X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb2%2Ftdb2.h;h=d78ef974b340cece0ac3306c7052edd21928deb5;hp=684bc0492a7260d9f284f8e5d59b3c3c0a097cf3;hb=0693529224e36235fc615fa323e57d5b07879e3f;hpb=a0e0927e1f34d80fd4d4ee2d68fa2acb94ae9eb2 diff --git a/ccan/tdb2/tdb2.h b/ccan/tdb2/tdb2.h index 684bc049..d78ef974 100644 --- a/ccan/tdb2/tdb2.h +++ b/ccan/tdb2/tdb2.h @@ -38,9 +38,14 @@ extern "C" { #include /* For uint64_t */ #include +/* For bool */ +#include +/* For memcmp */ +#include #endif #include #include +#include union tdb_attribute; struct tdb_context; @@ -74,6 +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. @@ -197,6 +203,43 @@ enum TDB_ERROR tdb_append(struct tdb_context *tdb, */ enum TDB_ERROR tdb_delete(struct tdb_context *tdb, struct tdb_data key); +/** + * tdb_exists - does a key exist in the database? + * @tdb: the tdb context returned from tdb_open() + * @key: the key to search for. + * + * Returns true if it exists, or false if it doesn't or any other error. + */ +bool tdb_exists(struct tdb_context *tdb, TDB_DATA key); + +/** + * tdb_deq - are struct tdb_data equal? + * @a: one struct tdb_data + * @b: another struct tdb_data + */ +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() @@ -245,6 +288,9 @@ enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb); * tdb_transaction_commit): if this succeeds then a transaction will only * fail if the write() or fsync() calls fail. * + * If this fails you must still call tdb_transaction_cancel() to cancel + * the transaction. + * * See Also: * tdb_transaction_commit() */ @@ -268,7 +314,7 @@ enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb); * a negative enum TDB_ERROR value. */ #define tdb_traverse(tdb, fn, p) \ - tdb_traverse_(tdb, typesafe_cb_preargs(int, (fn), (p), \ + tdb_traverse_(tdb, typesafe_cb_preargs(int, void *, (fn), (p), \ struct tdb_context *, \ TDB_DATA, TDB_DATA), (p)) @@ -276,6 +322,50 @@ int64_t tdb_traverse_(struct tdb_context *tdb, int (*fn)(struct tdb_context *, TDB_DATA, TDB_DATA, void *), void *p); +/** + * tdb_parse_record - operate directly on data in the database. + * @tdb: the tdb context returned from tdb_open() + * @key: the key whose record we should hand to @parse + * @parse: the function to call for the data + * @data: the private pointer to hand to @parse (types must match). + * + * This avoids a copy for many cases, by handing you a pointer into + * the memory-mapped database. It also locks the record to prevent + * other accesses at the same time. + * + * Do not alter the data handed to parse()! + */ +#define tdb_parse_record(tdb, key, parse, data) \ + tdb_parse_record_((tdb), (key), \ + typesafe_cb_preargs(enum TDB_ERROR, void *, \ + (parse), (data), \ + TDB_DATA, TDB_DATA), (data)) + +enum TDB_ERROR tdb_parse_record_(struct tdb_context *tdb, + TDB_DATA key, + enum TDB_ERROR (*parse)(TDB_DATA k, + TDB_DATA d, + void *data), + void *data); + +/** + * 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() @@ -308,7 +398,7 @@ enum TDB_ERROR tdb_nextkey(struct tdb_context *tdb, struct tdb_data *key); * @tdb: the tdb context returned from tdb_open() * @key: the key to lock. * - * This prevents any changes from occurring to a group of keys including @key, + * This prevents any access occurring to a group of keys including @key, * even if @key does not exist. This allows primitive atomic updates of * records without using transactions. * @@ -325,14 +415,85 @@ 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_chainlock_read - lock a record in the TDB, for reading + * @tdb: the tdb context returned from tdb_open() + * @key: the key to lock. + * + * This prevents any changes from occurring to a group of keys including @key, + * even if @key does not exist. This allows primitive atomic updates of + * records without using transactions. + * + * You cannot begin a transaction while holding a tdb_chainlock_read(), nor can + * you do any operations on any other keys in the database. This also means + * that you cannot hold more than one tdb_chainlock()/read() at a time. + * + * See Also: + * tdb_chainlock() + */ +enum TDB_ERROR tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key); + +/** + * tdb_chainunlock_read - unlock a record in the TDB for reading + * @tdb: the tdb context returned from tdb_open() + * @key: the key to unlock. + * + * The key must have previously been locked by tdb_chainlock_read(). + */ +void tdb_chainunlock_read(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() */ -enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key); +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() + */ +void tdb_unlockall_read(struct tdb_context *tdb); + +/** + * tdb_wipe_all - wipe the database clean + * @tdb: the tdb context returned from tdb_open() + * + * Completely erase the database. This is faster than iterating through + * each key and doing tdb_delete. + */ +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. + * @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 @@ -341,18 +502,29 @@ enum TDB_ERROR tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key); * * Returns TDB_SUCCESS or an error. */ -#define tdb_check(tdb, check, private) \ - tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, \ - (check), (private), \ +#define tdb_check(tdb, check, data) \ + tdb_check_((tdb), typesafe_cb_preargs(enum TDB_ERROR, void *, \ + (check), (data), \ struct tdb_data, \ struct tdb_data), \ - (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); + enum TDB_ERROR (*check)(struct tdb_data k, + struct tdb_data d, + void *data), + void *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. @@ -379,6 +551,57 @@ enum TDB_ERROR tdb_summary(struct tdb_context *tdb, enum tdb_summary_flags flags, char **summary); + +/** + * tdb_get_flags - return the flags for a tdb + * @tdb: the tdb context returned from tdb_open() + * + * This returns the flags on the current tdb. Some of these are caused by + * the flags argument to tdb_open(), others (such as TDB_CONVERT) are + * intuited. + */ +unsigned int tdb_get_flags(struct tdb_context *tdb); + +/** + * tdb_add_flag - set a flag for a tdb + * @tdb: the tdb context returned from tdb_open() + * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC. + * + * You can use this to set a flag on the TDB. You cannot set these flags + * on a TDB_INTERNAL tdb. + */ +void tdb_add_flag(struct tdb_context *tdb, unsigned flag); + +/** + * tdb_remove_flag - unset a flag for a tdb + * @tdb: the tdb context returned from tdb_open() + * @flag: one of TDB_NOLOCK, TDB_NOMMAP or TDB_NOSYNC. + * + * You can use this to clear a flag on the TDB. You cannot clear flags + * on a TDB_INTERNAL tdb. + */ +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. */ @@ -386,7 +609,8 @@ enum tdb_attribute_type { TDB_ATTRIBUTE_LOG = 0, TDB_ATTRIBUTE_HASH = 1, TDB_ATTRIBUTE_SEED = 2, - TDB_ATTRIBUTE_STATS = 3 + TDB_ATTRIBUTE_STATS = 3, + TDB_ATTRIBUTE_OPENHOOK = 4 }; /** @@ -420,11 +644,11 @@ enum tdb_log_level { */ struct tdb_attribute_log { struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_LOG */ - void (*log_fn)(struct tdb_context *tdb, - enum tdb_log_level level, - void *log_private, - const char *message); - void *log_private; + void (*fn)(struct tdb_context *tdb, + enum tdb_log_level level, + const char *message, + void *data); + void *data; }; /** @@ -441,9 +665,9 @@ struct tdb_attribute_log { */ struct tdb_attribute_hash { struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_HASH */ - uint64_t (*hash_fn)(const void *key, size_t len, uint64_t seed, - void *priv); - void *hash_private; + uint64_t (*fn)(const void *key, size_t len, uint64_t seed, + void *data); + void *data; }; /** @@ -496,6 +720,22 @@ struct tdb_attribute_stats { uint64_t lock_nonblock; }; +/** + * struct tdb_attribute_openhook - tdb special effects hook for open + * + * This attribute contains a function to call once we have the OPEN_LOCK + * for the tdb, but before we've examined its contents. If this succeeds, + * the tdb will be populated if it's then zero-length. + * + * This is a hack to allow support for TDB1-style TDB_CLEAR_IF_FIRST + * behaviour. + */ +struct tdb_attribute_openhook { + struct tdb_attribute_base base; /* .attr = TDB_ATTRIBUTE_OPENHOOK */ + enum TDB_ERROR (*fn)(int fd, void *data); + void *data; +}; + /** * union tdb_attribute - tdb attributes. * @@ -503,7 +743,8 @@ struct tdb_attribute_stats { * * See also: * struct tdb_attribute_log, struct tdb_attribute_hash, - * struct tdb_attribute_seed, struct tdb_attribute_stats. + * struct tdb_attribute_seed, struct tdb_attribute_stats, + * struct tdb_attribute_openhook. */ union tdb_attribute { struct tdb_attribute_base base; @@ -511,13 +752,9 @@ union tdb_attribute { struct tdb_attribute_hash hash; struct tdb_attribute_seed seed; struct tdb_attribute_stats stats; + struct tdb_attribute_openhook openhook; }; -/** - * tdb_null - a convenient value for errors. - */ -extern struct tdb_data tdb_null; - #ifdef __cplusplus } #endif