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XML::LibXML::Reader(3)User Contributed Perl DocumentatioXML::LibXML::Reader(3)

NAME
       XML::LibXML::Reader - XML::LibXML::Reader - interface to libxml2 pull
       parser

SYNOPSIS
         use XML::LibXML::Reader;

         my $reader = new XML::LibXML::Reader(location => "file.xml")
                or die "cannot read file.xml\n";
         while ($reader->read) {
           processNode($reader);
         }

         sub processNode {
             $reader = shift;
             printf "%d %d %s %d\n", ($reader->depth,
                                      $reader->nodeType,
                                      $reader->name,
                                      $reader->isEmptyElement);
         }

       or

         $reader = new XML::LibXML::Reader(location => "file.xml")
                or die "cannot read file.xml\n";
           $reader->preservePattern('//table/tr');
           $reader->finish;
           print $reader->document->toString(1);

DESCRIPTION
       This is a perl interface to libxml2's pull-parser implementation
       xmlTextReader http://xmlsoft.org/html/libxml-xmlreader.html. This
       feature requires at least libxml2-2.6.21. Pull-parser (StAX in Java,
       XmlReader in C#) use an iterator approach to parse a xml-file. They are
       easier to program than event-based parser (SAX) and much more
       lightweight than tree-based parser (DOM), which load the complete tree
       into memory.

       The Reader acts as a cursor going forward on the document stream and
       stopping at each node in the way. At every point DOM-like methods of
       the Reader object allow to examine the current node (name, namespace,
       attributes, etc.)

       The user's code keeps control of the progress and simply calls the
       "read()" function repeatedly to progress to the next node in the
       document order. Other functions provide means for skipping complete
       sub-trees, or nodes until a specific element, etc.

       At every time, only a very limited portion of the document is kept in
       the memory, which makes the API more memory-efficient than using DOM.
       However, it is also possible to mix Reader with DOM. At every point the
       user may copy the current node (optionally expanded into a complete
       sub-tree) from the processed document to another DOM tree, or to
       instruct the Reader to collect sub-document in form of a DOM tree
       consisting of selected nodes.

       Reader API also supports namespaces, xml:base, entity handling, and DTD
       validation. Schema and RelaxNG validation support will probably be
       added in some later revision of the Perl interface.

       The naming of methods compared to libxml2 and C# XmlTextReader has been
       changed slightly to match the conventions of XML::LibXML. Some
       functions have been changed or added with respect to the C interface.

CONSTRUCTOR
       Depending on the XML source, the Reader object can be created with
       either of:

         my $reader = XML::LibXML::Reader->new( location => "file.xml", ... );
           my $reader = XML::LibXML::Reader->new( string => $xml_string, ... );
           my $reader = XML::LibXML::Reader->new( IO => $file_handle, ... );
           my $reader = XML::LibXML::Reader->new( FD => fileno(STDIN), ... );
           my $reader = XML::LibXML::Reader->new( DOM => $dom, ... );

       where ... are (optional) reader options described below in "Reader
       options" or various parser options described in XML::LibXML::Parser.
       The constructor recognizes the following XML sources:

   Source specification
       location
           Read XML from a local file or URL.

       string
           Read XML from a string.

       IO  Read XML a Perl IO filehandle.

       FD  Read XML from a file descriptor (bypasses Perl I/O layer, only
           applicable to filehandles for regular files or pipes). Possibly
           faster than IO.

       DOM Use reader API to walk through a pre-parsed XML::LibXML::Document.

   Reader options
       encoding => $encoding
           override document encoding.

       RelaxNG => $rng_schema
           can be used to pass either a XML::LibXML::RelaxNG object or a
           filename or URL of a RelaxNG schema to the constructor. The schema
           is then used to validate the document as it is processed.

       Schema => $xsd_schema
           can be used to pass either a XML::LibXML::Schema object or a
           filename or URL of a W3C XSD schema to the constructor. The schema
           is then used to validate the document as it is processed.

       ... the reader further supports various parser options described in
           XML::LibXML::Parser (specificly those labeled by /reader/).

METHODS CONTROLLING PARSING PROGRESS
       read ()
           Moves the position to the next node in the stream, exposing its
           properties.

