Extrach PGconn* form $dbh (perl)

Hello.
     Sorry for my bad English.

I need to extract PGconn*-type variable from perl $dbh (e.g.
magicfunction(dbh)) to use it in my XS-function, but I can't
understand how  to get PGconn from my function using DBH (I send dbh
to my function and need to get PGconn variable as returned value from my function).

Please help me to write PGconn *magicfunction(SV*) function.
     for example:     
parser.pl:
...
my $dbh= DBI->connect("dbi:Pg:dbname=some_db","user","pass");
my $h=myfunction($dbh, "filename");
...

myfunction.xs:
HV *
myfunction( DBH, filename )       SV *DBH       char *filename   CODE:        HV *hash=newHV(); // some hash
PGconn*myconnection=magicfunction( DBH );        processfile ( hash, filename ); //fill hash from file.
writehash( hash, myconnection );        RETVAL=hash;   OUTPUT:        RETVAL
 


-- 
WBR,Dmitry                          mailto:hobbut@orionet.ru