=head1 NAME

XML::LibXML::Simple - XML::LibXML clone of XML::Simple::XMLin()

=head1 INHERITANCE

 XML::LibXML::Simple
   is a Exporter

=head1 SYNOPSIS

  use XML::LibXML::Simple   qw(XMLin);
  my $xml = XMLin <xml file or string>, OPTIONS;

Or the Object Oriented way:

  use XML::LibXML::Simple   ();
  my $xs = XML::Simple->new(OPTIONS);
  my $ref = $xs->XMLin(<xml file or string>, OPTIONS);

=head1 DESCRIPTION

This module is a blunt rewrite of XML::Simple (by Grant McLean) to
use the XML::LibXML parser for XML structures, where the original
uses plain Perl or SAX parsers.

=head1 METHODS

=head2 Constructors

XML::LibXML::Simple-E<gt>B<new>(OPTIONS)

=over 4

Instantiate an object, which can be used to call L<XMLin()|XML::LibXML::Simple/"Translators"> on.  You can
provide OPTIONS to this constructor (to be reused for each call to XMLin)
and with each call of XMLin (to be used once)

For XML-DATA and descriptions of the OPTIONS see the L</DETAILS>
section of this manual page.

=back

=head2 Translators

$obj-E<gt>B<XMLin>(XML-DATA, OPTIONS)

=over 4

For XML-DATA and descriptions of the OPTIONS see the L</DETAILS>
section of this manual page.

=back

=head1 FUNCTIONS

The functions C<XMLin> (exported implictly) and C<xml_in>
(exported on request) simply call C<< XML::Simple->new->XMLin() >>
with the provided parameters.

=head1 DETAILS

=head2 Differences with XML::Simple

In general, the output and the options are equivalent, although this
module has some differences with XML::Simple to be aware of.

=over 4

=item .

Only L<XMLin()|XML::LibXML::Simple/"Translators"> is supported: if you want to write XML the use a schema
(for instance with XML::Compile).  Do not attempt to create XML by
hand!  If you still think you need it, then have a look at XMLout() as
implemented by XML::Simple or any of a zillion template systems.

=item .

IMO, you should use a templating system if you want variables filled-in
in the input: it is not a task for this module.

=item .

Also, empty elements are not removed: being empty has a meaning which
should not be ignored.

=item .

There are a few small differences in the result of the C<forcearray> option,
because XML::Simple seems to behave inconsequently.

=back

=head2 Parameter XML-DATA

As first parameter to L<XMLin()|XML::LibXML::Simple/"Translators"> must provide the XML message to be
translated into a Perl structure.  Choose one of the following:

=over 4

=item A filename

If the filename contains no directory components, C<XMLin()> will look for the
file in each directory in the SearchPath (see OPTIONS below) and in the
current directory.  eg:

  $ref = XMLin('/etc/params.xml');

Note, the filename C<< - >> (dash) can be used to parse from STDIN.

=item undef

If there is no XML specifier, C<XMLin()> will check the script directory and
each of the SearchPath directories for a file with the same name as the script
but with the extension '.xml'.  Note: if you wish to specify options, you
must specify the value 'undef'.  eg:

  $ref = XMLin(undef, ForceArray => 1);

=item A string of XML

A string containing XML (recognised by the presence of '<' and '>' characters)
will be parsed directly.  eg:

  $ref = XMLin('<opt username="bob" password="flurp" />');

=item An IO::Handle object

An IO::Handle object will be read to EOF and its contents parsed. eg:

  $fh = IO::File->new('/etc/params.xml');
  $ref = XMLin($fh);

=back

=head2 OPTIONS

L<XML::LibXML::Simple|XML::LibXML::Simple> supports most options defined by XML::Simple, so
the interface is quite compatible.  Minor changes apply.  This explanation
is extracted from the XML::Simple manual-page.

=over 4

=item *

check out C<ForceArray> because you'll almost certainly want to turn it on

=item *

make sure you know what the C<KeyAttr> option does and what its default
value is because it may surprise you otherwise.

=item *

Option names are case in-sensitive so you can use the mixed case versions
shown here; you can add underscores between the words (eg: key_attr)
if you like.

=back

In alphabetic order:

=over 4

=item ContentKey => 'keyname' I<# seldom used>

When text content is parsed to a hash value, this option let's you specify a
name for the hash key to override the default 'content'.  So for example:

  XMLin('<opt one="1">Text</opt>', ContentKey => 'text')

will parse to:

  { 'one' => 1, 'text' => 'Text' }

instead of:

  { 'one' => 1, 'content' => 'Text' }

You can also prefix your selected key name with a '-' character to have 
C<XMLin()> try a little harder to eliminate unnecessary 'content' keys after
array folding.  For example:

  XMLin(
    '<opt><item name="one">First</item><item name="two">Second</item></opt>', 
    KeyAttr => {item => 'name'}, 
    ForceArray => [ 'item' ],
    ContentKey => '-content'
  )

will parse to:

