NAME¶
XML::Twig - A perl module for processing huge XML documents in tree mode.
SYNOPSIS¶
Note that this documentation is intended as a reference to the module.
Complete docs, including a tutorial, examples, an easier to use HTML version, a
quick reference card and a FAQ are available at
<
http://www.xmltwig.com/xmltwig>
Small documents (loaded in memory as a tree):
my $twig=XML::Twig->new(); # create the twig
$twig->parsefile( 'doc.xml'); # build it
my_process( $twig); # use twig methods to process it
$twig->print; # output the twig
Huge documents (processed in combined stream/tree mode):
# at most one div will be loaded in memory
my $twig=XML::Twig->new(
twig_handlers =>
{ title => sub { $_->set_tag( 'h2') }, # change title tags to h2
para => sub { $_->set_tag( 'p') }, # change para to p
hidden => sub { $_->delete; }, # remove hidden elements
list => \&my_list_process, # process list elements
div => sub { $_[0]->flush; }, # output and free memory
},
pretty_print => 'indented', # output will be nicely formatted
empty_tags => 'html', # outputs <empty_tag />
);
$twig->flush; # flush the end of the document
See XML::Twig 101 for other ways to use the module, as a filter for example.
DESCRIPTION¶
This module provides a way to process XML documents. It is build on top of
"XML::Parser".
The module offers a tree interface to the document, while allowing you to output
the parts of it that have been completely processed.
It allows minimal resource (CPU and memory) usage by building the tree only for
the parts of the documents that need actual processing, through the use of the
"twig_roots " and "twig_print_outside_roots " options. The
"finish " and "finish_print " methods also help to
increase performances.
XML::Twig tries to make simple things easy so it tries its best to takes care of
a lot of the (usually) annoying (but sometimes necessary) features that come
with XML and XML::Parser.
XML::Twig 101¶
XML::Twig can be used either on "small" XML documents (that fit in
memory) or on huge ones, by processing parts of the document and outputting or
discarding them once they are processed.
Loading an XML document and processing it¶
my $t= XML::Twig->new();
$t->parse( '<d><title>title</title><para>p 1</para><para>p 2</para></d>');
my $root= $t->root;
$root->set_tag( 'html'); # change doc to html
$title= $root->first_child( 'title'); # get the title
$title->set_tag( 'h1'); # turn it into h1
my @para= $root->children( 'para'); # get the para children
foreach my $para (@para)
{ $para->set_tag( 'p'); } # turn them into p
$t->print; # output the document
Other useful methods include:
att: "$elt->{'att'}->{'foo'}" return the "foo"
attribute for an element,
set_att : "$elt->set_att( foo => "bar")" sets the
"foo" attribute to the "bar" value,
next_sibling: "$elt->{next_sibling}" return the next sibling in the
document (in the example "$title->{next_sibling}" is the first
"para", you can also (and actually should) use
"$elt->next_sibling( 'para')" to get it
The document can also be transformed through the use of the cut, copy, paste and
move methods: "$title->cut; $title->paste( after => $p);"
for example
And much, much more, see XML::Twig::Elt.
Processing an XML document chunk by chunk¶
One of the strengths of XML::Twig is that it let you work with files that do not
fit in memory (BTW storing an XML document in memory as a tree is quite
memory-expensive, the expansion factor being often around 10).
To do this you can define handlers, that will be called once a specific element
has been completely parsed. In these handlers you can access the element and
process it as you see fit, using the navigation and the cut-n-paste methods,
plus lots of convenient ones like "prefix ". Once the element is
completely processed you can then "flush " it, which will output it
and free the memory. You can also "purge " it if you don't need to
output it (if you are just extracting some data from the document for
example). The handler will be called again once the next relevant element has
been parsed.
my $t= XML::Twig->new( twig_handlers =>
{ section => \§ion,
para => sub { $_->set_tag( 'p'); }
},
);
$t->parsefile( 'doc.xml');
$t->flush; # don't forget to flush one last time in the end or anything
# after the last </section> tag will not be output
# the handler is called once a section is completely parsed, ie when
# the end tag for section is found, it receives the twig itself and
# the element (including all its sub-elements) as arguments
sub section
{ my( $t, $section)= @_; # arguments for all twig_handlers
$section->set_tag( 'div'); # change the tag name.4, my favourite method...
# let's use the attribute nb as a prefix to the title
my $title= $section->first_child( 'title'); # find the title
my $nb= $title->{'att'}->{'nb'}; # get the attribute
$title->prefix( "$nb - "); # easy isn't it?
$section->flush; # outputs the section and frees memory
}
There is of course more to it: you can trigger handlers on more elaborate
conditions than just the name of the element, "section/title" for
example.
my $t= XML::Twig->new( twig_handlers =>
{ 'section/title' => sub { $_->print } }
)
->parsefile( 'doc.xml');
Here "sub { $_->print }" simply prints the current element ($_ is
aliased to the element in the handler).
You can also trigger a handler on a test on an attribute:
my $t= XML::Twig->new( twig_handlers =>
{ 'section[@level="1"]' => sub { $_->print } }
);
->parsefile( 'doc.xml');
You can also use "start_tag_handlers " to process an element as soon
as the start tag is found. Besides "prefix " you can also use
"suffix ",
Processing just parts of an XML document¶
The twig_roots mode builds only the required sub-trees from the document
Anything outside of the twig roots will just be ignored:
my $t= XML::Twig->new(
# the twig will include just the root and selected titles
twig_roots => { 'section/title' => \&print_n_purge,
'annex/title' => \&print_n_purge
}
);
$t->parsefile( 'doc.xml');
sub print_n_purge
{ my( $t, $elt)= @_;
print $elt->text; # print the text (including sub-element texts)
$t->purge; # frees the memory
}
You can use that mode when you want to process parts of a documents but are not
interested in the rest and you don't want to pay the price, either in time or
memory, to build the tree for the it.
Building an XML filter¶
You can combine the "twig_roots" and the
"twig_print_outside_roots" options to build filters, which let you
modify selected elements and will output the rest of the document as is.
This would convert prices in $ to prices in Euro in a document:
my $t= XML::Twig->new(
twig_roots => { 'price' => \&convert, }, # process prices
twig_print_outside_roots => 1, # print the rest
);
$t->parsefile( 'doc.xml');
sub convert
{ my( $t, $price)= @_;
my $currency= $price->{'att'}->{'currency'}; # get the currency
if( $currency eq 'USD')
{ $usd_price= $price->text; # get the price
# %rate is just a conversion table
my $euro_price= $usd_price * $rate{usd2euro};
$price->set_text( $euro_price); # set the new price
$price->set_att( currency => 'EUR'); # don't forget this!
}
$price->print; # output the price
}
XML::Twig and various versions of Perl, XML::Parser and
expat:¶
Before being uploaded to CPAN, XML::Twig 3.22 has been tested under the
following environments:
- linux-x86
- perl 5.6.2, expat 1.95.8, XML::Parser 2.34 perl 5.8.0,
expat 1.95.8, XML::Parser 2.34 perl 5.8.7, expat 1.95.8,
XML::Parser2.34
- Solaris
- perl 5.6.1, expat 1.95.2, XML::Parser 2.31
XML::Twig is a lot more sensitive to variations in versions of perl, XML::Parser
and expat than to the OS, so this should cover some reasonable configurations.
The "recommended configuration" is perl 5.8.3+ (for good Unicode
support), XML::Parser 2.31+ and expat 1.95.5+
See
http://testers.cpan.org/search?request=dist&dist=XML-Twig
<
http://testers.cpan.org/search?request=dist&dist=XML-Twig> for the
CPAN testers reports on XML::Twig, which list all tested configurations.
An Atom feed of the CPAN Testers results is available at
<
http://xmltwig.com/rss/twig_testers.rss>
Finally:
- XML::Twig does NOT work with expat 1.95.4
- XML::Twig only works with XML::Parser 2.27 in perl
5.6.*
- Note that I can't compile XML::Parser 2.27 anymore, so I
can't guarantee that it still works
- XML::Parser 2.28 does not really work
When in doubt, upgrade expat, XML::Parser and Scalar::Util
Finally, for some optional features, XML::Twig depends on some additional
modules. The complete list, which depends somewhat on the version of Perl that
you are running, is given by running "t/zz_dump_config.t"
Simplifying XML processing¶
- Whitespaces
- Whitespaces that look non-significant are discarded, this
behaviour can be controlled using the "keep_spaces ",
"keep_spaces_in " and "discard_spaces_in "
options.
- Encoding
- You can specify that you want the output in the same
encoding as the input (provided you have valid XML, which means you have
to specify the encoding either in the document or when you create the Twig
object) using the "keep_encoding " option
You can also use "output_encoding" to convert the internal UTF-8
format to the required encoding.
- Comments and Processing Instructions (PI)
- Comments and PI's can be hidden from the processing, but
still appear in the output (they are carried by the "real"
element closer to them)
- Pretty Printing
- XML::Twig can output the document pretty printed so it is
easier to read for us humans.
- Surviving an untimely death
- XML parsers are supposed to react violently when fed
improper XML. XML::Parser just dies.
XML::Twig provides the "safe_parse " and the "safe_parsefile
" methods which wrap the parse in an eval and return either the
parsed twig or 0 in case of failure.
- Private attributes
- Attributes with a name starting with # (illegal in XML)
will not be output, so you can safely use them to store temporary values
during processing. Note that you can store anything in a private
attribute, not just text, it's just a regular Perl variable, so a
reference to an object or a huge data structure is perfectly fine.
CLASSES¶
XML::Twig uses a very limited number of classes. The ones you are most likely to
use are "XML::Twig" of course, which represents a complete XML
document, including the document itself (the root of the document itself is
"root"), its handlers, its input or output filters... The other main
class is "XML::Twig::Elt", which models an XML element. Element here
has a very wide definition: it can be a regular element, or but also text,
with an element "tag" of "#PCDATA" (or
"#CDATA"), an entity (tag is "#ENT"), a Processing
Instruction ("#PI"), a comment ("#COMMENT").
Those are the 2 commonly used classes.
You might want to look the "elt_class" option if you want to subclass
"XML::Twig::Elt".
Attributes are just attached to their parent element, they are not objects per
se. (Please use the provided methods "att" and "set_att"
to access them, if you access them as a hash, then your code becomes
implementaion dependent and might break in the future).
Other classes that are seldom used are "XML::Twig::Entity_list" and
"XML::Twig::Entity".
If you use "XML::Twig::XPath" instead of "XML::Twig",
elements are then created as "XML::Twig::XPath::Elt"
METHODS¶
XML::Twig¶
A twig is a subclass of XML::Parser, so all XML::Parser methods can be called on
a twig object, including parse and parsefile. "setHandlers" on the
other hand cannot be used, see "BUGS "
- new
- This is a class method, the constructor for XML::Twig.
Options are passed as keyword value pairs. Recognized options are the same
as XML::Parser, plus some (in fact a lot!) XML::Twig specifics.
New Options:
- twig_handlers
- This argument consists of a hash "{ expression ="
\&handler}> where expression is a an XPath-like expression
(+ some others).
XPath expressions are limited to using the child and descendant axis (indeed
you can't specify an axis), and predicates cannot be nested. You can use
the "string", or "string(<tag>)" function
(except in "twig_roots" triggers).
Additionally you can use regexps (/ delimited) to match attribute and string
values.
Examples:
foo
foo/bar
foo//bar
/foo/bar
/foo//bar
/foo/bar[@att1 = "val1" and @att2 = "val2"]/baz[@a >= 1]
foo[string()=~ /^duh!+/]
/foo[string(bar)=~ /\d+/]/baz[@att != 3]
#CDATA can be used to call a handler for a CDATA section. #COMMENT can be
used to call a handler for comments
Some additional (non-XPath) expressions are also provided for
convenience:
- processing instructions
- '?' or '#PI' triggers the handler for any processing
instruction, and '?<target>' or '#PI <target>' triggers a
handler for processing instruction with the given target( ex: '#PI
xml-stylesheet').
- level(<level>)
- Triggers the handler on any element at that level in the
tree (root is level 1)
- _all_
- Triggers the handler for all elements in the
tree
- _default_
- Triggers the handler for each element that does NOT have
any other handler.
Expressions are evaluated against the input document. Which means that even if
you have changed the tag of an element (changing the tag of a parent element
from a handler for example) the change will not impact the expression
evaluation. There is an exception to this: "private" attributes
(which name start with a '#', and can only be created during the parsing, as
they are not valid XML) are checked against the current twig.
Handlers are triggered in fixed order, sorted by their type (xpath expressions
first, then regexps, then level), then by whether they specify a full path
(starting at the root element) or not, then by by number of steps in the
expression , then number of predicates, then number of tests in predicates.
Handlers where the last step does not specify a step ("foo/bar/*")
are triggered after other XPath handlers. Finally "_all_" handlers
are triggered last.
Important: once a handler has been triggered if it returns 0 then no
other handler is called, except a "_all_" handler which will be
called anyway.
If a handler returns a true value and other handlers apply, then the next
applicable handler will be called. Repeat, rinse, lather..; The exception to
that rule is when the "do_not_chain_handlers" option is set, in
which case only the first handler will be called.
Note that it might be a good idea to explicitly return a short true value (like
1) from handlers: this ensures that other applicable handlers are called even
if the last statement for the handler happens to evaluate to false. This might
also speedup the code by avoiding the result of the last statement of the code
to be copied and passed to the code managing handlers. It can really pay to
have 1 instead of a long string returned.
When the closing tag for an element is parsed the corresponding handler is
called, with 2 arguments: the twig and the "Element ". The twig
includes the document tree that has been built so far, the element is the
complete sub-tree for the element. The fact that the handler is called only
when the closing tag for the element is found means that handlers for inner
elements are called before handlers for outer elements.
$_ is also set to the element, so it is easy to write inline handlers like
para => sub { $_->set_tag( 'p'); }
Text is stored in elements whose tag name is #PCDATA (due to mixed content, text
and sub-element in an element there is no way to store the text as just an
attribute of the enclosing element).
Warning: if you have used purge or flush on the twig the element might
not be complete, some of its children might have been entirely flushed or
purged, and the start tag might even have been printed (by "flush")
already, so changing its tag might not give the expected result.
