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Bare(3)               User Contributed Perl Documentation              Bare(3)

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

VERSION
       0.45

SYNOPSIS
         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
         $ob2->save();

         ---

         # 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

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 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.

       o Node containing just text

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

       o Subset nodes

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

       o Attributes unquoted

           XML: <xml><a href=index.htm>Link</a></xml>
           PERL: $root->{xml}->{a}->{href}->{value} eq "index.htm";

       o Attributes quoted

           XML: <xml><a href="index.htm">Link</a></xml>
           PERL: $root->{xml}->{a}->{href}->{value} eq "index.htm";

       o CDATA nodes

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

       o Multiple nodes; form array

           XML: <xml><item>1</item><item>2</item></xml>
           PERL: $root->{xml}->{item}->[0]->{value} eq "1";

       o Forcing array creation

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

       o One comment supported per node

           XML: <xml><!--test--></xml>
           PERL: $root->{xml}->{comment} eq 'test';

   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:

       o The type of error

       o Where the error occured ( line and char )

       o A short snippet of the XML at the point of failure

   XBS ( XML::Bare Schema ) Format
       o Required nodes

           XML: <xml></xml>
           XBS: <xml/>

       o Optional nodes - allow one

           XML: <xml></xml>
           XBS: <xml item?/>
           or XBS: <xml><item?/></xml>

       o Optional nodes - allow 0 or more

           XML: <xml><item/></xml>
           XBS: <xml item*/>

       o Required nodes - allow 1 or more

           XML: <xml><item/><item/></xml>
           XBS: <xml item+/>

       o Nodes - specified minimum and maximum number

           XML: <xml><item/><item/></xml>
           XBS: <xml item{1,2}/>
           or XBS: <xml><item{1,2}/></xml>
           or XBS: <xml><item{1,2}></item{1,2}></xml>

       o Multiple acceptable node formats

           XML: <xml><item type=box volume=20/><item type=line length=10/></xml>
           XBS: <xml><item type=box volume/><item type=line length/></xml>

       o Regular expressions checking for values

           XML: <xml name=Bob dir=up num=10/>
           XBS: <xml name=[A-Za-z]+ dir=up|down num=[0-9]+/>

       o Require multi_ tags

           XML: <xml><multi_item/></xml>
           XBS: <xml item@/>

   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:

       o _i

         The character offset within the original parsed XML of where the node
         begins. This is used to provide line information for errors when XML
         fails a schema check.

       o _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.  ( note
         that multiple nodes of the same name are stored in order )

       o _att

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

   Parsing Limitations / Features
       o 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 of 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.

       o 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 back to XML, the nodes are then sorted and
         output in the correct order to XML. Note that nodes of the same name
         with the same parent will be grouped together; the position of the
         first item to appear will determine the output position of the group.

       o Comments are parsed but only one is stored per node.

         For each node, there can be a comment within it, and that comment
         will be saved and output back when dumping to XML.

       o Comments override output of immediate value

         If a node contains only a comment node and a text value, only the
         comment node will be displayed. This is in line with treating a
         comment node as a node and only displaying immediate values when a
         node contains no subnodes.

       o PI sections are parsed, but discarded

       o Unknown "<!" sections are parsed, but discarded

       o Attributes may use no quotes, single quotes, quotes

       o Quoted attributes cannot contain escaped quotes

         No escape character is recognized within quotes. As a result, regular
         quotes cannot be stored to XML, or the written XML will not be
         correct, due to all attributes always being written using quotes.

       o Attributes are always written back to XML with quotes

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

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

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

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

       o "$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() )

       o "$object = new XML::Bare( file => "data.xml", scheme => { file =>
         "scheme.xbs" } )"

         Create a new XML object and check to ensure it is valid xml by way of
         the XBS scheme.

       o "$tree = $object->parse()"

         Parse the xml of the object and return a tree reference

       o "$tree = $object->simple()"

         Alternate to the parse function which generates a tree similar to
         that generated by XML::Simple. Note that the sets of nodes are turned
         into arrays always, regardless of whether they have a 'name'
         attribute, unlike XML::Simple.

