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XML::LibXML::Devel(3)                User Contributed Perl Documentation               XML::LibXML::Devel(3)



NAME
       XML::LibXML::Devel - makes functions from LibXML.xs available

SYNOPSIS
         /**********************************************
          * C functions you want to access
          */
         xmlNode *return_node();
         void receive_node(xmlNode *);

         ###############################################
         # XS Code
         void *
           xs_return_node
           CODE:
               RETVAL = return_node();
           OUTPUT:
               RETVAL

         void
           xs_receive_node
               void *n
           CODE:
               receive_node(n);

         ###############################################
         # Perl code
         use XML::LibXML::Devel;

         sub return_node
         {
           my $raw_node = xs_return_node();
           my $node = XML::LibXML::Devel::node_to_perl($raw_node);
           XML::LibXML::Devel::refcnt_inc($raw_node);
           return $node;
         }

         sub receive_node
         {
           my ($node) = @_;
           my $raw_node = XML::LibXML::Devel::node_from_perl($node);
           xs_receive_node($raw_node);
           XML::LibXML::Devel::refcnt_inc($raw_node);
         }

DESCRIPTION
       "XML::LibXML::Devel" makes functions from LibXML.xs available that are needed to wrap libxml2 nodes
       in and out of XML::LibXML::Nodes.  This gives cleaner dependencies than using LibXML.so directly.

       To XS a library that uses libxml2 nodes the first step is to do this so that xmlNodePtr is passed as
       void *. These raw nodes are then turned into libxml nodes by using this "Devel" functions.

       Be aware that this module is currently rather experimental. The function names may change if I XS
       more functions and introduce a reasonable naming convention.

       Be also aware that this module is a great tool to cause segfaults and introduce memory leaks. It does
       however provide a partial cure by making "xmlMemUsed" available as "mem_used".

FUNCTIONS
   NODE MANAGEMENT
       node_to_perl
          node_to_perl($raw_node);

        Returns a LibXML::Node object. This has a proxy node with a reference counter and an owner attached.
        The raw node will be deleted as soon as the reference counter reaches zero.  If the C library is
        keeping a pointer to the raw node, you need to call refcnt_inc immediately.  You also need to
        replace xmlFreeNode by a call to refcnt_dec.

       node_to_perl
          node_from_perl($node);

        Returns a raw node. This is a void * pointer and you can do nothing but passing it to functions that
        treat it as an xmlNodePtr. The raw node will be freed as soon as its reference counter reaches zero.
        If the C library is keeping a pointer to the raw node, you need to call refcnt_inc immediately.  You
        also need to replace xmlFreeNode by a call to refcnt_dec.

       refcnt_inc
          refcnt_inc($raw_node);

        Increments the raw nodes reference counter. The raw node must already be known to perl to have a
        reference counter.

       refcnt_dec
          refcnt_dec($raw_node);

        Decrements the raw nodes reference counter and returns the value it had before. if the counter
        becomes zero or less, this method will free the proxy node holding the reference counter.  If the
        node is part of a subtree, refcnt_dec will fix the reference counts and delete the subtree if it is
        not required any more.

       refcnt
          refcnt($raw_node);

        Returns the value of the reference counter.

       fix_owner
          fix_owner($raw_node, $raw_parent);

        This functions fixes the reference counts for an entire subtree.  it is very important to fix an
        entire subtree after node operations where the documents or the owner node may get changed. this
        method is aware about nodes that already belong to a certain owner node.

   MEMORY DEBUGGING
       $ENV{DEBUG_MEMORY}
          BEGIN {$ENV{DEBUG_MEMORY} = 1;};
          use XML::LibXML;

        This turns on libxml2 memory debugging. It must be set before XML::LibXML is loaded.

       mem_used
          mem_used();

        Returns the number of bytes currently allocated.

   EXPORT
       None by default.

SEE ALSO
       This was created to support the needs of Apache2::ModXml2. So this can serve as an example.

AUTHOR
       Joachim Zobel <jz-2011@heute-morgen.de>

COPYRIGHT AND LICENSE
       Copyright (C) 2011 by Joachim Zobel

       This library is free software; you can redistribute it and/or modify it under the same terms as Perl
       itself, either Perl version 5.10.1 or, at your option, any later version of Perl 5 you may have
       available.



perl v5.16.2                                     2012-10-22                            XML::LibXML::Devel(3)