- twig_roots
- This argument let's you build the tree only for those
elements you are interested in.
Example: my $t= XML::Twig->new( twig_roots => { title => 1, subtitle => 1});
$t->parsefile( file);
my $t= XML::Twig->new( twig_roots => { 'section/title' => 1});
$t->parsefile( file);
return a twig containing a document including only "title" and
"subtitle" elements, as children of the root element.
You can use generic_attribute_condition, attribute_condition,
full_path, partial_path, tag, tag_regexp,
_default_ and _all_ to trigger the building of the twig.
string_condition and regexp_condition cannot be used as the
content of the element, and the string, have not yet been parsed when the
condition is checked.
WARNING: path are checked for the document. Even if the
"twig_roots" option is used they will be checked against the
full document tree, not the virtual tree created by XML::Twig
WARNING: twig_roots elements should NOT be nested, that would
hopelessly confuse XML::Twig ;--(
Note: you can set handlers (twig_handlers) using twig_roots
Example: my $t= XML::Twig->new( twig_roots =>
{ title => sub { $_{1]->print;},
subtitle => \&process_subtitle
}
);
$t->parsefile( file);
- twig_print_outside_roots
- To be used in conjunction with the "twig_roots"
argument. When set to a true value this will print the document outside of
the "twig_roots" elements.
Example: my $t= XML::Twig->new( twig_roots => { title => \&number_title },
twig_print_outside_roots => 1,
);
$t->parsefile( file);
{ my $nb;
sub number_title
{ my( $twig, $title);
$nb++;
$title->prefix( "$nb "; }
$title->print;
}
}
This example prints the document outside of the title element, calls
"number_title" for each "title" element, prints it,
and then resumes printing the document. The twig is built only for the
"title" elements.
If the value is a reference to a file handle then the document outside the
"twig_roots" elements will be output to this file handle:
open( OUT, ">out_file") or die "cannot open out file out_file:$!";
my $t= XML::Twig->new( twig_roots => { title => \&number_title },
# default output to OUT
twig_print_outside_roots => \*OUT,
);
{ my $nb;
sub number_title
{ my( $twig, $title);
$nb++;
$title->prefix( "$nb "; }
$title->print( \*OUT); # you have to print to \*OUT here
}
}
- start_tag_handlers
- A hash "{ expression =" \&handler}>. Sets
element handlers that are called when the element is open (at the end of
the XML::Parser "Start" handler). The handlers are called with 2
params: the twig and the element. The element is empty at that point, its
attributes are created though.
You can use generic_attribute_condition, attribute_condition,
full_path, partial_path, tag, tag_regexp,
_default_ and _all_ to trigger the handler.
string_condition and regexp_condition cannot be used as the
content of the element, and the string, have not yet been parsed when the
condition is checked.
The main uses for those handlers are to change the tag name (you might have
to do it as soon as you find the open tag if you plan to "flush"
the twig at some point in the element, and to create temporary attributes
that will be used when processing sub-element with
"twig_hanlders".
You should also use it to change tags if you use "flush". If you
change the tag in a regular "twig_handler" then the start tag
might already have been flushed.
Note: "start_tag" handlers can be called outside of
"twig_roots" if this argument is used, in this case handlers are
called with the following arguments: $t (the twig), $tag (the tag of the
element) and %att (a hash of the attributes of the element).
If the "twig_print_outside_roots" argument is also used, if the
last handler called returns a "true" value, then the the start
tag will be output as it appeared in the original document, if the handler
returns a a "false" value then the start tag will not be
printed (so you can print a modified string yourself for example).
Note that you can use the ignore method in "start_tag_handlers"
(and only there).
- end_tag_handlers
- A hash "{ expression =" \&handler}>. Sets
element handlers that are called when the element is closed (at the end of
the XML::Parser "End" handler). The handlers are called with 2
params: the twig and the tag of the element.
twig_handlers are called when an element is completely parsed, so
why have this redundant option? There is only one use for
"end_tag_handlers": when using the "twig_roots"
option, to trigger a handler for an element outside the roots. It
is for example very useful to number titles in a document using nested
sections:
my @no= (0);
my $no;
my $t= XML::Twig->new(
start_tag_handlers =>
{ section => sub { $no[$#no]++; $no= join '.', @no; push @no, 0; } },
twig_roots =>
{ title => sub { $_[1]->prefix( $no); $_[1]->print; } },
end_tag_handlers => { section => sub { pop @no; } },
twig_print_outside_roots => 1
);
$t->parsefile( $file);
Using the "end_tag_handlers" argument without
"twig_roots" will result in an error.
- do_not_chain_handlers
- If this option is set to a true value, then only one
handler will be called for each element, even if several satisfy the
condition
Note that the "_all_" handler will still be called regardless
- ignore_elts
- This option lets you ignore elements when building the
twig. This is useful in cases where you cannot use "twig_roots"
to ignore elements, for example if the element to ignore is a sibling of
elements you are interested in.
Example:
my $twig= XML::Twig->new( ignore_elts => { elt => 'discard' });
$twig->parsefile( 'doc.xml');
This will build the complete twig for the document, except that all
"elt" elements (and their children) will be left out.
The keys in the hash are triggers, limited to the same subset as
"start_tag_handlers". The values can be "discard", to
discard the element, "print", to output the element as-is,
"string" to store the text of the ignored element(s), including
markup, in a field of the twig: "$t->{twig_buffered_string}"
or a reference to a scalar, in which case the text of the ignored
element(s), including markup, will be stored in the scalar. Any other
value will be treated as "discard".
- char_handler
- A reference to a subroutine that will be called every time
"PCDATA" is found.
The subroutine receives the string as argument, and returns the modified
string:
# we want all strings in upper case
sub my_char_handler
{ my( $text)= @_;
$text= uc( $text);
return $text;
}
- elt_class
- The name of a class used to store elements. this class
should inherit from "XML::Twig::Elt" (and by default it is
"XML::Twig::Elt"). This option is used to subclass the element
class and extend it with new methods.
This option is needed because during the parsing of the XML, elements are
created by "XML::Twig", without any control from the user
code.
- keep_atts_order
- Setting this option to a true value causes the attribute
hash to be tied to a "Tie::IxHash" object. This means that
"Tie::IxHash" needs to be installed for this option to be
available. It also means that the hash keeps its order, so you will get
the attributes in order. This allows outputting the attributes in the same
order as they were in the original document.
- keep_encoding
- This is a (slightly?) evil option: if the XML document is
not UTF-8 encoded and you want to keep it that way, then setting
keep_encoding will use the"Expat" original_string method for
character, thus keeping the original encoding, as well as the original
entities in the strings.
See the "t/test6.t" test file to see what results you can expect
from the various encoding options.
WARNING: if the original encoding is multi-byte then attribute
parsing will be EXTREMELY unsafe under any Perl before 5.6, as it uses
regular expressions which do not deal properly with multi-byte characters.
You can specify an alternate function to parse the start tags with the
"parse_start_tag" option (see below)
WARNING: this option is NOT used when parsing with the non-blocking
parser ("parse_start", "parse_more", parse_done
methods) which you probably should not use with XML::Twig anyway as they
are totally untested!
- output_encoding
- This option generates an output_filter using
"Encode", "Text::Iconv" or "Unicode::Map8"
and "Unicode::Strings", and sets the encoding in the XML
declaration. This is the easiest way to deal with encodings, if you need
more sophisticated features, look at "output_filter" below
- output_filter
- This option is used to convert the character encoding of
the output document. It is passed either a string corresponding to a
predefined filter or a subroutine reference. The filter will be called
every time a document or element is processed by the "print"
functions ("print", "sprint", "flush").
Pre-defined filters:
- latin1
- uses either "Encode", "Text::Iconv" or
"Unicode::Map8" and "Unicode::String" or a regexp
(which works only with XML::Parser 2.27), in this order, to convert all
characters to ISO-8859-15 (usually latin1 is synonym to ISO-8859-1, but in
practice it seems that ISO-8859-15, which includes the euro sign, is more
useful and probably what most people want).
- html
- does the same conversion as "latin1", plus
encodes entities using "HTML::Entities" (oddly enough you will
need to have HTML::Entities installed for it to be available). This should
only be used if the tags and attribute names themselves are in US-ASCII,
or they will be converted and the output will not be valid XML any
more
- safe
- converts the output to ASCII (US) only plus character
entities ("&#nnn;") this should be used only if the tags
and attribute names themselves are in US-ASCII, or they will be converted
and the output will not be valid XML any more
- safe_hex
- same as "safe" except that the character entities
are in hexa ("&#xnnn;")
- encode_convert ($encoding)
- Return a subref that can be used to convert utf8 strings to
$encoding). Uses "Encode".
my $conv = XML::Twig::encode_convert( 'latin1');
my $t = XML::Twig->new(output_filter => $conv);
- iconv_convert ($encoding)
- this function is used to create a filter subroutine that
will be used to convert the characters to the target encoding using
"Text::Iconv" (which needs to be installed, look at the
documentation for the module and for the "iconv" library to find
out which encodings are available on your system)
my $conv = XML::Twig::iconv_convert( 'latin1');
my $t = XML::Twig->new(output_filter => $conv);
- unicode_convert ($encoding)
- this function is used to create a filter subroutine that
will be used to convert the characters to the target encoding using
"Unicode::Strings" and "Unicode::Map8" (which need to
be installed, look at the documentation for the modules to find out which
encodings are available on your system)
my $conv = XML::Twig::unicode_convert( 'latin1');
my $t = XML::Twig->new(output_filter => $conv);
The "text" and "att" methods do not use the filter, so their
result are always in unicode.
Those predeclared filters are based on subroutines that can be used by
themselves (as "XML::Twig::foo").
- html_encode ($string)
- Use "HTML::Entities" to encode a utf8 string
- safe_encode ($string)
- Use either a regexp (perl < 5.8) or "Encode"
to encode non-ascii characters in the string in
"&#<nnnn>;" format
- safe_encode_hex ($string)
- Use either a regexp (perl < 5.8) or "Encode"
to encode non-ascii characters in the string in
"&#x<nnnn>;" format
- regexp2latin1 ($string)
- Use a regexp to encode a utf8 string into latin 1
(ISO-8859-1). Does not work with Perl 5.8.0!
- output_text_filter
- same as output_filter, except it doesn't apply to the
brackets and quotes around attribute values. This is useful for all
filters that could change the tagging, basically anything that does not
just change the encoding of the output. "html", "safe"
and "safe_hex" are better used with this option.
- input_filter
- This option is similar to "output_filter" except
the filter is applied to the characters before they are stored in the
twig, at parsing time.
- remove_cdata
- Setting this option to a true value will force the twig to
output CDATA sections as regular (escaped) PCDATA
- parse_start_tag
- If you use the "keep_encoding" option then this
option can be used to replace the default parsing function. You should
provide a coderef (a reference to a subroutine) as the argument, this
subroutine takes the original tag (given by XML::Parser::Expat
"original_string()" method) and returns a tag and the attributes
in a hash (or in a list attribute_name/attribute value).
- expand_external_ents
- When this option is used external entities (that are
defined) are expanded when the document is output using "print"
functions such as "print ", "sprint ", "flush
" and "xml_string ". Note that in the twig the entity will
be stored as an element with a tag '"#ENT"', the entity will not
be expanded there, so you might want to process the entities before
outputting it.
If an external entity is not available, then the parse will fail.
A special case is when the value of this option is -1. In that case a
missing entity will not cause the parser to die, but its "name",
"sysid" and "pubid" will be stored in the twig as
"$twig->{twig_missing_system_entities}" (a reference to an
array of hashes { name => <name>, sysid => <sysid>,
pubid => <pubid> }). Yes, this is a bit of a hack, but it's
useful in some cases.
- load_DTD
- If this argument is set to a true value, "parse"
or "parsefile" on the twig will load the DTD information. This
information can then be accessed through the twig, in a
"DTD_handler" for example. This will load even an external DTD.
Default and fixed values for attributes will also be filled, based on the
DTD.
Note that to do this the module will generate a temporary file in the
current directory. If this is a problem let me know and I will add an
option to specify an alternate directory.
See "DTD Handling" for more information
- DTD_handler
- Set a handler that will be called once the doctype (and the
DTD) have been loaded, with 2 arguments, the twig and the DTD.
- no_prolog
- Does not output a prolog (XML declaration and DTD)
- id
- This optional argument gives the name of an attribute that
can be used as an ID in the document. Elements whose ID is known can be
accessed through the elt_id method. id defaults to 'id'. See "BUGS
"
- discard_spaces
- If this optional argument is set to a true value then
spaces are discarded when they look non-significant: strings containing
only spaces are discarded. This argument is set to true by default.
- keep_spaces
- If this optional argument is set to a true value then all
spaces in the document are kept, and stored as "PCDATA".
Warning: adding this option can result in changes in the twig
generated: space that was previously discarded might end up in a new text
element. see the difference by calling the following code with 0 and 1 as
arguments:
perl -MXML::Twig -e'print XML::Twig->new( keep_spaces => shift)->parse( "<d> \n<e/></d>")->_dump'
"keep_spaces" and "discard_spaces" cannot be both
set.
- discard_spaces_in
- This argument sets "keep_spaces" to true but will
cause the twig builder to discard spaces in the elements listed.
The syntax for using this argument is:
XML::Twig->new( discard_spaces_in => [ 'elt1', 'elt2']);
- keep_spaces_in
- This argument sets "discard_spaces" to true but
will cause the twig builder to keep spaces in the elements listed.
The syntax for using this argument is:
XML::Twig->new( keep_spaces_in => [ 'elt1', 'elt2']);
Warning: adding this option can result in changes in the twig
generated: space that was previously discarded might end up in a new text
element.
- pretty_print
- Set the pretty print method, amongst '"none"'
(default), '"nsgmls"', '"nice"',
'"indented"', '"indented_c"',
'"indented_a"', '"indented_close_tag"',
'"cvs"', '"wrapped"', '"record"' and
'"record_c"'
pretty_print formats:
- none
- The document is output as one ling string, with no line
breaks except those found within text elements
- nsgmls
- Line breaks are inserted in safe places: that is within
tags, between a tag and an attribute, between attributes and before the
> at the end of a tag.
This is quite ugly but better than "none", and it is very safe,
the document will still be valid (conforming to its DTD).
