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.

       AsPipe string
           This option will cause start_document to open a pipe and end_document to close it. The
           pipe is a normal shell command. Secure shell comes handy but has a 2GB limit on most
           systems.

       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

           CompactAttrIndent
               Places Attributes on the same line as the Element

           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 work in any Perl 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

       perl and XML::Parser::PerlSAX