+++ /dev/null
-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
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