This is how the SGML parser "sgmls" splits documents, hence the
name.
- nice
- This option inserts line breaks before any tag that does
not contain text (so element with textual content are not broken as the \n
is the significant).
WARNING: this option leaves the document well-formed but might make
it invalid (not conformant to its DTD). If you have elements declared as
<!ELEMENT foo (#PCDATA|bar)>
then a "foo" element including a "bar" one will be
printed as
<foo>
<bar>bar is just pcdata</bar>
</foo>
This is invalid, as the parser will take the line break after the
"foo" tag as a sign that the element contains PCDATA, it will
then die when it finds the "bar" tag. This may or may not be
important for you, but be aware of it!
- indented
- Same as "nice" (and with the same warning) but
indents elements according to their level
- indented_c
- Same as "indented" but a little more compact: the
closing tags are on the same line as the preceding text
- indented_close_tag
- Same as "indented" except that the closing tag is
also indented, to line up with the tags within the element
- idented_a
- This formats XML files in a line-oriented version control
friendly way. The format is described in <http://tinyurl.com/2kwscq>
(that's an Oracle document with an insanely long URL).
Note that to be totaly conformant to the "spec", the order of
attributes should not be changed, so if they are not already in
alphabetical order you will need to use the "keep_atts_order"
option.
- cvs
- Same as "idented_a".
- wrapped
- Same as "indented_c" but lines are wrapped using
Text::Wrap::wrap. The default length for lines is the default for
$Text::Wrap::columns, and can be changed by changing that variable.
- record
- This is a record-oriented pretty print, that display data
in records, one field per line (which looks a LOT like
"indented")
- record_c
- Stands for record compact, one record per line
- empty_tags
- Set the empty tag display style ('"normal"',
'"html"' or '"expand"').
"normal" outputs an empty tag '"<tag/>"',
"html" adds a space '"<tag />"' for elements
that can be empty in XHTML and "expand" outputs
'"<tag></tag>"'
- quote
- Set the quote character for attributes
('"single"' or '"double"').
- escape_gt
- By default XML::Twig does not escape the character > in
its output, as it is not mandated by the XML spec. With this option on,
> will be replaced by ">"
- comments
- Set the way comments are processed: '"drop"'
(default), '"keep"' or '"process"'
Comments processing options:
- drop
- drops the comments, they are not read, nor printed to the
output
- keep
- comments are loaded and will appear on the output, they are
not accessible within the twig and will not interfere with processing
though
Note: comments in the middle of a text element such as
<p>text <!-- comment --> more text --></p>
are kept at their original position in the text. Using EeX"print"
methods like "print" or "sprint" will return the
comments in the text. Using "text" or "field" on the
other hand will not.
Any use of "set_pcdata" on the "#PCDATA" element
(directly or through other methods like "set_content") will
delete the comment(s).
- process
- comments are loaded in the twig and will be treated as
regular elements (their "tag" is "#COMMENT") this can
interfere with processing if you expect "$elt->{first_child}"
to be an element but find a comment there. Validation will not protect you
from this as comments can happen anywhere. You can use
"$elt->first_child( 'tag')" (which is a good habit anyway) to
get where you want.
Consider using "process" if you are outputting SAX events from
XML::Twig.
- pi
- Set the way processing instructions are processed:
'"drop"', '"keep"' (default) or '"process"'
Note that you can also set PI handlers in the "twig_handlers"
option:
'?' => \&handler
'?target' => \&handler 2
The handlers will be called with 2 parameters, the twig and the PI element
if "pi" is set to "process", and with 3, the twig, the
target and the data if "pi" is set to "keep". Of
course they will not be called if "pi" is set to
"drop".
If "pi" is set to "keep" the handler should return a
string that will be used as-is as the PI text (it should look like
"" <?target data?" >" or '' if you want to
remove the PI),
Only one handler will be called, "?target" or "?" if no
specific handler for that target is available.
- map_xmlns
- This option is passed a hashref that maps uri's to
prefixes. The prefixes in the document will be replaced by the ones in the
map. The mapped prefixes can (actually have to) be used to trigger
handlers, navigate or query the document.
Here is an example:
my $t= XML::Twig->new( map_xmlns => {'http://www.w3.org/2000/svg' => "svg"},
twig_handlers =>
{ 'svg:circle' => sub { $_->set_att( r => 20) } },
pretty_print => 'indented',
)
->parse( '<doc xmlns:gr="http://www.w3.org/2000/svg">
<gr:circle cx="10" cy="90" r="10"/>
</doc>'
)
->print;
This will output:
<doc xmlns:svg="http://www.w3.org/2000/svg">
<svg:circle cx="10" cy="90" r="20"/>
</doc>
- keep_original_prefix
- When used with "map_xmlns" this option will make
"XML::Twig" use the original namespace prefixes when outputting
a document. The mapped prefix will still be used for triggering handlers
and in navigation and query methods.
my $t= XML::Twig->new( map_xmlns => {'http://www.w3.org/2000/svg' => "svg"},
twig_handlers =>
{ 'svg:circle' => sub { $_->set_att( r => 20) } },
keep_original_prefix => 1,
pretty_print => 'indented',
)
->parse( '<doc xmlns:gr="http://www.w3.org/2000/svg">
<gr:circle cx="10" cy="90" r="10"/>
</doc>'
)
->print;
This will output:
<doc xmlns:gr="http://www.w3.org/2000/svg">
<gr:circle cx="10" cy="90" r="20"/>
</doc>
- index ($arrayref or $hashref)
- This option creates lists of specific elements during the
parsing of the XML. It takes a reference to either a list of triggering
expressions or to a hash name => expression, and for each one generates
the list of elements that match the expression. The list can be accessed
through the "index" method.
- att_accessors <list of attribute names>
- creates methods that give direct access to attribute:
my $t= XML::Twig->new( att_accessors => [ 'href', 'src'])
->parsefile( $file);
my $first href= $t->first_elt( 'img')->src; # same as ->att( 'src')
$t->first_elt( 'img')->src( 'new_logo.png') # changes the attribute value
- elt_accessors
- creates methods that give direct access to the first child
element:
my $t= XML::Twig->new( elt_accessors => [ 'head'])
->parsefile( $file);
my $title_text= $t->root->head->field( 'title');
# same as $title_text= $t->root->first_child( 'head')->field( 'title');
- field_accessors
- creates methods that give direct access to the first child
element text:
my $t= XML::Twig->new( field_accessors => [ 'h1'])
->parsefile( $file);
my $div_title_text= $t->first_elt( 'div')->title;
# same as $title_text= $t->first_elt( 'div')->field( 'title');
example:
# using an array ref
my $t= XML::Twig->new( index => [ 'div', 'table' ])
->parsefile( "foo.xml');
my $divs= $t->index( 'div');
my $first_div= $divs->[0];
my $last_table= $t->index( table => -1);
# using a hashref to name the indexes
my $t= XML::Twig->new( index => { email => 'a[@href=~/^\s*mailto:/]')
->parsefile( "foo.xml');
my $last_emails= $t->index( email => -1);
Note that the index is not maintained after the parsing. If elements are
deleted, renamed or otherwise hurt during processing, the index is NOT
updated.
Note: I _HATE_ the Java-like name of arguments used by most XML modules.
So in pure TIMTOWTDI fashion all arguments can be written either as
"UglyJavaLikeName" or as "readable_perl_name":
"twig_print_outside_roots" or "TwigPrintOutsideRoots" (or
even "twigPrintOutsideRoots" {shudder}). XML::Twig normalizes them
before processing them.
- parse ( $source)
- The $source parameter should either be a string containing
the whole XML document, or it should be an open "IO::Handle".
Constructor options to "XML::Parser::Expat" given as
keyword-value pairs may follow the$source parameter. These override, for
this call, any options or attributes passed through from the XML::Parser
instance.
A die call is thrown if a parse error occurs. Otherwise it will return the
twig built by the parse. Use "safe_parse" if you want the
parsing to return even when an error occurs.
If this method is called as a class method ("XML::Twig->parse(
$some_xml_or_html)") then an XML::Twig object is created, using the
parameters except the last one (eg "XML::Twig->parse( pretty_print
=> 'indented', $some_xml_or_html)") and "xparse" is
called on it.
- parsestring
- This is just an alias for "parse" for backwards
compatibility.
- parsefile (FILE [, OPT => OPT_VALUE [...]])
- Open "FILE" for reading, then call
"parse" with the open handle. The file is closed no matter how
"parse" returns.
A "die" call is thrown if a parse error occurs. Otherwise it will
return the twig built by the parse. Use "safe_parsefile" if you
want the parsing to return even when an error occurs.
- parsefile_inplace ( $file, $optional_extension)
- Parse and update a file "in place". It does this
by creating a temp file, selecting it as the default for print()
statements (and methods), then parsing the input file. If the parsing is
successful, then the temp file is moved to replace the input file.
If an extension is given then the original file is backed-up (the rules for
the extension are the same as the rule for the -i option in perl).
- parsefile_html_inplace ( $file, $optional_extension)
- Same as parsefile_inplace, except that it parses HTML
instead of XML
- parseurl ($url $optional_user_agent)
- Gets the data from $url and parse it. The data is piped to
the parser in chunks the size of the XML::Parser::Expat buffer, so memory
consumption and hopefully speed are optimal.
For most (read "small") XML it is probably as efficient (and
easier to debug) to just "get" the XML file and then parse it as
a string.
use XML::Twig;
use LWP::Simple;
my $twig= XML::Twig->new();
$twig->parse( LWP::Simple::get( $URL ));
or
use XML::Twig;
my $twig= XML::Twig->nparse( $URL);
If the $optional_user_agent argument is used then it is used, otherwise a
new one is created.
- safe_parse ( SOURCE [, OPT => OPT_VALUE [...]])
- This method is similar to "parse" except that it
wraps the parsing in an "eval" block. It returns the twig on
success and 0 on failure (the twig object also contains the parsed twig).
$@ contains the error message on failure.
Note that the parsing still stops as soon as an error is detected, there is
no way to keep going after an error.
- safe_parsefile (FILE [, OPT => OPT_VALUE [...]])
- This method is similar to "parsefile" except that
it wraps the parsing in an "eval" block. It returns the twig on
success and 0 on failure (the twig object also contains the parsed twig) .
$@ contains the error message on failure
Note that the parsing still stops as soon as an error is detected, there is
no way to keep going after an error.
- safe_parseurl ($url $optional_user_agent)
- Same as "parseurl" except that it wraps the
parsing in an "eval" block. It returns the twig on success and 0
on failure (the twig object also contains the parsed twig) . $@ contains
the error message on failure
- parse_html ($string_or_fh)
- parse an HTML string or file handle (by converting it to
XML using HTML::TreeBuilder, which needs to be available).
This works nicely, but some information gets lost in the process: newlines
are removed, and (at least on the version I use), comments get get an
extra CDATA section inside ( <!-- foo --> becomes <!--
<![CDATA[ foo ]]> -->
- parsefile_html ($file)
- parse an HTML file (by converting it to XML using
HTML::TreeBuilder, which needs to be available, or HTML::Tidy if the
"use_tidy" option was used). The file is loaded completely in
memory and converted to XML before being parsed.
- parseurl_html ($url $optional_user_agent)
- parse an URL as html the same way "parse_html"
does
- safe_parseurl_html ($url $optional_user_agent)
- Same as "parseurl_html"> except that it wraps
the parsing in an "eval" block. It returns the twig on success
and 0 on failure (the twig object also contains the parsed twig) . $@
contains the error message on failure
- safe_parsefile_html ($file $optional_user_agent)
- Same as "parsefile_html"> except that it wraps
the parsing in an "eval" block. It returns the twig on success
and 0 on failure (the twig object also contains the parsed twig) . $@
contains the error message on failure
- safe_parse_html ($string_or_fh)
- Same as "parse_html" except that it wraps the
parsing in an "eval" block. It returns the twig on success and 0
on failure (the twig object also contains the parsed twig) . $@ contains
the error message on failure
- xparse ($thing_to_parse)
- parse the $thing_to_parse, whether it is a filehandle, a
string, an HTML file, an HTML URL, an URL or a file.
Note that this is mostly a convenience method for one-off scripts. For
example files that end in '.htm' or '.html' are parsed first as XML, and
if this fails as HTML. This is certainly not the most efficient way to do
this in general.
- nparse ($optional_twig_options, $thing_to_parse)
- create a twig with the $optional_options, and parse the
$thing_to_parse, whether it is a filehandle, a string, an HTML file, an
HTML URL, an URL or a file.
Examples:
XML::Twig->nparse( "file.xml");
XML::Twig->nparse( error_context => 1, "file://file.xml");
- nparse_pp ($optional_twig_options, $thing_to_parse)
- same as "nparse" but also sets the
"pretty_print" option to "indented".
- nparse_e ($optional_twig_options, $thing_to_parse)
- same as "nparse" but also sets the
"error_context" option to 1.
- nparse_ppe ($optional_twig_options, $thing_to_parse)
- same as "nparse" but also sets the
"pretty_print" option to "indented" and the
"error_context" option to 1.
- parser
- This method returns the "expat" object (actually
the XML::Parser::Expat object) used during parsing. It is useful for
example to call XML::Parser::Expat methods on it. To get the line of a tag
for example use "$t->parser->current_line".
- setTwigHandlers ($handlers)
- Set the twig_handlers. $handlers is a reference to a hash
similar to the one in the "twig_handlers" option of new. All
previous handlers are unset. The method returns the reference to the
previous handlers.
- setTwigHandler ($exp $handler)
- Set a single twig_handler for elements matching $exp.
$handler is a reference to a subroutine. If the handler was previously set
then the reference to the previous handler is returned.
- setStartTagHandlers ($handlers)
- Set the start_tag handlers. $handlers is a reference to a
hash similar to the one in the "start_tag_handlers" option of
new. All previous handlers are unset. The method returns the reference to
the previous handlers.
- setStartTagHandler ($exp $handler)
- Set a single start_tag handlers for elements matching $exp.
$handler is a reference to a subroutine. If the handler was previously set
then the reference to the previous handler is returned.
- setEndTagHandlers ($handlers)
- Set the end_tag handlers. $handlers is a reference to a
hash similar to the one in the "end_tag_handlers" option of new.
