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Edit File: Node.pod

=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 );
  $num = $node->unique_key;
  $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( $childnode );
  $node = $parent->addNewChild( $nsURI, $name );
  $node->addSibling($newNode);
  $newnode =$node->cloneNode( $deep );
  $parentnode = $node->parentNode;
  $nextnode = $node->nextSibling();
  $nextnode = $node->nextNonBlankSibling();
  $prevnode = $node->previousSibling();
  $prevnode = $node->previousNonBlankSibling();
  $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 );
  $bool = $node->exists( $xpath_expression );
  @childnodes = $node->childNodes();
  @childnodes = $node->nonBlankChildNodes();
  $xmlstring = $node->toString($format,$docencoding);
  $c14nstring = $node->toStringC14N();
  $c14nstring = $node->toStringC14N($with_comments, $xpath_expression , $xpath_context);
  $c14nstring = $node->toStringC14N_v1_1();
  $c14nstring = $node->toStringC14N_v1_1($with_comments, $xpath_expression , $xpath_context);
  $ec14nstring = $node->toStringEC14N();
  $ec14nstring = $node->toStringEC14N($with_comments, $xpath_expression, $inclusive_prefix_list);
  $ec14nstring = $node->toStringEC14N($with_comments, $xpath_expression, $xpath_context, $inclusive_prefix_list);
  $str = $doc->serialize($format);
  $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();
  $strURI = $node->baseURI();
  $node->setBaseURI($strURI);
  $node->nodePath();
  $lineno = $node->line_number();

=head1 DESCRIPTION

XML::LibXML::Node defines functions that are common to all Node Types. An
XML::LibXML::Node should never be created standalone, but as an instance of a
high level class such as XML::LibXML::Element or XML::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.

=head1 METHODS

Many functions listed here are extensively documented in the DOM Level 3 specification (L<<<<<< http://www.w3.org/TR/DOM-Level-3-Core/ >>>>>>). Please refer to the specification for extensive documentation.

=over 4

=item nodeName

$name = $node->nodeName;

Returns the node's name. This function is aware of namespaces and returns the
full name of the current node (C<<<<<< 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 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 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 isEqual

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

deprecated version of isSameNode().

I<<<<<< NOTE >>>>>> isEqual will change behaviour to follow the DOM specification

=item unique_key

$num = $node->unique_key;

This function is not specified for any DOM level. It returns a key guaranteed
to be unique for this node, and to always be the same value for this node. In
other words, two node objects return the same key if and only if isSameNode
indicates that they are the same node.

The returned key value is useful as a key in hashes.

=item nodeValue

$content = $node->nodeValue;

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

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

=item 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 nodeType

$type = $node->nodeType;

Return a numeric value representing the node type of this node. The module
XML::LibXML by default exports constants for the node types (see the EXPORT
section in the L<<<<<< XML::LibXML >>>>>> manual page).

=item 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 terminates. From a low level view, the unbound node is
stripped from the context it is and inserted into a (hidden) document-fragment.

=item removeChild

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

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

=item replaceChild

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

Replaces the C<<<<<< $oldNode >>>>>> with the C<<<<<< $newNode >>>>>>. The C<<<<<< $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 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 appendChild

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

The function will add the C<<<<<< $childnode >>>>>> to the end of C<<<<<< $node >>>>>>'s children. The function should fail, if the new childnode is already a child
of C<<<<<< $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 addChild

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

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 (C<<<<<< 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 addNewChild

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

Similar to C<<<<<< addChild() >>>>>>, this function uses low level libxml2 functionality to provide faster
interface for DOM building. I<<<<<< addNewChild() >>>>>> uses C<<<<<< 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. I<<<<<< NOTE >>>>>> this function is not part of the DOM specification and its use will limit your
code to XML::LibXML.