           Returns 1 if the node was read successfully, 0 if there is no more
           nodes to read, or -1 in case of error

       readAttributeValue ()
           Parses an attribute value into one or more Text and EntityReference
           nodes.

           Returns 1 in case of success, 0 if the reader was not positioned on
           an attribute node or all the attribute values have been read, or -1
           in case of error.

       readState ()
           Gets the read state of the reader. Returns the state value, or -1
           in case of error. The module exports constants for the Reader
           states, see STATES below.

       depth ()
           The depth of the node in the tree, starts at 0 for the root node.

       next ()
           Skip to the node following the current one in the document order
           while avoiding the sub-tree if any. Returns 1 if the node was read
           successfully, 0 if there is no more nodes to read, or -1 in case of
           error.

       nextElement (localname?,nsURI?)
           Skip nodes following the current one in the document order until a
           specific element is reached. The element's name must be equal to a
           given localname if defined, and its namespace must equal to a given
           nsURI if defined. Either of the arguments can be undefined (or
           omitted, in case of the latter or both).

           Returns 1 if the element was found, 0 if there is no more nodes to
           read, or -1 in case of error.

       nextPatternMatch (compiled_pattern)
           Skip nodes following the current one in the document order until an
           element matching a given compiled pattern is reached. See
           XML::LibXML::Pattern for information on compiled patterns. See also
           the "matchesPattern" method.

           Returns 1 if the element was found, 0 if there is no more nodes to
           read, or -1 in case of error.

       skipSiblings ()
           Skip all nodes on the same or lower level until the first node on a
           higher level is reached. In particular, if the current node occurs
           in an element, the reader stops at the end tag of the parent
           element, otherwise it stops at a node immediately following the
           parent node.

           Returns 1 if successful, 0 if end of the document is reached, or -1
           in case of error.

       nextSibling ()
           It skips to the node following the current one in the document
           order while avoiding the sub-tree if any.

           Returns 1 if the node was read successfully, 0 if there is no more
           nodes to read, or -1 in case of error

       nextSiblingElement (name?,nsURI?)
           Like nextElement but only processes sibling elements of the current
           node (moving forward using "nextSibling ()" rather than "read ()",
           internally).

           Returns 1 if the element was found, 0 if there is no more sibling
           nodes, or -1 in case of error.

       finish ()
           Skip all remaining nodes in the document, reaching end of the
           document.

           Returns 1 if successful, 0 in case of error.

       close ()
           This method releases any resources allocated by the current
           instance and closes any underlying input. It returns 0 on failure
           and 1 on success. This method is automatically called by the
           destructor when the reader is forgotten, therefore you do not have
           to call it directly.

METHODS EXTRACTING INFORMATION
       name ()
           Returns the qualified name of the current node, equal to
           (Prefix:)LocalName.

       nodeType ()
           Returns the type of the current node. See NODE TYPES below.

       localName ()
           Returns the local name of the node.

       prefix ()
           Returns the prefix of the namespace associated with the node.

       namespaceURI ()
           Returns the URI defining the namespace associated with the node.

       isEmptyElement ()
           Check if the current node is empty, this is a bit bizarre in the
           sense that <a/> will be considered empty while <a></a> will not.

       hasValue ()
           Returns true if the node can have a text value.

       value ()
           Provides the text value of the node if present or undef if not
           available.

       readInnerXml ()
           Reads the contents of the current node, including child nodes and
           markup.  Returns a string containing the XML of the node's content,
           or undef if the current node is neither an element nor attribute,
           or has no child nodes.

       readOuterXml ()
           Reads the contents of the current node, including child nodes and
           markup.

           Returns a string containing the XML of the node including its
           content, or undef if the current node is neither an element nor
           attribute.

       nodePath()
           Returns a cannonical location path to the current element from the
           root node to the current node. Namespaced elements are matched by
           '*', because there is no way to declare prefixes within XPath
           patterns. Unlike "XML::LibXML::Node::nodePath()", this function
           does not provide sibling counts (i.e. instead of e.g. '/a/b[1]' and
           '/a/b[2]' you get '/a/b' for both matches).

       matchesPattern(compiled_pattern)
           Returns a true value if the current node matches a compiled
           pattern. See XML::LibXML::Pattern for information on compiled
           patterns. See also the "nextPatternMatch" method.