All previous handlers are unset. The method returns the reference to the
previous handlers.
- setEndTagHandler ($exp $handler)
- Set a single end_tag handlers for elements matching $exp.
$handler is a reference to a subroutine. If the handler was previously set
then the reference to the previous handler is returned.
- setTwigRoots ($handlers)
- Same as using the "twig_roots" option when
creating the twig
- setCharHandler ($exp $handler)
- Set a "char_handler"
- setIgnoreEltsHandler ($exp)
- Set a "ignore_elt" handler (elements that match
$exp will be ignored
- setIgnoreEltsHandlers ($exp)
- Set all "ignore_elt" handlers (previous handlers
are replaced)
- dtd
- Return the dtd (an XML::Twig::DTD object) of a twig
- xmldecl
- Return the XML declaration for the document, or a default
one if it doesn't have one
- doctype
- Return the doctype for the document
- doctype_name
- returns the doctype of the document from the doctype
declaration
- system_id
- returns the system value of the DTD of the document from
the doctype declaration
- public_id
- returns the public doctype of the document from the doctype
declaration
- internal_subset
- returns the internal subset of the DTD
- dtd_text
- Return the DTD text
- dtd_print
- Print the DTD
- model ($tag)
- Return the model (in the DTD) for the element $tag
- root
- Return the root element of a twig
- set_root ($elt)
- Set the root of a twig
- first_elt ($optional_condition)
- Return the first element matching $optional_condition of a
twig, if no condition is given then the root is returned
- last_elt ($optional_condition)
- Return the last element matching $optional_condition of a
twig, if no condition is given then the last element of the twig is
returned
- elt_id ($id)
- Return the element whose "id" attribute is
$id
- getEltById
- Same as "elt_id"
- index ($index_name, $optional_index)
- If the $optional_index argument is present, return the
corresponding element in the index (created using the "index"
option for "XML::Twig-"new>)
If the argument is not present, return an arrayref to the index
- normalize
- merge together all consecutive pcdata elements in the
document (if for example you have turned some elements into pcdata using
"erase", this will give you a "clean" document in
which there all text elements are as long as possible).
- encoding
- This method returns the encoding of the XML document, as
defined by the "encoding" attribute in the XML declaration (ie
it is "undef" if the attribute is not defined)
- set_encoding
- This method sets the value of the "encoding"
attribute in the XML declaration. Note that if the document did not have a
declaration it is generated (with an XML version of 1.0)
- xml_version
- This method returns the XML version, as defined by the
"version" attribute in the XML declaration (ie it is
"undef" if the attribute is not defined)
- set_xml_version
- This method sets the value of the "version"
attribute in the XML declaration. If the declaration did not exist it is
created.
- standalone
- This method returns the value of the "standalone"
declaration for the document
- set_standalone
- This method sets the value of the "standalone"
attribute in the XML declaration. Note that if the document did not have a
declaration it is generated (with an XML version of 1.0)
- set_output_encoding
- Set the "encoding" "attribute" in the
XML declaration
- set_doctype ($name, $system, $public, $internal)
- Set the doctype of the element. If an argument is
"undef" (or not present) then its former value is retained, if a
false ('' or 0) value is passed then the former value is deleted;
- entity_list
- Return the entity list of a twig
- entity_names
- Return the list of all defined entities
- entity ($entity_name)
- Return the entity
- change_gi ($old_gi, $new_gi)
- Performs a (very fast) global change. All elements $old_gi
are now $new_gi. This is a bit dangerous though and should be avoided if
< possible, as the new tag might be ignored in subsequent processing.
See "BUGS "
- flush ($optional_filehandle, %options)
- Flushes a twig up to (and including) the current element,
then deletes all unnecessary elements from the tree that's kept in memory.
"flush" keeps track of which elements need to be open/closed, so
if you flush from handlers you don't have to worry about anything. Just
keep flushing the twig every time you're done with a sub-tree and it will
come out well-formed. After the whole parsing don't forget
to"flush" one more time to print the end of the document. The
doctype and entity declarations are also printed.
flush take an optional filehandle as an argument.
options: use the "update_DTD" option if you have updated the
(internal) DTD and/or the entity list and you want the updated DTD to be
output
The "pretty_print" option sets the pretty printing of the
document.
Example: $t->flush( Update_DTD => 1);
$t->flush( $filehandle, pretty_print => 'indented');
$t->flush( \*FILE);
- flush_up_to ($elt, $optional_filehandle, %options)
- Flushes up to the $elt element. This allows you to keep
part of the tree in memory when you "flush".
options: see flush.
- purge
- Does the same as a "flush" except it does not
print the twig. It just deletes all elements that have been completely
parsed so far.
- purge_up_to ($elt)
- Purges up to the $elt element. This allows you to keep part
of the tree in memory when you "purge".
- print ($optional_filehandle, %options)
- Prints the whole document associated with the twig. To be
used only AFTER the parse.
options: see "flush".
- print_to_file ($filename, %options)
- Prints the whole document associated with the twig to file
$filename. To be used only AFTER the parse.
options: see "flush".
- sprint
- Return the text of the whole document associated with the
twig. To be used only AFTER the parse.
options: see "flush".
- trim
- Trim the document: gets rid of initial and trailing spaces,
and replaces multiple spaces by a single one.
- toSAX1 ($handler)
- Send SAX events for the twig to the SAX1 handler
$handler
- toSAX2 ($handler)
- Send SAX events for the twig to the SAX2 handler
$handler
- flush_toSAX1 ($handler)
- Same as flush, except that SAX events are sent to the SAX1
handler $handler instead of the twig being printed
- flush_toSAX2 ($handler)
- Same as flush, except that SAX events are sent to the SAX2
handler $handler instead of the twig being printed
- ignore
- This method should be called during parsing, usually in
"start_tag_handlers". It causes the element to be skipped during
the parsing: the twig is not built for this element, it will not be
accessible during parsing or after it. The element will not take up any
memory and parsing will be faster.
Note that this method can also be called on an element. If the element is a
parent of the current element then this element will be ignored (the twig
will not be built any more for it and what has already been built will be
deleted).
- set_pretty_print ($style)
- Set the pretty print method, amongst '"none"'
(default), '"nsgmls"', '"nice"',
'"indented"', "indented_c", '"wrapped"',
'"record"' and '"record_c"'
WARNING: the pretty print style is a GLOBAL variable, so once
set it's applied to ALL "print"'s (and
"sprint"'s). Same goes if you use XML::Twig with
"mod_perl" . This should not be a problem as the XML that's
generated is valid anyway, and XML processors (as well as HTML processors,
including browsers) should not care. Let me know if this is a big problem,
but at the moment the performance/cleanliness trade-off clearly favors the
global approach.
- set_empty_tag_style ($style)
- Set the empty tag display style ('"normal"',
'"html"' or '"expand"'). As with
"set_pretty_print" this sets a global flag.
"normal" outputs an empty tag '"<tag/>"',
"html" adds a space '"<tag />"' for elements
that can be empty in XHTML and "expand" outputs
'"<tag></tag>"'
- set_remove_cdata ($flag)
- set (or unset) the flag that forces the twig to output
CDATA sections as regular (escaped) PCDATA
- print_prolog ($optional_filehandle, %options)
- Prints the prolog (XML declaration + DTD + entity
declarations) of a document.
options: see "flush".
- prolog ($optional_filehandle, %options)
- Return the prolog (XML declaration + DTD + entity
declarations) of a document.
options: see "flush".
- finish
- Call Expat "finish" method. Unsets all handlers
(including internal ones that set context), but expat continues parsing to
the end of the document or until it finds an error. It should finish up a
lot faster than with the handlers set.
- finish_print
- Stops twig processing, flush the twig and proceed to finish
printing the document as fast as possible. Use this method when modifying
a document and the modification is done.
- finish_now
- Stops twig processing, does not finish parsing the document
(which could actually be not well-formed after the point where
"finish_now" is called). Execution resumes after the
"Lparse"> or "parsefile" call. The content of the
twig is what has been parsed so far (all open elements at the time
"finish_now" is called are considered closed).
- set_expand_external_entities
- Same as using the "expand_external_ents" option
when creating the twig
- set_input_filter
- Same as using the "input_filter" option when
creating the twig
- set_keep_atts_order
- Same as using the "keep_atts_order" option when
creating the twig
- set_keep_encoding
- Same as using the "keep_encoding" option when
creating the twig
- escape_gt
- usually XML::Twig does not escape > in its output. Using
this option makes it replace > by >
- do_not_escape_gt
- reverts XML::Twig behavior to its default of not escaping
> in its output.
- set_output_filter
- Same as using the "output_filter" option when
creating the twig
- set_output_text_filter
- Same as using the "output_text_filter" option
when creating the twig
- add_stylesheet ($type, @options)
- Adds an external stylesheet to an XML document.
Supported types and options:
- xsl
- option: the url of the stylesheet
Example:
$t->add_stylesheet( xsl => "xsl_style.xsl");
will generate the following PI at the beginning of the document:
<?xml-stylesheet type="text/xsl" href="xsl_style.xsl"?>
- css
- option: the url of the stylesheet
- Methods inherited from XML::Parser::Expat
- A twig inherits all the relevant methods from
XML::Parser::Expat. These methods can only be used during the parsing
phase (they will generate a fatal error otherwise).
Inherited methods are:
- depth
- Returns the size of the context list.
- in_element
- Returns true if NAME is equal to the name of the innermost
curaXX rently opened element. If namespace processing is being used and
you want to check against a name that may be in a namespace, then use the
generate_ns_name method to create the NAME argument.
- within_element
- Returns the number of times the given name appears in the
context list. If namespace processing is being used and you want to check
against a name that may be in a namespace, then use the generaXX
ate_ns_name method to create the NAME argument.
- context
- Returns a list of element names that represent open
elements, with the last one being the innermost. Inside start and end tag
hanaXX dlers, this will be the tag of the parent element.
- current_line
- Returns the line number of the current position of the
parse.
- current_column
- Returns the column number of the current position of the
parse.
- current_byte
- Returns the current position of the parse.
- position_in_context
- Returns a string that shows the current parse position.
LINES should be an integer >= 0 that represents the number of lines on
either side of the current parse line to place into the returned
string.
- base ([NEWBASE])
- Returns the current value of the base for resolving
relative URIs. If NEWBASE is supplied, changes the base to that
value.
- current_element
- Returns the name of the innermost currently opened element.
Inside start or end handlers, returns the parent of the element associated
with those tags.
- element_index
- Returns an integer that is the depth-first visit order of
the curaXX rent element. This will be zero outside of the root element.
For example, this will return 1 when called from the start handler for the
root element start tag.
- recognized_string
- Returns the string from the document that was recognized in
order to call the current handler. For instance, when called from a start
handler, it will give us the the start-tag string. The string is encoded
in UTF-8. This method doesn't return a meaningful string inside
declaration handlers.
- original_string
- Returns the verbatim string from the document that was
recognized in order to call the current handler. The string is in the
original document encoding. This method doesn't return a meaningful string
inside declaration handlers.
- xpcroak
- Concatenate onto the given message the current line number
within the XML document plus the message implied by ErrorContext. Then
croak with the formed message.
- xpcarp
- Concatenate onto the given message the current line number
within the XML document plus the message implied by ErrorContext. Then
carp with the formed message.
- xml_escape(TEXT [, CHAR [, CHAR ...]])
- Returns TEXT with markup characters turned into character
entities. Any additional characters provided as arguments are also turned
into character references where found in TEXT.
(this method is broken on some versions of expat/XML::Parser)
- path ( $optional_tag)
- Return the element context in a form similar to XPath's
short form: '"/root/tag1/../tag"'
- get_xpath ( $optional_array_ref, $xpath,
$optional_offset)
- Performs a "get_xpath" on the document root (see
<Elt|"Elt">)
If the $optional_array_ref argument is used the array must contain elements.
The $xpath expression is applied to each element in turn and the result is
union of all results. This way a first query can be refined in further
steps.
- find_nodes ( $optional_array_ref, $xpath,
$optional_offset)
- same as "get_xpath"
- findnodes ( $optional_array_ref, $xpath,
$optional_offset)
- same as "get_xpath" (similar to the XML::LibXML
method)
- findvalue ( $optional_array_ref, $xpath,
$optional_offset)
- Return the "join" of all texts of the results of
applying "get_xpath" to the node (similar to the XML::LibXML
method)
- subs_text ($regexp, $replace)
- subs_text does text substitution on the whole document,
similar to perl's " s///" operator.
- dispose
- Useful only if you don't have "Scalar::Util" or
"WeakRef" installed.
Reclaims properly the memory used by an XML::Twig object. As the object has
circular references it never goes out of scope, so if you want to parse
lots of XML documents then the memory leak becomes a problem. Use
"$twig->dispose" to clear this problem.
- att_accessors (list_of_attribute_names)
- A convenience method that creates l-valued accessors for
attributes. So "$twig->create_accessors( 'foo')" will create
a "foo" method that can be called on elements:
$elt->foo; # equivalent to $elt->{'att'}->{'foo'};
$elt->foo( 'bar'); # equivalent to $elt->set_att( foo => 'bar');
The methods are l-valued only under those perl's that support this feature
(5.6 and above)
- create_accessors (list_of_attribute_names)
- Same as att_accessors
- elt_accessors (list_of_attribute_names)
- A convenience method that creates accessors for elements.
So "$twig->create_accessors( 'foo')" will create a
"foo" method that can be called on elements:
$elt->foo; # equivalent to $elt->first_child( 'foo');
- field_accessors (list_of_attribute_names)
- A convenience method that creates accessors for element
values ("field"). So "$twig->create_accessors(
'foo')" will create a "foo" method that can be called on
elements:
$elt->foo; # equivalent to $elt->field( 'foo');
- set_do_not_escape_amp_in_atts
- An evil method, that I only document because
Test::Pod::Coverage complaints otherwise, but really, you don't want to
know about it.