=item addSibling

$node->addSibling($newNode);

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

=item cloneNode

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

I<<<<<< cloneNode >>>>>> creates a copy of C<<<<<< $node >>>>>>. When $deep is set to 1 (true) the function will copy all child nodes 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 parentNode

$parentnode = $node->parentNode;

Returns simply the Parent Node of the current node.

=item nextSibling

$nextnode = $node->nextSibling();

Returns the next sibling if any .

=item nextNonBlankSibling

$nextnode = $node->nextNonBlankSibling();

Returns the next non-blank sibling if any (a node is blank if it is a Text or
CDATA node consisting of whitespace only). This method is not defined by DOM.

=item previousSibling

$prevnode = $node->previousSibling();

Analogous to I<<<<<< getNextSibling >>>>>> the function returns the previous sibling if any.

=item previousNonBlankSibling

$prevnode = $node->previousNonBlankSibling();

Returns the previous non-blank sibling if any (a node is blank if it is a Text
or CDATA node consisting of whitespace only). This method is not defined by
DOM.

=item hasChildNodes

$boolean = $node->hasChildNodes();

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

=item firstChild

$childnode = $node->firstChild;

If a node has child nodes this function will return the first node in the child
list.

=item lastChild

$childnode = $node->lastChild;

If the C<<<<<< $node >>>>>> has child nodes this function returns the last child node.

=item ownerDocument

$documentnode = $node->ownerDocument;

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

=item 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 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 L<<<<<< XML::LibXML::Document >>>>>>'s adoptNode() function. Because of this it has the same limitations with
Entity References as adoptNode().

=item insertBefore

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

The method inserts C<<<<<< $newNode >>>>>> before C<<<<<< $refNode >>>>>>. If C<<<<<< $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 insertAfter

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

The method inserts C<<<<<< $newNode >>>>>> after C<<<<<< $refNode >>>>>>. If C<<<<<< $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 findnodes

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

I<<<<<< 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 an L<<<<<< XML::LibXML::NodeList >>>>>> object.

The xpath expression can be passed either as a string, or as a L<<<<<< XML::LibXML::XPathExpression >>>>>> object.

I<<<<<< 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 C<<<<<< $node-E<gt>find('/html') >>>>>> since C<<<<<< '/html' >>>>>> would only match if the root element C<<<<<< E<lt>htmlE<gt> >>>>>> had no namespace, but all XHTML elements belong to the namespace
http://www.w3.org/1999/xhtml. (Note that C<<<<<< 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 L<<<<<< 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), C<<<<<< 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 find

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

I<<<<<< 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 L<<<<<< XML::LibXML::Number >>>>>> object being returned. Other expressions might return an L<<<<<< XML::LibXML::Boolean >>>>>> object, or an L<<<<<< XML::LibXML::Literal >>>>>> object (a string). Each of those objects uses Perl's overload feature to "do
the right thing" in different contexts.

The xpath expression can be passed either as a string, or as a L<<<<<< XML::LibXML::XPathExpression >>>>>> object.

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

=item findvalue

print $node->findvalue( $xpath );

I<<<<<< 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 L<<<<<< XML::LibXML::XPathContext >>>>>>->findvalue.

The xpath expression can be passed either as a string, or as a L<<<<<< XML::LibXML::XPathExpression >>>>>> object.

=item exists

$bool = $node->exists( $xpath_expression );

This method behaves like I<<<<<< findnodes >>>>>>, except that it only returns a boolean value (1 if the expression matches a
node, 0 otherwise) and may be faster than I<<<<<< findnodes >>>>>>, because the XPath evaluation may stop early on the first match (this is true
for libxml2 >= 2.6.27).

For XPath expressions that do not return node-set, the method returns true if
the returned value is a non-zero number or a non-empty string.

=item childNodes

@childnodes = $node->childNodes();

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

=item nonBlankChildNodes

@childnodes = $node->nonBlankChildNodes();

This is like I<<<<<< childNodes >>>>>>, but returns only non-blank nodes (where a node is blank if it is a Text or
CDATA node consisting of whitespace only). This method is not defined by DOM.