METHODS EXTRACTING DOM NODES
       document ()
           Provides access to the document tree built by the reader. This
           function can be used to collect the preserved nodes (see
           "preserveNode()" and preservePattern).

           CAUTION: Never use this function to modify the tree unless reading
           of the whole document is completed!

       copyCurrentNode (deep)
           This function is similar a DOM function "copyNode()". It returns a
           copy of the currently processed node as a corresponding DOM object.
           Use deep = 1 to obtain the full sub-tree.

       preserveNode ()
           This tells the XML Reader to preserve the current node in the
           document tree. A document tree consisting of the preserved nodes
           and their content can be obtained using the method "document()"
           once parsing is finished.

           Returns the node or NULL in case of error.

       preservePattern (pattern,\%ns_map)
           This tells the XML Reader to preserve all nodes matched by the
           pattern (which is a streaming XPath subset). A document tree
           consisting of the preserved nodes and their content can be obtained
           using the method "document()" once parsing is finished.

           An optional second argument can be used to provide a HASH reference
           mapping prefixes used by the XPath to namespace URIs.

           The XPath subset available with this function is described at

             http://www.w3.org/TR/xmlschema-1/#Selector

           and matches the production

             Path ::= ('.//')? ( Step '/' )* ( Step | '@' NameTest )

           Returns a positive number in case of success and -1 in case of
           error

METHODS PROCESSING ATTRIBUTES
       attributeCount ()
           Provides the number of attributes of the current node.

       hasAttributes ()
           Whether the node has attributes.

       getAttribute (name)
           Provides the value of the attribute with the specified qualified
           name.

           Returns a string containing the value of the specified attribute,
           or undef in case of error.

       getAttributeNs (localName, namespaceURI)
           Provides the value of the specified attribute.

           Returns a string containing the value of the specified attribute,
           or undef in case of error.

       getAttributeNo (no)
           Provides the value of the attribute with the specified index
           relative to the containing element.

           Returns a string containing the value of the specified attribute,
           or undef in case of error.

       isDefault ()
           Returns true if the current attribute node was generated from the
           default value defined in the DTD.

       moveToAttribute (name)
           Moves the position to the attribute with the specified local name
           and namespace URI.

           Returns 1 in case of success, -1 in case of error, 0 if not found

       moveToAttributeNo (no)
           Moves the position to the attribute with the specified index
           relative to the containing element.

           Returns 1 in case of success, -1 in case of error, 0 if not found

       moveToAttributeNs (localName,namespaceURI)
           Moves the position to the attribute with the specified local name
           and namespace URI.

           Returns 1 in case of success, -1 in case of error, 0 if not found

       moveToFirstAttribute ()
           Moves the position to the first attribute associated with the
           current node.

           Returns 1 in case of success, -1 in case of error, 0 if not found

       moveToNextAttribute ()
           Moves the position to the next attribute associated with the
           current node.

           Returns 1 in case of success, -1 in case of error, 0 if not found

       moveToElement ()
           Moves the position to the node that contains the current attribute
           node.

           Returns 1 in case of success, -1 in case of error, 0 if not moved

       isNamespaceDecl ()
           Determine whether the current node is a namespace declaration
           rather than a regular attribute.

           Returns 1 if the current node is a namespace declaration, 0 if it
           is a regular attribute or other type of node, or -1 in case of
           error.

OTHER METHODS
       lookupNamespace (prefix)
           Resolves a namespace prefix in the scope of the current element.

           Returns a string containing the namespace URI to which the prefix
           maps or undef in case of error.

       encoding ()
           Returns a string containing the encoding of the document or undef
           in case of error.

       standalone ()
           Determine the standalone status of the document being read. Returns
           1 if the document was declared to be standalone, 0 if it was
           declared to be not standalone, or -1 if the document did not
           specify its standalone status or in case of error.

       xmlVersion ()
           Determine the XML version of the document being read. Returns a
           string containing the XML version of the document or undef in case
           of error.

       baseURI ()
           Returns the base URI of a given node.

       isValid ()
           Retrieve the validity status from the parser.

