> Date: Thu, 27 Oct 2011 14:14:03 -0400
> From: bro...@deseret.com
> To: martin.ev...@easysoft.com
> CC: dbi-users@perl.org
> Subject: Re: DBD-Oracle - obtaining OCI handles from $dbh
>
>
> 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();
>
>
>
Yup that should work I didn't put two and two together and figure you already
had XS for the C++.
It could be something we could add to DBD::Oracle but I would return all of
the handles not just the few you need.
I wonder how much it would be used though??
Cheers
>
>
> 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
> > >>>
> > >
> >
