Provided by: libxml-autowriter-perl_0.40-4_all 
NAME
XML::ValidWriter - DOCTYPE driven valid XML output
SYNOPSIS
## As a normal perl object:
$writer = XML::ValidWriter->new(
DOCTYPE => $xml_doc_type,
OUTPUT => \*FH
) ;
$writer->startTag( 'b1' ) ;
$writer->startTag( 'c2' ) ;
$writer->end ;
## Writing to a scalar:
$writer = XML::ValidWriter->new(
DOCTYPE => $xml_doc_type,
OUTPUT => \$buf
) ;
## Or, in scripting mode:
use XML::Doctype NAME => a, SYSTEM_ID => 'a.dtd' ;
use XML::ValidWriter qw( :all :dtd_tags ) ;
b1 ; # Emits <a><b1>
c2( attr=>"val" ) ; # Emits </b1><b2><c2 attr="val">
endAllTags ; # Emits </c2></b2></a>
## If you've got an XML::Doctype object handy:
use XML::ValidWriter qw( :dtd_tags ), DOCTYPE => $doctype ;
## If you've saved a preparsed DTD as a perl module
use FooML::Doctype::v1_0001 ;
use XML::ValidWriter qw( :dtd_tags ) ;
#
# This all assumes that the DTD contains:
#
# <!ELEMENT a ( b1, b2?, b3* ) >
# <!ATTLIST a aa1 CDATA #REQUIRED >
# <!ELEMENT b1 ( c1 ) >
# <!ELEMENT b2 ( c2 ) >
#
STATUS
Alpha. Use and patch, don't depend on things not changing drastically.
Many methods supplied by XML::Writer are not yet supplied here.
DESCRIPTION
This module uses the DTD contained in an XML::Doctype to enable compile- and run-time
checks of XML output validity. It also provides methods and functions named after the
elements mentioned in the DTD. If an XML::ValidWriter uses a DTD that mentions the
element type TABLE, that instance will provide the methods
$writer->TABLE( $content, ...attrs... ) ;
$writer->start_TABLE( ...attrs... ) ;
$writer->end_TABLE() ;
$writer->empty_TABLE( ...attrs... ) ;
. These are created for undeclared elements--those elements not explicitly declared with
an <!ELEMENT ..> declaration--as well. If an element type name conflicts with a method,
it will not override the internal method.
When an XML::Doctype is parsed, the name of the doctype defines the root node of the
document. This name can be changed, though, see XML::Doctype for details.
In addition to the object-oriented API, a function API is also provided. This allows you
to import most of the methods of XML::ValidWriter as functions using standard import
specifications:
use XML::ValidWriter qw( :all ) ; ## Could list function names instead
":all" does not import the functions named after elements mentioned in the DTD, you need
to import those tags using ":dtd_tags":
use XML::Doctype NAME => 'foo', SYSTEM_ID => 'fooml.dtd' ;
use XML::ValidWriter qw( :all :dtd_tags ) ;
or
BEGIN {
$doctype = XML::Doctype->new( ... ) ;
}
use XML::ValidWriter DOCTYPE => $doctype, qw( :all :dtd_tags ) ;
XML::Writer API compatibility
Much of the interface is patterned after XML::Writer so that it can possibly be used as a
drop-in replacement. It will take awhile before this module emulates enough of
XML::Writer to be a drop-in replacement in situations where the more advanced XML::Writer
methods are used. If you find you need a method not suported here, write it and send it
in!
This was not derived from XML::Writer because XML::Writer does not expose it's stack.
Even if it did, it's might be difficult to store enough state in it's stack.
Unlike XML::Writer, this does not call in all of the IO::* family, and method dispatch
should be faster. DTD-specific methods are also supported (see "AUTOLOAD").
Quick and Easy Unix Filter Apps
For quick applications that provide Unix filter application functionality,
XML::ValidWriter and XML::Doctype cooperate to allow you to
1. Parse a DTD at compile-time and set that as the default DTD for the current package.
This is done using the
use XML::Doctype NAME => 'FooML, SYSTEM_ID => 'fooml.dtd' ;
syntax.
2. Define and export a set of functions corresponding to start and end tags for all
declared and undeclared ELEMENTs in the DTD. This is done by using the ":dtd_tags"
export symbol like so:
use XML::Doctype NAME => 'FooML, SYSTEM_ID => 'fooml.dtd' ;
use XML::ValidWriter qw(:dtd_tags) ;
If the elements a, b_c, and d-e are referred to in the DTD, the following functions
will be exported:
a() end_a() # like startTag( 'a', ... ) and endTag( 'a' )
b_c() end_b_c()
d_e() end_d_e() {'d-e'}() {'end_d-e'}()
These functions emit only tags, unlike the similar functions found in CGI.pm and
XML::Generator, which also allow you to pass content in as parameters.