         Note that currently the generated tree cannot be used with any of the
         functions in this module that operate upon trees. The function is
         provided purely as a quick and dirty way to read simple XML files.

       o "$tree = xmlin( $xmlext, keeproot => 1 )"

         The xmlin function is a shortcut to creating an XML::Bare object and
         parsing it using the simple function. It behaves similarly to the
         XML::Simple function by the same name. The keeproot option is
         optional and if left out the root node will be discarded, same as the
         function in XML::Simple.

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

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

       o "$text = $object->html( [root], [root node name] )"

         Take the hash tree in [root] and turn it into nicely colorized and
         styled html. [root node name] is optional.

       o "$object->save()"

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

       o "$value = xval $node, $default"

         Returns the value of $node or $default if the node does not exist.
         If default is not passed to the function, then '' is returned as a
         default value when the node does not exist.

       o "( $name, $age ) = xget( $personnode, qw/name age/ )"

         Shortcut function to grab a number of values from a node all at the
         same time. Note that this function assumes that all of the subnodes
         exist; it will fail if they do not.

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

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

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

         Similar to previous.

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

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

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

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

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

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

       o "$html = XML::Bare::tohtml( text => "[some xml]", root => 'xml' )"

         Shortcut to creating an xml object and immediately turning it into
         html.  Root is optional, and specifies the name of the root node for
         the xml ( which defaults to 'xml' )

       o "$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>

       o "$object->add_node_after( [node], [subnode within node to add after],
         [nodeset name], ... )"

       o "$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>

       o "$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>

       o "$object->find_by_perl( [nodeset], "[perl code]" )"

         find_by_perl evaluates some perl code for each node in a set of
         nodes, and returns the nodes where the perl code evaluates as true.
         In order to easily reference node values, node values can be directly
         referred to from within the perl code by the name of the node with a
         dash(-) in front of the name. See the example below.

         Note that this function returns an array reference as opposed to a
         single node unlike the find_node function.

           Example:
             Starting XML:
               <xml>
                 <ob>
                   <key>1</key>
                   <val>a</val>
                 </ob>
                 <ob>
                   <key>2</key>
                   <val>b</val>
                 </ob>
               </xml>

             Code:
               $object->find_by_perl( $root->{xml}->{ob}, "-key eq '1'" )->[0]->{val}->{value} = 'test';

             Ending XML:
               <xml>
                 <ob>
                   <key>1</key>
                   <val>test</val>
                 </ob>
                 <ob>
                   <key>2</key>
                   <val>b</val>
                 </ob>
               </xml>

       o "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>

       o "XML::Bare::del_by_perl( ... )"

         Works exactly like find_by_perl, but deletes whatever matches.

       o "XML::Bare::forcearray( [noderef] )"

         Turns the node reference into an array reference, whether that node
         is just a single node, or is already an array reference.

       o "XML::Bare::new_node( ... )"

         Creates a new node...

       o "XML::Bare::newhash( ... )"

         Creates a new hash with the specified value.

       o "XML::Bare::simplify( [noderef] )"

         Take a node with children that have immediate values and creates a
         hashref to reference those values by the name of each child.

   Functions Used Internally
       o "check() checkone() readxbs() free_tree_c()"

       o "lineinfo() c_parse() c_parsefile() free_tree() xml2obj()"

       o "obj2xml() get_root() obj2html() xml2obj_simple()"

   Performance
       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::Parser::EasyTree
         XML::Handler::Trees
         XML::Twig
         XML::Smart
         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
         XML::TreePP
         XML::Trivial
         XML::SAX::Simple
         XML::Grove::Builder
         XML::XPath::XMLParser
         XML::DOM

       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

LICENSE
         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
         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
         GNU General Public License for more details.

perl v5.12.1                      2009-08-02                           Bare(3)
 

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