=pod

=head1 NAME

DC_PLUG_new, DC_PLUG_free, DC_PLUG_to_select, DC_PLUG_io - basic DC_PLUG functions

=head1 SYNOPSIS

 #include <distcache/dc_plug.h>

 DC_PLUG *DC_PLUG_new(NAL_CONNECTION *conn, unsigned int flags);
 int DC_PLUG_free(DC_PLUG *plug);
 void DC_PLUG_to_select(DC_PLUG *plug, NAL_SELECTOR *sel);
 int DC_PLUG_io(DC_PLUG *plug, NAL_SELECTOR *sel);

=head1 DESCRIPTION

DC_PLUG_new() allocates and initialises a B<DC_PLUG> structure encapsulating the
specified connection. The B<flags> parameter is zero or a bitmask combining one or
more of the following flags;

 #define DC_PLUG_FLAG_TO_SERVER         (unsigned int)0x0001
 #define DC_PLUG_FLAG_NOFREE_CONN       (unsigned int)0x0002

If the I<DC_PLUG_FLAG_TO_SERVER> flag is specified, the plug object will expect
to be sending ``request'' messages and receiving ``response'' messages,
otherwise will default to the opposite sense.

DC_PLUG_free() frees the B<DC_PLUG> structure and, unless it had been created
with the I<DC_PLUG_FLAG_NOFREE_CONN> flag, will also destroy the connection
object it encapsulates.

DC_PLUG_to_select() is used to add a plug object to the B<sel> selector so that
it can be tested for network events it is waiting on. This will automatically
handle selection of flags depending on the plug object's state. Ie. it will
select for writability on its underlying connection only if there is data
waiting to be sent, and likewise will select for readability only if it is
ready to receive any data that may have arrived.

DC_PLUG_io() is used to allow network I/O to be performed on a plug object's
underlying connection depending on the results of the last select operation on
B<sel>.

=head1 RETURN VALUES

DC_PLUG_new() returns the new plug object on success, otherwise B<NULL> for
failure.

DC_PLUG_free() should never fail and should only return non-zero results.

DC_PLUG_to_select() has no return value.

DC_PLUG_io() return zero on an error, otherwise non-zero.

None of the B<DC_PLUG> functions sets (or clears) B<errno> because it is
implemented on top of the I<libnal> library which in turn is an abstraction
layer for the system's networking interfaces. As such, any B<errno> codes set
by failure in system libraries will not be overwritten by these functions.

=head1 SEE ALSO

L<DC_PLUG_read(2)> - Provides documentation for other B<DC_PLUG>
functions also.

L<distcache(8)> - Overview of the distcache architecture.

F<http://www.distcache.org/> - Distcache home page.

=head1 AUTHOR

This toolkit was designed and implemented by Geoff Thorpe for Cryptographic
Appliances Incorporated. Since the project was released into open source, it
has a home page and a project environment where development, mailing lists, and
releases are organised. For problems with the software or this man page please
check for new releases at the project web-site below, mail the users mailing
list described there, or contact the author at F<geoff@geoffthorpe.net>.

Home Page: F<http://www.distcache.org>