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Expat(3) |
User Contributed Perl Documentation |
Expat(3) |
XML::Parser::Expat - Lowlevel access to James Clark's expat XML parser
use XML::Parser::Expat;
$parser = XML::Parser::Expat->new;
$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
...
}
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.
- 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.
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 automagicly
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.
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.
- 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.
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.
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