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.