David Helkowski > XML-Bare-0.45 > XML::Bare



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Module Version: 0.45   Source   Latest Release: XML-Bare-0.53


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




  use XML::Bare;
  my $ob = new XML::Bare( text => '<xml><name>Bob</name></xml>' );
  # Parse the xml into a hash tree
  my $root = $ob->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 $ob2 = new XML::Bare( file => 'test.xml' );
  my $root2 = $ob2->parse();
  $root2->{xml}->{name}->{value} = 'Tim';
  # Save the changes back to the file
  # Load xml and verify against XBS ( XML Bare Schema )
  my $xml_text = '<xml><item name=bob/></xml>''
  my $schema_text = '<xml><item* name=[a-z]+></item*></xml>'
  my $ob = new XML::Bare( text => $xml_text, schema => { text => $schema_text } );
  $ob->parse(); # this will error out if schema is invalid


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 struct tree from input text. That C struct 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.

The parser itself will only cease parsing if it encounters tags that are not closed properly. All other inputs will parse, even invalid inputs. To allowing checking for validity, a schema checker is included in the module as well.

The schema format is custom and is meant to be as simple as possible. It is based loosely around the way multiplicity is handled in Perl regular expressions.

Supported XML

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

Schema Checking

Schema checking is done by providing the module with an XBS (XML::Bare Schema) to check the XML against. If the XML checks as valid against the schema, parsing will continue as normal. If the XML is invalid, the parse function will die, providing information about the failure.

The following information is provided in the error message:

XBS ( XML::Bare Schema ) Format

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 3 additional subnodes:

Parsing Limitations / Features

Module Functions

Functions Used Internally


In comparison to other available perl xml parsers that create trees, XML::Bare is extremely fast. In order to measure the performance of loading and parsing compared to the alternatives, a templated speed comparison mechanism has been created and included with XML::Bare.

The include makebench.pl file runs when you make the module and creates perl files within the bench directory corresponding to the .tmpl contained there.

Currently there are three types of modules that can be tested against, executable parsers ( exe.tmpl ), tree parsers ( tree.tmpl ), and parsers that do not generated trees ( notree.tmpl ).

A full list of modules currently tested against is as follows:

  Tiny XML (exe)
  EzXML (exe)
  XMLIO (exe)
  XML::LibXML (notree)
  XML::Parser (notree)
  XML::Parser::Expat (notree)
  XML::Descent (notree)
  XML::Simple using XML::Parser
  XML::Simple using XML::SAX::PurePerl
  XML::Simple using XML::LibXML::SAX::Parser
  XML::Simple using XML::Bare::SAX::Parser

To run the comparisons, run the appropriate perl file within the bench directory. ( exe.pl, tree.pl, or notree.pl )

The script measures the milliseconds of loading and parsing, and compares the time against the time of XML::Bare. So a 7 means it takes 7 times as long as XML::Bare.

Here is a combined table of the script run against each alternative using the included test.xml:

  -Module-                   load     parse    total
  XML::Bare                  1        1        1
  XML::TreePP                2.3063   33.1776  6.1598
  XML::Parser::EasyTree      4.9405   25.7278  7.4571
  XML::Handler::Trees        7.2303   26.5688  9.6447
  XML::Trivial               5.0636   12.4715  7.3046
  XML::Smart                 6.8138   78.7939  15.8296
  XML::Simple (XML::Parser)  2.3346   50.4772  10.7455
  XML::Simple (PurePerl)     2.361    261.4571 33.6524
  XML::Simple (LibXML)       2.3187   163.7501 23.1816
  XML::Simple (XML::Bare)    2.3252   59.1254  10.9163
  XML::SAX::Simple           8.7792   170.7313 28.3634
  XML::Twig                  27.8266  56.4476  31.3594
  XML::Grove::Builder        7.1267   26.1672  9.4064
  XML::XPath::XMLParser      9.7783   35.5486  13.0002
  XML::LibXML (notree)       11.0038  4.5758   10.6881
  XML::Parser (notree)       4.4698   17.6448  5.8609
  XML::Parser::Expat(notree) 3.7681   50.0382  6.0069
  XML::Descent (notree)      6.0525   37.0265  11.0322
  Tiny XML (exe)                               1.0095
  EzXML (exe)                                  1.1284
  XMLIO (exe)                                  1.0165

Here is a combined table of the script run against each alternative using the included feed2.xml:

  -Module-                   load     parse    total
  XML::Bare                  1        1        1
  XML::TreePP                2.3068   23.7554  7.6921
  XML::Parser::EasyTree      4.8799   25.3691  9.6257
  XML::Handler::Trees        6.8545   33.1007  13.0575
  XML::Trivial               5.0105   32.0043  11.4113
  XML::Simple (XML::Parser)  2.3498   41.9007  12.3062
  XML::Simple (PurePerl)     2.3551   224.3027 51.7832
  XML::Simple (LibXML)       2.3617   88.8741  23.215
  XML::Simple (XML::Bare)    2.4319   37.7355  10.2343
  XML::Simple                2.7168   90.7203  26.7525
  XML::SAX::Simple           8.7386   94.8276  29.2166
  XML::Twig                  28.3206  48.1014  33.1222
  XML::Grove::Builder        7.2021   30.7926  12.9334
  XML::XPath::XMLParser      9.6869   43.5032  17.4941
  XML::LibXML (notree)       11.0023  5.022    10.5214
  XML::Parser (notree)       4.3748   25.0213  5.9803
  XML::Parser::Expat(notree) 3.6555   51.6426  7.4316
  XML::Descent (notree)      5.9206   155.0289 18.7767
  Tiny XML (exe)                               1.2212
  EzXML (exe)                                  1.3618
  XMLIO (exe)                                  1.0145

These results show that XML::Bare is, at least on the test machine, running all tests within cygwin, faster at loading and parsing than everything being tested against.

The following things are shown as well: - XML::Bare can parse XML and create a hash tree in less time than it takes LibXML just to parse. - XML::Bare can parse XML and create a tree in less time than all three binary parsers take just to parse.

Note that the executable parsers are not perl modules and are timed using dummy programs that just uses the library to load and parse the example files. The executables are not included with this program. Any source modifications used to generate the shown test results can be found in the bench/src directory of the distribution


  Copyright (C) 2008 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
  GNU General Public License for more details.
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