X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb2%2Ftdb2.h;h=84228bdcb95eb66292e30cb40e5ba9713cc099a6;hp=811d9120458d3b720c670be0179a48db437c5533;hb=f1069e4a2d5a8115695fb8ea3e78dbdcf389aead;hpb=a4393df8ed138b853b4ff212db7e1a50aba0b8c7 diff --git a/ccan/tdb2/tdb2.h b/ccan/tdb2/tdb2.h index 811d9120..84228bdc 100644 --- a/ccan/tdb2/tdb2.h +++ b/ccan/tdb2/tdb2.h @@ -45,6 +45,7 @@ extern "C" { #endif #include #include +#include union tdb_attribute; struct tdb_context; @@ -78,6 +79,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags, #define TDB_NOMMAP 8 /* don't use mmap */ #define TDB_CONVERT 16 /* convert endian */ #define TDB_NOSYNC 64 /* don't use synchronous transactions */ +#define TDB_SEQNUM 128 /* maintain a sequence number */ /** * tdb_close - close and free a tdb. @@ -220,6 +222,24 @@ static inline bool tdb_deq(struct tdb_data a, struct tdb_data b) return a.dsize == b.dsize && memcmp(a.dptr, b.dptr, a.dsize) == 0; } +/** + * tdb_mkdata - make a struct tdb_data from const data + * @p: the constant pointer + * @len: the length + * + * As the dptr member of struct tdb_data is not constant, you need to + * cast it. This function keeps thost casts in one place, as well as + * suppressing the warning some compilers give when casting away a + * qualifier (eg. gcc with -Wcast-qual) + */ +static inline struct tdb_data tdb_mkdata(const void *p, size_t len) +{ + struct tdb_data d; + d.dptr = cast_const(void *, p); + d.dsize = len; + return d; +} + /** * tdb_transaction_start - start a transaction * @tdb: the tdb context returned from tdb_open() @@ -323,6 +343,25 @@ enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb, TDB_DATA data, void *p), void *p); + +/** + * tdb_get_seqnum - get a database sequence number + * @tdb: the tdb context returned from tdb_open() + * + * This returns a sequence number: any change to the database from a + * tdb context opened with the TDB_SEQNUM flag will cause that number + * to increment. Note that the incrementing is unreliable (it is done + * without locking), so this is only useful as an optimization. + * + * For example, you may have a regular database backup routine which + * does not operate if the sequence number is unchanged. In the + * unlikely event of a failed increment, it will be backed up next + * time any way. + * + * Returns an enum TDB_ERROR (ie. negative) on error. + */ +int64_t tdb_get_seqnum(struct tdb_context *tdb); + /** * tdb_firstkey - get the "first" key in a TDB * @tdb: the tdb context returned from tdb_open() @@ -372,8 +411,43 @@ enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key); * tdb_chainunlock - unlock a record in the TDB * @tdb: the tdb context returned from tdb_open() * @key: the key to unlock. + * + * The key must have previously been locked by tdb_chainlock(). + */ +void tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key); + +/** + * tdb_lockall - lock the entire TDB + * @tdb: the tdb context returned from tdb_open() + * + * You cannot hold a tdb_chainlock while calling this. It nests, so you + * must call tdb_unlockall as many times as you call tdb_lockall. + */ +enum TDB_ERROR tdb_lockall(struct tdb_context *tdb); + +/** + * tdb_unlockall - unlock the entire TDB + * @tdb: the tdb context returned from tdb_open() + */ +void tdb_unlockall(struct tdb_context *tdb); + +/** + * tdb_lockall_read - lock the entire TDB for reading + * @tdb: the tdb context returned from tdb_open() + * + * This prevents others writing to the database, eg. tdb_delete, tdb_store, + * tdb_append, but not tdb_fetch. + * + * You cannot hold a tdb_chainlock while calling this. It nests, so you + * must call tdb_unlockall_read as many times as you call tdb_lockall_read. + */ +enum TDB_ERROR tdb_lockall_read(struct tdb_context *tdb); + +/** + * tdb_unlockall_read - unlock the entire TDB for reading + * @tdb: the tdb context returned from tdb_open() */ -enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key); +void tdb_unlockall_read(struct tdb_context *tdb); /** * tdb_wipe_all - wipe the database clean @@ -388,7 +462,7 @@ enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb); * tdb_check - check a TDB for consistency * @tdb: the tdb context returned from tdb_open() * @check: function to check each key/data pair (or NULL) - * @private: argument for @check, must match type. + * @private_data: argument for @check, must match type. * * This performs a consistency check of the open database, optionally calling * a check() function on each record so you can do your own data consistency @@ -397,18 +471,29 @@ enum TDB_ERROR tdb_wipe_all(struct tdb_context *tdb); * * Returns TDB_SUCCESS or an error. */ -#define tdb_check(tdb, check, private) \ +#define tdb_check(tdb, check, private_data) \ tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, \ - (check), (private), \ + (check), (private_data), \ struct tdb_data, \ struct tdb_data), \ - (private)) + (private_data)) enum TDB_ERROR tdb_check_(struct tdb_context *tdb, enum TDB_ERROR (*check)(struct tdb_data key, struct tdb_data data, - void *private), - void *private); + void *private_data), + void *private_data); + +/** + * tdb_error - get the last error (not threadsafe) + * @tdb: the tdb context returned from tdb_open() + * + * Returns the last error returned by a TDB function. + * + * This makes porting from TDB1 easier, but note that the last error is not + * reliable in threaded programs. + */ +enum TDB_ERROR tdb_error(struct tdb_context *tdb); /** * enum tdb_summary_flags - flags for tdb_summary. @@ -466,6 +551,26 @@ void tdb_add_flag(struct tdb_context *tdb, unsigned flag); */ void tdb_remove_flag(struct tdb_context *tdb, unsigned flag); +/** + * tdb_name - get the name of a tdb + * @tdb: the tdb context returned from tdb_open() + * + * This returns a copy of the name string, made at tdb_open() time. If that + * argument was NULL (possible for a TDB_INTERNAL db) this will return NULL. + * + * This is mostly useful for logging. + */ +const char *tdb_name(const struct tdb_context *tdb); + +/** + * tdb_fd - get the file descriptor of a tdb + * @tdb: the tdb context returned from tdb_open() + * + * This returns the file descriptor for the underlying database file, or -1 + * for TDB_INTERNAL. + */ +int tdb_fd(const struct tdb_context *tdb); + /** * enum tdb_attribute_type - descriminator for union tdb_attribute. */ @@ -600,11 +705,6 @@ union tdb_attribute { struct tdb_attribute_stats stats; }; -/** - * tdb_null - a convenient value for errors. - */ -extern struct tdb_data tdb_null; - #ifdef __cplusplus } #endif