NAME
       XML::Handler::YAWriter - Yet another Perl SAX XML Writer

SYNOPSIS
         use XML::Handler::YAWriter;

         my $ya = new XML::Handler::YAWriter( %options );
         my $perlsax = new XML::Parser::PerlSAX( 'Handler' => $ya );


DESCRIPTION
       YAWriter implements Yet Another XML::Handler::Writer. The
       reasons for this one are that I needed a flexible escaping
       technique, and want some kind of pretty printing. If an
       instance of YAWriter is created without any options, the
       default behavior is to produce an array of strings
       containing the XML in :

         @{$ya->{Strings}}


       Options

       Options are given in the usual 'key' => 'value' idiom.

       Output IO::File
           This option tells YAWriter to use an already open file
           for output, instead of using $ya->{Strings} to store
           the array of strings. It should be noted that the only
           thing the object needs to implement is the print
           method. So anything can be used to receive a stream of
           strings from YAWriter.

       AsFile string
           This option will cause start_document to open named
           file and end_document to close it. Use the literal
           dash "-" if you want to print on standard output.

       AsArray boolean
           This option will force storage of the XML in
           $ya->{Strings}, even if the Output option is given.

       AsString boolean
           This option will cause end_document to return the
           complete XML document in a single string. Most SAX
           drivers return the value of end_document as a result
           of their parse method. As this may not work with some
           combinations of SAX drivers and filters, a join of
           $ya->{Strings} in the controlling method is preferred.

       Encoding string
           This will change the default encoding from UTF-8 to
           anything you like.  You should ensure that given data
           are already in this encoding or provide an Escape
           hash, to tell YAWriter about the recoding.

       Escape hash
           The Escape hash defines substitutions that have to be
           done to any string, with the exception of the
           processing_instruction and doctype_decl methods, where
           I think that escaping of target and data would cause
           more trouble than necessary.

           The default value for Escape is

               $XML::Handler::YAWriter::escape = {
                       '&'  => '&',
                       '<'  => '&lt;',
                       '>'  => '&gt;',
                       '"'  => '&quot;',
                       '--' => '&#45;&#45;'
                       };

           YAWriter will use an evaluated sub to make the
           recoding based on a given Escape hash reasonably fast.
           Future versions may use XS to improve this performance
           bottleneck.

       Pretty hash
           Hash of string => boolean tuples, to define kind of
           prettyprinting. Default to undef. Possible string
           values:

           AddHiddenNewline boolean
               Add hidden newline before ">"

           AddHiddenAttrTab boolean
               Add hidden tabulation for attributes

           CatchEmptyElement boolean
               Catch empty Elements, apply "/>" compression

           CatchWhiteSpace boolean
               Catch whitespace with comments

           IsSGML boolean
               This option will cause start_document,
               processing_instruction and doctype_decl to appear
               as SGML. The SGML is still well-formed of course,
               if your SAX events are well-formed.

           NoComments boolean
               Supress Comments

           NoDTD boolean
               Supress DTD

           NoPI boolean
               Supress Processing Instructions

           NoProlog boolean
               Supress <?xml ... ?> Prolog

           NoWhiteSpace boolean
               Supress WhiteSpace to clean documents from prior
               pretty printing.

           PrettyWhiteIndent boolean
               Add visible indent before any eventstring

           PrettyWhiteNewline boolean
               Add visible newlines before any eventstring

           SAX1 boolean (not yet implemented)
               Output only SAX1 compliant eventstrings

       Notes:

       Correct handling of start_document and end_document is
       required!

       The YAWriter Object initialises its structures during
       start_document and does its cleanup during end_document.
       If you forget to call start_document, any other method
       will break during the run. Most likely place is the encode
       method, trying to eval undef as a subroutine. If you
       forget to call end_document, you should not use a single
       instance of YAWriter more than once.

       For small documents AsArray may be the fastest method and
       AsString the easiest one to receive the output of
       YAWriter. But AsString and AsArray may run out of memory
       with infinite SAX streams. The only method
       XML::Handler::Writer calls on a given Output object is the
       print method. So it's easy to use a self written Output
       object to improve streaming.

       A single instance of XML::Handler::YAWriter is able to
       produce more than one file in a single run. Be sure to
       provide a fresh IO::File as Output before you call
       start_document and close this File after calling
       end_document. Or provide a filename in AsFile, so
       start_document and end_document can open and close its own
       filehandle.

       Automatic recoding between 8bit and 16bit does not yet
       work correctly !

       I have Perl-5.00563 at home and here I can specify "use
       utf8;" in the right places to make recoding work. But I
       dislike saying "use 5.00555;" because many systems run
       5.00503.

       If you use some 8bit character set internally and want use
       national characters, either state your character as
       Encoding to be ISO-8859-1, or provide an Escape hash
       similar to the following :

           $ya->{'Escape'} = {
                           '&'  => '&amp;',
                           '<'  => '&lt;',
                           '>'  => '&gt;',
                           '"'  => '&quot;',
                           '--' => '&#45;&#45;'
                           'ö' => '&ouml;'
                           'ä' => '&auml;'
                           'ü' => '&uuml;'
                           'Ö' => '&Ouml;'
                           'Ä' => '&Auml;'
                           'Ü' => '&Uuml;'
                           'ß' => '&szlig;'
                           };

       You may abuse YAWriter to clean whitespace from XML
       documents. Take a look at test.pl, doing just that with an
       XML::Edifact message, without querying the DTD. This may
       work in 99% of the cases where you want to get rid of
       ignorable whitespace caused by the various forms of pretty
       printing.

           my $ya = new XML::Handler::YAWriter(
               'Output' => new IO::File ( ">-" );
               'Pretty' => {
                   'NoWhiteSpace'=>1,
                   'NoComments'=>1,
                   'AddHiddenNewline'=>1,
                   'AddHiddenAttrTab'=>1,
               } );

       XML::Handler::Writer implements any method
       XML::Parser::PerlSAX wants.  This extends the Java SAX1.0
       specification. I have in mind using Pretty=>SAX1=>1 to
       disable this feature, if abusing YAWriter for a SAX proxy.

AUTHOR
       Michael Koehne, Kraehe@Copyleft.De

Thanks
       "Derksen, Eduard (Enno), CSCIO" <enno@att.com> helped me
       with the Escape hash and gave quite a lot of useful
       comments.

SEE ALSO
       the perl manpage and the XML::Parser::PerlSAX manpage