http://www.perlmonks.org?node_id=916626

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

Is it possible to stop parsing once you find what you are looking for in a big XML file? My code looks like this: 
use XML::SAX::ExpatXS;
use WDSTreeHandler;
...
my $tree = read_file("/x/y/z/aap.xml");
my $handler = WDSTreeHandler->new;
my $parser = XML::SAX::ExpatXS->new(Handler => $handler);
$parser->parse_string($tree);

[download]
With the WDSTreeHandler looking like so: 
package WDSTreeHandler;
use base qw(XML::SAX::Base);
...
sub start_document
{
    my ($self, $doc) = @_;
}

sub start_element
{
    my ($self, $el) = @_;
    ...
    if ($level >= 0 && $el->{'LocalName'} =~ /folder|leaf/)
    {
        ## do some stuff and try to STOP PARSING
    }
}
sub end_element
{
    ...
}
sub end_document
{
}
1;

[download]
How do you stop parsing?

Replies are listed 'Best First'.
Re: XML::SAX::ExpatXS - stop parsing?
by ikegami (Patriarch) on Jul 25, 2011 at 21:58 UTC
    How about 
    die "DONE\n";

...

if (!eval {
   $parser->parse_string($tree);
   1 # No exception
}) {
   die $@ if $@ ne "DONE\n";
}

    [download]
[reply]
[d/l]
      Hmm why didn't i think of that? Is that stuff safe with mod_perl?
[reply]
        die in one thread and process does not affect other threads or processes.
[reply]
Re: XML::SAX::ExpatXS - stop parsing?
by grantm (Parson) on Jul 26, 2011 at 21:43 UTC
    An alternative to the SAX API is the 'Pull' parser API as implemented in XML::LibXML::Reader. This API is well suited to the pattern of stopping the parse when you've found what you want.
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