XML::Twig::Elt¶
- new ($optional_tag, $optional_atts, @optional_content)
- The "tag" is optional (but then you can't have a
content ), the $optional_atts argument is a reference to a hash of
attributes, the content can be just a string or a list of strings and
element. A content of '"#EMPTY"' creates an empty element;
Examples: my $elt= XML::Twig::Elt->new();
my $elt= XML::Twig::Elt->new( para => { align => 'center' });
my $elt= XML::Twig::Elt->new( para => { align => 'center' }, 'foo');
my $elt= XML::Twig::Elt->new( br => '#EMPTY');
my $elt= XML::Twig::Elt->new( 'para');
my $elt= XML::Twig::Elt->new( para => 'this is a para');
my $elt= XML::Twig::Elt->new( para => $elt3, 'another para');
The strings are not parsed, the element is not attached to any twig.
WARNING: if you rely on ID's then you will have to set the id
yourself. At this point the element does not belong to a twig yet, so the
ID attribute is not known so it won't be stored in the ID list.
Note that "#COMMENT", "#PCDATA" or "#CDATA"
are valid tag names, that will create text elements.
To create an element "foo" containing a CDATA section:
my $foo= XML::Twig::Elt->new( '#CDATA' => "content of the CDATA section")
->wrap_in( 'foo');
An attribute of '#CDATA', will create the content of the element as CDATA:
my $elt= XML::Twig::Elt->new( 'p' => { '#CDATA' => 1}, 'foo < bar');
creates an element
<p><![CDATA[foo < bar]]></>
- parse ($string, %args)
- Creates an element from an XML string. The string is
actually parsed as a new twig, then the root of that twig is returned. The
arguments in %args are passed to the twig. As always if the parse fails
the parser will die, so use an eval if you want to trap syntax errors.
As obviously the element does not exist beforehand this method has to be
called on the class:
my $elt= parse XML::Twig::Elt( "<a> string to parse, with <sub/>
<elements>, actually tons of </elements>
h</a>");
- set_inner_xml ($string)
- Sets the content of the element to be the tree created from
the string
- set_inner_html ($string)
- Sets the content of the element, after parsing the string
with an HTML parser (HTML::Parser)
- set_outer_xml ($string)
- Replaces the element with the tree created from the
string
- print ($optional_filehandle,
$optional_pretty_print_style)
- Prints an entire element, including the tags, optionally to
a $optional_filehandle, optionally with a $pretty_print_style.
The print outputs XML data so base entities are escaped.
- print_to_file ($filename, %options)
- Prints the element to file $filename.
options: see "flush". =item sprint ($elt,
$optional_no_enclosing_tag)
Return the xml string for an entire element, including the tags. If the
optional second argument is true then only the string inside the element
is returned (the start and end tag for $elt are not). The text is
XML-escaped: base entities (& and < in text, & < and "
in attribute values) are turned into entities.
- gi
- Return the gi of the element (the gi is the "generic
identifier" the tag name in SGML parlance).
"tag" and "name" are synonyms of "gi".
- tag
- Same as "gi"
- name
- Same as "tag"
- set_gi ($tag)
- Set the gi (tag) of an element
- set_tag ($tag)
- Set the tag (="tag") of an element
- set_name ($name)
- Set the name (="tag") of an element
- root
- Return the root of the twig in which the element is
contained.
- twig
- Return the twig containing the element.
- parent ($optional_condition)
- Return the parent of the element, or the first ancestor
matching the $optional_condition
- first_child ($optional_condition)
- Return the first child of the element, or the first child
matching the $optional_condition
- has_child ($optional_condition)
- Return the first child of the element, or the first child
matching the $optional_condition (same as first_child)
- has_children ($optional_condition)
- Return the first child of the element, or the first child
matching the $optional_condition (same as first_child)
- first_child_text ($optional_condition)
- Return the text of the first child of the element, or the
first child
matching the $optional_condition If there is no first_child then returns
''. This avoids getting the child, checking for its existence then getting
the text for trivial cases.
Similar methods are available for the other navigation methods:
- last_child_text
- prev_sibling_text
- next_sibling_text
- prev_elt_text
- next_elt_text
- child_text
- parent_text
All this methods also exist in "trimmed" variant:
- first_child_trimmed_text
- last_child_trimmed_text
- prev_sibling_trimmed_text
- next_sibling_trimmed_text
- prev_elt_trimmed_text
- next_elt_trimmed_text
- child_trimmed_text
- parent_trimmed_text
- field ($condition)
- Same method as "first_child_text" with a
different name
- fields ($condition_list)
- Return the list of field (text of first child matching the
conditions), missing fields are returned as the empty string.
Same method as "first_child_text" with a different name
- trimmed_field ($optional_condition)
- Same method as "first_child_trimmed_text" with a
different name
- set_field ($condition, $optional_atts,
@list_of_elt_and_strings)
- Set the content of the first child of the element that
matches $condition, the rest of the arguments is the same as for
"set_content"
If no child matches $condition _and_ if $condition is a valid XML element
name, then a new element by that name is created and inserted as the last
child.
- first_child_matches ($optional_condition)
- Return the element if the first child of the element (if it
exists) passes the $optional_condition "undef" otherwise
if( $elt->first_child_matches( 'title')) ...
is equivalent to
if( $elt->{first_child} && $elt->{first_child}->passes( 'title'))
"first_child_is" is an other name for this method
Similar methods are available for the other navigation methods:
- last_child_matches
- prev_sibling_matches
- next_sibling_matches
- prev_elt_matches
- next_elt_matches
- child_matches
- parent_matches
- is_first_child ($optional_condition)
- returns true (the element) if the element is the first
child of its parent (optionally that satisfies the
$optional_condition)
- is_last_child ($optional_condition)
- returns true (the element) if the element is the last child
of its parent (optionally that satisfies the $optional_condition)
- prev_sibling ($optional_condition)
- Return the previous sibling of the element, or the previous
sibling matching $optional_condition
- next_sibling ($optional_condition)
- Return the next sibling of the element, or the first one
matching $optional_condition.
- next_elt ($optional_elt, $optional_condition)
- Return the next elt (optionally matching
$optional_condition) of the element. This is defined as the next element
which opens after the current element opens. Which usually means the first
child of the element. Counter-intuitive as it might look this allows you
to loop through the whole document by starting from the root.
The $optional_elt is the root of a subtree. When the "next_elt" is
out of the subtree then the method returns undef. You can then walk a sub
tree with:
my $elt= $subtree_root;
while( $elt= $elt->next_elt( $subtree_root)
{ # insert processing code here
}
- prev_elt ($optional_condition)
- Return the previous elt (optionally matching
$optional_condition) of the element. This is the first element which opens
before the current one. It is usually either the last descendant of the
previous sibling or simply the parent
- next_n_elt ($offset, $optional_condition)
- Return the $offset-th element that matches the
$optional_condition
- following_elt
- Return the following element (as per the XPath following
axis)
- preceding_elt
- Return the preceding element (as per the XPath preceding
axis)
- following_elts
- Return the list of following elements (as per the XPath
following axis)
- preceding_elts
- Return the pst of preceding elements (as per the XPath
preceding axis)
- children ($optional_condition)
- Return the list of children (optionally which matches
$optional_condition) of the element. The list is in document order.
- children_count ($optional_condition)
- Return the number of children of the element (optionally
which matches $optional_condition)
- children_text ($optional_condition)
- In array context, reeturns an array containing the text of
children of the element (optionally which matches $optional_condition)
In scalar context, returns the concatenation of the text of children of the
element
- children_trimmed_text ($optional_condition)
- In array context, returns an array containing the trimmed
text of children of the element (optionally which matches
$optional_condition)
In scalar context, returns the concatenation of the trimmed text of children
of the element
- children_copy ($optional_condition)
- Return a list of elements that are copies of the children
of the element, optionally which matches $optional_condition
- descendants ($optional_condition)
- Return the list of all descendants (optionally which
matches $optional_condition) of the element. This is the equivalent of the
"getElementsByTagName" of the DOM (by the way, if you are really
a DOM addict, you can use "getElementsByTagName" instead)
- getElementsByTagName ($optional_condition)
- Same as "descendants"
- find_by_tag_name ($optional_condition)
- Same as "descendants"
- descendants_or_self ($optional_condition)
- Same as "descendants" except that the element
itself is included in the list if it matches the $optional_condition
- first_descendant ($optional_condition)
- Return the first descendant of the element that matches the
condition
- last_descendant ($optional_condition)
- Return the last descendant of the element that matches the
condition
- ancestors ($optional_condition)
- Return the list of ancestors (optionally matching
$optional_condition) of the element. The list is ordered from the
innermost ancestor to the outermost one
NOTE: the element itself is not part of the list, in order to include it you
will have to use ancestors_or_self
- ancestors_or_self ($optional_condition)
- Return the list of ancestors (optionally matching
$optional_condition) of the element, including the element (if it matches
the condition>). The list is ordered from the innermost ancestor to the
outermost one
- passes ($condition)
- Return the element if it passes the $condition
- att ($att)
- Return the value of attribute $att or
"undef"
- latt ($att)
- Return the value of attribute $att or "undef"
this method is an lvalue, so you can do "$elt->latt( 'foo')=
'bar'" or "$elt->latt( 'foo')++;"
- set_att ($att, $att_value)
- Set the attribute of the element to the given value
You can actually set several attributes this way:
$elt->set_att( att1 => "val1", att2 => "val2");
- del_att ($att)
- Delete the attribute for the element
You can actually delete several attributes at once:
$elt->del_att( 'att1', 'att2', 'att3');
- att_exists ($att)
- Returns true if the attribute $att exists for the element,
false otherwise
- cut
- Cut the element from the tree. The element still exists, it
can be copied or pasted somewhere else, it is just not attached to the
tree anymore.
Note that the "old" links to the parent, previous and next
siblings can still be accessed using the former_* methods
- former_next_sibling
- Returns the former next sibling of a cut node (or undef if
the node has not been cut)
This makes it easier to write loops where you cut elements:
my $child= $parent->first_child( 'achild');
while( $child->{'att'}->{'cut'})
{ $child->cut; $child= $child->former_next_sibling; }
- former_prev_sibling
- Returns the former previous sibling of a cut node (or undef
if the node has not been cut)
- former_parent
- Returns the former parent of a cut node (or undef if the
node has not been cut)
- cut_children ($optional_condition)
- Cut all the children of the element (or all of those which
satisfy the $optional_condition).
Return the list of children
- cut_descendants ($optional_condition)
- Cut all the descendants of the element (or all of those
which satisfy the $optional_condition).
Return the list of descendants
- copy ($elt)
- Return a copy of the element. The copy is a
"deep" copy: all sub elements of the element are
duplicated.
- paste ($optional_position, $ref)
- Paste a (previously "cut" or newly generated)
element. Die if the element already belongs to a tree.
Note that the calling element is pasted:
$child->paste( first_child => $existing_parent);
$new_sibling->paste( after => $this_sibling_is_already_in_the_tree);
or
my $new_elt= XML::Twig::Elt->new( tag => $content);
$new_elt->paste( $position => $existing_elt);
Example:
my $t= XML::Twig->new->parse( 'doc.xml')
my $toc= $t->root->new( 'toc');
$toc->paste( $t->root); # $toc is pasted as first child of the root
foreach my $title ($t->findnodes( '/doc/section/title'))
{ my $title_toc= $title->copy;
# paste $title_toc as the last child of toc
$title_toc->paste( last_child => $toc)
}
Position options:
- first_child (default)
- The element is pasted as the first child of $ref
- last_child
- The element is pasted as the last child of $ref
- before
- The element is pasted before $ref, as its previous
sibling.
- after
- The element is pasted after $ref, as its next sibling.
- within
- In this case an extra argument, $offset, should be
supplied. The element will be pasted in the reference element (or in its
first text child) at the given offset. To achieve this the reference
element will be split at the offset.
Note that you can call directly the underlying method:
- paste_before
- paste_after
- paste_first_child
- paste_last_child
- paste_within
- move ($optional_position, $ref)
- Move an element in the tree. This is just a "cut"
then a "paste". The syntax is the same as
"paste".
- replace ($ref)
- Replaces an element in the tree. Sometimes it is just not
possible to"cut" an element then "paste" another in
its place, so "replace" comes in handy. The calling element
replaces $ref.
- replace_with (@elts)
- Replaces the calling element with one or more elements
- delete
- Cut the element and frees the memory.
- prefix ($text, $optional_option)
- Add a prefix to an element. If the element is a
"PCDATA" element the text is added to the pcdata, if the
elements first child is a "PCDATA" then the text is added to
it's pcdata, otherwise a new "PCDATA" element is created and
pasted as the first child of the element.
If the option is "asis" then the prefix is added asis: it is
created in a separate "PCDATA" element with an "asis"
property. You can then write:
$elt1->prefix( '<b>', 'asis');
to create a "<b>" in the output of "print".
- suffix ($text, $optional_option)
- Add a suffix to an element. If the element is a
"PCDATA" element the text is added to the pcdata, if the
elements last child is a "PCDATA" then the text is added to it's
pcdata, otherwise a new PCDATA element is created and pasted as the last
child of the element.
If the option is "asis" then the suffix is added asis: it is
created in a separate "PCDATA" element with an "asis"
property. You can then write:
$elt2->suffix( '</b>', 'asis');
- trim
- Trim the element in-place: spaces at the beginning and at
the end of the element are discarded and multiple spaces within the
element (or its descendants) are replaced by a single space.
Note that in some cases you can still end up with multiple spaces, if they
are split between several elements:
<doc> text <b> hah! </b> yep</doc>
gets trimmed to
<doc>text <b> hah! </b> yep</doc>
This is somewhere in between a bug and a feature.
- normalize
- merge together all consecutive pcdata elements in the
element (if for example you have turned some elements into pcdata using
"erase", this will give you a "clean" element in which
there all text fragments are as long as possible).
- simplify (%options)
- Return a data structure suspiciously similar to
XML::Simple's. Options are identical to XMLin options, see XML::Simple doc
for more details (or use DATA::dumper or YAML to dump the data
structure)
- content_key
- forcearray
- keyattr
- noattr
- normalize_space
- aka normalise_space
- variables (%var_hash)
- %var_hash is a hash { name => value }
This option allows variables in the XML to be expanded when the file is
read. (there is no facility for putting the variable names back if you
regenerate XML using XMLout).
A 'variable' is any text of the form ${name} (or $name) which occurs in an
attribute value or in the text content of an element. If 'name' matches a
key in the supplied hashref, ${name} will be replaced with the
corresponding value from the hashref. If no matching key is found, the
variable will not be replaced.
