P:RD and XML (minor code review)

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

Hello,

I'm attempting to parse XML files with Parse::RecDescent. I'm trying to implement all of the productions described in the XML Spec. I'm concerned about production 14

The production is: [14] CharData ::= [^<&]* - ([^<&]* ']]>' [^<&]*)

Here's what I've implemented for my P::RD grammar:

  CharData : /[^<&]*/
  {
    my $s = $item[1];

    if($s =~ /(.*)(]]>.*)/s) {
      $s = $1;
      $text = $2 . $text;
      Parse::RecDescent::LineCounter::resync($thisline);
    }

    $return = XML::CharData->new($s);
  }
[download]

Note: The class XML::CharData is my own creation.

Could some of you help review this implementation? Is this the correct/best way to implement production 14? It seems to work OK in my unit tests, but it seems very inefficient because it may read a lot of extra data until it hits an "&" or "<".

Thanks, Glen Hein

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Re: P:RD and XML (minor code review) by ikegami (Patriarch) on Feb 17, 2010 at 16:15 UTC
I'm attempting to parse XML files with Parse::RecDescent Gotta ask why! Anyway, Perl can handle that with zero-width lookaheads. `CharData : /(?:(?!\]\]>)[^<&])/ { XML::CharData->new($item[1]) }` [download] or `CharData : /(?:(?!<\|&\|\]\]>).)/ { XML::CharData->new($item[1]) }` [download] or `CharData : /(?:[^<&\]]\|\](?!\]>))*/ { XML::CharData->new($item[1]) }` [download]	[reply] [d/l] [select]
Re^2: P:RD and XML (minor code review) by glenhein (Initiate) on Feb 17, 2010 at 16:29 UTC
Why, you ask? The short answer is for shits-n-giggles :-) I wanted to learn more about P::RD, and I wanted to study the finer details of the XML spec. I don't plan on using my XML parser for anything more than a learning exercise. Thanks for for suggestions. I've never played with the zero-width regular expressions. I'll have to experiment with them. BTW, I didn't mean to post as Anonymous. I thought I was logged in when I posted, by I guess I wasn't!	[reply]