483 * The hash function seed is normally taken from /dev/urandom (or equivalent)
484 * but can be set manually here. This is mainly for testing purposes.
486 struct tdb_attribute_seed {
487 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
492 * struct tdb_attribute_stats - tdb operational statistics
494 * This attribute records statistics of various low-level TDB operations.
495 * This can be used to assist performance evaluation.
497 * New fields will be added at the end, hence the "size" argument which
498 * indicates how large your structure is. If your size is larger than
499 * that known about by this version of tdb, the size will be reduced to
500 * the known structure size. Thus you can detect older versions, and
501 * thus know that newer stats will not be updated.
503 struct tdb_attribute_stats {
504 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
505 size_t size; /* = sizeof(struct tdb_attribute_stats) */
507 uint64_t alloc_subhash;
508 uint64_t alloc_chain;
509 uint64_t alloc_bucket_exact;
510 uint64_t alloc_bucket_max;
511 uint64_t alloc_leftover;
512 uint64_t alloc_coalesce_tried;
513 uint64_t alloc_coalesce_lockfail;
514 uint64_t alloc_coalesce_race;
515 uint64_t alloc_coalesce_succeeded;
516 uint64_t alloc_coalesce_num_merged;
518 uint64_t compare_wrong_bucket;
519 uint64_t compare_wrong_offsetbits;
520 uint64_t compare_wrong_keylen;
521 uint64_t compare_wrong_rechash;
522 uint64_t compare_wrong_keycmp;
526 uint64_t lock_lowlevel;
527 uint64_t lock_nonblock;
531 * union tdb_attribute - tdb attributes.
533 * This represents all the known attributes.
536 * struct tdb_attribute_log, struct tdb_attribute_hash,
537 * struct tdb_attribute_seed, struct tdb_attribute_stats.
539 union tdb_attribute {
540 struct tdb_attribute_base base;
541 struct tdb_attribute_log log;
542 struct tdb_attribute_hash hash;
543 struct tdb_attribute_seed seed;
544 struct tdb_attribute_stats stats;
548 * tdb_null - a convenient value for errors.
550 extern struct tdb_data tdb_null;