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=head1 NAME
XML::LibXML - Perl Binding for libxml2
=head1 SYNOPSIS
use XML::LibXML;
my $dom = XML::LibXML->load_xml(string => <<'EOT');
<some-xml/>
EOT
$Version_String = XML::LibXML::LIBXML_DOTTED_VERSION;
$Version_ID = XML::LibXML::LIBXML_VERSION;
$DLL_Version = XML::LibXML::LIBXML_RUNTIME_VERSION;
$libxmlnode = XML::LibXML->import_GDOME( $node, $deep );
$gdomenode = XML::LibXML->export_GDOME( $node, $deep );
=head1 DESCRIPTION
This module is an interface to libxml2, providing XML and HTML parsers with
DOM, SAX and XMLReader interfaces, a large subset of DOM Layer 3 interface
and
a XML::XPath-like interface to XPath API of libxml2. The module is split
into
several packages which are not described in this section; unless stated
otherwise, you only need to C<<<<<< use XML::LibXML;
>>>>>> in your programs.
Check out XML::LibXML by Example (L<<<<<<
http://grantm.github.io/perl-libxml-by-example/ >>>>>>)
for a tutorial.
For further information, please check the following documentation:
=over 4
=item L<<<<<< XML::LibXML::Parser
>>>>>>
Parsing XML files with XML::LibXML
=item L<<<<<< XML::LibXML::DOM >>>>>>
XML::LibXML Document Object Model (DOM) Implementation
=item L<<<<<< XML::LibXML::SAX >>>>>>
XML::LibXML direct SAX parser
=item L<<<<<< XML::LibXML::Reader
>>>>>>
Reading XML with a pull-parser
=item L<<<<<< XML::LibXML::Dtd >>>>>>
XML::LibXML frontend for DTD validation
=item L<<<<<< XML::LibXML::RelaxNG
>>>>>>
XML::LibXML frontend for RelaxNG schema validation
=item L<<<<<< XML::LibXML::Schema
>>>>>>
XML::LibXML frontend for W3C Schema schema validation
=item L<<<<<< XML::LibXML::XPathContext
>>>>>>
API for evaluating XPath expressions with enhanced support for the
evaluation
context
=item L<<<<<< XML::LibXML::InputCallback
>>>>>>
Implementing custom URI Resolver and input callbacks
=item L<<<<<< XML::LibXML::Common
>>>>>>
Common functions for XML::LibXML related Classes
=back
The nodes in the Document Object Model (DOM) are represented by the
following
classes (most of which "inherit" from L<<<<<<
XML::LibXML::Node >>>>>>):
=over 4
=item L<<<<<< XML::LibXML::Document
>>>>>>
XML::LibXML class for DOM document nodes
=item L<<<<<< XML::LibXML::Node >>>>>>
Abstract base class for XML::LibXML DOM nodes
=item L<<<<<< XML::LibXML::Element
>>>>>>
XML::LibXML class for DOM element nodes
=item L<<<<<< XML::LibXML::Text >>>>>>
XML::LibXML class for DOM text nodes
=item L<<<<<< XML::LibXML::Comment
>>>>>>
XML::LibXML class for comment DOM nodes
=item L<<<<<< XML::LibXML::CDATASection
>>>>>>
XML::LibXML class for DOM CDATA sections
=item L<<<<<< XML::LibXML::Attr >>>>>>
XML::LibXML DOM attribute class
=item L<<<<<< XML::LibXML::DocumentFragment
>>>>>>
XML::LibXML's DOM L2 Document Fragment implementation
=item L<<<<<< XML::LibXML::Namespace
>>>>>>
XML::LibXML DOM namespace nodes
=item L<<<<<< XML::LibXML::PI >>>>>>
XML::LibXML DOM processing instruction nodes
=back
=head1 ENCODINGS SUPPORT IN XML::LIBXML
Recall that since version 5.6.1, Perl distinguishes between character
strings
(internally encoded in UTF-8) and so called binary data and, accordingly,
applies either character or byte semantics to them. A scalar representing a
character string is distinguished from a byte string by special flag
(UTF8).
