NAME
XML::Bare - Minimal XML parser implemented via a C state engine
VERSION
version 0.47
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 $ob3 = new XML::Bare( text => $xml_text, schema => { text => $schema_text } );
$ob3->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.
* 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";
* 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:
* The type of error
* Where the error occurred ( line and char )
* A short snippet of the XML at the point of failure
XBS ( XML::Bare Schema ) Format
* Required nodes
XML: <xml></xml>
XBS: <xml/>
* Optional nodes - allow one
XML: <xml></xml>
XBS: <xml item?/>
or XBS: <xml><item?/></xml>
* Optional nodes - allow 0 or more
XML: <xml><item/></xml>
XBS: <xml item*/>
* Required nodes - allow 1 or more
XML: <xml><item/><item/></xml>
XBS: <xml item+/>
* 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>
* 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>
* 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]+/>
* 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:
* _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.
* _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 )
* _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 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.
* Standard XML quoted characters are decoded
The basic XML quoted characters - "&" ">" "<" "quot;" and
"'" - are recognised and decoded when reading values. However
when writing the builder will put any values that need quoting into a
CDATA wrapper as described above.
* 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.
* 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.
* 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.
* PI sections are parsed, but discarded
* Unknown "<!" sections are parsed, but discarded
* Attributes may use no quotes, single quotes, quotes
* 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.
* 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() )
* "$object = new XML::Bare( file => "data.xml", scheme => { file =>
"scheme.xbs" } )"
Create a new XML object and check to ensure it is valid xml by way of
the XBS scheme.
* "$tree = $object->parse()"
Parse the xml of the object and return a tree reference
* "$tree = $object->simple()"
Alternate to the parse function which generates a tree similar to that
generated by XML::Simple. Note that the sets of nodes are turned into
arrays always, regardless of whether they have a 'name' attribute,
unlike XML::Simple.
Note that currently the generated tree cannot be used with any of the
functions in this module that operate upon trees. The function is
provided purely as a quick and dirty way to read simple XML files.
* "$tree = xmlin( $xmlext, keeproot => 1 )"
The xmlin function is a shortcut to creating an XML::Bare object and
parsing it using the simple function. It behaves similarly to the
XML::Simple function by the same name. The keeproot option is optional
and if left out the root node will be discarded, same as the function
in XML::Simple.
* "$text = $object->xml( [root] )"
Take the hash tree in [root] and turn it into cleanly indented ( 2
spaces ) XML text.
* "$text = $object->html( [root], [root node name] )"
Take the hash tree in [root] and turn it into nicely colorized and
styled html. [root node name] is optional.
* "$object->save()"
The the current tree in the object, cleanly indent it, and save it to
the file parameter specified when creating the object.
* "$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.
* "( $name, $age ) = xget( $personnode, qw/name age/ )"
Shortcut function to grab a number of values from a node all at the
same time. Note that this function assumes that all of the subnodes
exist; it will fail if they do not.
* "$text = XML::Bare::clean( text => "[some xml]" )"
Shortcut to creating an xml object and immediately turning it into
clean xml text.
* "$text = XML::Bare::clean( file => "[filename]" )"
Similar to previous.
* "XML::Bare::clean( file => "[filename]", save => 1 )"
Clean up the xml in the file, saving the results back to the file
* "XML::Bare::clean( text => "[some xml]", save => "[filename]" )"
Clean up the xml provided, and save it into the specified file.
* "XML::Bare::clean( file => "[filename1]", save => "[filename2]" )"
Clean up the xml in filename1 and save the results to filename2.
* "$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' )
* "$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->add_node_after( [node], [subnode within node to add after],
[nodeset name], ... )"
* "$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( $root->{xml}, 'ob', key => '1' )->{val}->{value} = 'test';
Ending XML:
<xml>
<ob>
<key>1</key>
<val>test</val>
</ob>
<ob>
<key>2</key>
<val>b</val>
</ob>
</xml>
* "$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>
* "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>
* "XML::Bare::del_by_perl( ... )"
Works exactly like find_by_perl, but deletes whatever matches.
* "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.
* "XML::Bare::new_node( ... )"
Creates a new node...
* "XML::Bare::newhash( ... )"
Creates a new hash with the specified value.
* "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
* "check() checkone() readxbs() free_tree_c()"
* "lineinfo() c_parse() c_parsefile() free_tree() xml2obj()"
* "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
CONTRIBUTED CODE
The XML dequoting code used is taken from XML::Quote by *Sergey
Skvortsov* (*GDSL* on CPAN) with very minor modifications.
INSTALLATION
See perlmodinstall for information and options on installing Perl
modules.
BUGS AND LIMITATIONS
No bugs have been reported.
Please report any bugs or feature requests through the web interface at
<http://rt.cpan.org/Public/Dist/Display.html?Name=XML-Bare>.
AVAILABILITY
The project homepage is <https://metacpan.org/release/XML-Bare>.
The latest version of this module is available from the Comprehensive
Perl Archive Network (CPAN). Visit <http://www.perl.com/CPAN/> to find a
CPAN site near you, or see <http://search.cpan.org/dist/XML-Bare/>.
The development version lives at <http://github.com/nigelm/xml-bare> and
may be cloned from <git://github.com/nigelm/xml-bare.git>. Instead of
sending patches, please fork this project using the standard git and
github infrastructure.
AUTHORS
* David Helkowski <cpan@codechild.com>
* Nigel Metheringham <nigelm@cpan.org>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2012 by David Helkowski.
This is free software, licensed under:
The GNU General Public License, Version 2, June 1991