           Returns 1 if valid, 0 if no, and -1 in case of error.

       xmlLang ()
           The xml:lang scope within which the node resides.

       lineNumber ()
           Provide the line number of the current parsing point.

       columnNumber ()
           Provide the column number of the current parsing point.

       byteConsumed ()
           This function provides the current index of the parser relative to
           the start of the current entity. This function is computed in bytes
           from the beginning starting at zero and finishing at the size in
           bytes of the file if parsing a file. The function is of constant
           cost if the input is UTF-8 but can be costly if run on non-UTF-8
           input.

       setParserProp (prop => value, ...)
           Change the parser processing behaviour by changing some of its
           internal properties. The following properties are available with
           this function: ``load_ext_dtd'', ``complete_attributes'',
           ``validation'', ``expand_entities''.

           Since some of the properties can only be changed before any read
           has been done, it is best to set the parsing properties at the
           constructor.

           Returns 0 if the call was successful, or -1 in case of error

       getParserProp (prop)
           Get value of an parser internal property. The following property
           names can be used: ``load_ext_dtd'', ``complete_attributes'',
           ``validation'', ``expand_entities''.

           Returns the value, usually 0 or 1, or -1 in case of error.

DESTRUCTION
       XML::LibXML takes care of the reader object destruction when the last
       reference to the reader object goes out of scope. The document tree is
       preserved, though, if either of $reader->document or
       $reader->preserveNode was used and references to the document tree
       exist.

NODE TYPES
       The reader interface provides the following constants for node types
       (the constant symbols are exported by default or if tag ":types" is
       used).

         XML_READER_TYPE_NONE                    => 0
         XML_READER_TYPE_ELEMENT                 => 1
         XML_READER_TYPE_ATTRIBUTE               => 2
         XML_READER_TYPE_TEXT                    => 3
         XML_READER_TYPE_CDATA                   => 4
         XML_READER_TYPE_ENTITY_REFERENCE        => 5
         XML_READER_TYPE_ENTITY                  => 6
         XML_READER_TYPE_PROCESSING_INSTRUCTION  => 7
         XML_READER_TYPE_COMMENT                 => 8
         XML_READER_TYPE_DOCUMENT                => 9
         XML_READER_TYPE_DOCUMENT_TYPE           => 10
         XML_READER_TYPE_DOCUMENT_FRAGMENT       => 11
         XML_READER_TYPE_NOTATION                => 12
         XML_READER_TYPE_WHITESPACE              => 13
         XML_READER_TYPE_SIGNIFICANT_WHITESPACE  => 14
         XML_READER_TYPE_END_ELEMENT             => 15
         XML_READER_TYPE_END_ENTITY              => 16
         XML_READER_TYPE_XML_DECLARATION         => 17

STATES
       The following constants represent the values returned by "readState()".
       They are exported by default, or if tag ":states" is used:

         XML_READER_NONE      => -1
         XML_READER_START     =>  0
         XML_READER_ELEMENT   =>  1
         XML_READER_END       =>  2
         XML_READER_EMPTY     =>  3
         XML_READER_BACKTRACK =>  4
         XML_READER_DONE      =>  5
         XML_READER_ERROR     =>  6

SEE ALSO
       XML::LibXML::Pattern for information about compiled patterns.

       http://xmlsoft.org/html/libxml-xmlreader.html

       http://dotgnu.org/pnetlib-doc/System/Xml/XmlTextReader.html

ORIGINAL IMPLEMENTATION
       Heiko Klein, <H.Klein@gmx.net<gt> and Petr Pajas

AUTHORS
       Matt Sergeant, Christian Glahn, Petr Pajas

VERSION
       1.70

COPYRIGHT
       2001-2007, AxKit.com Ltd.

       2002-2006, Christian Glahn.

       2006-2009, Petr Pajas.

perl v5.12.1                      2009-10-07            XML::LibXML::Reader(3)
 

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Gedruckt am: 20.09.2017 16:50 GMT+0200 (2017-09-20T16:50:45+02:00)