Debugging exercise

Here is how I would tackle the problem.

Finding a suspect.

I can see that the output of Digest::MD5 in OO mode is incorrect.

By comparing with some independent programs, you realize that the output of md5sum and mysql is the same as the functional interface of Digest::MD5

$ perl -e 'use Digest::MD5; print Digest::MD5->new->md5_hex("foobarbaz
+")
,$/'
e05e07ceb87ddb19ccba8a51a57ac120

$ perl -e 'use Digest::MD5 qw(md5_hex); print md5_hex("foobarbaz"),$/'
6df23dc03f9b54cc38a0fc1483df6e21

$ echo -n foobarbaz | md5sum 
6df23dc03f9b54cc38a0fc1483df6e21 *-

$ mysql -e "select md5('foobarbaz')"
+----------------------------------+
| md5('foobarbaz')                 |
+----------------------------------+
| 6df23dc03f9b54cc38a0fc1483df6e21 |
+----------------------------------+
[download]

Getting the evidence

Now, let's apply a constitutional principle, according tro which, everybody is innocent until proved guilty. So I would say that the OO interface is innocent, and look at the docs. They say that this is the regular format of the OO interface.

    use Digest::MD5;
    
    $md5 = Digest::MD5->new;
    $md5->add('foo', 'bar');
    $md5->add('baz');
    $digest = $md5->hexdigest;
[download]

This is different from what you have done. Let's try it the "official" way.

sub create_checksum {

    my $self = shift;
    my $data = shift;

    my $foo = $$data;

    my $ctx = Digest::MD5->new;
    $ctx->add($foo);
    my $cs = $ctx->hexdigest();
    return $cs;
}
[download]

This works fine. Proof of concept:

$ perl -e 'use Digest::MD5; my $x= Digest::MD5->new; $x->add("foobarba
+z"); 
print $x->hexdigest,$/'
6df23dc03f9b54cc38a0fc1483df6e21
[download]

The verdict

The OO interface is innocent.

Your implementation is guilty. :)

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