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samba-mirror/lib/param/README
Andrew Bartlett aca475b6bc lib/param: Add documentation on how loadparm works
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Oct 16 11:39:41 CEST 2013 on sn-devel-104
2013-10-16 11:39:41 +02:00

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libsamba-hostconfig
-------------------
This directory contains "libsamba-hostconfig".
The libsamba-hostconfig library provides access to all host-wide configuration
such as the configured shares, default parameter values and host secret keys.
Adding a parameter
------------------
To add or change an smb.conf option, you only have to modify
lib/param/param_table.c and lib/param/param_functions.c. The rest is
generated for you.
Using smb.conf parameters in the code
-------------------------------------
Call the lpcfg_*() function. To get the lp_ctx, have the caller pass
it to you. To get a lp_ctx for the source3/param loadparm system, use:
struct loadparm_context *lp_ctx = loadparm_init_s3(tmp_ctx, loadparm_s3_helpers());
Remember to talloc_unlink(tmp_ctx, lp_ctx) the result when you are done!
To get a lp_ctx for the lib/param loadparm system, typically the
pointer is already set up by popt at startup, and is passed down from
cmdline_lp_ctx.
In pure source3/ code, you may use lp_*() functions, but are
encouraged to use the lpcfg_*() functions so that code can be made
common.
How does loadparm_init_s3() work?
---------------------------------
loadparm_s3_helpers() returns a initialised table of function
pointers, pointing at all global lp_*() functions, except for those
that return substituted strings (% macros). The lpcfg_*() function
then calls this plugged in function, allowing the one function and
pattern to use either loadparm system.
There is a lot of generated code, here, what generates what?
------------------------------------------------------------
The regular format of the CPP macros in param_functions.c is used to
generate up the prototypes (mkproto.pl, mks3param_proto.pl), the service
and globals table (mkparamdefs.pl), the glue table (mmks3param.pl) and
the initilisation of the glue table (mks3param_ctx_table.pl).
I have tried combining some of these, but it just makes the scripts more
complex.
The CPP macros are defined in and expand in lib/param/loadparm.c and
source3/param/loadparm.c to read the values from the generated
stuctures. They are CPP #included into these files so that the same
macro has two definitions, depending on the system it is loading into.
Why was this done, rather than a 'proper' fix, or just using one system or the other?
-------------------------------------------------------------------------------------
This was done to allow merging from both ends - merging more parts of
the loadparm handling, and merging code that needs to read the
smb.conf, without having to do it all at once. Ideally
param_functions.c would be generated from param_table.c or (even
better) our XML manpage source, and the CPP macros would instead be
generated expanded as generated C files, but this is a task nobody has
taken on yet.