  {
    'item' => {
      'one' =>  'First'
      'two' =>  'Second'
    }
  }

rather than this (without the '-'):

  {
    'item' => {
      'one' => { 'content' => 'First' }
      'two' => { 'content' => 'Second' }
    }
  }

=item ForceArray => 1 I<# important>

This option should be set to '1' to force nested elements to be represented
as arrays even when there is only one.  Eg, with ForceArray enabled, this
XML:

    <opt>
      <name>value</name>
    </opt>

would parse to this:

    {
      'name' => [
                  'value'
                ]
    }

instead of this (the default):

    {
      'name' => 'value'
    }

This option is especially useful if the data structure is likely to be written
back out as XML and the default behaviour of rolling single nested elements up
into attributes is not desirable. 

If you are using the array folding feature, you should almost certainly
enable this option.  If you do not, single nested elements will not be
parsed to arrays and therefore will not be candidates for folding to a
hash.  (Given that the default value of 'KeyAttr' enables array folding,
the default value of this option should probably also have been enabled
as well).

=item ForceArray => [ names ] I<# important>

This alternative (and preferred) form of the 'ForceArray' option allows you to
specify a list of element names which should always be forced into an array
representation, rather than the 'all or nothing' approach above.

It is also possible to include compiled regular
expressions in the list --any element names which match the pattern
will be forced to arrays.  If the list contains only a single regex,
then it is not necessary to enclose it in an arrayref.  Eg:

  ForceArray => qr/_list$/

=item ForceContent => 1 I<# seldom used>

When C<XMLin()> parses elements which have text content as well as attributes,
the text content must be represented as a hash value rather than a simple
scalar.  This option allows you to force text content to always parse to
a hash value even when there are no attributes.  So for example:

  XMLin('<opt><x>text1</x><y a="2">text2</y></opt>', ForceContent => 1)

will parse to:

  {
    'x' => {           'content' => 'text1' },
    'y' => { 'a' => 2, 'content' => 'text2' }
  }

instead of:

  {
    'x' => 'text1',
    'y' => { 'a' => 2, 'content' => 'text2' }
  }

=item GroupTags => { grouping tag => grouped tag } I<# handy>

You can use this option to eliminate extra levels of indirection in your Perl
data structure.  For example this XML:

  <opt>
   <searchpath>
     <dir>/usr/bin</dir>
     <dir>/usr/local/bin</dir>
     <dir>/usr/X11/bin</dir>
   </searchpath>
 </opt>

Would normally be read into a structure like this:

  {
    searchpath => {
                    dir => [ '/usr/bin', '/usr/local/bin', '/usr/X11/bin' ]
                  }
  }

But when read in with the appropriate value for 'GroupTags':

  my $opt = XMLin($xml, GroupTags => { searchpath => 'dir' });

It will return this simpler structure:

  {
    searchpath => [ '/usr/bin', '/usr/local/bin', '/usr/X11/bin' ]
  }

The grouping element (C<< <searchpath> >> in the example) must not contain any
attributes or elements other than the grouped element.

You can specify multiple 'grouping element' to 'grouped element' mappings in
the same hashref.  If this option is combined with C<KeyAttr>, the array
folding will occur first and then the grouped element names will be eliminated.

=item KeepRoot => 1 I<# handy>

In its attempt to return a data structure free of superfluous detail and
unnecessary levels of indirection, C<XMLin()> normally discards the root
element name.  Setting the 'KeepRoot' option to '1' will cause the root element
name to be retained.  So after executing this code:

  $config = XMLin('<config tempdir="/tmp" />', KeepRoot => 1)

You'll be able to reference the tempdir as
C<$config-E<gt>{config}-E<gt>{tempdir}> instead of the default
C<$config-E<gt>{tempdir}>.

=item KeyAttr => [ list ] I<# important>

This option controls the 'array folding' feature which translates nested
elements from an array to a hash.  It also controls the 'unfolding' of hashes
to arrays.

For example, this XML:

    <opt>
      <user login="grep" fullname="Gary R Epstein" />
      <user login="stty" fullname="Simon T Tyson" />
    </opt>

would, by default, parse to this:

    {
      'user' => [
                  {
                    'login' => 'grep',
                    'fullname' => 'Gary R Epstein'
                  },
                  {
                    'login' => 'stty',
                    'fullname' => 'Simon T Tyson'
                  }
                ]
    }

If the option 'KeyAttr => "login"' were used to specify that the 'login'
attribute is a key, the same XML would parse to:

    {
      'user' => {
                  'stty' => {
                              'fullname' => 'Simon T Tyson'
                            },
                  'grep' => {
                              'fullname' => 'Gary R Epstein'
                            }
                }
    }

The key attribute names should be supplied in an arrayref if there is more
than one.  C<XMLin()> will attempt to match attribute names in the order
supplied.