- var_att ($attribute_name)
- This option gives the name of an attribute that will be
used to create variables in the XML:
<dirs>
<dir name="prefix">/usr/local</dir>
<dir name="exec_prefix">$prefix/bin</dir>
</dirs>
use "var => 'name'" to get $prefix replaced by /usr/local in
the generated data structure
By default variables are captured by the following regexp: /$(\w+)/
- var_regexp (regexp)
- This option changes the regexp used to capture variables.
The variable name should be in $1
- group_tags { grouping tag => grouped tag, grouping tag 2
=> grouped tag 2...}
- Option used to simplify the structure: elements listed will
not be used. Their children will be, they will be considered children of
the element parent.
If the element is:
<config host="laptop.xmltwig.com">
<server>localhost</server>
<dirs>
<dir name="base">/home/mrodrigu/standards</dir>
<dir name="tools">$base/tools</dir>
</dirs>
<templates>
<template name="std_def">std_def.templ</template>
<template name="dummy">dummy</template>
</templates>
</config>
Then calling simplify with "group_tags => { dirs => 'dir',
templates => 'template'}" makes the data structure be exactly as
if the start and end tags for "dirs" and "templates"
were not there.
A YAML dump of the structure
base: '/home/mrodrigu/standards'
host: laptop.xmltwig.com
server: localhost
template:
- std_def.templ
- dummy.templ
tools: '$base/tools'
- split_at ($offset)
- Split a text ("PCDATA" or "CDATA")
element in 2 at $offset, the original element now holds the first part of
the string and a new element holds the right part. The new element is
returned
If the element is not a text element then the first text child of the
element is split
- split ( $optional_regexp, $tag1, $atts1, $tag2,
$atts2...)
- Split the text descendants of an element in place, the text
is split using the $regexp, if the regexp includes () then the matched
separators will be wrapped in elements. $1 is wrapped in $tag1, with
attributes $atts1 if $atts1 is given (as a hashref), $2 is wrapped in
$tag2...
if $elt is "<p>tati tata <b>tutu tati titi</b> tata
tati tata</p>"
$elt->split( qr/(ta)ti/, 'foo', {type => 'toto'} )
will change $elt to
<p><foo type="toto">ta</foo> tata <b>tutu <foo type="toto">ta</foo>
titi</b> tata <foo type="toto">ta</foo> tata</p>
The regexp can be passed either as a string or as "qr//" (perl
5.005 and later), it defaults to \s+ just as the "split"
built-in (but this would be quite a useless behaviour without the
$optional_tag parameter)
$optional_tag defaults to PCDATA or CDATA, depending on the initial element
type
The list of descendants is returned (including un-touched original elements
and newly created ones)
- mark ( $regexp, $optional_tag,
$optional_attribute_ref)
- This method behaves exactly as split, except only the newly
created elements are returned
- wrap_children ( $regexp_string, $tag,
$optional_attribute_hashref)
- Wrap the children of the element that match the regexp in
an element $tag. If $optional_attribute_hashref is passed then the new
element will have these attributes.
The $regexp_string includes tags, within pointy brackets, as in
"<title><para>+" and the usual Perl modifiers
(+*?...). Tags can be further qualified with attributes: "<para
type="warning" classif="cosmic_secret">+". The
values for attributes should be xml-escaped: "<candy
type="M&Ms">*" ("<",
"&" ">" and
""" should be escaped).
Note that elements might get extra "id" attributes in the process.
See add_id. Use strip_att to remove unwanted id's.
Here is an example:
If the element $elt has the following content:
<elt>
<p>para 1</p>
<l_l1_1>list 1 item 1 para 1</l_l1_1>
<l_l1>list 1 item 1 para 2</l_l1>
<l_l1_n>list 1 item 2 para 1 (only para)</l_l1_n>
<l_l1_n>list 1 item 3 para 1</l_l1_n>
<l_l1>list 1 item 3 para 2</l_l1>
<l_l1>list 1 item 3 para 3</l_l1>
<l_l1_1>list 2 item 1 para 1</l_l1_1>
<l_l1>list 2 item 1 para 2</l_l1>
<l_l1_n>list 2 item 2 para 1 (only para)</l_l1_n>
<l_l1_n>list 2 item 3 para 1</l_l1_n>
<l_l1>list 2 item 3 para 2</l_l1>
<l_l1>list 2 item 3 para 3</l_l1>
</elt>
Then the code
$elt->wrap_children( q{<l_l1_1><l_l1>*} , li => { type => "ul1" });
$elt->wrap_children( q{<l_l1_n><l_l1>*} , li => { type => "ul" });
$elt->wrap_children( q{<li type="ul1"><li type="ul">+}, "ul");
$elt->strip_att( 'id');
$elt->strip_att( 'type');
$elt->print;
will output:
<elt>
<p>para 1</p>
<ul>
<li>
<l_l1_1>list 1 item 1 para 1</l_l1_1>
<l_l1>list 1 item 1 para 2</l_l1>
</li>
<li>
<l_l1_n>list 1 item 2 para 1 (only para)</l_l1_n>
</li>
<li>
<l_l1_n>list 1 item 3 para 1</l_l1_n>
<l_l1>list 1 item 3 para 2</l_l1>
<l_l1>list 1 item 3 para 3</l_l1>
</li>
</ul>
<ul>
<li>
<l_l1_1>list 2 item 1 para 1</l_l1_1>
<l_l1>list 2 item 1 para 2</l_l1>
</li>
<li>
<l_l1_n>list 2 item 2 para 1 (only para)</l_l1_n>
</li>
<li>
<l_l1_n>list 2 item 3 para 1</l_l1_n>
<l_l1>list 2 item 3 para 2</l_l1>
<l_l1>list 2 item 3 para 3</l_l1>
</li>
</ul>
</elt>
- subs_text ($regexp, $replace)
- subs_text does text substitution, similar to perl's "
s///" operator.
$regexp must be a perl regexp, created with the "qr" operator.
$replace can include "$1, $2"... from the $regexp. It can also be
used to create element and entities, by using "&elt( tag => {
att => val }, text)" (similar syntax as "new") and
"&ent( name)".
Here is a rather complex example:
$elt->subs_text( qr{(?<!do not )link to (http://([^\s,]*))},
'see &elt( a =>{ href => $1 }, $2)'
);
This will replace text like link to http://www.xmltwig.com by see
<a href="www.xmltwig.com">www.xmltwig.com</a>,
but not do not link to...
Generating entities (here replacing spaces with ):
$elt->subs_text( qr{ }, '&ent( " ")');
or, using a variable:
my $ent=" ";
$elt->subs_text( qr{ }, "&ent( '$ent')");
Note that the substitution is always global, as in using the "g"
modifier in a perl substitution, and that it is performed on all text
descendants of the element.
Bug: in the $regexp, you can only use "\1",
"\2"... if the replacement expression does not include elements
or attributes. eg
t->subs_text( qr/((t[aiou])\2)/, '$2'); # ok, replaces toto, tata, titi, tutu by to, ta, ti, tu
t->subs_text( qr/((t[aiou])\2)/, '&elt(p => $1)' ); # NOK, does not find toto...
- add_id ($optional_coderef)
- Add an id to the element.
The id is an attribute, "id" by default, see the "id"
option for XML::Twig "new" to change it. Use an id starting with
"#" to get an id that's not output by print, flush or sprint,
yet that allows you to use the elt_id method to get the element easily.
If the element already has an id, no new id is generated.
By default the method create an id of the form
"twig_id_<nnnn>", where "<nnnn>" is a
number, incremented each time the method is called successfully.
- set_id_seed ($prefix)
- by default the id generated by "add_id" is
"twig_id_<nnnn>", "set_id_seed" changes the
prefix to $prefix and resets the number to 1
- strip_att ($att)
- Remove the attribute $att from all descendants of the
element (including the element)
Return the element
- change_att_name ($old_name, $new_name)
- Change the name of the attribute from $old_name to
$new_name. If there is no attribute $old_name nothing happens.
- lc_attnames
- Lower cases the name all the attributes of the
element.
- sort_children_on_value( %options)
- Sort the children of the element in place according to
their text. All children are sorted.
Return the element, with its children sorted.
%options are
type : numeric | alpha (default: alpha)
order : normal | reverse (default: normal)
Return the element, with its children sorted
- sort_children_on_att ($att, %options)
- Sort the children of the element in place according to
attribute $att. %options are the same as for
"sort_children_on_value"
Return the element.
- sort_children_on_field ($tag, %options)
- Sort the children of the element in place, according to the
field $tag (the text of the first child of the child with this tag).
%options are the same as for "sort_children_on_value".
Return the element, with its children sorted
- sort_children( $get_key, %options)
- Sort the children of the element in place. The $get_key
argument is a reference to a function that returns the sort key when
passed an element.
For example:
$elt->sort_children( sub { $_[0]->{'att'}->{"nb"} + $_[0]->text },
type => 'numeric', order => 'reverse'
);
- field_to_att ($cond, $att)
- Turn the text of the first sub-element matched by $cond
into the value of attribute $att of the element. If $att is omitted then
$cond is used as the name of the attribute, which makes sense only if
$cond is a valid element (and attribute) name.
The sub-element is then cut.
- att_to_field ($att, $tag)
- Take the value of attribute $att and create a sub-element
$tag as first child of the element. If $tag is omitted then $att is used
as the name of the sub-element.
- get_xpath ($xpath, $optional_offset)
- Return a list of elements satisfying the $xpath. $xpath is
an XPATH-like expression.
A subset of the XPATH abbreviated syntax is covered:
tag
tag[1] (or any other positive number)
tag[last()]
tag[@att] (the attribute exists for the element)
tag[@att="val"]
tag[@att=~ /regexp/]
tag[att1="val1" and att2="val2"]
tag[att1="val1" or att2="val2"]
tag[string()="toto"] (returns tag elements which text (as per the text method)
is toto)
tag[string()=~/regexp/] (returns tag elements which text (as per the text
method) matches regexp)
expressions can start with / (search starts at the document root)
expressions can start with . (search starts at the current element)
// can be used to get all descendants instead of just direct children
* matches any tag
So the following examples from the XPath
recommendationhttp://www.w3.org/TR/xpath.html#path-abbrev
<http://www.w3.org/TR/xpath.html#path-abbrev> work:
para selects the para element children of the context node
* selects all element children of the context node
para[1] selects the first para child of the context node
para[last()] selects the last para child of the context node
*/para selects all para grandchildren of the context node
/doc/chapter[5]/section[2] selects the second section of the fifth chapter
of the doc
chapter//para selects the para element descendants of the chapter element
children of the context node
//para selects all the para descendants of the document root and thus selects
all para elements in the same document as the context node
//olist/item selects all the item elements in the same document as the
context node that have an olist parent
.//para selects the para element descendants of the context node
.. selects the parent of the context node
para[@type="warning"] selects all para children of the context node that have
a type attribute with value warning
employee[@secretary and @assistant] selects all the employee children of the
context node that have both a secretary attribute and an assistant
attribute
The elements will be returned in the document order.
If $optional_offset is used then only one element will be returned, the one
with the appropriate offset in the list, starting at 0
Quoting and interpolating variables can be a pain when the Perl syntax and
the XPATH syntax collide, so use alternate quoting mechanisms like q or qq
(I like q{} and qq{} myself).
Here are some more examples to get you started:
my $p1= "p1";
my $p2= "p2";
my @res= $t->get_xpath( qq{p[string( "$p1") or string( "$p2")]});
my $a= "a1";
my @res= $t->get_xpath( qq{//*[@att="$a"]});
my $val= "a1";
my $exp= qq{//p[ \@att='$val']}; # you need to use \@ or you will get a warning
my @res= $t->get_xpath( $exp);
Note that the only supported regexps delimiters are / and that you must
backslash all / in regexps AND in regular strings.
XML::Twig does not provide natively full XPATH support, but you can use
"XML::Twig::XPath" to get "findnodes" to use
"XML::XPath" as the XPath engine, with full coverage of the
spec.
"XML::Twig::XPath" to get "findnodes" to use
"XML::XPath" as the XPath engine, with full coverage of the
spec.
- find_nodes
- same as"get_xpath"
- findnodes
- same as "get_xpath"
- text @optional_options
- Return a string consisting of all the "PCDATA"
and "CDATA" in an element, without any tags. The text is not
XML-escaped: base entities such as "&" and "<"
are not escaped.
The '"no_recurse"' option will only return the text of the
element, not of any included sub-elements (same as
"text_only").
- text_only
- Same as "text" except that the text returned
doesn't include the text of sub-elements.
- trimmed_text
- Same as "text" except that the text is trimmed:
leading and trailing spaces are discarded, consecutive spaces are
collapsed
- set_text ($string)
- Set the text for the element: if the element is a
"PCDATA", just set its text, otherwise cut all the children of
the element and create a single "PCDATA" child for it, which
holds the text.
- merge ($elt2)
- Move the content of $elt2 within the element
- insert ($tag1, [$optional_atts1], $tag2,
[$optional_atts2],...)
- For each tag in the list inserts an element $tag as the
only child of the element. The element gets the optional attributes
in"$optional_atts<n>." All children of the element are set
as children of the new element. The upper level element is returned.
$p->insert( table => { border=> 1}, 'tr', 'td')
put $p in a table with a visible border, a single "tr" and a
single "td" and return the "table" element:
<p><table border="1"><tr><td>original content of p</td></tr></table></p>
- wrap_in (@tag)
- Wrap elements in @tag as the successive ancestors of the
element, returns the new element. "$elt->wrap_in( 'td', 'tr',
'table')" wraps the element as a single cell in a table for example.
Optionally each tag can be followed by a hashref of attributes, that will be
set on the wrapping element:
$elt->wrap_in( p => { class => "advisory" }, div => { class => "intro", id => "div_intro });
- insert_new_elt ($opt_position, $tag, $opt_atts_hashref,
@opt_content)
- Combines a "new " and a "paste ":
creates a new element using $tag, $opt_atts_hashref and @opt_content which
are arguments similar to those for "new", then paste it, using
$opt_position or 'first_child', relative to $elt.
Return the newly created element
- erase
- Erase the element: the element is deleted and all of its
children are pasted in its place.
