=head1 NAME

XML::LibXML::Pattern - XML::LibXML::Pattern - interface to libxml2 XPath patterns

=head1 SYNOPSIS



  use XML::LibXML;
  my $pattern = new XML::LibXML::Pattern('/x:html/x:body//x:div', { 'x' => 'http://www.w3.org/1999/xhtml' });
  # test a match on a XML::LibXML::Node $node

  if ($pattern->matchesNode($node)) { ... }

  # or on a XML::LibXML::Reader

  if ($reader->matchesPattern($pattern)) { ... }

  # or skip reading all nodes that do not match

  print $reader->nodePath while $reader->nextPatternMatch($pattern);

  $pattern = XML::LibXML::Pattern->new( pattern, { prefix => namespace_URI, ... } );
  $bool = $pattern->matchesNode($node);

=head1 DESCRIPTION

This is a perl interface to libxml2's pattern matching support I<<<<<< http://xmlsoft.org/html/libxml-pattern.html >>>>>>. This feature requires recent versions of libxml2.

Patterns are a small subset of XPath language, which is limitted to
(disjunctions of) location paths involving the child and descendant axes in
abbreviated form as described by the extended BNF given below: 



  Selector ::=     Path ( '|' Path )*
  Path     ::=     ('.//' | '//' | '/' )? Step ( '/' Step )*
  Step     ::=     '.' | NameTest
  NameTest ::=     QName | '*' | NCName ':' '*'

For readability, whitespace may be used in selector XPath expressions even
though not explicitly allowed by the grammar: whitespace may be freely added
within patterns before or after any token, where



  token     ::=     '.' | '/' | '//' | '|' | NameTest

Note that no predicates or attribute tests are allowed.

Patterns are particularly useful for stream parsing provided via the C<<<<<< XML::LibXML::Reader >>>>>> interface.

=over 4

=item new()

  $pattern = XML::LibXML::Pattern->new( pattern, { prefix => namespace_URI, ... } );

The constructor of a pattern takes a pattern expression (as described by the
BNF grammar above) and an optional HASH reference mapping prefixes to namespace
URIs. The method returns a compiled pattern object. 

Note that if the document has a default namespace, it must still be given an
prefix in order to be matched (as demanded by the XPath 1.0 specification). For
example, to match an element C<<<<<< <a xmlns="http://foo.bar"</a> >>>>>>, one should use a pattern like this: 



  $pattern = XML::LibXML::Pattern->new( 'foo:a', { foo => 'http://foo.bar' });


=item matchesNode($node)

  $bool = $pattern->matchesNode($node);

Given a XML::LibXML::Node object, returns a true value if the node is matched
by the compiled pattern expression.



=back


=head1 SEE ALSO

L<<<<<< XML::LibXML::Reader >>>>>> for other methods involving compiled patterns.

=head1 AUTHORS

Matt Sergeant, 
Christian Glahn, 
Petr Pajas


=head1 VERSION

1.70

=head1 COPYRIGHT

2001-2007, AxKit.com Ltd.

2002-2006, Christian Glahn.

2006-2009, Petr Pajas.

=cut
