=head1 NAME

XML::LibXML::Node - Abstract Base Class of XML::LibXML Nodes

=head1 SYNOPSIS

  use XML::LibXML;

  $name = $node->nodeName;
  $node->setNodeName( $newName );
  $bool = $node->isSameNode( $other_node );
  $bool = $node->isEqual( $other_node );
  $content = $node->nodeValue;
  $content = $node->textContent;
  $type = $node->nodeType;
  $node->unbindNode();
  $childnode = $node->removeChild( $childnode );
  $oldnode = $node->replaceChild( $newNode, $oldNode );
  $node->replaceNode($newNode);
  $childnode = $node->appendChild( $childnode );
  $childnode = $node->addChild( $chilnode );
  $node = $parent->addNewChild( $nsURI, $name );
  $node->addSibling($newNode);
  $newnode =$node->cloneNode( $deep );
  $parentnode = $node->parentNode;
  $nextnode = $node->nextSibling();
  $prevnode = $node->previousSibling();
  $boolean = $node->hasChildNodes();
  $childnode = $node->firstChild;
  $childnode = $node->lastChild;
  $documentnode = $node->ownerDocument;
  $node = $node->getOwner;
  $node->setOwnerDocument( $doc );
  $node->insertBefore( $newNode, $refNode );
  $node->insertAfter( $newNode, $refNode );
  @nodes = $node->findnodes( $xpath_expression );
  $result = $node->find( $xpath );
  print $node->findvalue( $xpath );
  @childnodes = $node->childNodes;
  $xmlstring = $node->toString($format,$docencoding);
  $c14nstring = $node->toStringC14N($with_comments, $xpath_expression);
  $ec14nstring = $node->toStringEC14N($with_comments, $xpath_expression, $inclusive_prefix_list);
  $str = $doc->serialize($format); 
  $c14nstr = $doc->serialize_c14n($comment_flag,$xpath); 
  $ec14nstr = $doc->serialize_ec14n($comment_flag,$xpath,$inclusive_prefix_list); 
  $localname = $node->localname;
  $nameprefix = $node->prefix;
  $uri = $node->namespaceURI();
  $boolean = $node->hasAttributes();
  @attributelist = $node->attributes();
  $URI = $node->lookupNamespaceURI( $prefix );
  $prefix = $node->lookupNamespacePrefix( $URI );
  $node->normalize;
  @nslist = $node->getNamespaces;
  $node->removeChildNodes();
  $node->nodePath();
  $lineno = $node->line_number();


=head1 DESCRIPTION

XML::LibXML::Node defines functions that are common to all Node Types. A
LibXML::Node should never be created standalone, but as an instance of a high
level class such as LibXML::Element or LibXML::Text. The class itself should
provide only common functionality. In XML::LibXML each node is part either of a
document or a document-fragment. Because of this there is no node without a
parent. This may causes confusion with "unbound" nodes.

=over 4

=item B<nodeName>

  $name = $node->nodeName;

Returns the node's name. This function is aware of namespaces and returns the
full name of the current node (prefix:localname).

Since 1.62 this function also returns the correct DOM names for node types with
constant names, namely: #text, #cdata-section, #comment, #document,
#document-fragment.


=item B<setNodeName>

  $node->setNodeName( $newName );

In very limited situations, it is useful to change a nodes name. In the DOM
specification this should throw an error. This Function is aware of namespaces.


=item B<isSameNode>

  $bool = $node->isSameNode( $other_node );

returns TRUE (1) if the given nodes refer to the same node structure, otherwise
FALSE (0) is returned.


=item B<isEqual>

  $bool = $node->isEqual( $other_node );

deprecated version of isSameNode().

NOTE isEqual will change behaviour to follow the DOM specification


=item B<nodeValue>

  $content = $node->nodeValue;

If the node has any content (such as stored in a text node) it can get
requested through this function.

NOTE: Element Nodes have no content per definition. To get the text value of an
Element use textContent() instead!


=item B<textContent>

  $content = $node->textContent;

this function returns the content of all text nodes in the descendants of the
given node as specified in DOM.


=item B<nodeType>

  $type = $node->nodeType;

Return the node's type. The possible types are described in the libxml2 tree.h
documentation. The return value of this function is a numeric value. Therefore
it differs from the result of perl ref function.


=item B<unbindNode>

  $node->unbindNode();

Unbinds the Node from its siblings and Parent, but not from the Document it
belongs to. If the node is not inserted into the DOM afterwards it will be lost
after the program terminated. From a low level view, the unbound node is
stripped from the context it is and inserted into a (hidden) document-fragment.


