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>
48 * tdb_open - open a database file
49 * @name: the file name (can be NULL if flags contains TDB_INTERNAL)
50 * @tdb_flags: options for this database
51 * @open_flags: flags argument for tdb's open() call.
52 * @mode: mode argument for tdb's open() call.
53 * @attributes: linked list of extra attributes for this tdb.
55 * This call opens (and potentially creates) a database file.
56 * Multiple processes can have the TDB file open at once.
58 * On failure it will return NULL, and set errno: it may also call
59 * any log attribute found in @attributes.
64 struct tdb_context *tdb_open(const char *name, int tdb_flags,
65 int open_flags, mode_t mode,
66 union tdb_attribute *attributes);
69 /* flags for tdb_open() */
70 #define TDB_DEFAULT 0 /* just a readability place holder */
71 #define TDB_INTERNAL 2 /* don't store on disk */
72 #define TDB_NOLOCK 4 /* don't do any locking */
73 #define TDB_NOMMAP 8 /* don't use mmap */
74 #define TDB_CONVERT 16 /* convert endian */
75 #define TDB_NOSYNC 64 /* don't use synchronous transactions */
78 * tdb_close - close and free a tdb.
79 * @tdb: the tdb context returned from tdb_open()
81 * This always succeeds, in that @tdb is unusable after this call. But if
82 * some unexpected error occurred while closing, it will return non-zero
83 * (the only clue as to cause will be via the log attribute).
85 int tdb_close(struct tdb_context *tdb);
88 * struct tdb_data - representation of keys or values.
89 * @dptr: the data pointer
90 * @dsize: the size of the data pointed to by dptr.
92 * This is the "blob" representation of keys and data used by TDB.
94 typedef struct tdb_data {
100 * enum TDB_ERROR - error returns for TDB
106 TDB_SUCCESS = 0, /* No error. */
107 TDB_ERR_CORRUPT = -1, /* We read the db, and it was bogus. */
108 TDB_ERR_IO = -2, /* We couldn't read/write the db. */
109 TDB_ERR_LOCK = -3, /* Locking failed. */
110 TDB_ERR_OOM = -4, /* Out of Memory. */
111 TDB_ERR_EXISTS = -5, /* The key already exists. */
112 TDB_ERR_NOEXIST = -6, /* The key does not exist. */
113 TDB_ERR_EINVAL = -7, /* You're using it wrong. */
114 TDB_ERR_RDONLY = -8, /* The database is read-only. */
115 TDB_ERR_LAST = TDB_ERR_RDONLY
119 * tdb_store - store a key/value pair in a tdb.
120 * @tdb: the tdb context returned from tdb_open()
122 * @dbuf: the data to associate with the key.
123 * @flag: TDB_REPLACE, TDB_INSERT or TDB_MODIFY.
125 * This inserts (or overwrites) a key/value pair in the TDB. If flag
126 * is TDB_REPLACE, it doesn't matter whether the key exists or not;
127 * TDB_INSERT means it must not exist (returns TDB_ERR_EXISTS otherwise),
128 * and TDB_MODIFY means it must exist (returns TDB_ERR_NOEXIST otherwise).
130 * On success, this returns TDB_SUCCESS.
133 * tdb_fetch, tdb_transaction_start, tdb_append, tdb_delete.
135 enum TDB_ERROR tdb_store(struct tdb_context *tdb,
137 struct tdb_data dbuf,
140 /* flags to tdb_store() */
141 #define TDB_REPLACE 1 /* A readability place holder */
142 #define TDB_INSERT 2 /* Don't overwrite an existing entry */
143 #define TDB_MODIFY 3 /* Don't create an existing entry */
146 * tdb_fetch - fetch a value from a tdb.
147 * @tdb: the tdb context returned from tdb_open()
149 * @data: pointer to data.
151 * This looks up a key in the database and sets it in @data.
153 * If it returns TDB_SUCCESS, the key was found: it is your
154 * responsibility to call free() on @data->dptr.
156 * Otherwise, it returns an error (usually, TDB_ERR_NOEXIST) and @data is
159 enum TDB_ERROR tdb_fetch(struct tdb_context *tdb, struct tdb_data key,
160 struct tdb_data *data);
163 * tdb_errorstr - map the tdb error onto a constant readable string
164 * @ecode: the enum TDB_ERROR to map.
166 * This is useful for displaying errors to users.
168 const char *tdb_errorstr(enum TDB_ERROR ecode);
171 * tdb_append - append a value to a key/value pair in a tdb.
172 * @tdb: the tdb context returned from tdb_open()
174 * @dbuf: the data to append.
176 * This is equivalent to fetching a record, reallocating .dptr to add the
177 * data, and writing it back, only it's much more efficient. If the key
178 * doesn't exist, it's equivalent to tdb_store (with an additional hint that
179 * you expect to expand the record in future).
