I am trying to use XML::Twig to convert a policy (call it a firewall policy, but that's not strictly true) from one format to another. Call the existing file format "OLDFW" and the new format "NEWFW." I have boiled the problem down to bare-essentials XML below.

OLDFW has a root called "policy" which contains one element and one only: "policyrules". That element contains many "Rule" elements which in turn have sub-elements, etc.

NEWFW should be the same (actually there are changes, but I don't need help with that), except the <policyrules> element is eliminated -- that is, all the "Rule" elements are directly underneath "<policy>".

I know that if I simply ignore or delete <policyrules>, I lose all the children. I want to build a handler to skip over it, but that's the problem.

I have kludged around the problem by filtering out <policyrules> before XML-parsing the file, but I am now wondering whether there is a more elegant solution where I can simply tell XML::Twig (or whatever) to "promote" all the "Rule" elements to the same level as "policyrules" and then delete the latter.

Here's a sample OLDFW:

<?xml version="1.0" encoding="UTF-8"?>
<policy name="Cur_policy" version="3.2.1">
  <policyrules>
    <Rule Action="allow" Enabled="true" RuleID="F68E32">
      <source addr="10.4.5.3" srcport="any"/>
      <dest addr="199.5.4.3" destport="80"/>
    </Rule>
    <Rule Action="allow" Enabled="true" RuleID="78E21D">
      <source addr="10.4.0.0-10.4.255.255" srcport="any"/>
      <dest addr="any" destport="80"/>
    </Rule>
  </policyrules>
</policy>
[download]

The NEWFW I'd like to get:

<?xml version="1.0" encoding="UTF-8"?>
<policy name="Cur_policy" version="3.2.1">
  <Rule Action="allow" Enabled="true" RuleID="F68E32">
    <source addr="10.4.5.3" srcport="any"/>
    <dest addr="199.5.4.3" destport="80"/>
  </Rule>
  <Rule Action="allow" Enabled="true" RuleID="78E21D">
    <source addr="10.4.0.0-10.4.255.255" srcport="any"/>
    <dest addr="any" destport="80"/>
  </Rule>
</policy>
[download]

The code I'm playing with -- what I need is "what goes into policyrules_handler?"

#!/usr/bin/perl

use warnings;
use strict;

use XML::Twig;

my ( $in_XML_file, $out_XML_file ) = @ARGV;

# create objects
my $ref_reader = XML::Twig->new( twig_handlers =>
                                 {
                                    'policyrules' => \&policyrules_
+handler,
                                    'Rule' => \&rule_handler
                                    }
                                 );
$ref_reader->parsefile( $in_XML_file )
   or die "    $in_XML_file is not parsable\n";

open my $out_fh, '>', $out_XML_file
    or die "    $out_XML_file cannot be written: $!";

$ref_reader->print( $out_fh );

close $out_fh;


sub policyrules_handler
{
   my( $t, $elt)= @_;      # arguments for all twig_handlers

#   $elt->delete;
}

sub rule_handler
{
   my( $t, $elt)= @_;      # arguments for all twig_handlers

   $elt->set_att( 'new_attr' => 'dummyValue' );
}
[download]

Thank you for any assistance you can provide here.

jd

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