=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 - A perl module for parsing XML documents

=head1 SYNOPSIS

  use XML::Parser;

  $p1 = new XML::Parser(Style => 'Debug');

  $p1->parsefile('REC-xml-19980210.xml');

  $p1->parse('<foo id="me">Hello World</foo>');

  # Alternative

  $p2 = new XML::Parser(Handlers => {Start => \&handle_start,

				     End   => \&handle_end,

				     Char  => \&handle_char});

  $p2->parse($socket);

  # Another alternative

  $p3 = new XML::Parser(ErrorContext => 2);

  $p3->setHandlers(Char    => \&text,

		   Default => \&other);

  open(FOO, 'xmlgenerator |');

  $p3->parse(*FOO, ProtocolEncoding => 'ISO-8859-1');

  close(FOO);

  $p3->parsefile('junk.xml', ErrorContext => 3);

=head1 DESCRIPTION

This module provides ways to parse XML documents. It is built on top of

L<XML::Parser::Expat>, which is a lower level interface to James Clark's

expat library. Each call to one of the parsing methods creates a new

instance of XML::Parser::Expat which is then used to parse the document.

Expat options may be provided when the XML::Parser object is created.

These options are then passed on to the Expat object on each parse call.

They can also be given as extra arguments to the parse methods, in which

case they override options given at XML::Parser creation time.

The behavior of the parser is controlled either by C<L</Style>> and/or

C<L</Handlers>> options, or by L</setHandlers> method. These all provide

mechanisms for XML::Parser to set the handlers needed by XML::Parser::Expat.

If neither C<Style> nor C<Handlers> are specified, then parsing just

checks the document for being well-formed.

When underlying handlers get called, they receive as their first parameter

the I<Expat> object, not the Parser object.

=head1 METHODS

=over 4

=item new

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

as keyword value pairs. Recognized options are:

=over 4

=item * Style

This option provides an easy way to create a given style of parser. The

built in styles are: L<"Debug">, L<"Subs">, L<"Tree">, L<"Objects">,

and L<"Stream">.

Custom styles can be provided by giving a full package name containing

at least one '::'. This package should then have subs defined for each

handler it wishes to have installed. See L<"STYLES"> below

for a discussion of each built in style.

=item * Handlers

When provided, this option should be an anonymous hash containing as

keys the type of handler and as values a sub reference to handle that

type of event. All the handlers get passed as their 1st parameter the

instance of expat that is parsing the document. Further details on

handlers can be found in L<"HANDLERS">. Any handler set here

overrides the corresponding handler set with the Style option.

=item * Pkg

Some styles will refer to subs defined in this package. If not provided,

it defaults to the package which called the constructor.

=item * ErrorContext

This is an Expat option. When this option is defined, errors are reported

in context. The value should be the number of lines to show on either side

of the line in which the error occurred.

=item * ProtocolEncoding

This is an Expat option. This sets the protocol encoding name. It defaults

to none. The 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. Check L<"ENCODINGS"> for

more information on encoding maps. Setting the protocol encoding overrides

any encoding in the XML declaration.

=item * Namespaces

This is an Expat option. If this is set to a true value, then namespace

processing is done during the parse. See L<XML::Parser::Expat/"Namespaces">

for further discussion of namespace processing.

=item * NoExpand

This is an Expat option. 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 is an Expat option. It 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 * ParseParamEnt

This is an Expat option. 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 * Non-Expat-Options

If provided, this should be an anonymous hash whose keys are options that

shouldn't be passed to Expat. This should only be of concern to those

subclassing XML::Parser.

=back

=item  setHandlers(TYPE, HANDLER [, TYPE, HANDLER [...]])

This method registers handlers for various parser events. It overrides any

previous handlers registered through the Style or Handler options or through

earlier calls to setHandlers. By providing a false or undefined value as

the handler, the existing handler can be unset.

This method returns a list of type, handler pairs corresponding to the

input. The handlers returned are the ones that were in effect prior to

the call.

See a description of the handler types in L<"HANDLERS">.

=item parse(SOURCE [, OPT => OPT_VALUE [...]])

The SOURCE parameter should either be a string containing the whole XML

document, or it should be an open IO::Handle. Constructor options to

XML::Parser::Expat given as keyword-value pairs may follow the SOURCE

parameter. These override, for this call, any options or attributes passed

through from the XML::Parser instance.

A die call is thrown if a parse error occurs. Otherwise it will return 1

or whatever is returned from the B<Final> handler, if one is installed.

In other words, what parse may return depends on the style.

=item parsestring

This is just an alias for parse for backwards compatibility.

=item parsefile(FILE [, OPT => OPT_VALUE [...]])

Open FILE for reading, then call parse with the open handle. The file

is closed no matter how parse returns. Returns what parse returns.

=item parse_start([ OPT => OPT_VALUE [...]])

Create and return a new instance of XML::Parser::ExpatNB. Constructor

options may be provided. If an init handler has been provided, it is

called before returning the ExpatNB object. Documents are parsed by

making incremental calls to the parse_more method of this object, which

takes a string. A single call to the parse_done method of this object,

which takes no arguments, indicates that the document is finished.

If there is a final handler installed, it is executed by the parse_done

method before returning and the parse_done method returns whatever is

returned by the final handler.