See below for details on conflict resolution in the mapping of entity names containing
/\W/ to Perl subroutine names.
If the elements declared in the DTD might conflict with functions in your package
namespace, simple put them in some safe namespace:
package FooML ;
use XML::Doctype NAME => 'FooML', SYSTEM_ID => 'fooml.dtd' ;
use XML::ValidWriter qw(:dtd_tags) ;
package Whatever ;
The advantage of importing these subroutine names is that perl can then detect use of
unknown tags at compile time.
If you don't want to use the default DTD, use the "-dtd" option:
BEGIN { $dtd = XML::Doctype->new( .... ) }
use XML::ValidWriter qw(:dtd_tags), -dtd => \$dtd ;
3. Use the default DTD to validate emitted XML. startTag() and endTag() will check the
tag being emitted against the list of currently open tags and either emit a minimal
set of missing end and start tags necessary to achieve document validity or produce
errors or warnings.
Since the functions created by the ":dtd_tags" export symbol are wrappers around
startTag() and endTag(), they provide this functionality as well.
So, if you have a DTD like
<!ELEMENT a ( b1, b2?, b3* ) >
<!ATTLIST a aa1 CDATA #REQUIRED >
<!ELEMENT b1 ( c1 ) >
<!ELEMENT b2 ( c2 ) >
<!ELEMENT b3 ( c3 ) >
you can do this:
use XML::Doctype NAME => 'a', SYSTEM_ID => 'a.dtd' ;
use XML::ValidWriter ':dtd_tags' ;
getDoctype->element_decl('a')->attdef('aa1')->default_on_write('foo') ;
a ;
b1 ;
c1 ;
end_c1 ;
end_b1 ;
b3 ;
c3( -attr => val ) ;
end_c3 ;
end_b3 ;
end_a ;
and emit a document like
<a aa1="foo">
<b1>
<c1 />
</b1>
<b3>
<c3 attr => "val" />
</b3>
</a>
.
OUTPUT OPTIMIZATION
XML is a very simple language and does not offer a lot of room for optimization. As the
spec says "Terseness in XML markup is of minimal importance." XML::ValidWriter does
optimize the following on output:
"<a...></a>" becomes '<a... />'
Spurious emissions of "]]><![CDATA[" are supressed.
XML::ValidWriter chooses whether or not to use a <![CDATA[...]]> section or simply escape
'<' and '&'. If you are emitting content for an element in multiple calls to
"characters", the first call decides whether or not to use CDATA, so it's to your
advantage to emit as much in the first call as possible. You can do
characters( @lots_of_segments ) ;
if it helps.
METHODS AND FUNCTIONS
All of the routines in this module can be called as either functions or methods unless
otherwise noted.
To call these routines as functions use either the DOCTYPE or :dtd_tags options in the
parameters to the use statement:
use XML::ValidWriter DOCTYPE => XML::Doctype->new( ... ) ;
use XML::ValidWriter qw( :dtd_tags ) ;
This associates an XML::ValidWriter and an XML::Doctype with the package. These are used
by the routines when called as functions.
new
$writer = XML::ValidWriter->new( DTD => $dtd, OUTPUT => \*FH ) ;
Creates an XML::ValidWriter.
The value passed for OUTPUT may be:
a SCALAR ref
if you want to direct output to append to a scalar. This scalar is truncated
whenever the XML::ValidWriter object is reset() or DESTROY()ed
a file handle glob ref or a reference to an IO object
XML::ValidWriter does not load IO. This is the only mode compatible with
XML::Writer.
a file name
A simple scalar is taken to be a filename to be created or truncated and emitted
to. This file will be closed when the XML::ValidWriter object is reset or
deatroyed.