182 * tdb_fetch(), tdb_store()
184 enum TDB_ERROR tdb_append(struct tdb_context *tdb,
185 struct tdb_data key, struct tdb_data dbuf);
188 * tdb_delete - delete a key from a tdb.
189 * @tdb: the tdb context returned from tdb_open()
190 * @key: the key to delete.
192 * Returns TDB_SUCCESS on success, or an error (usually TDB_ERR_NOEXIST).
195 * tdb_fetch(), tdb_store()
197 enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key);
200 * tdb_transaction_start - start a transaction
201 * @tdb: the tdb context returned from tdb_open()
203 * This begins a series of atomic operations. Other processes will be able
204 * to read the tdb, but not alter it (they will block), nor will they see
205 * any changes until tdb_transaction_commit() is called.
208 * tdb_transaction_cancel, tdb_transaction_commit.
210 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb);
213 * tdb_transaction_cancel - abandon a transaction
214 * @tdb: the tdb context returned from tdb_open()
216 * This aborts a transaction, discarding any changes which were made.
217 * tdb_close() does this implicitly.
219 void tdb_transaction_cancel(struct tdb_context *tdb);
222 * tdb_transaction_commit - commit a transaction
223 * @tdb: the tdb context returned from tdb_open()
225 * This completes a transaction, writing any changes which were made.
227 * fsync() is used to commit the transaction (unless TDB_NOSYNC is set),
228 * making it robust against machine crashes, but very slow compared to
229 * other TDB operations.
231 * A failure can only be caused by unexpected errors (eg. I/O or
232 * memory); this is no point looping on transaction failure.
235 * tdb_transaction_prepare_commit()
237 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb);
240 * tdb_transaction_prepare_commit - prepare to commit a transaction
241 * @tdb: the tdb context returned from tdb_open()
243 * This ensures we have the resources to commit a transaction (using
244 * tdb_transaction_commit): if this succeeds then a transaction will only
245 * fail if the write() or fsync() calls fail.
248 * tdb_transaction_commit()
250 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb);
252 /* FIXME: Make typesafe */
253 typedef int (*tdb_traverse_func)(struct tdb_context *, TDB_DATA, TDB_DATA, void *);
256 * tdb_traverse - traverse a TDB
257 * @tdb: the tdb context returned from tdb_open()
258 * @fn: the function to call for every key/value pair (or NULL)
259 * @p: the pointer to hand to @f
261 * This walks the TDB until all they keys have been traversed, or @fn
262 * returns non-zero. If the traverse function or other processes are
263 * changing data or adding or deleting keys, the traverse may be
264 * unreliable: keys may be skipped or (rarely) visited twice.
266 * There is one specific exception: the special case of deleting the
267 * current key does not undermine the reliability of the traversal.
269 * On success, returns the number of keys iterated. On error returns
270 * a negative enum TDB_ERROR value.
272 int64_t tdb_traverse(struct tdb_context *tdb, tdb_traverse_func fn, void *p);
275 * tdb_firstkey - get the "first" key in a TDB
276 * @tdb: the tdb context returned from tdb_open()
277 * @key: pointer to key.
279 * This returns an arbitrary key in the database; with tdb_nextkey() it allows
280 * open-coded traversal of the database, though it is slightly less efficient
283 * It is your responsibility to free @key->dptr on success.
285 * Returns TDB_ERR_NOEXIST if the database is empty.
287 enum TDB_ERROR tdb_firstkey(struct tdb_context *tdb, struct tdb_data *key);
290 * tdb_nextkey - get the "next" key in a TDB
291 * @tdb: the tdb context returned from tdb_open()
292 * @key: a key returned by tdb_firstkey() or tdb_nextkey().
294 * This returns another key in the database; it will free @key.dptr for
297 * Returns TDB_ERR_NOEXIST if there are no more keys.
299 enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key);
302 * tdb_chainlock - lock a record in the TDB
303 * @tdb: the tdb context returned from tdb_open()
304 * @key: the key to lock.
306 * This prevents any changes from occurring to a group of keys including @key,
307 * even if @key does not exist. This allows primitive atomic updates of
308 * records without using transactions.
310 * You cannot begin a transaction while holding a tdb_chainlock(), nor can
311 * you do any operations on any other keys in the database. This also means
312 * that you cannot hold more than one tdb_chainlock() at a time.
317 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);
320 * tdb_chainunlock - unlock a record in the TDB
321 * @tdb: the tdb context returned from tdb_open()
322 * @key: the key to unlock.
324 enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key);
327 * tdb_check - check a TDB for consistency
328 * @tdb: the tdb context returned from tdb_open()
329 * @check: function to check each key/data pair (or NULL)
330 * @private_data: pointer for @check
332 * This performs a consistency check of the open database, optionally calling
333 * a check() function on each record so you can do your own data consistency
334 * checks as well. If check() returns an error, that is returned from
337 enum TDB_ERROR tdb_check(struct tdb_context *tdb,
338 enum TDB_ERROR (*check)(TDB_DATA key,
344 * enum tdb_summary_flags - flags for tdb_summary.