Please refer to I<<<<<< perlunicode
>>>>>> for details.
XML::LibXML's API is designed to deal with many encodings of XML
documents
completely transparently, so that the application using XML::LibXML can be
completely ignorant about the encoding of the XML documents it works with.
On
the other hand, functions like C<<<<<<
XML::LibXML::Document-E<gt>setEncoding >>>>>> give
the user control over the document encoding.
To ensure the aforementioned transparency and uniformity, most functions of
XML::LibXML that work with in-memory trees accept and return data as
character
strings (i.e. UTF-8 encoded with the UTF8 flag on) regardless of the
original
document encoding; however, the functions related to I/O operations (i.e.
parsing and saving) operate with binary data (in the original document
encoding) obeying the encoding declaration of the XML documents.
Below we summarize basic rules and principles regarding encoding:
=over 4
=item 1.
Do NOT apply any encoding-related PerlIO layers (C<<<<<<
:utf8 >>>>>> or C<<<<<< :encoding(...)
>>>>>>) to file handles that are an input for the parses
or an output for a
serializer of (full) XML documents. This is because the conversion of the
data
to/from the internal character representation is provided by libxml2 itself
which must be able to enforce the encoding specified by the
C<<<<<< E<lt>?xml version="1.0"
encoding="..."?E<gt> >>>>>> declaration.
Here is an example to follow:
use XML::LibXML;
# load
open my $fh, '<', 'file.xml';
binmode $fh; # drop all PerlIO layers possibly created by a use open
pragma
$doc = XML::LibXML->load_xml(IO => $fh);
# save
open my $out, '>', 'out.xml';
binmode $out; # as above
$doc->toFH($out);
# or
print {$out} $doc->toString();
=item 2.
All functions working with DOM accept and return character strings (UTF-8
encoded with UTF8 flag on). E.g.
my $doc = XML::LibXML::Document->new('1.0',$some_encoding);
my $element = $doc->createElement($name);
$element->appendText($text);
$xml_fragment = $element->toString(); # returns a character string
$xml_document = $doc->toString(); # returns a byte string
where C<<<<<< $some_encoding >>>>>> is
the document encoding that will be used when saving the document, and
C<<<<<< $name >>>>>> and
C<<<<<< $text >>>>>> contain character
strings (UTF-8 encoded with UTF8 flag on). Note that the
method C<<<<<< toString >>>>>> returns
XML as a character string if applied to other node than the Document
node and a byte string containing the appropriate
<?xml version="1.0" encoding="..."?>
declaration if applied to a L<<<<<< XML::LibXML::Document
>>>>>>.
=item 3.
DOM methods also accept binary strings in the original encoding of the
document
to which the node belongs (UTF-8 is assumed if the node is not attached to
any
document). Exploiting this feature is NOT RECOMMENDED since it is
considered
bad practice.
my $doc =
XML::LibXML::Document->new('1.0','iso-8859-2');
my $text = $doc->createTextNode($some_latin2_encoded_byte_string);
# WORKS, BUT NOT RECOMMENDED!
=back
I<<<<<< NOTE: >>>>>> libxml2 support
for many encodings is based on the iconv library. The actual
list of supported encodings may vary from platform to platform. To test if
your
platform works correctly with your language encoding, build a simple
document
in the particular encoding and try to parse it with XML::LibXML to see if
the
parser produces any errors. Occasional crashes were reported on rare
platforms
that ship with a broken version of iconv.
=head1 THREAD SUPPORT
XML::LibXML since 1.67 partially supports Perl threads in Perl >= 5.8.8.
XML::LibXML can be used with threads in two ways:
By default, all XML::LibXML classes use CLONE_SKIP class method to prevent
Perl
from copying XML::LibXML::* objects when a new thread is spawn. In this
mode,
all XML::LibXML::* objects are thread specific. This is the safest way to
work
with XML::LibXML in threads.
