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XML::LibXML::Pattern.3pm

NAME

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

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);
 
 

DESCRIPTION

This is a perl interface to libxml2's pattern matching support 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 "XML::LibXML::Reader" interface.

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 "<a xmlns="http://foo.bar"</a>", one should use a pattern like this:

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

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.

SEE ALSO

XML::LibXML::Reader for other methods involving compiled patterns.

AUTHORS

Matt Sergeant, Christian Glahn, Petr Pajas

VERSION

1.70

COPYRIGHT

2001-2007, AxKit.com Ltd.

2002-2006, Christian Glahn.

2006-2009, Petr Pajas.