346 enum tdb_summary_flags {
347 TDB_SUMMARY_HISTOGRAMS = 1 /* Draw graphs in the summary. */
351 * tdb_summary - return a string describing the TDB state
352 * @tdb: the tdb context returned from tdb_open()
353 * @flags: flags to control the summary output.
354 * @summary: pointer to string to allocate.
356 * This returns a developer-readable string describing the overall
357 * state of the tdb, such as the percentage used and sizes of records.
358 * It is designed to provide information about the tdb at a glance
359 * without displaying any keys or data in the database.
361 * On success, sets @summary to point to a malloc()'ed nul-terminated
362 * multi-line string. It is your responsibility to free() it.
364 enum TDB_ERROR tdb_summary(struct tdb_context *tdb,
365 enum tdb_summary_flags flags,
369 * enum tdb_attribute_type - descriminator for union tdb_attribute.
371 enum tdb_attribute_type {
372 TDB_ATTRIBUTE_LOG = 0,
373 TDB_ATTRIBUTE_HASH = 1,
374 TDB_ATTRIBUTE_SEED = 2,
375 TDB_ATTRIBUTE_STATS = 3
379 * struct tdb_attribute_base - common fields for all tdb attributes.
381 struct tdb_attribute_base {
382 enum tdb_attribute_type attr;
383 union tdb_attribute *next;
387 * enum tdb_log_level - log levels for tdb_attribute_log
388 * @TDB_LOG_ERROR: used to log unrecoverable errors such as I/O errors
389 * or internal consistency failures.
390 * @TDB_LOG_USE_ERROR: used to log usage errors such as invalid parameters
391 * or writing to a read-only database.
392 * @TDB_LOG_WARNING: used for informational messages on issues which
393 * are unusual but handled by TDB internally, such
394 * as a failure to mmap or failure to open /dev/urandom.
403 * struct tdb_attribute_log - log function attribute
405 * This attribute provides a hook for you to log errors.
407 struct tdb_attribute_log {
408 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */
409 void (*log_fn)(struct tdb_context *tdb,
410 enum tdb_log_level level,
412 const char *message);
417 * struct tdb_attribute_hash - hash function attribute
419 * This attribute allows you to provide an alternative hash function.
420 * This hash function will be handed keys from the database; it will also
421 * be handed the 8-byte TDB_HASH_MAGIC value for checking the header (the
422 * tdb_open() will fail if the hash value doesn't match the header).
424 * Note that if your hash function gives different results on
425 * different machine endians, your tdb will no longer work across
426 * different architectures!
428 struct tdb_attribute_hash {
429 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */
430 uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed,
436 * struct tdb_attribute_seed - hash function seed attribute
438 * The hash function seed is normally taken from /dev/urandom (or equivalent)
439 * but can be set manually here. This is mainly for testing purposes.
441 struct tdb_attribute_seed {
442 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_SEED */
447 * struct tdb_attribute_stats - tdb operational statistics
449 * This attribute records statistics of various low-level TDB operations.
450 * This can be used to assist performance evaluation.
452 * New fields will be added at the end, hence the "size" argument which
453 * indicates how large your structure is. If your size is larger than
454 * that known about by this version of tdb, the size will be reduced to
455 * the known structure size. Thus you can detect older versions, and
456 * thus know that newer stats will not be updated.
458 struct tdb_attribute_stats {
459 struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_STATS */
460 size_t size; /* = sizeof(struct tdb_attribute_stats) */
462 uint64_t alloc_subhash;
463 uint64_t alloc_chain;
464 uint64_t alloc_bucket_exact;
465 uint64_t alloc_bucket_max;
466 uint64_t alloc_leftover;
467 uint64_t alloc_coalesce_tried;
468 uint64_t alloc_coalesce_lockfail;
469 uint64_t alloc_coalesce_race;
470 uint64_t alloc_coalesce_succeeded;
471 uint64_t alloc_coalesce_num_merged;
473 uint64_t compare_wrong_bucket;
474 uint64_t compare_wrong_offsetbits;
475 uint64_t compare_wrong_keylen;
476 uint64_t compare_wrong_rechash;
477 uint64_t compare_wrong_keycmp;
481 uint64_t lock_lowlevel;
482 uint64_t lock_nonblock;
486 * union tdb_attribute - tdb attributes.
488 * This represents all the known attributes.
491 * struct tdb_attribute_log, struct tdb_attribute_hash,
492 * struct tdb_attribute_seed, struct tdb_attribute_stats.
494 union tdb_attribute {
495 struct tdb_attribute_base base;
496 struct tdb_attribute_log log;
497 struct tdb_attribute_hash hash;
498 struct tdb_attribute_seed seed;
499 struct tdb_attribute_stats stats;
503 * tdb_null - a convenient value for errors.
505 extern struct tdb_data tdb_null;