=head1 WARNING

This manual page was copied from the XML::Parser distribution (version 2.27)

written by Clark Cooper. You can find newer versions at CPAN.

=head1 NAME

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

=head1 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

   ...

 } 

=head1 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.

=head1 METHODS

=over 4

=item new

This is a class method, the constructor for XML::Parser::Expat. Options are

passed as keyword value pairs. The recognized options are:

=over 4

=item * ProtocolEncoding

The protocol encoding name. The default is none. The expat built-in

encodings are: C<UTF-8>, C<ISO-8859-1>, C<UTF-16>, and C<US-ASCII>.

Other encodings may be used if they have encoding maps in one of the

directories in the @Encoding_Path list. Setting the protocol encoding

overrides any encoding in the XML declaration.

=item * Namespaces

When this option is given with a true value, then the parser does namespace

processing. By default, namespace processing is turned off. When it is

turned on, the parser consumes I<xmlns> attributes and strips off prefixes

from element and attributes names where those prefixes have a defined

namespace. A name's namespace can be found using the L<"namespace"> method

and two names can be checked for absolute equality with the L<"eq_name">

method.

=item * NoExpand

Normally, the parser will try to expand references to entities defined in

the internal subset. If this option is set to a true value, and a default

handler is also set, then the default handler will be called when an

entity reference is seen in text. This has no effect if a default handler

has not been registered, and it has no effect on the expansion of entity

references inside attribute values.

=item * Stream_Delimiter

This option takes a string value. When this string is found alone on a line

while parsing from a stream, then the parse is ended as if it saw an end of

file. The intended use is with a stream of xml documents in a MIME multipart

format. The string should not contain a trailing newline.

=item * ErrorContext

When this option is defined, errors are reported in context. The value

of ErrorContext should be the number of lines to show on either side of

the line in which the error occurred.

=item * ParseParamEnt

Unless standalone is set to "yes" in the XML declaration, setting this to

a true value allows the external DTD to be read, and parameter entities

to be parsed and expanded.

=item * Base

The base to use for relative pathnames or URLs. This can also be done by

using the base method.

=back

=item 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:

=over 4

=item * Start		(Parser, Element [, Attr, Val [,...]])

This event is generated when an XML start tag is recognized. Parser is

an XML::Parser::Expat instance. Element is the name of the XML element that

is opened with the start tag. The Attr & Val pairs are generated for each

attribute in the start tag.

=item * End		(Parser, Element)

This event is generated when an XML end tag is recognized. Note that

an XML empty tag (<foo/>) generates both a start and an end event.

There is always a lower level start and end handler installed that wrap

the corresponding callbacks. This is to handle the context mechanism.

A consequence of this is that the default handler (see below) will not

see a start tag or end tag unless the default_current method is called.

=item * Char		(Parser, String)

This event is generated when non-markup is recognized. The non-markup

sequence of characters is in String. A single non-markup sequence of

characters may generate multiple calls to this handler. Whatever the

encoding of the string in the original document, this is given to the

handler in UTF-8.

=item * Proc		(Parser, Target, Data)

This event is generated when a processing instruction is recognized.

=item * Comment		(Parser, String)

This event is generated when a comment is recognized.

=item * CdataStart	(Parser)

This is called at the start of a CDATA section.

=item * CdataEnd	(Parser)

This is called at the end of a CDATA section.

=item * Default		(Parser, String)

This is called for any characters that don't have a registered handler.

This includes both characters that are part of markup for which no

events are generated (markup declarations) and characters that

could generate events, but for which no handler has been registered.

Whatever the encoding in the original document, the string is returned to

the handler in UTF-8.

=item * Unparsed		(Parser, Entity, Base, Sysid, Pubid, Notation)

This is called for a declaration of an unparsed entity. Entity is the name

of the entity. Base is the base to be used for resolving a relative URI.

Sysid is the system id. Pubid is the public id. Notation is the notation

name. Base and Pubid may be undefined.

=item * Notation		(Parser, Notation, Base, Sysid, Pubid)

This is called for a declaration of notation. Notation is the notation name.

Base is the base to be used for resolving a relative URI. Sysid is the system

id. Pubid is the public id. Base, Sysid, and Pubid may all be undefined.

