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 XML::Parser::Expat - Lowlevel access to James Clark's expat XML parser


NAME

XML::Parser::Expat - Lowlevel access to James Clark's expat XML parser


SYNOPSIS

 use XML::Parser::Expat;
 $parser = new XML::Parser::Expat;
 $parser->setHandlers('Start' => \&sh,
                      'End'   => \&eh,
                      'Char'  => \&ch);
 open(FOO, 'info.xml') or die "Couldn't open";
 $parser->parse(*FOO);
 close(FOO);
 # $parser->parse('<foo id="me"> here <em>we</em> go </foo>');
 sub sh
 {
   my ($p, $el, %atts) = @_;
   $p->setHandlers('Char' => \&spec)
     if ($el eq 'special');
   ...
 }
 sub eh
 {
   my ($p, $el) = @_;
   $p->setHandlers('Char' => \&ch)  # Special elements won't contain
     if ($el eq 'special');         # other special elements
   ...
 }


DESCRIPTION

This module provides an interface to James Clark's XML parser, expat. As in expat, a single instance of the parser can only parse one document. Calls to parsestring after the first for a given instance will die.

Expat (and XML::Parser::Expat) are event based. As the parser recognizes parts of the document (say the start or end of an XML element), then any handlers registered for that type of an event are called with suitable parameters.


METHODS

new
This is a class method, the constructor for XML::Parser::Expat. Options are passed as keyword value pairs. The recognized options are:
setHandlers(TYPE, HANDLER [, TYPE, HANDLER [...]])
This method registers handlers for the various events. If no handlers are registered, then a call to parsestring or parsefile will only determine if the corresponding XML document is well formed (by returning without error.) This may be called from within a handler, after the parse has started.

Setting a handler to something that evaluates to false unsets that handler.

This method returns a list of type, handler pairs corresponding to the input. The handlers returned are the ones that were in effect before the call to setHandlers.

The recognized events and the parameters passed to the corresponding handlers are:

namespace(name)
Return the URI of the namespace that the name belongs to. If the name doesn't belong to any namespace, an undef is returned. This is only valid on names received through the Start or End handlers from a single document, or through a call to the generate_ns_name method. In other words, don't use names generated from one instance of XML::Parser::Expat with other instances.

eq_name(name1, name2)
Return true if name1 and name2 are identical (i.e. same name and from the same namespace.) This is only meaningful if both names were obtained through the Start or End handlers from a single document, or through a call to the generate_ns_name method.

generate_ns_name(name, namespace)
Return a name, associated with a given namespace, good for using with the above 2 methods. The namespace argument should be the namespace URI, not a prefix.

new_ns_prefixes
When called from a start tag handler, returns namespace prefixes declared with this start tag. If called elsewere (or if there were no namespace prefixes declared), it returns an empty list. Setting of the default namespace is indicated with '#default' as a prefix.

expand_ns_prefix(prefix)
Return the uri to which the given prefix is currently bound. Returns undef if the prefix isn't currently bound. Use '#default' to find the current binding of the default namespace (if any).

current_ns_prefixes
Return a list of currently bound namespace prefixes. The order of the the prefixes in the list has no meaning. If the default namespace is currently bound, '#default' appears in the list.

recognized_string
Returns the string from the document that was recognized in order to call the current handler. For instance, when called from a start handler, it will give us the the start-tag string. The string is encoded in UTF-8.

original_string
Returns the verbatim string from the document that was recognized in order to call the current handler. The string is in the original document encoding.

default_current
When called from a handler, causes the sequence of characters that generated the corresponding event to be sent to the default handler (if one is registered). Use of this method is deprecated in favor the recognized_string method, which you can use without installing a default handler.

xpcroak(message)
Concatenate onto the given message the current line number within the XML document plus the message implied by ErrorContext. Then croak with the formed message.

xpcarp(message)
Concatenate onto the given message the current line number within the XML document plus the message implied by ErrorContext. Then carp with the formed message.

current_line
Returns the line number of the current position of the parse.

current_column
Returns the column number of the current position of the parse.

current_byte
Returns the current position of the parse.

base([NEWBASE]);
Returns the current value of the base for resolving relative URIs. If NEWBASE is supplied, changes the base to that value.