NOTE: if you leave OUTPUT undefined, then the currently select()ed output is used at
each emission (ie calling select() can alter the destination mid-stream). This eases
writing command line filter applications, the select() interaction is unintentional,
and please don't depend on it. I reserve the right to cache the select()ed filehandle
at creation time or at time of first emission at some point in the future.
import
Can't think of why you'd call this method directly, it gets called when you use this
module:
use XML::ValidWriter qw( :all ) ;
In addition to the normal functionality of exporting functions like startTag() and
endTag(), XML::ValidWriter's import() can create functions corresponding to all
elements in a DTD. This is done using the special ":dtd_tags" export symbol. For
example,
use XML::Doctype NAME => 'FooML', SYSTEM_ID => 'fooml.dtd' ;
use XML::ValidWriter qw( :dtd_tags ) ;
where fooml.dtd referse to a tag type of 'blurb' causes these functions to be
imported:
blurb() # calls defaultWriter->startTag( 'blurb', @_ ) ;
blurb_element() # calls defaultWriter->dataElement( 'blurb', @_ ) ;
empty_blurb() # calls defaultWriter->emptyTag( 'blurb', @_ ) ;
end_blurb() # calls defaultWriter->endTag( 'blurb' ) ;
The range of characters for element types is much larger than the range of characters
for bareword perl subroutine names, which are limited to [a-zA-Z0-9_]. In this case,
XML::ValidWriter will export an oddly named function that you can use a symbolic
reference to call (you will need "no strict 'refs' ;" if you are doing a "use strict
;"):
&{"space-1999:moonbase"}( ...attributes ... ) ;
. XML::ValidWriter will also try to fold the name in to bareword space by converting
/\W/ symbols to '_'. If the resulting function name,
space_1999_moonbase( ...attributes... ) ;
has not been generated and is not the name of an element type, then it will also be
exported.
If you are using a DTD that might introduce function names that conflict with existing
ones, simple export them in to their own namespace:
package ML ;
use XML::Doctype NAME => 'foo', SYSTEM_ID => 'fooml.dtd' ;
use XML::ValidWriter qw( :dtd_tags ) ;
package main ;
use XML::ValidWriter qw( :all ) ;
ML::foo ;
ML::c2 ;
ML::c1 ;
ML::end_a ;
I gave serious thought to converting ':' in element names to '::' in function
declarations, which might work well in the functions-in-their-own- namespace case, but
not in the default case, since Perl does not (yet) have relative namespaces. Another
alternative is to allow a mapping of XML namespaces to Perl namespaces to be done.
characters
characters( "escaped text", "& more" ) ;
$writer->characters( "escaped text", "& more" ) ;
Emits character data. Character data will be escaped before output, by either
transforming '<' and '&' to < and &, or by enclosing in a '"<![CDATA[...]]>"'
bracket, depending on which will be more human-readable, according to the module.
dataElement
$writer->dataElement( $tag ) ;
$writer->dataElement( $tag, $content ) ;
$writer->dataElement( $tag, $content, attr1 => $val1, ... ) ;
dataElement( $tag ) ;
dataElement( $tag, $content ) ;
dataElement( $tag, $content, attr1 => $val1, ... ) ;
Does the equivalent to
## Split the optional args in to attributes and elements arrays.
$writer->startTag( $tag, @attributes ) ;
$writer->characters( $content ) ;
$writer->endTag( $tag ) ;
This function is exportable as dataElement(), and is also exported for each element
'foo' found in the DTD as foo().
defaultWriter
$writer = defaultWriter ; ## Not a method!
$writer = defaultWriter( 'Foo::Bar' ) ;
Returns the default XML::ValidWriter for the given package, or the current package if
none is specified. This is useful for getting at methods like "reset" that are not
also functions.
Croaks if no default writer has been defined (see "import").
doctype
# Using the writer's associated DTD:
doctype ;
# Ignoring the writer's associated DTD:
doctype( $type ) ;
doctype( $type, undef, $system ) ;
doctype( $type, $public, $system ) ;
$writer->doctype ;
...etc
See "internalDoctype" to emit the entire DTD in the document.
This checks to make sure that no doctype or elements have been emitted.
A warning is emitted if standalone="yes" was specified in the <?xml..?> declaration
and a system id is specified. This is extremely likely to be an error. If you need
to silence the warning, write me (see below).
Passing '' or '0' (zero) as a $public_id or as a $system_id also generates a warning,
as these are extremely likely to be errors.
emptyTag
emptyTag( $tag[, attr1 => $val1... ] ) ;
$writer->emptyTag( $tag[, attr1 => $val1... ] ) ;
Emits an empty tag like '<foo />'. The extra space is for compatibility with XHTML.
endTag
endTag ;
endTag( 'a' ) ;
$writer->endTag ;
$writer->endTag( 'a' ) ;
Prints one or more end tags. The tag name is optional and defaults to the most
recently emitted start tag if not present.
This will emit as many close tags as necessary to close the supplied tag name, or will
emit an error if the tag name specified is not open in the output document.
end
$writer->end ; # Not a function!!
