Thanks for those pointers.
I do agree with what Martin points out. My Perl script using DBI
and some XS bindings to the legacy C++ libraries would share the
same address space (not using threads in my application). This
is why I thought I could return the handles/pointers as scalars.
Taking John's suggestions, here is a quick code hack that I made
to Oracle.xs (I haven't tested this ...other than it compiles).
"Looks like it should work." ;-)
void
ora_oci_handles(dbh)
SV *dbh
PREINIT:
D_imp_dbh(dbh);
PPCODE:
/* Verify what is passed in is a $dbh object */
if ( ! sv_derived_from(ST(0), "DBI::db")) {
Perl_croak(aTHX_ "dbh is not of type DBI::db");
}
mXPUSHi( (IV) imp_dbh->envhp ); /* Environment handle */
mXPUSHi( (IV) imp_dbh->svchp ); /* Service Context handle */
mXPUSHi( (IV) imp_dbh->srvhp ); /* Server handle */
mXPUSHi( (IV) imp_dbh->authp ); /* Session handle */
XSRETURN(4);
Then my idea is to use this in Perl space...
my($envhp, $svchp, $srvhp, $authp) = $dbh->ora_oci_handles();
# Now share the OCI handles from DBI with the custom
# C++ libraries.
my $cpp_dbh = MyCppOracleClass->new(); # creates custom C++ object
$cpp_dbh->envhp($envhp);
$cpp_dbh->svchp($svchp);
$cpp_dbh->srvhp($srvhp);
$cpp_dbh->authp($authp);
# Do something interesting with the C++ object
$cpp_dbh->make_legacy_call_to_db();
Quoting Martin J. Evans (martin.ev...@easysoft.com):
> On 27/10/2011 17:43, John Scoles wrote:
> >Hmm....!!
> >
> >Well yes could be done but not as part of any release of DBD::Oracle it
> >would have to be you own hacked version
> >
> Why is that John? What is the problem with returning a C pointer via a
> DBD::Oracle attribute? It is just a pointer to some memory and loads of
> XS modules do this. There is an Oracle OCI module I played with for a
> short time but it is problematic to build. I looked at it as I could
> implement OCI calls separately from DBD::Oracle. I don't seem the harm
> in exposing OCI handles via DBD::Oracle - it would be useful for people
> like the OP.
>
> >A few pointers to start.
> >
> >You will not be able to 'get' a handle and retrun it as a Scalar it will
> >only ever be a pointer so you will just get some sort of number,
> >
> >You would simly edit the Oracle.xs file
> >
> >add in the includes to your C++ .h files
> >
> >then add a few extra
> >
> >'ora_'
> >
> >functions to take care of you C++ calls;
> >
> >A quick example
> >
> >void
> >ora_some_c_call(dbh)
> > SV *dbh
> > PREINIT:
> > D_imp_dbh(dbh); //this gets all the OCI handles for you (see dbdimp.h
> > for the sturct imp_dbh_st)
> > CODE:
> > MYSomeC_Plus_Plus_method(dbh->envhp,dbh->svchp,dbh->seshp,dbh->srvhp);
> >
> >
> He does not need to do this surely. So long as the C++ code and
> DBD::Oracle XS is running in the same process the pointers obtained from
> DBD::Oracle are just as valid in the C++ code as XS. However, if the
> code is multi-threaded there could be issues of multiple threads
> accessing the OCI handles at the same time.
>
> >
> >Myself I would write a small 'c' wrapper that would call you c++ and just
> >a single .XS function that calls that small 'c' wrapper to fire your
> >function.
> >
> My impression was that this was already done.
> I quote:
>
> "I have created some Perl bindings for some existing custom C++ libraries."
>
> Martin
> --
>
> Martin J. Evans
> Easysoft Limited
> http://www.easysoft.com
>
>
> >Hope this helps
> >
> >Cheers
> >John
> >
> >
> >>Date: Thu, 27 Oct 2011 09:48:54 -0400
> >>From: bro...@deseret.com
> >>To: byter...@hotmail.com
> >>CC: dbi-users@perl.org
> >>Subject: Re: DBI-Users> RE: DBD-Oracle - obtaining OCI handles from $dbh
> >>
> >>Yes, I assumed I would need to extend DBD::Oracle is some manner
> >>to allow those handles to be extracted from a $dbh object.
> >>
> >>The specific OCI handles that the C++ libraries use are
> >>
> >>- Environment handle
> >>- Service Context handle
> >>- Session handle
> >>- Server handle
> >>
> >>My initial thought process on how it might work is this
> >>
> >>Create a method in the DBD::Oracle XS code to retrieve those
> >>handles and return them back to Perl space as a scalar.
> >>
> >>Then with the Perl scalars that hold the OCI handles obtained from
> >>$dbh, pass those values to my Perl bindings to the custom C++ libraries.
> >>(I would need to extend the C++ libraries to allow the set methods
> >>to the objects that hold those OCI handles).
> >>
> >>...then the C++ libraries should work the same.
> >>
> >>The motivation for this approach is that I have a large code base
> >>of these C++ libraries that have been tested, so it would cost
> >>prohibitive to simply replace them with a pure Perl implementation.
> >>
> >>However, it is so much easier to work with Perl and DBI, it would
> >>be useful to have DBI connect to the database and do some table
> >>lookups. The C++ code could then be integrated seemlessly with my
> >>Perl code. As time allows, I would gradually peel away functionality
> >>from the legacy C++ libraries and implement it in Perl. But to
> >>ease the migration path, this approach seemed to have some merits.
> >>
> >>
> >>Quoting John Scoles (byter...@hotmail.com):
> >>>
> >>>
> >>>
> >>>>Date: Wed, 26 Oct 2011 21:46:30 -0400
> >>>>From: bro...@deseret.com
> >>>>To: dbi-users@perl.org
> >>>>Subject: DBD-Oracle - obtaining OCI handles from $dbh
> >>>>
> >>>>I have created some Perl bindings for some existing custom C++
> >>>>libraries.
> >>>>
> >>>>One of these C++ libraries implements a class that uses Oracle
> >>>>OCI calls.
> >>>>
> >>>>I would like to create a connection to the Oracle database
> >>>>using Perl's DBI (DBD::Oracle) module, and then ideally share
> >>>>that connection with the C++ libraries.
> >>>>
> >>>>This would require me to extract the Oracle OCI handles from
> >>>>the $dbh object...and then pass them to the C++ libraries.
> >>>>
> >>>>What would be the best way to get access to the underlying
> >>>>Oracle OCI handles from a $dbh object?
> >>>Hmm! Interesting concept. Which OCI handles are we talking about??
> >>>Like Matin said you would have to do that with .XS and you would pass I
> >>>guess a pointer to the
> >>>'C' struct that holds the pointers to DBD::Oraclles pointers?
> >>>
> >>>You would have to cast that struct into you C++ somehow??
> >>>
> >>>There would be a good number of handles to pass over. You might be able
> >>>to find them by looking at the Perl process tree
> >>>and finding the SV that holds the struct and then sening that over?
> >>>
> >>>All just guesses on my part.
> >>>
> >>>Interesting concept non the less.
> >>>
> >>>Cheers
> >>>John
> >>>
> >
>