=item B<removeChild>

  $childnode = $node->removeChild( $childnode );

This will unbind the Child Node from its parent $node. The function returns the
unbound node. If oldNode is not a child of the given Node the function will
fail.


=item B<replaceChild>

  $oldnode = $node->replaceChild( $newNode, $oldNode );

Replaces the $oldNode with the $newNode. The $oldNode will be unbound from the
Node. This function differs from the DOM L2 specification, in the case, if the
new node is not part of the document, the node will be imported first.


=item B<replaceNode>

  $node->replaceNode($newNode);

This function is very similar to replaceChild(), but it replaces the node
itself rather than a childnode. This is useful if a node found by any XPath
function, should be replaced.


=item B<appendChild>

  $childnode = $node->appendChild( $childnode );

The function will add the $childnode to the end of $node's children. The
function should fail, if the new childnode is already a child of $node. This
function differs from the DOM L2 specification, in the case, if the new node is
not part of the document, the node will be imported first.


=item B<addChild>

  $childnode = $node->addChild( $chilnode );

As an alternative to appendChild() one can use the addChild() function. This
function is a bit faster, because it avoids all DOM conformity checks.
Therefore this function is quite useful if one builds XML documents in memory
where the order and ownership (ownerDocument) is assured.

addChild() uses libxml2's own xmlAddChild() function. Thus it has to be used
with extra care: If a text node is added to a node and the node itself or its
last childnode is as well a text node, the node to add will be merged with the
one already available. The current node will be removed from memory after this
action. Because perl is not aware of this action, the perl instance is still
available. XML::LibXML will catch the loss of a node and refuse to run any
function called on that node.

   my $t1 = $doc->createTextNode( "foo" );
   my $t2 = $doc->createTextNode( "bar" );
   $t1->addChild( $t2 );       # is OK
   my $val = $t2->nodeValue(); # will fail, script dies

Also addChild() will not check if the added node belongs to the same document
as the node it will be added to. This could lead to inconsistent documents and
in more worse cases even to memory violations, if one does not keep track of
this issue.

Although this sounds like a lot of trouble, addChild() is useful if a document
is built from a stream, such as happens sometimes in SAX handlers or filters.

If you are not sure about the source of your nodes, you better stay with
appendChild(), because this function is more user friendly in the sense of
being more error tolerant.


=item B<addNewChild>

  $node = $parent->addNewChild( $nsURI, $name );

Similar to addChild(), this function uses low level libxml2 functionality to
provide faster interface for DOM building. addNewChild() uses xmlNewChild() to
create a new node on a given parent element.

addNewChild() has two parameters $nsURI and $name, where $nsURI is an
(optional) namespace URI. $name is the fully qualified element name;
addNewChild() will determine the correct prefix if necessary.

The function returns the newly created node.

This function is very useful for DOM building, where a created node can be
directly associated with its parent. NOTE this function is not part of the DOM
specification and its use will limit your code to XML::LibXML.


=item B<addSibling>

  $node->addSibling($newNode);

addSibling() allows adding an additional node to the end of a nodelist, defined
by the given node.


=item B<cloneNode>

  $newnode =$node->cloneNode( $deep );

cloneNode creates a copy of $node. When $deep is set to 1 (true) the function
will copy all childnodes as well. If $deep is 0 only the current node will be
copied. Note that in case of element, attributes are copied even if $deep is 0.

Note that the behavior of this function for $deep=0 has changed in 1.62 in
order to be consistent with the DOM spec (in older versions attributes and
namespace information was not copied for elements).


=item B<parentNode>

  $parentnode = $node->parentNode;

Returns simply the Parent Node of the current node.


=item B<nextSibling>

  $nextnode = $node->nextSibling();

Returns the next sibling if any .


=item B<previousSibling>

  $prevnode = $node->previousSibling();

Analogous to getNextSibling the function returns the previous sibling if any.


=item B<hasChildNodes>

  $boolean = $node->hasChildNodes();

If the current node has Childnodes this function returns TRUE (1), otherwise it
returns FALSE (0, not undef).


=item B<firstChild>

  $childnode = $node->firstChild;

If a node has childnodes this function will return the first node in the
childlist.


=item B<lastChild>

  $childnode = $node->lastChild;

If the $node has childnodes this function returns the last child node.


=item B<ownerDocument>

  $documentnode = $node->ownerDocument;

Through this function it is always possible to access the document the current
node is bound to.


=item B<getOwner>

  $node = $node->getOwner;

This function returns the node the current node is associated with. In most
cases this will be a document node or a document fragment node.


=item B<setOwnerDocument>

  $node->setOwnerDocument( $doc );

This function binds a node to another DOM. This method unbinds the node first,
if it is already bound to another document.