- set_content ( $optional_atts, @list_of_elt_and_strings) (
$optional_atts, '#EMPTY')
- Set the content for the element, from a list of strings and
elements. Cuts all the element children, then pastes the list elements as
the children. This method will create a "PCDATA" element for any
strings in the list.
The $optional_atts argument is the ref of a hash of attributes. If this
argument is used then the previous attributes are deleted, otherwise they
are left untouched.
WARNING: if you rely on ID's then you will have to set the id
yourself. At this point the element does not belong to a twig yet, so the
ID attribute is not known so it won't be stored in the ID list.
A content of '"#EMPTY"' creates an empty element;
- namespace ($optional_prefix)
- Return the URI of the namespace that $optional_prefix or
the element name belongs to. If the name doesn't belong to any namespace,
"undef" is returned.
- local_name
- Return the local name (without the prefix) for the
element
- ns_prefix
- Return the namespace prefix for the element
- current_ns_prefixes
- Return a list of namespace prefixes valid for the element.
The order of the prefixes in the list has no meaning. If the default
namespace is currently bound, '' appears in the list.
- inherit_att ($att, @optional_tag_list)
- Return the value of an attribute inherited from parent
tags. The value returned is found by looking for the attribute in the
element then in turn in each of its ancestors. If the @optional_tag_list
is supplied only those ancestors whose tag is in the list will be
checked.
- all_children_are ($optional_condition)
- return 1 if all children of the element pass the
$optional_condition, 0 otherwise
- level ($optional_condition)
- Return the depth of the element in the twig (root is 0). If
$optional_condition is given then only ancestors that match the condition
are counted.
WARNING: in a tree created using the "twig_roots" option
this will not return the level in the document tree, level 0 will be the
document root, level 1 will be the "twig_roots" elements. During
the parsing (in a "twig_handler") you can use the
"depth" method on the twig object to get the real parsing
depth.
- in ($potential_parent)
- Return true if the element is in the potential_parent
($potential_parent is an element)
- in_context ($cond, $optional_level)
- Return true if the element is included in an element which
passes $cond optionally within $optional_level levels. The returned value
is the including element.
- pcdata
- Return the text of a "PCDATA" element or
"undef" if the element is not "PCDATA".
- pcdata_xml_string
- Return the text of a "PCDATA" element or undef if
the element is not "PCDATA". The text is "XML-escaped"
('&' and '<' are replaced by '&' and '<')
- set_pcdata ($text)
- Set the text of a "PCDATA" element. This method
does not check that the element is indeed a "PCDATA" so usually
you should use "set_text" instead.
- append_pcdata ($text)
- Add the text at the end of a "PCDATA"
element.
- is_cdata
- Return 1 if the element is a "CDATA" element,
returns 0 otherwise.
- is_text
- Return 1 if the element is a "CDATA" or
"PCDATA" element, returns 0 otherwise.
- cdata
- Return the text of a "CDATA" element or
"undef" if the element is not "CDATA".
- cdata_string
- Return the XML string of a "CDATA" element,
including the opening and closing markers.
- set_cdata ($text)
- Set the text of a "CDATA" element.
- append_cdata ($text)
- Add the text at the end of a "CDATA"
element.
- remove_cdata
- Turns all "CDATA" sections in the element into
regular "PCDATA" elements. This is useful when converting XML to
HTML, as browsers do not support CDATA sections.
- extra_data
- Return the extra_data (comments and PI's) attached to an
element
- set_extra_data ($extra_data)
- Set the extra_data (comments and PI's) attached to an
element
- append_extra_data ($extra_data)
- Append extra_data to the existing extra_data before the
element (if no previous extra_data exists then it is created)
- set_asis
- Set a property of the element that causes it to be output
without being XML escaped by the print functions: if it contains "a
< b" it will be output as such and not as "a <
b". This can be useful to create text elements that will be output as
markup. Note that all "PCDATA" descendants of the element are
also marked as having the property (they are the ones that are actually
impacted by the change).
If the element is a "CDATA" element it will also be output asis,
without the "CDATA" markers. The same goes for any
"CDATA" descendant of the element
- set_not_asis
- Unsets the "asis" property for the element and
its text descendants.
- is_asis
- Return the "asis" property status of the element
( 1 or "undef")
- closed
- Return true if the element has been closed. Might be useful
if you are somewhere in the tree, during the parse, and have no idea
whether a parent element is completely loaded or not.
- get_type
- Return the type of the element: '"#ELT"' for
"real" elements, or '"#PCDATA"', '"#CDATA"',
'"#COMMENT"', '"#ENT"', '"#PI"'
- is_elt
- Return the tag if the element is a "real"
element, or 0 if it is "PCDATA", "CDATA"...
- contains_only_text
- Return 1 if the element does not contain any other
"real" element
- contains_only ($exp)
- Return the list of children if all children of the element
match the expression $exp
if( $para->contains_only( 'tt')) { ... }
- contains_a_single ($exp)
- If the element contains a single child that matches the
expression $exp returns that element. Otherwise returns 0.
- is_field
- same as "contains_only_text"
- is_pcdata
- Return 1 if the element is a "PCDATA" element,
returns 0 otherwise.
- is_ent
- Return 1 if the element is an entity (an unexpanded entity)
element, return 0 otherwise.
- is_empty
- Return 1 if the element is empty, 0 otherwise
- set_empty
- Flags the element as empty. No further check is made, so if
the element is actually not empty the output will be messed. The only
effect of this method is that the output will be "<tag
att="value""/>".
- set_not_empty
- Flags the element as not empty. if it is actually empty
then the element will be output as "<tag
att="value""></tag>"
- is_pi
- Return 1 if the element is a processing instruction
("#PI") element, return 0 otherwise.
- target
- Return the target of a processing instruction
- set_target ($target)
- Set the target of a processing instruction
- data
- Return the data part of a processing instruction
- set_data ($data)
- Set the data of a processing instruction
- set_pi ($target, $data)
- Set the target and data of a processing instruction
- pi_string
- Return the string form of a processing instruction
("<?target data?>")
- is_comment
- Return 1 if the element is a comment ("#COMMENT")
element, return 0 otherwise.
- set_comment ($comment_text)
- Set the text for a comment
- comment
- Return the content of a comment (just the text, not the
"<!--" and "-->")
- comment_string
- Return the XML string for a comment ("<!-- comment
-->")
Note that an XML comment cannot start or end with a '-', or include '--'
(http://www.w3.org/TR/2008/REC-xml-20081126/#sec-comments), if that is the
case (because you have created the comment yourself presumably, as it
could not be in the input XML), then a space will be inserted before an
initial '-', after a trailing one or between two '-' in the comment (which
could presumably mangle javascript "hidden" in an XHTML
comment);
- set_ent ($entity)
- Set an (non-expanded) entity ("#ENT"). $entity)
is the entity text ("&ent;")
- ent
- Return the entity for an entity ("#ENT") element
("&ent;")
- ent_name
- Return the entity name for an entity ("#ENT")
element ("ent")
- ent_string
- Return the entity, either expanded if the expanded version
is available, or non-expanded ("&ent;") otherwise
- child ($offset, $optional_condition)
- Return the $offset-th child of the element, optionally the
$offset-th child that matches $optional_condition. The children are
treated as a list, so "$elt->child( 0)" is the first child,
while "$elt->child( -1)" is the last child.
- child_text ($offset, $optional_condition)
- Return the text of a child or "undef" if the
sibling does not exist. Arguments are the same as child.
- last_child ($optional_condition)
- Return the last child of the element, or the last child
matching $optional_condition (ie the last of the element children matching
the condition).
- last_child_text ($optional_condition)
- Same as "first_child_text" but for the last
child.
- sibling ($offset, $optional_condition)
- Return the next or previous $offset-th sibling of the
element, or the $offset-th one matching $optional_condition. If $offset is
negative then a previous sibling is returned, if $offset is positive then
a next sibling is returned. "$offset=0" returns the element if
there is no condition or if the element matches the condition>,
"undef" otherwise.
- sibling_text ($offset, $optional_condition)
- Return the text of a sibling or "undef" if the
sibling does not exist. Arguments are the same as
"sibling".
- prev_siblings ($optional_condition)
- Return the list of previous siblings (optionally matching
$optional_condition) for the element. The elements are ordered in document
order.
- next_siblings ($optional_condition)
- Return the list of siblings (optionally matching
$optional_condition) following the element. The elements are ordered in
document order.
- siblings ($optional_condition)
- Return the list of siblings (optionally matching
$optional_condition) of the element (excluding the element itself). The
elements are ordered in document order.
- pos ($optional_condition)
- Return the position of the element in the children list.
The first child has a position of 1 (as in XPath).
If the $optional_condition is given then only siblings that match the
condition are counted. If the element itself does not match the condition
then 0 is returned.
- atts
- Return a hash ref containing the element attributes
- set_atts ({ att1=>$att1_val, att2=> $att2_val...
})
- Set the element attributes with the hash ref supplied as
the argument. The previous attributes are lost (ie the attributes set by
"set_atts" replace all of the attributes of the element).
You can also pass a list instead of a hashref: "$elt->set_atts( att1
=> 'val1',...)"
- del_atts
- Deletes all the element attributes.
- att_nb
- Return the number of attributes for the element
- has_atts
- Return true if the element has attributes (in fact return
the number of attributes, thus being an alias to "att_nb"
- has_no_atts
- Return true if the element has no attributes, false (0)
otherwise
- att_names
- return a list of the attribute names for the element
- att_xml_string ($att, $options)
- Return the attribute value, where '&', '<' and quote
(" or the value of the quote option at twig creation) are
XML-escaped.
The options are passed as a hashref, setting "escape_gt" to a true
value will also escape '>' ($elt( 'myatt', { escape_gt => 1 });
- set_id ($id)
- Set the "id" attribute of the element to the
value. See "elt_id " to change the id attribute name
- id
- Gets the id attribute value
- del_id ($id)
- Deletes the "id" attribute of the element and
remove it from the id list for the document
- class
- Return the "class" attribute for the element
(methods on the "class" attribute are quite convenient when
dealing with XHTML, or plain XML that will eventually be displayed using
CSS)
- lclass
- same as class, except that this method is an lvalue, so you
can do "$elt->lclass= "foo""
- set_class ($class)
- Set the "class" attribute for the element to
$class
- add_class ($class)
- Add $class to the element "class" attribute: the
new class is added only if it is not already present.
Note that classes are then sorted alphabetically, so the "class"
attribute can be changed even if the class is already there
- remove_class ($class)
- Remove $class from the element "class" attribute.
Note that classes are then sorted alphabetically, so the "class"
attribute can be changed even if the class is already there
- add_to_class ($class)
- alias for add_class
- att_to_class ($att)
- Set the "class" attribute to the value of
attribute $att
- add_att_to_class ($att)
- Add the value of attribute $att to the "class"
attribute of the element
- move_att_to_class ($att)
- Add the value of attribute $att to the "class"
attribute of the element and delete the attribute
- tag_to_class
- Set the "class" attribute of the element to the
element tag
- add_tag_to_class
- Add the element tag to its "class" attribute
- set_tag_class ($new_tag)
- Add the element tag to its "class" attribute and
sets the tag to $new_tag
- in_class ($class)
- Return true (1) if the element is in the class $class (if
$class is one of the tokens in the element "class"
attribute)
- tag_to_span
- Change the element tag tp "span" and set its
class to the old tag
- tag_to_div
- Change the element tag tp "div" and set its class
to the old tag
- DESTROY
- Frees the element from memory.
- start_tag
- Return the string for the start tag for the element,
including the "/>" at the end of an empty element tag
- end_tag
- Return the string for the end tag of an element. For an
empty element, this returns the empty string ('').
- xml_string @optional_options
- Equivalent to "$elt->sprint( 1)", returns the
string for the entire element, excluding the element's tags (but nested
element tags are present)
The '"no_recurse"' option will only return the text of the
element, not of any included sub-elements (same as
"xml_text_only").
- inner_xml
- Another synonym for xml_string
- outer_xml
- An other synonym for sprint
- xml_text
- Return the text of the element, encoded (and processed by
the current "output_filter" or "output_encoding"
options, without any tag.
- xml_text_only
- Same as "xml_text" except that the text returned
doesn't include the text of sub-elements.
- set_pretty_print ($style)
- Set the pretty print method, amongst '"none"'
(default), '"nsgmls"', '"nice"',
'"indented"', '"record"' and '"record_c"'
pretty_print styles:
- none
- the default, no "\n" is used
- nsgmls
- nsgmls style, with "\n" added within tags
- nice
- adds "\n" wherever possible (NOT SAFE, can lead
to invalid XML)
- indented
- same as "nice" plus indents elements (NOT SAFE,
can lead to invalid XML)
- record
- table-oriented pretty print, one field per line
- record_c
- table-oriented pretty print, more compact than
"record", one record per line
- set_empty_tag_style ($style)
- Set the method to output empty tags, amongst
'"normal"' (default), '"html"', and
'"expand"',
"normal" outputs an empty tag '"<tag/>"',
"html" adds a space '"<tag />"' for elements
that can be empty in XHTML and "expand" outputs
'"<tag></tag>"'
- set_remove_cdata ($flag)
- set (or unset) the flag that forces the twig to output
CDATA sections as regular (escaped) PCDATA
- set_indent ($string)
- Set the indentation for the indented pretty print style
(default is 2 spaces)
- set_quote ($quote)
- Set the quotes used for attributes. can be
'"double"' (default) or '"single"'
- cmp ($elt)
-
Compare the order of the 2 elements in a twig.
C<$a> is the <A>..</A> element, C<$b> is the <B>...</B> element
document $a->cmp( $b)
<A> ... </A> ... <B> ... </B> -1
<A> ... <B> ... </B> ... </A> -1
<B> ... </B> ... <A> ... </A> 1
<B> ... <A> ... </A> ... </B> 1
$a == $b 0
$a and $b not in the same tree undef
- before ($elt)
- Return 1 if $elt starts before the element, 0 otherwise. If
the 2 elements are not in the same twig then return "undef".
if( $a->cmp( $b) == -1) { return 1; } else { return 0; }
- after ($elt)
- Return 1 if $elt starts after the element, 0 otherwise. If
the 2 elements are not in the same twig then return "undef".
if( $a->cmp( $b) == -1) { return 1; } else { return 0; }
- other comparison methods
- path
- Return the element context in a form similar to XPath's
short form: '"/root/tag1/../tag"'
- xpath
- Return a unique XPath expression that can be used to find
the element again.