=back

=head1 HANDLERS

Expat is an event based parser. As the parser recognizes parts of the

document (say the start or end tag for an XML element), then any handlers

registered for that type of an event are called with suitable parameters.

All handlers receive an instance of XML::Parser::Expat as their first

argument. See L<XML::Parser::Expat/"METHODS"> for a discussion of the

methods that can be called on this object.

=head2 Init		(Expat)

This is called just before the parsing of the document starts.

=head2 Final		(Expat)

This is called just after parsing has finished, but only if no errors

occurred during the parse. Parse returns what this returns.

=head2 Start		(Expat, Element [, Attr, Val [,...]])

This event is generated when an XML start tag is recognized. Element is the

name of the XML element type that is opened with the start tag. The Attr &

Val pairs are generated for each attribute in the start tag.

=head2 End		(Expat, 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.

=head2 Char		(Expat, 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.

=head2 Proc		(Expat, Target, Data)

This event is generated when a processing instruction is recognized.

=head2 Comment		(Expat, Data)

This event is generated when a comment is recognized.

=head2 CdataStart	(Expat)

This is called at the start of a CDATA section.

=head2 CdataEnd		(Expat)

This is called at the end of a CDATA section.

=head2 Default		(Expat, 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.

=head2 Unparsed		(Expat, 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.

=head2 Notation		(Expat, 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.

=head2 ExternEnt	(Expat, 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.

A default handler, XML::Parser::default_ext_ent_handler, is installed

for this. It only handles the file URL method and it assumes "file:" if

it isn't there. The expat base method can be used to set a basename for

relative pathnames. If no basename is given, or if the basename is itself

a relative name, then it is relative to the current working directory.

=head2 Entity		(Expat, 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.

=head2 Element		(Expat, 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.

=head2 Attlist		(Expat, 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.

=head2 Doctype		(Expat, 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.

=head2 XMLDecl		(Expat, 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.

=head1 STYLES

=head2 Debug

This just prints out the document in outline form. Nothing special is

returned by parse.

=head2 Subs

Each time an element starts, a sub by that name in the package specified

by the Pkg option is called with the same parameters that the Start

handler gets called with.

Each time an element ends, a sub with that name appended with an underscore

("_"), is called with the same parameters that the End handler gets called

with.

Nothing special is returned by parse.

=head2 Tree

Parse will return a parse tree for the document. Each node in the tree

takes the form of a tag, content pair. Text nodes are represented with

a pseudo-tag of "0" and the string that is their content. For elements,

the content is an array reference. The first item in the array is a

(possibly empty) hash reference containing attributes. The remainder of

the array is a sequence of tag-content pairs representing the content

of the element.

So for example the result of parsing:

  <foo><head id="a">Hello <em>there</em></head><bar>Howdy<ref/></bar>do</foo>

would be:

             Tag   Content

  ==================================================================

  [foo, [{}, head, [{id => "a"}, 0, "Hello ",  em, [{}, 0, "there"]],

	      bar, [         {}, 0, "Howdy",  ref, [{}]],

	        0, "do"

	]

  ]

The root document "foo", has 3 children: a "head" element, a "bar"

element and the text "do". After the empty attribute hash, these are

represented in it's contents by 3 tag-content pairs.

=head2 Objects

This is similar to the Tree style, except that a hash object is created for

each element. The corresponding object will be in the class whose name

is created by appending "::" and the element name to the package set with

the Pkg option. Non-markup text will be in the ::Characters class. The

contents of the corresponding object will be in an anonymous array that

is the value of the Kids property for that object.

=head2 Stream

This style also uses the Pkg package. If none of the subs that this

style looks for is there, then the effect of parsing with this style is

to print a canonical copy of the document without comments or declarations.

All the subs receive as their 1st parameter the Expat instance for the

document they're parsing.

It looks for the following routines:

=over 4

=item * StartDocument

Called at the start of the parse .

=item * StartTag

Called for every start tag with a second parameter of the element type. The $_

variable will contain a copy of the tag and the %_ variable will contain

attribute values supplied for that element.

=item * EndTag

Called for every end tag with a second parameter of the element type. The $_

variable will contain a copy of the end tag.

=item * Text

Called just before start or end tags with accumulated non-markup text in

the $_ variable.

=item * PI

Called for processing instructions. The $_ variable will contain a copy of

the PI and the target and data are sent as 2nd and 3rd parameters

respectively.

=item * EndDocument

Called at conclusion of the parse.

=back

=head1 ENCODINGS

XML documents may be encoded in character sets other than Unicode as

long as they may be mapped into the Unicode character set. Expat has

further restrictions on encodings. Read the xmlparse.h header file in

the expat distribution to see details on these restrictions.

Expat has built-in encodings for: C<UTF-8>, C<ISO-8859-1>, C<UTF-16>, and

C<US-ASCII>. Encodings are set either through the XML declaration

encoding attribute or through the ProtocolEncoding option to XML::Parser

or XML::Parser::Expat.

For encodings other than the built-ins, expat calls the function

load_encoding in the Expat package with the encoding name. This function

looks for a file in the path list @XML::Parser::Expat::Encoding_Path, that

matches the lower-cased name with a '.enc' extension. The first one it

finds, it loads.

If you wish to build your own encoding maps, check out the XML::Encoding

module from CPAN.

=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