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XML::Bare.3pm

NAME

XML::Bare - Minimal XML parser implemented via a C state engine

VERSION

0.11

SYNOPSIS

  use XML::Bare;

  my $xml = new XML::Bare( text => '<xml><name>Bob</name></xml>' );

  # Parse the xml into a hash tree

  my $root = $xml->parse();

  # Print the content of the name node

  print $root->{xml}->{name}->{value};

  # Load xml from a file ( assume same contents as first example )

  my $xml2 = new XML::Bare( file => 'test.xml' );

  my $root2 = $xml2->parse();

  $root2->{xml}->{name}->{value} = 'Tim';

  # Save the changes back to the file

  $xml2->save();

DESCRIPTION

This module is a 'Bare' XML parser. It is implemented in C++. The parser itself is a simple state engine that is less than 500 lines of C++. The parser builds a C++ class tree from input text. That C++ class tree is converted to a Perl hash by a Perl function that makes basic calls back to the C++ to go through the nodes sequentially.

Supported XML

To demonstrate what sort of XML is supported, consider the following examples. Each of the PERL statements evaluates to true.

* Node containing just text

  XML: <xml>blah</xml>

  PERL: $root->{xml}->{value} eq "blah";

* Subset nodes

  XML: <xml><name>Bob</name></xml>

  PERL: $root->{xml}->{name}->{value} eq "Bob";

* Attributes unquoted

  XML: <xml><a href=index.htm>Link</a></xml>

  PERL: $root->{xml}->{a}->{href}->{value} eq "index.htm";

* Attributes quoted

  XML: <xml><a href="index.htm">Link</a></xml>

  PERL: $root->{xml}->{a}->{href}->{value} eq "index.htm";

* CDATA nodes

  XML: <xml><raw><![CDATA[some raw $~<!bad xml<>]]></raw></xml>

  PERL: $root->{xml}->{raw}->{value} eq "some raw \$~<!bad xml<>";

* Multiple nodes; form array

  XML: <xml><item>1</item><item>2</item></xml>

  PERL: $root->{xml}->{item}->[0]->{value} eq "1";

* Forcing array creation

  XML: <xml><multi_item/><item>1</item></xml>

  PERL: $root->{xml}->{item}->[0]->{value} eq "1";

Parsed Hash Structure

The hash structure returned from XML parsing is created in a specific format. Besides as described above, the structure contains some additional nodes in order to preserve information that will allow that structure to be correctly converted back to XML.

Nodes may contain the following 2 additional subnodes:

* pos

This is a number indicating the ordering of nodes. It is used to allow items in a perl hash to be sorted when writing back to xml. Note that items are not sorted after parsing in order to save time if all you are doing is reading and you do not care about the order.

In future versions of this module an option will be added to allow you to sort your nodes so that you can read them in order.

* att

This is a boolean value that exists and is 1 iff the node is an attribute.

Parsing Limitations / Features

* CDATA parsed correctly, but stripped if unneeded

Currently the contents of a node that are CDATA are read and put into the value hash, but the hash structure does not have a value indicating the node contains CDATA.

When converting back to XML, the contents are the value hash are parsed to check for xml incompatible data using a regular expression. If 'CDATA like' stuff is encountered, the node is output as CDATA.

* Node position stored, but hash remains unsorted

The ordering of nodes is noted using the 'pos' value, but the hash itself is not ordered after parsing. Currently items will be out of order when looking at them in the hash.

Note that when converted but to XML, the nodes are then sorted and output in the correct order to XML.

* Comments are parsed, but discarded

Comments can exist in the XML, but they are thrown away during parsing.

* PI sections are parsed, but discarded

* Unknown <! sections are parsed, but discarded

* Attributes must use double quotes if quoted

Attributes in XML can be used, with or without quotes, but if quotes are used they must be double quotes. If single quotes are used, the value will end up starting with a single quote and continue until a space or a node end.

* Quoted attributes cannot contain escaped quotes

No escape character is recognized within quotes. As a result, there is no way to store a double quote character in an attribute value.

* Attributes are always written back to XML with quotes

* Nodes cannot contain subnodes as well as an immediate value

Actually nodes can in fact contain a value as well, but that value will be discarded if you write back to XML. That value is equal to the first continuous string of text besides a subnode.

