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Diffstat (limited to 'source4/lib/tdb/docs')
| -rw-r--r-- | source4/lib/tdb/docs/README | 167 | ||||
| -rw-r--r-- | source4/lib/tdb/docs/tdb.magic | 10 |
2 files changed, 177 insertions, 0 deletions
diff --git a/source4/lib/tdb/docs/README b/source4/lib/tdb/docs/README new file mode 100644 index 0000000000..fac3eacb4d --- /dev/null +++ b/source4/lib/tdb/docs/README @@ -0,0 +1,167 @@ +tdb - a trivial database system +tridge@linuxcare.com December 1999 +================================== + +This is a simple database API. It was inspired by the realisation that +in Samba we have several ad-hoc bits of code that essentially +implement small databases for sharing structures between parts of +Samba. As I was about to add another I realised that a generic +database module was called for to replace all the ad-hoc bits. + +I based the interface on gdbm. I couldn't use gdbm as we need to be +able to have multiple writers to the databases at one time. + +Compilation +----------- + +add HAVE_MMAP=1 to use mmap instead of read/write +add TDB_DEBUG=1 for verbose debug info +add NOLOCK=1 to disable locking code + +Testing +------- + +Compile tdbtest.c and link with gdbm for testing. tdbtest will perform +identical operations via tdb and gdbm then make sure the result is the +same + +Also included is tdbtool, which allows simple database manipulation +on the commandline. + +tdbtest and tdbtool are not built as part of Samba, but are included +for completeness. + +Interface +--------- + +The interface is very similar to gdbm except for the following: + +- different open interface. The tdb_open call is more similar to a + traditional open() +- no tdbm_reorganise() function +- no tdbm_sync() function. No operations are cached in the library anyway +- added a tdb_traverse() function for traversing the whole database + +A general rule for using tdb is that the caller frees any returned +TDB_DATA structures. Just call free(p.dptr) to free a TDB_DATA +return value called p. This is the same as gdbm. + +here is a full list of tdb functions with brief descriptions. + + +---------------------------------------------------------------------- +TDB_CONTEXT *tdb_open(char *name, int hash_size, int tdb_flags, + int open_flags, mode_t mode) + + open the database, creating it if necessary + + The open_flags and mode are passed straight to the open call on the database + file. A flags value of O_WRONLY is invalid + + The hash size is advisory, use zero for a default value. + + return is NULL on error + + possible tdb_flags are: + TDB_CLEAR_IF_FIRST - clear database if we are the only one with it open + TDB_INTERNAL - don't use a file, instaed store the data in + memory. The filename is ignored in this case. + TDB_NOLOCK - don't do any locking + TDB_NOMMAP - don't use mmap + +---------------------------------------------------------------------- +char *tdb_error(TDB_CONTEXT *tdb); + + return a error string for the last tdb error + +---------------------------------------------------------------------- +int tdb_close(TDB_CONTEXT *tdb); + + close a database + +---------------------------------------------------------------------- +int tdb_update(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA dbuf); + + update an entry in place - this only works if the new data size + is <= the old data size and the key exists. + on failure return -1 + +---------------------------------------------------------------------- +TDB_DATA tdb_fetch(TDB_CONTEXT *tdb, TDB_DATA key); + + fetch an entry in the database given a key + if the return value has a null dptr then a error occurred + + caller must free the resulting data + +---------------------------------------------------------------------- +int tdb_exists(TDB_CONTEXT *tdb, TDB_DATA key); + + check if an entry in the database exists + + note that 1 is returned if the key is found and 0 is returned if not found + this doesn't match the conventions in the rest of this module, but is + compatible with gdbm + +---------------------------------------------------------------------- +int tdb_traverse(TDB_CONTEXT *tdb, int (*fn)(TDB_CONTEXT *tdb, + TDB_DATA key, TDB_DATA dbuf, void *state), void *state); + + traverse the entire database - calling fn(tdb, key, data, state) on each + element. + + return -1 on error or the record count traversed + + if fn is NULL then it is not called + + a non-zero return value from fn() indicates that the traversal should stop + +---------------------------------------------------------------------- +TDB_DATA tdb_firstkey(TDB_CONTEXT *tdb); + + find the first entry in the database and return its key + + the caller must free the returned data + +---------------------------------------------------------------------- +TDB_DATA tdb_nextkey(TDB_CONTEXT *tdb, TDB_DATA key); + + find the next entry in the database, returning its key + + the caller must free the returned data + +---------------------------------------------------------------------- +int tdb_delete(TDB_CONTEXT *tdb, TDB_DATA key); + + delete an entry in the database given a key + +---------------------------------------------------------------------- +int tdb_store(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA dbuf, int flag); + + store an element in the database, replacing any existing element + with the same key + + If flag==TDB_INSERT then don't overwrite an existing entry + If flag==TDB_MODIFY then don't create a new entry + + return 0 on success, -1 on failure + +---------------------------------------------------------------------- +int tdb_writelock(TDB_CONTEXT *tdb); + + lock the database. If we already have it locked then don't do anything + +---------------------------------------------------------------------- +int tdb_writeunlock(TDB_CONTEXT *tdb); + unlock the database + +---------------------------------------------------------------------- +int tdb_lockchain(TDB_CONTEXT *tdb, TDB_DATA key); + + lock one hash chain. This is meant to be used to reduce locking + contention - it cannot guarantee how many records will be locked + +---------------------------------------------------------------------- +int tdb_unlockchain(TDB_CONTEXT *tdb, TDB_DATA key); + + unlock one hash chain diff --git a/source4/lib/tdb/docs/tdb.magic b/source4/lib/tdb/docs/tdb.magic new file mode 100644 index 0000000000..f5619e7327 --- /dev/null +++ b/source4/lib/tdb/docs/tdb.magic @@ -0,0 +1,10 @@ +# Magic file(1) information about tdb files. +# +# Install this into /etc/magic or the corresponding location for your +# system, or pass as a -m argument to file(1). + +# You may use and redistribute this file without restriction. + +0 string TDB\ file TDB database +>32 lelong =0x2601196D version 6, little-endian +>>36 lelong x hash size %d bytes |