I am in the progress of changing some code that uses DBD::Oracle to use the
documented ora_lob_read function instead of the undocumented blob_read, and I
suddenly hit the error "Malformed UTF-8 character (unexpected end of string) in
length".
As it turns out, Perl's length function returns the number of characters in the
string. If Perl thinks the string contains text and the text is in utf-8, then
this can be different from the number of bytes in the string. I regret to say
that I am very unfamiliar with how Perl handles utf-8, but I am familiar enough
with Oracle to see that treating BLOB data as character data is incorrect.
I see the call to SvUTF8_on in ora_lob_read in Oracle.xs, I see how the value
of NLS_LANG plays in, and I see how it affects both CLOB and BLOB data, so I
understand why I am getting the result I am getting. But I have some questions:
(For someone who understands utf-8 in Perl:) Is there danger in binary data
being treated as utf-8, other than the length function crashing? Is there a
workaround? (I see "use bytes", but Perl 5.10 doc for the length function says
"the internal encoding is variable, and the number of bytes usually
meaningless" which scares me.)
(For someone who understands the stuff in Oracle.xs:) Is it even possible to
change ora_lob_read to only call SvUTF8_on for CLOB data and not for BLOB data?
My test case is included below. Connection info will need to be altered before
it runs. Commenting out the line with AL32UTF8 makes the problem go away.
use strict;
use DBI;
use DBD::Oracle qw(:ora_types);
$ENV{'NLS_LANG'} = '_.AL32UTF8';
my $hDB = DBI->connect('dbi:Oracle:TEST', 'SCOTT', 'TIGER');
my $hSQL = $hDB->prepare(qq{
DECLARE
b blob;
BEGIN
dbms_lob.createtemporary(b,true);
dbms_lob.writeappend(b,256,utl_raw.xrange('00','FF'));
:b := b;
END;
}, { ora_auto_lob => 0 });
my $b;
$hSQL->bind_param_inout( ':b', \$b, 0, { ora_type => ORA_BLOB } );
$hSQL->execute;
my $data = $hDB->ora_lob_read( $b, 1, 1024 );
print "Read ", length($data), " bytes.\n";
--
Be Yourself @ mail.com!
Choose From 200+ Email Addresses
Get a Free Account at www.mail.com