This function is the opposite calling of XML::LibXML::Document's adoptNode()
function. Because of this it has the same limitations with Entity References as
adoptNode().


=item B<insertBefore>

  $node->insertBefore( $newNode, $refNode );

The method inserts $newNode before $refNode. If $refNode is undefined, the
newNode will be set as the new last child of the parent node. This function
differs from the DOM L2 specification, in the case, if the new node is not part
of the document, the node will be imported first, automatically.

$refNode has to be passed to the function even if it is undefined:

   $node->insertBefore( $newNode, undef ); # the same as $node->appendChild( $newNode );
   $node->insertBefore( $newNode ); # wrong

Note, that the reference node has to be a direct child of the node the function
is called on. Also, $newChild is not allowed to be an ancestor of the new
parent node.


=item B<insertAfter>

  $node->insertAfter( $newNode, $refNode );

The method inserts $newNode after $refNode. If $refNode is undefined, the
newNode will be set as the new last child of the parent node.

Note, that $refNode has to be passed explicitly even if it is undef.


=item B<findnodes>

  @nodes = $node->findnodes( $xpath_expression );

findnodes evaluates the xpath expression (XPath 1.0) on the current node and
returns the resulting node set as an array. In scalar context returns a
XML::LibXML::NodeList object.

NOTE ON NAMESPACES AND XPATH:

A common mistake about XPath is to assume that node tests consisting of an
element name with no prefix match elements in the default namespace. This
assumption is wrong - by XPath specification, such node tests can only match
elements that are in no (i.e. null) namespace.

So, for example, one cannot match the root element of an XHTML document with
$node->find('/html') since '/html' would only match if the root element <html>
had no namespace, but all XHTML elements belong to the namespace
http://www.w3.org/1999/xhtml. (Note that xmlns="..." namespace declarations can
also be specified in a DTD, which makes the situation even worse, since the XML
document looks as if there was no default namespace).

There are several possible ways to deal with namespaces in XPath:


=over 4

=item *

The recommended way is to use the XML::LibXML::XPathContext module to define an
explicit context for XPath evaluation, in which a document independent
prefix-to-namespace mapping can be defined. For example:

  my $xpc = XML::LibXML::XPathContext->new;
  $xpc->registerNs('x', 'http://www.w3.org/1999/xhtml');
  $xpc->find('/x:html',$node);



=item *

Another possibility is to use prefixes declared in the queried document (if
known). If the document declares a prefix for the namespace in question (and
the context node is in the scope of the declaration), XML::LibXML allows you to
use the prefix in the XPath expression, e.g.:

  $node->find('/x:html');



=back

See also XML::LibXML::XPathContext->findnodes.


=item B<find>

  $result = $node->find( $xpath );

find evaluates the XPath 1.0 expression using the current node as the context
of the expression, and returns the result depending on what type of result the
XPath expression had. For example, the XPath "1 * 3 + 52" results in a
XML::LibXML::Number object being returned. Other expressions might return a
XML::LibXML::Boolean object, or a XML::LibXML::Literal object (a string). Each
of those objects uses Perl's overload feature to "do the right thing" in
different contexts.

See also XML::LibXML::XPathContext->find.


=item B<findvalue>

  print $node->findvalue( $xpath );

findvalue is exactly equivalent to:

   $node->find( $xpath )->to_literal;              

That is, it returns the literal value of the results. This enables you to
ensure that you get a string back from your search, allowing certain shortcuts.
This could be used as the equivalent of XSLT's <xsl:value-of
select="some_xpath"/>.

See also XML::LibXML::XPathContext->findvalue.


=item B<childNodes>

  @childnodes = $node->childNodes;

getChildnodes implements a more intuitive interface to the childnodes of the
current node. It enables you to pass all children directly to a map or grep. If
this function is called in scalar context, a XML::LibXML::NodeList object will
be returned.


=item B<toString>

  $xmlstring = $node->toString($format,$docencoding);

This is the equivalent to XML::LibXML::Document::toString for a single node.
This means a node and all its childnodes will be dumped into the result string.

Additionally to the $format flag of XML::LibXML::Document, this version accepts
the optional $docencoding flag. If this flag is set this function returns the
string in its original encoding (the encoding of the document) rather than
UTF-8.


=item B<toStringC14N>

  $c14nstring = $node->toStringC14N($with_comments, $xpath_expression);

The function is similar to toString(). Instead of simply serializing the
document tree, it transforms it as it is specified in the XML-C14N
Specification (see http://www.w3.org/TR/xml-c14n). Such transformation is known
as canonization.

