Expat(3pm) User Contributed Perl Documentation Expat(3pm)
NAME
XML::Parser::Expat - Lowlevel access to James Clark's expat XML parser
SYNOPSIS
use XML::Parser::Expat;
$parser = XML::Parser::Expat->new;
$parser->setHandlers('Start' => \&sh,
'End' => \&eh,
'Char' => \&ch);
open(my $fh, '<', 'info.xml') or die "Couldn't open";
$parser->parse($fh);
close($fh);
# $parser->parse('<foo id="me"> here <em>we</em> go </foo>');
sub sh
{
my ($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:
• ProtocolEncoding
The protocol encoding name. The default is none. The expat
built-in encodings are: "UTF-8", "ISO-8859-1", "UTF-16", and
"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.
• 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 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 "namespace" method and two
names can be checked for absolute equality with the "eq_name"
method.
• 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.
• 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.
• 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.
• 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.
• Base
The base to use for relative pathnames or URLs. This can also be
done by using the base method.
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:
• 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.
• 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.
• 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.
• Proc (Parser, Target, Data)
This event is generated when a processing instruction is
recognized.
• Comment (Parser, String)
This event is generated when a comment is recognized.
• CdataStart (Parser)
This is called at the start of a CDATA section.
• CdataEnd (Parser)
This is called at the end of a CDATA section.
• 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.
• 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.
• 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.
• 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).
• ExternEntFin (Parser)
This is called after an external entity has been parsed. It
allows applications to perform cleanup on actions performed in
the above ExternEnt handler.
• Entity (Parser, Name, Val, Sysid, Pubid, Ndata,
IsParam)
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 the IsParam parameter is true.
Note that this handler and the Unparsed handler above overlap.
If both are set, then this handler will not be called for
unparsed entities.
• 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 an XML::Parser::ContentModel object. See
"XML::Parser::ContentModel Methods" for methods available for
this class.
• 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.
• 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 will be true or false, indicating
whether or not the doctype declaration contains an internal
subset.
• DoctypeFin (Parser)
This handler is called after parsing of the DOCTYPE declaration
has finished, including any internal or external DTD
declarations.
• XMLDecl (Parser, Version, Encoding, Standalone)
This handler is called for XML declarations. Version is a string
containing the version. Encoding is either undefined or contains
an encoding string. Standalone is either undefined, or true or
false. Undefined indicates that no standalone parameter was
given in the XML declaration. True or false indicates "yes" or
"no" respectively.
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 elsewhere (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 start-tag string. The string is encoded
in UTF-8. This method doesn't return a meaningful string inside
declaration handlers.
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. This method doesn't return a meaningful string
inside declaration handlers.
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. This method doesn't deliver a meaningful string to
the default handler when called from inside declaration handlers.
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::ContentModel Methods
The element declaration handlers are passed objects of this class as the
content model of the element declaration. They also represent content
particles, components of a content model.
When referred to as a string, these objects are automagically converted
to a string representation of the model (or content particle).
isempty
This method returns true if the object is "EMPTY", false otherwise.
isany
This method returns true if the object is "ANY", false otherwise.
ismixed
This method returns true if the object is "(#PCDATA)" or
"(#PCDATA|...)*", false otherwise.
isname
This method returns if the object is an element name.
ischoice
This method returns true if the object is a choice of content
particles.
isseq
This method returns true if the object is a sequence of content
particles.
quant
This method returns undef or a string representing the quantifier
('?', '*', '+') associated with the model or particle.
children
This method returns undef or (for mixed, choice, and sequence types)
an array of component content particles. There will always be at
least one component for choices and sequences, but for a mixed
content model of pure PCDATA, "(#PCDATA)", then an undef is
returned.
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 automatically 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.
perl v5.40.1 2026-03-21 Expat(3pm)
Generated by dwww version 1.16 on Sat Oct 3 05:01:08 CEST 2026.