Alternatively, one may use
use threads;
use XML::LibXML qw(:threads_shared);
to indicate, that all XML::LibXML node and parser objects should be shared
between the main thread and any thread spawn from there. For example, in
my $doc = XML::LibXML->load_xml(location => $filename);
my $thr = threads->new(sub{
# code working with $doc
1;
});
$thr->join;
the variable C<<<<<< $doc >>>>>> refers
to the exact same XML::LibXML::Document in the spawned thread as in the
main thread.
Without using mutex locks, parallel threads may read the same document
(i.e.
any node that belongs to the document), parse files, and modify different
documents.
However, if there is a chance that some of the threads will attempt to
modify a
document (or even create new nodes based on that document, e.g. with
C<<<<<< $doc-E<gt>createElement
>>>>>>) that other threads may be reading at the same
time, the user is responsible
for creating a mutex lock and using it in I<<<<<< both
>>>>>> in the thread that modifies and the thread that
reads:
my $doc = XML::LibXML->load_xml(location => $filename);
my $mutex : shared;
my $thr = threads->new(sub{
lock $mutex;
my $el = $doc->createElement('foo');
# ...
1;
});
{
lock $mutex;
my $root = $doc->documentElement;
say $root->name;
}
$thr->join;
Note that libxml2 uses dictionaries to store short strings and these
dictionaries are kept on a document node. Without mutex locks, it could
happen
in the previous example that the thread modifies the dictionary while other
threads attempt to read from it, which could easily lead to a crash.
=head1 VERSION INFORMATION
Sometimes it is useful to figure out, for which version XML::LibXML was
compiled for. In most cases this is for debugging or to check if a given
installation meets all functionality for the package. The functions
XML::LibXML::LIBXML_DOTTED_VERSION and XML::LibXML::LIBXML_VERSION provide
this
version information. Both functions simply pass through the values of the
similar named macros of libxml2. Similarly,
XML::LibXML::LIBXML_RUNTIME_VERSION
returns the version of the (usually dynamically) linked libxml2.
=over 4
=item XML::LibXML::LIBXML_DOTTED_VERSION
$Version_String = XML::LibXML::LIBXML_DOTTED_VERSION;
Returns the version string of the libxml2 version XML::LibXML was compiled
for.
This will be "2.6.2" for "libxml2 2.6.2".
=item XML::LibXML::LIBXML_VERSION
$Version_ID = XML::LibXML::LIBXML_VERSION;
Returns the version id of the libxml2 version XML::LibXML was compiled for.
This will be "20602" for "libxml2 2.6.2". Don't
mix this version id with
$XML::LibXML::VERSION. The latter contains the version of XML::LibXML
itself
while the first contains the version of libxml2 XML::LibXML was compiled
for.
=item XML::LibXML::LIBXML_RUNTIME_VERSION
$DLL_Version = XML::LibXML::LIBXML_RUNTIME_VERSION;
Returns a version string of the libxml2 which is (usually dynamically)
linked
by XML::LibXML. This will be "20602" for libxml2 released as
"2.6.2" and
something like "20602-CVS2032" for a CVS build of libxml2.
XML::LibXML issues a warning if the version of libxml2 dynamically linked
to it
is less than the version of libxml2 which it was compiled against.
=back
=head1 EXPORTS
By default the module exports all constants and functions listed in the
:all
tag, described below.
=head1 EXPORT TAGS
=over 4
=item C<<<<<< :all >>>>>>
Includes the tags C<<<<<< :libxml
>>>>>>, C<<<<<< :encoding
>>>>>>, and C<<<<<< :ns
>>>>>> described below.
=item C<<<<<< :libxml >>>>>>
Exports integer constants for DOM node types.