Note 1: The default value for 'KeyAttr' is C<< ['name', 'key', 'id'] >>.
If you do not want folding on input or unfolding on output you must
setting this option to an empty list to disable the feature.

Note 2: If you wish to use this option, you should also enable the
C<ForceArray> option.  Without 'ForceArray', a single nested element will be
rolled up into a scalar rather than an array and therefore will not be folded
(since only arrays get folded).

=item KeyAttr => { list } I<# important>

This alternative (and preferred) method of specifiying the key attributes
allows more fine grained control over which elements are folded and on which
attributes.  For example the option 'KeyAttr => { package => 'id' } will cause
any package elements to be folded on the 'id' attribute.  No other elements
which have an 'id' attribute will be folded at all. 

Two further variations are made possible by prefixing a '+' or a '-' character
to the attribute name:

The option 'KeyAttr => { user => "+login" }' will cause this XML:

    <opt>
      <user login="grep" fullname="Gary R Epstein" />
      <user login="stty" fullname="Simon T Tyson" />
    </opt>

to parse to this data structure:

    {
      'user' => {
                  'stty' => {
                              'fullname' => 'Simon T Tyson',
                              'login'    => 'stty'
                            },
                  'grep' => {
                              'fullname' => 'Gary R Epstein',
                              'login'    => 'grep'
                            }
                }
    }

The '+' indicates that the value of the key attribute should be copied
rather than moved to the folded hash key.

A '-' prefix would produce this result:

    {
      'user' => {
                  'stty' => {
                              'fullname' => 'Simon T Tyson',
                              '-login'    => 'stty'
                            },
                  'grep' => {
                              'fullname' => 'Gary R Epstein',
                              '-login'    => 'grep'
                            }
                }
    }

=item NoAttr => 1 I<# handy>

When used with C<XMLin()>, any attributes in the XML will be ignored.

=item NormaliseSpace => 0 | 1 | 2 I<# handy>

This option controls how whitespace in text content is handled.  Recognised
values for the option are:

=over 4

=item 0

(default) whitespace is passed through unaltered (except of course for the
normalisation of whitespace in attribute values which is mandated by the XML
recommendation)

=item 1

whitespace is normalised in any value used as a hash key (normalising means
removing leading and trailing whitespace and collapsing sequences of whitespace
characters to a single space)

=item 2

whitespace is normalised in all text content

=back

Note: you can spell this option with a 'z' if that is more natural for you.

=item SearchPath => [ list ] I<# handy>

If you pass C<XMLin()> a filename, but the filename include no directory
component, you can use this option to specify which directories should be
searched to locate the file.  You might use this option to search first in the
user's home directory, then in a global directory such as /etc.

If a filename is provided to C<XMLin()> but SearchPath is not defined, the
file is assumed to be in the current directory.

If the first parameter to C<XMLin()> is undefined, the default SearchPath
will contain only the directory in which the script itself is located.
Otherwise the default SearchPath will be empty.  

=item ValueAttr => [ names ] I<# in - handy>

Use this option to deal elements which always have a single attribute and no
content.  Eg:

  <opt>
    <colour value="red" />
    <size   value="XXL" />
  </opt>

Setting C<< ValueAttr => [ 'value' ] >> will cause the above XML to parse to:

  {
    colour => 'red',
    size   => 'XXL'
  }

instead of this (the default):

  {
    colour => { value => 'red' },
    size   => { value => 'XXL' }
  }

=item NsExpand => 0  I<advised>

When name-spaces are used, the default behavior is to include the
prefix in the key name.  However, this is very dangerous: the prefixes
can be changed without a change of the XML message meaning.  Therefore,
you can better use this C<NsExpand> option.  The downside, however, is
that the labels get very long.

Without this option:

  <record xmlns:x="http://xyz">
    <x:field1>42</x:field1>
  </record>
  <record xmlns:y="http://xyz">
    <y:field1>42</y:field1>
  </record>

translates into

  { 'x:field1' => 42 }
  { 'y:field1' => 42 }

but both source component have exactly the same meaning.  When C<NsExpand>
is used, the result is:

  { '{http://xyz}field1' => 42 }
  { '{http://xyz}field1' => 42 }

Of course, addressing these fields is more work.  It is advised to implement
it like this:

  my $ns = 'http://xyz';
  $data->{"{$ns}field1"};

=item NsStrip => 0 I<sloppy coding>

[not available in XML::Simple]
Namespaces are really important to avoid name collissions, but they are
a bit of a hassle.  To do it correctly, use option C<NsExpand>.  To do
it sloppy, use C<NsStrip>.  With this option set, the above example will
return

  { field1 => 42 }
  { field1 => 42 }

=back

=head1 COPYRIGHT

The interface design and large parts of the documentation were taken
from the L<XML::Simple> module, written by
Grant McLean E<lt>grantm@cpan.orgE<gt>

This version was composed by Mark Overmeer F<perl@overmeer.net>
See L<http://perl.overmeer.net/xml-libxml-simple>