It looks like "/doc/sect[3]/title": unique elements do not have an
index, the others do.
- private methods
- Low-level methods on the twig:
- set_parent ($parent)
- set_first_child ($first_child)
- set_last_child ($last_child)
- set_prev_sibling ($prev_sibling)
- set_next_sibling ($next_sibling)
- set_twig_current
- del_twig_current
- twig_current
- flush
- This method should NOT be used, always flush the twig, not
an element.
- contains_text
Those methods should not be used, unless of course you find some creative and
interesting, not to mention useful, ways to do it.
cond¶
Most of the navigation functions accept a condition as an optional argument The
first element (or all elements for "children " or "ancestors
") that passes the condition is returned.
The condition is a single step of an XPath expression using the XPath subset
defined by "get_xpath". Additional conditions are:
The condition can be
- #ELT
- return a "real" element (not a PCDATA, CDATA,
comment or pi element)
- #TEXT
- return a PCDATA or CDATA element
- regular expression
- return an element whose tag matches the regexp. The regexp
has to be created with "qr//" (hence this is available only on
perl 5.005 and above)
- code reference
- applies the code, passing the current element as argument,
if the code returns true then the element is returned, if it returns false
then the code is applied to the next candidate.
XML::Twig::XPath¶
XML::Twig implements a subset of XPath through the "get_xpath" method.
If you want to use the whole XPath power, then you can use
"XML::Twig::XPath" instead. In this case "XML::Twig" uses
"XML::XPath" to execute XPath queries. You will of course need
"XML::XPath" installed to be able to use
"XML::Twig::XPath".
See XML::XPath for more information.
The methods you can use are:
- findnodes ($path)
- return a list of nodes found by $path.
- findnodes_as_string ($path)
- return the nodes found reproduced as XML. The result is not
guaranteed to be valid XML though.
- findvalue ($path)
- return the concatenation of the text content of the result
nodes
In order for "XML::XPath" to be used as the XPath engine the following
methods are included in "XML::Twig":
in XML::Twig
- getRootNode
- getParentNode
- getChildNodes
in XML::Twig::Elt
- string_value
- toString
- getName
- getRootNode
- getNextSibling
- getPreviousSibling
- isElementNode
- isTextNode
- isPI
- isPINode
- isProcessingInstructionNode
- isComment
- isCommentNode
- getTarget
- getChildNodes
- getElementById
XML::Twig::XPath::Elt¶
The methods you can use are the same as on "XML::Twig::XPath"
elements:
- findnodes ($path)
- return a list of nodes found by $path.
- findnodes_as_string ($path)
- return the nodes found reproduced as XML. The result is not
guaranteed to be valid XML though.
- findvalue ($path)
- return the concatenation of the text content of the result
nodes
XML::Twig::Entity_list¶
- new
- Create an entity list.
- add ($ent)
- Add an entity to an entity list.
- add_new_ent ($name, $val, $sysid, $pubid, $ndata,
$param)
- Create a new entity and add it to the entity list
- delete ($ent or $tag).
- Delete an entity (defined by its name or by the Entity
object) from the list.
- print ($optional_filehandle)
- Print the entity list.
- list
- Return the list as an array
XML::Twig::Entity¶
- new ($name, $val, $sysid, $pubid, $ndata, $param)
- Same arguments as the Entity handler for XML::Parser.
- print ($optional_filehandle)
- Print an entity declaration.
- name
- Return the name of the entity
- val
- Return the value of the entity
- sysid
- Return the system id for the entity (for NDATA
entities)
- pubid
- Return the public id for the entity (for NDATA
entities)
- ndata
- Return true if the entity is an NDATA entity
- param
- Return true if the entity is a parameter entity
- text
- Return the entity declaration text.
EXAMPLES¶
Additional examples (and a complete tutorial) can be found on the
XML::Twig
Page<http://www.xmltwig.com/xmltwig/>
To figure out what flush does call the following script with an XML file and an
element name as arguments
use XML::Twig;
my ($file, $elt)= @ARGV;
my $t= XML::Twig->new( twig_handlers =>
{ $elt => sub {$_[0]->flush; print "\n[flushed here]\n";} });
$t->parsefile( $file, ErrorContext => 2);
$t->flush;
print "\n";
NOTES¶
Subclassing XML::Twig¶
Useful methods:
- elt_class
- In order to subclass "XML::Twig" you will
probably need to subclass also "XML::Twig::Elt". Use the
"elt_class" option when you create the "XML::Twig"
object to get the elements created in a different class (which should be a
subclass of "XML::Twig::Elt".
- add_options
- If you inherit "XML::Twig" new method but want to
add more options to it you can use this method to prevent XML::Twig to
issue warnings for those additional options.
DTD Handling¶
There are 3 possibilities here. They are:
- No DTD
- No doctype, no DTD information, no entity information, the
world is simple...
- Internal DTD
- The XML document includes an internal DTD, and maybe entity
declarations.
If you use the load_DTD option when creating the twig the DTD information
and the entity declarations can be accessed.
The DTD and the entity declarations will be "flush"'ed (or
"print"'ed) either as is (if they have not been modified) or as
reconstructed (poorly, comments are lost, order is not kept, due to it's
content this DTD should not be viewed by anyone) if they have been
modified. You can also modify them directly by changing the
"$twig->{twig_doctype}->{internal}" field (straight from
XML::Parser, see the "Doctype" handler doc)
- External DTD
- The XML document includes a reference to an external DTD,
and maybe entity declarations.
If you use the "load_DTD" when creating the twig the DTD
information and the entity declarations can be accessed. The entity
declarations will be "flush"'ed (or "print"'ed) either
as is (if they have not been modified) or as reconstructed (badly,
comments are lost, order is not kept).
You can change the doctype through the "$twig->set_doctype"
method and print the dtd through the "$twig->dtd_text" or
"$twig->dtd_print"
methods.
If you need to modify the entity list this is probably the easiest way to do
it.
Flush¶
If you set handlers and use "flush", do not forget to flush the twig
one last time AFTER the parsing, or you might be missing the end of the
document.
Remember that element handlers are called when the element is CLOSED, so if you
have handlers for nested elements the inner handlers will be called first. It
makes it for example trickier than it would seem to number nested clauses.
BUGS¶
- entity handling
- Due to XML::Parser behaviour, non-base entities in
attribute values disappear: "att="val&ent;"" will
be turned into "att => val", unless you use the
"keep_encoding" argument to "XML::Twig->new"
- DTD handling
- The DTD handling methods are quite bugged. No one uses them
and it seems very difficult to get them to work in all cases, including
with several slightly incompatible versions of XML::Parser and of
libexpat.
Basically you can read the DTD, output it back properly, and update
entities, but not much more.
So use XML::Twig with standalone documents, or with documents refering to an
external DTD, but don't expect it to properly parse and even output back
the DTD.
- memory leak
- If you use a lot of twigs you might find that you leak
quite a lot of memory (about 2Ks per twig). You can use the "dispose
" method to free that memory after you are done.
If you create elements the same thing might happen, use the
"delete" method to get rid of them.
Alternatively installing the "Scalar::Util" (or
"WeakRef") module on a version of Perl that supports it
(>5.6.0) will get rid of the memory leaks automagically.
- ID list
- The ID list is NOT updated when elements are cut or
deleted.
- change_gi
- This method will not function properly if you do:
$twig->change_gi( $old1, $new);
$twig->change_gi( $old2, $new);
$twig->change_gi( $new, $even_newer);
- sanity check on XML::Parser method calls
- XML::Twig should really prevent calls to some XML::Parser
methods, especially the "setHandlers" method.
- pretty printing
- Pretty printing (at least using the '"indented"'
style) is hard to get right! Only elements that belong to the document
will be properly indented. Printing elements that do not belong to the
twig makes it impossible for XML::Twig to figure out their depth, and thus
their indentation level.
Also there is an unavoidable bug when using "flush" and pretty
printing for elements with mixed content that start with an embedded
element:
<elt><b>b</b>toto<b>bold</b></elt>
will be output as
<elt>
<b>b</b>toto<b>bold</b></elt>
if you flush the twig when you find the "<b>" element
Globals¶
These are the things that can mess up calling code, especially if threaded. They
might also cause problem under mod_perl.
- Exported constants
- Whether you want them or not you get them! These are
subroutines to use as constant when creating or testing elements
PCDATA return '#PCDATA'
CDATA return '#CDATA'
PI return '#PI', I had the choice between PROC and PI :--(
- Module scoped values: constants
- these should cause no trouble:
%base_ent= ( '>' => '>',
'<' => '<',
'&' => '&',
"'" => ''',
'"' => '"',
);
CDATA_START = "<![CDATA[";
CDATA_END = "]]>";
PI_START = "<?";
PI_END = "?>";
COMMENT_START = "<!--";
COMMENT_END = "-->";
pretty print styles
( $NSGMLS, $NICE, $INDENTED, $INDENTED_C, $WRAPPED, $RECORD1, $RECORD2)= (1..7);
empty tag output style
( $HTML, $EXPAND)= (1..2);
- Module scoped values: might be changed
- Most of these deal with pretty printing, so the worst that
can happen is probably that XML output does not look right, but is still
valid and processed identically by XML processors.
$empty_tag_style can mess up HTML bowsers though and changing $ID would most
likely create problems.
$pretty=0; # pretty print style
$quote='"'; # quote for attributes
$INDENT= ' '; # indent for indented pretty print
$empty_tag_style= 0; # how to display empty tags
$ID # attribute used as an id ('id' by default)
- Module scoped values: definitely changed
- These 2 variables are used to replace tags by an index,
thus saving some space when creating a twig. If they really cause you too
much trouble, let me know, it is probably possible to create either a
switch or at least a version of XML::Twig that does not perform this
optimization.
%gi2index; # tag => index
@index2gi; # list of tags
If you need to manipulate all those values, you can use the following methods on
the XML::Twig object:
- global_state
- Return a hashref with all the global variables used by
XML::Twig
The hash has the following fields: "pretty", "quote",
"indent", "empty_tag_style",
"keep_encoding", "expand_external_entities",
"output_filter", "output_text_filter",
"keep_atts_order"
- set_global_state ($state)
- Set the global state, $state is a hashref
- save_global_state
- Save the current global state
- restore_global_state
- Restore the previously saved (using
"Lsave_global_state"> state
TODO¶
- SAX handlers
- Allowing XML::Twig to work on top of any SAX parser
- multiple twigs are not well supported
- A number of twig features are just global at the moment.
These include the ID list and the "tag pool" (if you use
"change_gi" then you change the tag for ALL twigs).
A future version will try to support this while trying not to be to hard on
performance (at least when a single twig is used!).
AUTHOR¶
Michel Rodriguez <mirod@cpan.org>
LICENSE¶
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
Bug reports should be sent using:
RT
http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-Twig
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-Twig>
Comments can be sent to mirod@cpan.org
The XML::Twig page is at <
http://www.xmltwig.com/xmltwig/> It includes the
development version of the module, a slightly better version of the
documentation, examples, a tutorial and a:
Processing XML efficiently with
Perl and XML::Twig:
<http://www.xmltwig.com/xmltwig/tutorial/index.html>
SEE ALSO¶
Complete docs, including a tutorial, examples, an easier to use HTML version of
the docs, a quick reference card and a FAQ are available at
<
http://www.xmltwig.com/xmltwig/>
git repository at <
http://github.com/mirod/xmltwig>
XML::Parser, XML::Parser::Expat, XML::XPath, Encode, Text::Iconv, Scalar::Utils
Alternative Modules¶
XML::Twig is not the only XML::Processing module available on CPAN (far from
it!).
The main alternative I would recommend is XML::LibXML.
Here is a quick comparison of the 2 modules:
XML::LibXML, actually "libxml2" on which it is based, sticks to the
standards, and implements a good number of them in a rather strict way: XML,
XPath, DOM, RelaxNG, I must be forgetting a couple (XInclude?). It is fast and
rather frugal memory-wise.
XML::Twig is older: when I started writing it XML::Parser/expat was the only
game in town. It implements XML and that's about it (plus a subset of XPath,
and you can use XML::Twig::XPath if you have XML::XPathEngine installed for
full support). It is slower and requires more memory for a full tree than
XML::LibXML. On the plus side (yes, there is a plus side!) it lets you process
a big document in chunks, and thus let you tackle documents that couldn't be
loaded in memory by XML::LibXML, and it offers a lot (and I mean a LOT!) of
higher-level methods, for everything, from adding structure to
"low-level" XML, to shortcuts for XHTML conversions and more. It
also DWIMs quite a bit, getting comments and non-significant whitespaces out
of the way but preserving them in the output for example. As it does not stick
to the DOM, is also usually leads to shorter code than in XML::LibXML.
Beyond the pure features of the 2 modules, XML::LibXML seems to be prefered by
"XML-purists", while XML::Twig seems to be more used by Perl Hackers
who have to deal with XML. As you have noted, XML::Twig also comes with quite
a lot of docs, but I am sure if you ask for help about XML::LibXML here or on
Perlmonks you will get answers.
Note that it is actually quite hard for me to compare the 2 modules: on one hand
I know XML::Twig inside-out and I can get it to do pretty much anything I need
to (or I improve it ;--), while I have a very basic knowledge of XML::LibXML.
So feature-wise, I'd rather use XML::Twig ;--). On the other hand, I am
painfully aware of some of the deficiencies, potential bugs and plain ugly
code that lurk in XML::Twig, even though you are unlikely to be affected by
them (unless for example you need to change the DTD of a document
programatically), while I haven't looked much into XML::LibXML so it still
looks shinny and clean to me.
That said, if you need to process a document that is too big to fit memory and
XML::Twig is too slow for you, my reluctant advice would be to use
"bare" XML::Parser. It won't be as easy to use as XML::Twig:
basically with XML::Twig you trade some speed (depending on what you do from a
factor 3 to... none) for ease-of-use, but it will be easier IMHO than using
SAX (albeit not standard), and at this point a LOT faster (see the last test
in <
http://www.xmltwig.com/article/simple_benchmark/>).