=item toString

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

This method is similar to the method C<<<<<< toString >>>>>> of a L<<<<<< XML::LibXML::Document >>>>>> but for a single node. It returns a string consisting of XML serialization of
the given node and all its descendants. Unlike C<<<<<< XML::LibXML::Document::toString >>>>>>, in this case the resulting string is by default a character string (UTF-8
encoded with UTF8 flag on). An optional flag $format controls indentation, as
in C<<<<<< XML::LibXML::Document::toString >>>>>>. If the second optional $docencoding flag is true, the result will be a byte
string in the document encoding (see C<<<<<< XML::LibXML::Document::actualEncoding >>>>>>).

=item toStringC14N

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

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 L<<<<<< 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, using the following XPath expressions: with comments

(. | .//node() | .//@* | .//namespace::*)

and without comments

(. | .//node() | .//@* | .//namespace::*)[not(self::comment())]

An optional parameter $xpath_context can be used to pass an L<<<<<< XML::LibXML::XPathContext >>>>>> object defining the context for evaluation of $xpath_expression. This is useful
for mapping namespace prefixes used in the XPath expression to namespace URIs.
Note, however, that $node will be used as the context node for the evaluation,
not the context node of $xpath_context!

=item toStringC14N_v1_1

$c14nstring = $node->toStringC14N_v1_1();
  $c14nstring = $node->toStringC14N_v1_1($with_comments, $xpath_expression , $xpath_context);

This function behaves like toStringC14N() except that it uses the
"XML_C14N_1_1" constant for canonicalising using the "C14N 1.1 spec".

=item toStringEC14N

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

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

The arguments $with_comments, $xpath_expression, $xpath_context are as in
toStringC14N(). An ARRAY reference can be passed as the last argument
$inclusive_prefix_list, 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 serialize

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

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

=item serialize_c14n

An alias for toStringC14N().

=item serialize_exc_c14n

An alias for toStringEC14N().

=item localname

$localname = $node->localname;

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

=item prefix

$nameprefix = $node->prefix;

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

=item namespaceURI

$uri = $node->namespaceURI();

returns the URI of the current namespace.

=item hasAttributes

$boolean = $node->hasAttributes();

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

=item 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 L<<<<<< XML::LibXML::NamedNodeMap >>>>>> object.

=item lookupNamespaceURI

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

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

=item lookupNamespacePrefix

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

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

I<<<<<< 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 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 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 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 baseURI ()

$strURI = $node->baseURI();

Searches for the base URL of the node. The method should work on both XML and
HTML documents even if base mechanisms for these are completely different. It
returns the base as defined in RFC 2396 sections "5.1.1. Base URI within
Document Content" and "5.1.2. Base URI from the Encapsulating Entity". However
it does not return the document base (5.1.3), use method C<<<<<< URI >>>>>> of C<<<<<< XML::LibXML::Document >>>>>> for this.

=item setBaseURI ($strURI)

$node->setBaseURI($strURI);

This method only does something useful for an element node in an XML document.
It sets the xml:base attribute on the node to $strURI, which effectively sets
the base URI of the node to the same value.

Note: For HTML documents this behaves as if the document was XML which may not
be desired, since it does not effectively set the base URI of the node. See RFC
2396 appendix D for an example of how base URI can be specified in HTML.

=item nodePath

$node->nodePath();

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

=item 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.

IMPORTANT: Due to limitations in the libxml2 library line numbers greater than
65535 will be returned as 65535. Please see L<<<<<< http://bugzilla.gnome.org/show_bug.cgi?id=325533 >>>>>> for more details.

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

2.0134

=head1 COPYRIGHT

2001-2007, AxKit.com Ltd.

2002-2006, Christian Glahn.

2006-2009, Petr Pajas.

=cut

=head1 LICENSE

This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.

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