context
Returns a list of element names that represent open elements, with the last one being the innermost. Inside start and end tag handlers, this will be the tag of the parent element.

current_element
Returns the name of the innermost currently opened element. Inside start or end handlers, returns the parent of the element associated with those tags.

in_element(NAME)
Returns true if NAME is equal to the name of the innermost currently opened element. If namespace processing is being used and you want to check against a name that may be in a namespace, then use the generate_ns_name method to create the NAME argument.

within_element(NAME)
Returns the number of times the given name appears in the context list. If namespace processing is being used and you want to check against a name that may be in a namespace, then use the generate_ns_name method to create the NAME argument.

depth
Returns the size of the context list.

element_index
Returns an integer that is the depth-first visit order of the current element. This will be zero outside of the root element. For example, this will return 1 when called from the start handler for the root element start tag.

skip_until(INDEX)
INDEX is an integer that represents an element index. When this method is called, all handlers are suspended until the start tag for an element that has an index number equal to INDEX is seen. If a start handler has been set, then this is the first tag that the start handler will see after skip_until has been called.

position_in_context(LINES)
Returns a string that shows the current parse position. LINES should be an integer >= 0 that represents the number of lines on either side of the current parse line to place into the returned string.

xml_escape(TEXT [, CHAR [, CHAR ...]])
Returns TEXT with markup characters turned into character entities. Any additional characters provided as arguments are also turned into character references where found in TEXT.

parse (SOURCE)
The SOURCE parameter should either be a string containing the whole XML document, or it should be an open IO::Handle. Only a single document may be parsed for a given instance of XML::Parser::Expat, so this will croak if it's been called previously for this instance.

parsestring(XML_DOC_STRING)
Parses the given string as an XML document. Only a single document may be parsed for a given instance of XML::Parser::Expat, so this will die if either parsestring or parsefile has been called for this instance previously.

This method is deprecated in favor of the parse method.

parsefile(FILENAME)
Parses the XML document in the given file. Will die if parsestring or parsefile has been called previously for this instance.

is_defaulted(ATTNAME)
NO LONGER WORKS. To find out if an attribute is defaulted please use the specified_attr method.

specified_attr
When the start handler receives lists of attributes and values, the non-defaulted (i.e. explicitly specified) attributes occur in the list first. This method returns the number of specified items in the list. So if this number is equal to the length of the list, there were no defaulted values. Otherwise the number points to the index of the first defaulted attribute name.

finish
Unsets all handlers (including internal ones that set context), but expat continues parsing to the end of the document or until it finds an error. It should finish up a lot faster than with the handlers set.

release
There are data structures used by XML::Parser::Expat that have circular references. This means that these structures will never be garbage collected unless these references are explicitly broken. Calling this method breaks those references (and makes the instance unusable.)

Normally, higher level calls handle this for you, but if you are using XML::Parser::Expat directly, then it's your responsibility to call it.

XML::Parser::ExpatNB Methods

The class XML::Parser::ExpatNB is a subclass of XML::Parser::Expat used for non-blocking access to the expat library. It does not support the parse, parsestring, or parsefile methods, but it does have these additional methods:

parse_more(DATA)
Feed expat more text to munch on.

parse_done
Tell expat that it's gotten the whole document.


FUNCTIONS

XML::Parser::Expat::load_encoding(ENCODING)
Load an external encoding. ENCODING is either the name of an encoding or the name of a file. The basename is converted to lowercase and a '.enc' extension is appended unless there's one already there. Then, unless it's an absolute pathname (i.e. begins with '/'), the first file by that name discovered in the @Encoding_Path path list is used.

The encoding in the file is loaded and kept in the %Encoding_Table table. Earlier encodings of the same name are replaced.

This function is automaticly called by expat when it encounters an encoding it doesn't know about. Expat shouldn't call this twice for the same encoding name. The only reason users should use this function is to explicitly load an encoding not contained in the @Encoding_Path list.


AUTHORS

Larry Wall <larry@wall.org> wrote version 1.0.

Clark Cooper <coopercc@netheaven.com> picked up support, changed the API for this version (2.x), provided documentation, and added some standard package features.

 XML::Parser::Expat - Lowlevel access to James Clark's expat XML parser