Emits all necessary end tags to close the document. Available as a method only, since
'end' is a little to generic to be exported as a function name, IMHO. See
'endAllTags' for the plain function equivalent function.
endAllTags
endAllTags ;
$writer->endAllTags ;
A plain function that emits all necessart end tags to close the document. Corresponds
to the method "end", but is exportable as a function/
exportDTDTags
$writer->exportDTDTags() ;
$writer->exportDTDTags( $to_pkg ) ;
Exports the tags found in the DTD to the caller's namespace.
getDataMode
$m = getDataMode ;
$m = $writer->getDataMode ;
Returns TRUE if the writer is in DATA_MODE.
getDoctype
$dtd = getDoctype ;
$dtd = $writer->getDoctype ;
This is used to get the writer's XML::Doctype object.
getOutput
$fh = getOutput ;
$fh = $writer->getOutput ;
Gets the filehandle an XML::ValidWriter sends output to.
rawCharacters
rawCharacters( "<unescaped text>", "& more text" ) ;
$writer->rawCharacters( "<unescaped text>", "& more text" ) ;
This allows you to emit raw text without any escape processing. The text is not
examined for tags, so you can invalidate your document and even corrupt it's well-
formedness.
reset
$writer->reset ; # Not a function!
Resets a writer to be initialized, but not have emitted anything.
This is useful if you need to abort output, but want to reuse the XML::ValidWriter.
setDataMode
setDataMode( 1 ) ;
$writer->setDataMode( 1 ) ;
Enable or disable data mode.
setDoctype
setDoctype $doctype ;
$writer->setDoctype( $doctype ) ;
This is used to set the doctype object.
select_xml
select_xml OUTHANDLE ; # Nnot a method!!
Selects a filehandle to send the XML output to when not using the object oriented
interface. This is similar to perl's builtin select, but only affects startTag and
endTag functions, (not methods).
This is only needed if you want to interleave output to the selected output files
(usually STDOUT, see "select" in perlfunc and to an XML file on another filehandle.
If you want to redirect all output (yours and XML::Writer's) to the same file, just
use Perl's built-in select(), since startTag and endTag emit to the currently selected
filehandle by default.
Like select, this returns the old value.
setOutput
setOutput( \*FH ) ;
$writer->setOutput( \*FH ) ;
Sets the filehandle an XML::ValidWriter sends output to.
startTag
startTag( 'a', attr => val ) ; # use default XML::ValidWriter for
# current package.
$writer->startTag( 'a', attr => val ) ;
Emits a named start tag with optional attributes. If the named tag cannot be a child
of the most recently started tag, then any tags that need to be opened between that
one and the named tag are opened.
If the named tag cannot be enclosed within the most recently opened tag, no matter how
deep, then startTag() tries to end as few started tags as necessary to allow the named
tag to be emitted within a tag already on the stack.
This warns (once) if no <?xml?> declaration has been emitted. It does not check to
see if a <!DOCTYPE...> has been emitted. It dies if an attempt is made to emit a
second root element.
xmlDecl([[$encoding][, $standalone])
xmlDecl ;
xmlDecl( "UTF-8" ) ;
xmlDecl( "UTF-8", "yes" ) ;
$writer->xmlDecl( ... ) ;
Emits an XML declaration. Must be called before any of the other output routines.
If $encoding is not defined, it is not output. This is slightly different than
XML::Writer, which outputs 'UTF-8' if you pass in undef, 0, or ''.
If $encoding is '' or 0, then it is output as "" or "0" and a warning is generated.
If $standalone is defined and is not 'no', 0, or '', it is output as 'yes'. If it is
'no', then it is output as 'no'. If it's 0 or '' it is not output.
AUTOLOAD
This function is called whenever a function or method is not found in
XML::ValidWriter.
If it was a method being called, and the desired method name is a start or end tag
found in the DTD, then a method is cooked up on the fly.
These methods are slower than normal methods, but they are cached so that they don't
need to be recompiled. The speed penalty is probably not significant since they do
I/O and are thus usually orders of magnitude slower than normal Perl methods.
DESTROY
DESTROY is called when an XML::ValidWriter is cleaned up. This is used to
automatically close all tags that remain open. This will not work if you have closed
the output filehandle that the ValidWriter was using.
This method will also warn if anything was emitted bit no root node was emitted. This
warning can be silenced by calling
$writer->reset() ;
when you abandon output.
AUTHOR
Barrie Slaymaker <barries@slaysys.com>
COPYRIGHT
This module is Copyright 2000, 2005 Barrie Slaymaker. All rights reserved.
This module is licensed under your choice of the Artistic, BSD or General Public License.