  <node>text<subnode/>text2</node>

  ( the value of node is text )

  <node><subnode/>text</node>

  ( the value of node is text )

  <node>

    <subnode/>text

  </node>

  ( the value of node is "\n  " )

Module Functions

* $ob = new XML::Bare( text => [some xml] )

Create a new XML object, with the given text as the xml source.

* $object = new XML::Bare( file => [filename] )

Create a new XML object, with the given filename/path as the xml source

* $object = new XML::Bare( text => [some xml], file => [filename] )

Create a new XML object, with the given text as the xml input, and the given filename/path as the potential output ( used by save() )

* $tree = $object->parse()

Parse the xml of the object and return a tree reference

* $text = $object->xml( [root] )

Take the hash tree in [root] and turn it into cleanly indented ( 2 spaces ) XML text.

* $object->save()

The the current tree in the object, cleanly indent it, and save it to the file paramter specified when creating the object.

* $text = XML::Bare::clean( text => [some xml] )

Shortcut to creating an xml object and immediately turning it into clean xml text.

* $text = XML::Bare::clean( file => [filename] )

Similar to previous.

* XML::Bare::clean( file => [filename], save => 1 )

Clean up the xml in the file, saving the results back to the file

* XML::Bare::clean( text => [some xml], save => [filename] )

Clean up the xml provided, and save it into the specified file.

* XML::Bare::clean( file => [filename1], save => [filename2] )

Clean up the xml in filename1 and save the results to filename2.

* $object->add_node( [node], [nodeset name], name => value, name2 => value2, ... )

  Example:

    $object->add_node( $root->{xml}, 'item', name => 'Bob' );

  Result:

    <xml>

      <item>

        <name>Bob</name>

      </item>

    </xml>

* $object->del_node( [node], [nodeset name], name => value )

  Example:

    Starting XML:

      <xml>

        <a>

          <b>1</b>

        </a>

        <a>

          <b>2</b>

        </a>

      </xml>

    Code:

      $xml->del_node( $root->{xml}, 'a', b=>'1' );

    Ending XML:

      <xml>

        <a>

          <b>2</b>

        </a>

      </xml>

* $object->find_node( [node], [nodeset name], name => value )

  Example:

    Starting XML:

      <xml>

        <ob>

          <key>1</key>

          <val>a</val>

        </ob>

        <ob>

          <key>2</key>

          <val>b</val>

        </ob>

      </xml>

    Code:

      $object->find_node( $root->{xml}, 'ob', key => '1' )->{val}->{value} = 'test';

    Ending XML:

      <xml>

        <ob>

          <key>1</key>

          <val>test</val>

        </ob>

        <ob>

          <key>2</key>

          <val>b</val>

        </ob>

      </xml>

* XML::Bare::merge( [nodeset1], [nodeset2], [id node name] )

Merges the nodes from nodeset2 into nodeset1, matching the contents of each node based up the content in the id node.

Example:

  Code:

    my $ob1 = new XML::Bare( text => "

      <xml>

        <multi_a/>

        <a>bob</a>

        <a>

          <id>1</id>

          <color>blue</color>

        </a>

      </xml>" );

    my $ob2 = new XML::Bare( text => "

      <xml>

        <multi_a/>

        <a>john</a>

        <a>

          <id>1</id>

          <name>bob</name>

          <bob>1</bob>

        </a>

      </xml>" );

    my $root1 = $ob1->parse();

    my $root2 = $ob2->parse();

    merge( $root1->{'xml'}->{'a'}, $root2->{'xml'}->{'a'}, 'id' );

    print $ob1->xml( $root1 );

  Output:

    <xml>

      <multi_a></multi_a>

      <a>bob</a>

      <a>

        <id>1</id>

        <color>blue</color>

        <name>bob</name>

        <bob>1</bob>

      </a>

    </xml>

LICENSE

  Copyright (C) 2007 David Helkowski

  This program is free software; you can redistribute it and/or

  modify it under the terms of the GNU General Public License as

  published by the Free Software Foundation; either version 2 of the

  License, or (at your option) any later version.  You may also can

  redistribute it and/or modify it under the terms of the Perl

  Artistic License.

  This program is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  GNU General Public License for more details.