If $with_comments is 0 or not defined, the result-document will not contain any
comments that exist in the original document. To include comments into the
canonized document, $with_comments has to be set to 1.

The parameter $xpath_expression defines the nodeset of nodes that should be
visible in the resulting document. This can be used to filter out some nodes.
One has to note, that only the nodes that are part of the nodeset, will be
included into the result-document. Their child-nodes will not exist in the
resulting document, unless they are part of the nodeset defined by the xpath
expression.

If $xpath_expression is omitted or empty, toStringC14N() will include all nodes
in the given sub-tree.


=item B<toStringEC14N>

  $ec14nstring = $node->toStringEC14N($with_comments, $xpath_expression, $inclusive_prefix_list);

The function is similar to toStringC14N() but follows the XML-EXC-C14N
Specification (see http://www.w3.org/TR/xml-exc-c14n) for exclusive
canonization of XML.

The first two arguments are as above. If $inclusive_prefix_list is used, it
should be an ARRAY reference listing namespace prefixes that are to be handled
in the manner described by the Canonical XML Recommendation (i.e. preserved in
the output even if the namespace is not used). C.f. the spec for details.


=item B<serialize>

  $str = $doc->serialize($format); 

An alias for toString(). This function was name added to be more consistent
with libxml2.


=item B<serialize_c14n>

  $c14nstr = $doc->serialize_c14n($comment_flag,$xpath); 

An alias for toStringC14N().


=item B<serialize_exc_c14n>

  $ec14nstr = $doc->serialize_ec14n($comment_flag,$xpath,$inclusive_prefix_list); 

An alias for toStringEC14N().


=item B<localname>

  $localname = $node->localname;

Returns the local name of a tag. This is the part behind the colon.


=item B<prefix>

  $nameprefix = $node->prefix;

Returns the prefix of a tag. This is the part before the colon.


=item B<namespaceURI>

  $uri = $node->namespaceURI();

returns the URI of the current namespace.


=item B<hasAttributes>

  $boolean = $node->hasAttributes();

returns 1 (TRUE) if the current node has any attributes set, otherwise 0
(FALSE) is returned.


=item B<attributes>

  @attributelist = $node->attributes();

This function returns all attributes and namespace declarations assigned to the
given node.

Because XML::LibXML does not implement namespace declarations and attributes
the same way, it is required to test what kind of node is handled while
accessing the functions result.

If this function is called in array context the attribute nodes are returned as
an array. In scalar context the function will return a
XML::LibXML::NamedNodeMap object.


=item B<lookupNamespaceURI>

  $URI = $node->lookupNamespaceURI( $prefix );

Find a namespace URI by its prefix starting at the current node.


=item B<lookupNamespacePrefix>

  $prefix = $node->lookupNamespacePrefix( $URI );

Find a namespace prefix by its URI starting at the current node.

NOTE Only the namespace URIs are meant to be unique. The prefix is only
document related. Also the document might have more than a single prefix
defined for a namespace.


=item B<normalize>

  $node->normalize;

This function normalizes adjacent text nodes. This function is not as strict as
libxml2's xmlTextMerge() function, since it will not free a node that is still
referenced by the perl layer.


=item B<getNamespaces>

  @nslist = $node->getNamespaces;

If a node has any namespaces defined, this function will return these
namespaces. Note, that this will not return all namespaces that are in scope,
but only the ones declared explicitly for that node.

Although getNamespaces is available for all nodes, it only makes sense if used
with element nodes.


=item B<removeChildNodes>

  $node->removeChildNodes();

This function is not specified for any DOM level: It removes all childnodes
from a node in a single step. Other than the libxml2 function itself
(xmlFreeNodeList), this function will not immediately remove the nodes from the
memory. This saves one from getting memory violations, if there are nodes still
referred to from the Perl level.


=item B<nodePath>

  $node->nodePath();

This function is not specified for any DOM level: It returns a canonical
structure based XPath for a given node.


=item B<line_number>

  $lineno = $node->line_number();

This function returns the line number where the tag was found during parsing.
If a node is added to the document the line number is 0. Problems may occur, if
a node from one document is passed to another one.

Note: line_number() is special to XML::LibXML and not part of the DOM
specification.

If the line_numbers flag of the parser was not activated before parsing,
line_number() will always return 0.



=back

=head1 AUTHORS

Matt Sergeant, 
Christian Glahn, 
Petr Pajas, 

=head1 VERSION

1.64

=head1 COPYRIGHT

2001-2007, AxKit.com Ltd; 2002-2006 Christian Glahn; 2006-2007 Petr Pajas, All rights reserved.

=cut