XML_ELEMENT_NODE => 1
XML_ATTRIBUTE_NODE => 2
XML_TEXT_NODE => 3
XML_CDATA_SECTION_NODE => 4
XML_ENTITY_REF_NODE => 5
XML_ENTITY_NODE => 6
XML_PI_NODE => 7
XML_COMMENT_NODE => 8
XML_DOCUMENT_NODE => 9
XML_DOCUMENT_TYPE_NODE => 10
XML_DOCUMENT_FRAG_NODE => 11
XML_NOTATION_NODE => 12
XML_HTML_DOCUMENT_NODE => 13
XML_DTD_NODE => 14
XML_ELEMENT_DECL => 15
XML_ATTRIBUTE_DECL => 16
XML_ENTITY_DECL => 17
XML_NAMESPACE_DECL => 18
XML_XINCLUDE_START => 19
XML_XINCLUDE_END => 20
=item C<<<<<< :encoding >>>>>>
Exports two encoding conversion functions from XML::LibXML::Common.
encodeToUTF8()
decodeFromUTF8()
=item C<<<<<< :ns >>>>>>
Exports two convenience constants: the implicit namespace of the reserved
C<<<<<< xml: >>>>>> prefix, and the
implicit namespace for the reserved C<<<<<< xmlns:
>>>>>> prefix.
XML_XML_NS => 'http://www.w3.org/XML/1998/namespace'
XML_XMLNS_NS => 'http://www.w3.org/2000/xmlns/'
=back
=head1 RELATED MODULES
The modules described in this section are not part of the XML::LibXML
package
itself. As they support some additional features, they are mentioned here.
=over 4
=item L<<<<<< XML::LibXSLT >>>>>>
XSLT 1.0 Processor using libxslt and XML::LibXML
=item L<<<<<< XML::LibXML::Iterator
>>>>>>
XML::LibXML Implementation of the DOM Traversal Specification
=item L<<<<<< XML::CompactTree::XS
>>>>>>
Uses XML::LibXML::Reader to very efficiently to parse XML document or
element
into native Perl data structures, which are less flexible but significantly
faster to process then DOM.
=back
=head1 XML::LIBXML AND XML::GDOME
Note: I<<<<<< THE FUNCTIONS DESCRIBED HERE ARE STILL
EXPERIMENTAL >>>>>>
Although both modules make use of libxml2's XML capabilities, the DOM
implementation of both modules are not compatible. But still it is possible
to
exchange nodes from one DOM to the other. The concept of this exchange is
pretty similar to the function cloneNode(): The particular node is copied
on
the low-level to the opposite DOM implementation.
Since the DOM implementations cannot coexist within one document, one is
forced
to copy each node that should be used. Because you are always keeping two
nodes
this may cause quite an impact on a machines memory usage.
XML::LibXML provides two functions to export or import GDOME nodes:
import_GDOME() and export_GDOME(). Both function have two parameters: the
node
and a flag for recursive import. The flag works as in cloneNode().
The two functions allow one to export and import XML::GDOME nodes
explicitly,
however, XML::LibXML also allows the transparent import of XML::GDOME nodes
in
functions such as appendChild(), insertAfter() and so on. While native
nodes
are automatically adopted in most functions XML::GDOME nodes are always
cloned
in advance. Thus if the original node is modified after the operation, the
node
in the XML::LibXML document will not have this information.
=over 4
=item import_GDOME
$libxmlnode = XML::LibXML->import_GDOME( $node, $deep );
This clones an XML::GDOME node to an XML::LibXML node explicitly.
=item export_GDOME
$gdomenode = XML::LibXML->export_GDOME( $node, $deep );
Allows one to clone an XML::LibXML node into an XML::GDOME node.
=back
=head1 CONTACTS
For bug reports, please use the CPAN request tracker on
http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-LibXML
For suggestions etc., and other issues related to XML::LibXML you may use
the
perl XML mailing list (C<<<<<<
perl-xml@listserv.ActiveState.com >>>>>>), where most
XML-related Perl modules are discussed. In case of problems you
should check the archives of that list first. Many problems are already
discussed there. You can find the list's archives and subscription
options at L<<<<<<
http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml
>>>>>>.
=head1 AUTHORS
Matt Sergeant,
Christian Glahn,
Petr Pajas
=head1 VERSION
2.0210
=head1 COPYRIGHT
2001-2007, AxKit.com Ltd.
2002-2006, Christian Glahn.
2006-2009, Petr Pajas.
=cut
=head1 LICENSE
This program is free software; you can redistribute it and/or modify it
under
the same terms as Perl itself.