v_thunder has asked for the wisdom of the Perl Monks concerning the following question:

Hi everyone,

I have a rather puzzling problem. I have invested quite some time in developing a set of applications that speak via xml-rpc using Frontier::Client and Frontier::Daemon. Everything seems to work fine, except I can't run strings through Digest::MD5 after they have gone through xml-rpc. I get the following error:

Use of uninitialized value in subroutine entry at ...

Digest::MD5::md5_hex does execute, but it returns the same hash that it would return if I were to pass it an empty string. I can print the string, however, no problem.

I've tried copying the string to another variable, I've tried using sprintf to make sure I get a new string back. Nothing seems to work. I am utterly confused! My next step will be to write it to a file and read it back, and failing that, to try to execute a separate process to do the md5sum. But, I figure someone here might have some insight as to what's going on.

Thanks!
-Dan

Replies are listed 'Best First'.
Re: Frontier::RPC and Digest::MD5
by bear0053 (Hermit) on Aug 29, 2003 at 19:40 UTC
    can we see some code?
[reply]

      Ok, I wrote some simple code to show this, and managed to narrow the problem down a little. Here is the code:

      This is the server:

      #!/usr/bin/perl -w

use strict;
use Frontier::Daemon;
use Digest::MD5 qw/md5_hex/;

Frontier::Daemon->new (LocalPort => 12345,
                       methods =>{md5=>sub {return md5_hex (shift)}});

__END__

      [download]

      And the client:

      #!/usr/bin/perl -w

use strict;
use Frontier::Client;

my $rpc = Frontier::Client->new (url =>"http://localhost:12345/RPC2");
print $rpc->call ("md5", "1234"), $/;

__END__

      [download]

      For reference:

      md5 of "1234": 81dc9bdb52d04dc20036dbd8313ed055
      md5 of "": d41d8cd98f00b204e9800998ecf8427e

      Now, here's what I found. If I run the server on my desktop (perl 5.8.0), I get the expected result (81dc..). If I run the server on an older system (perl 5.6.1), I get the erroneous one (d41d..), along with the error on the console:

      Use of uninitialized value in subroutine entry at ./srv line 8.

      I have also found that even in the older system, the following code works:

      sub my_md5_hex {
    my ($str) = @_;
    my $cmd = "perl -MDigest::MD5 -e " .
        "'print Digest::MD5::md5_hex (\"$str\"), \$/'";
    my $md5 = `$cmd`;
    chomp ($md5);
    return $md5;
}

      [download]

      It's pretty gross, though.

[reply]
[d/l]
[select]

Back to Seekers of Perl Wisdom