=item * ExternEnt		(Parser, Base, Sysid, Pubid)

This is called when an external entity is referenced. Base is the base to be

used for resolving a relative URI. Sysid is the system id. Pubid is the public

id. Base, and Pubid may be undefined.

This handler should either return a string, which represents the contents of

the external entity, or return an open filehandle that can be read to obtain

the contents of the external entity, or return undef, which indicates the

external entity couldn't be found and will generate a parse error.

If an open filehandle is returned, it must be returned as either a glob

(*FOO) or as a reference to a glob (e.g. an instance of IO::Handle). The

parser will close the filehandle after using it.

=item * Entity			(Parser, Name, Val, Sysid, Pubid, Ndata)

This is called when an entity is declared. For internal entities, the Val

parameter will contain the value and the remaining three parameters will

be undefined. For external entities, the Val parameter

will be undefined, the Sysid parameter will have the system id, the Pubid

parameter will have the public id if it was provided (it will be undefined

otherwise), the Ndata parameter will contain the notation for unparsed

entities. If this is a parameter entity declaration, then a '%' will be

prefixed to the name.

Note that this handler and the Unparsed handler above overlap. If both are

set, then this handler will not be called for unparsed entities.

=item * Element			(Parser, Name, Model)

The element handler is called when an element declaration is found. Name is

the element name, and Model is the content model as a string.

=item * Attlist			(Parser, Elname, Attname, Type, Default, Fixed)

This handler is called for each attribute in an ATTLIST declaration.

So an ATTLIST declaration that has multiple attributes

will generate multiple calls to this handler. The Elname parameter is the

name of the element with which the attribute is being associated. The Attname

parameter is the name of the attribute. Type is the attribute type, given as

a string. Default is the default value, which will either be "#REQUIRED",

"#IMPLIED" or a quoted string (i.e. the returned string will begin and end

with a quote character). If Fixed is true, then this is a fixed attribute.

=item * Doctype			(Parser, Name, Sysid, Pubid, Internal)

This handler is called for DOCTYPE declarations. Name is the document type

name. Sysid is the system id of the document type, if it was provided,

otherwise it's undefined. Pubid is the public id of the document type,

which will be undefined if no public id was given. Internal is the internal

subset, given as a string. If there was no internal subset, it will be

undefined. Internal will contain all whitespace, comments, processing

instructions, and declarations seen in the internal subset. The declarations

will be there whether or not they have been processed by another handler

(except for unparsed entities processed by the Unparsed handler). However,

comments and processing instructions will not appear if they've been processed

by their respective handlers.

=item * XMLDecl			(Parser, Version, Encoding, Standalone)

This handler is called for xml declarations. Version is a string containg

the version. Encoding is either undefined or contains an encoding string.

Standalone will be either true, false, or undefined if the standalone attribute

is yes, no, or not made respectively.

=back

=item 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.

=item 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.

=item 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.

=item 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.

=item 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).

=item 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.

=item 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.

=item 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.

=item 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.

=item 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.

=item 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.

=item current_line

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

=item current_column

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

=item current_byte

Returns the current position of the parse.

=item base([NEWBASE]);

Returns the current value of the base for resolving relative URIs. If

NEWBASE is supplied, changes the base to that value.

=item 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.

=item 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.

=item 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.

=item 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.

=item depth

Returns the size of the context list.

=item 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.

=item 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.

=item 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.

=item 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.

=item 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.

=item 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.

=item parsefile(FILENAME)

Parses the XML document in the given file. Will die if parsestring or

parsefile has been called previously for this instance.

=item is_defaulted(ATTNAME)

NO LONGER WORKS. To find out if an attribute is defaulted please use

the specified_attr method.

=item 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.

=item 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.

=item 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.

=back

=head2 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:

=over 4

=item parse_more(DATA)

Feed expat more text to munch on.

=item parse_done

Tell expat that it's gotten the whole document.

=back

=head1 FUNCTIONS

=over 4

=item 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.

=back

=head1 AUTHORS

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

Clark Cooper <F<coopercc@netheaven.com>> picked up support, changed the API

for this version (2.x), provided documentation, and added some standard

package features.

=cut