YAWriter(3) User Contributed Perl Documentation YAWriter(3)NAMEXML::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_docu-
ment 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 doc-
ument 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 encod-
ing 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 doc-
type_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 = {
'&' => '&',
'<' => '<',
'>' => '>',
'"' => '"',
'--' => '--'
};
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 print-
ing.
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'} = {
'&' => '&',
'<' => '<',
'>' => '>',
'"' => '"',
'--' => '--'
'' => 'ö'
'' => 'ä'
'' => 'ü'
'' => 'Ö'
'' => 'Ä'
'' => 'Ü'
'' => 'ß'
};
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
perl v5.8.8 2002-01-28 YAWriter(3)
