NAME

XML::SAX::Pipeline - Manage a linear pipeline of SAX processors

SYNOPSIS

    use XML::SAX::Machines qw( Pipeline );   ## Most common way
    use XML::Fitler::Foo;

    my $m = Pipeline(
        XML::Filter::Foo->new,  ## Create it manually
        "XML::Filter::Bar",     ## Or let Pipeline load & create it
        "XML::Filter::Baz",
        {
            ## Normal options
            Handler => $h,
        }
    );

    ## To choose the default parser automatically if XML::Filter::Foo
    ## does not implement a parse_file method, just pretend the Pipeline
    ## is a parser:
    $m->parse_file( "blah" );

    ## To feed the pipeline from an upstream processor, treat it like
    ## any other SAX filter:
    my $p = Some::SAX::Generator->new( Handler => $m );

    ## To read a file or the output from a subprocess:
    my $m = Pipeline( "<infile.txt" );
    my $m = Pipeline( "spew_xml |" );

    ## To send output to a file handle, file, or process:
    my $m = Pipeline( ...,  \*STDOUT );
    my $m = Pipeline( ..., ">outfile.txt" );
    my $m = Pipeline( ..., "| xmllint --format -" );

DESCRIPTION

An XML::SAX::Pipeline is a linear sequence SAX processors. Events passed to the pipeline are received by the Intake end of the pipeline and the last filter to process events in the pipeline passes the events out the Exhaust to the filter set as the pipeline's handler:

   +-----------------------------------------------------------+
   |                 An XML:SAX::Pipeline                      |
   |    Intake                                                 |
   |   +---------+    +---------+         +---------+  Exhaust |
 --+-->| Stage_0 |--->| Stage_1 |-->...-->| Stage_N |----------+----->
   |   +---------+    +---------+         +---------+          |
   +-----------------------------------------------------------+

As with all SAX machines, a pipeline can also create an ad hoc parser (using XML::SAX::ParserFactory) if you ask it to parse something and the first SAX processer in the pipeline can't handle a parse request:

   +-------------------------------------------------------+
   |                 An XML:SAX::Pipeline                  |
   |                 Intake                                |
   | +--------+   +---------+         +---------+  Exhaust |
   | | Parser |-->| Stage_0 |-->...-->| Stage_N |----------+----->
   | +--------+   +---------+         +---------+          |
   +-------------------------------------------------------+

or if you specify an input file like so:

   my $m = Pipeline(qw(
       <input_file.xml
       XML::Filter::Bar
       XML::Filter::Baz
   ));

Pipelines (and machines) can also create ad hoc XML::SAX::Writer instances when you specify an output file handle (as shown in the SYNOPSIS) or an output file:

   my $m = Pipeline(qw(
       XML::Filter::Bar
       XML::Filter::Baz
       >output_file.xml
   ));

And, thanks to Perl's magic open (see perlopentut), you can read and write from processes:

   my $m = Pipeline(
       "gen_xml.pl |",
       "XML::Filter::Bar",
       "XML::Filter::Baz",
       "| consume_xml.pl",
   );

This can be used with an XML::SAX::Tap to place a handy debugging tap in a pipeline (or other machine):

   my $m = Pipeline(
       "<input_file.xml"
       "XML::Filter::Bar",
       Tap( "| xmllint --format -" ),
       "XML::Filter::Baz",
       ">output_file.xml",
   );

METHODS

See XML::SAX::Machine for most of the methods.

new

    my $pipeline = XML::SAX::Pipeline->new( @processors, \%options );

Creates a pipeline and links all of the given processors together. Longhand for Pipeline().

AUTHOR

    Barrie Slaymaker <barries@slaysys.com>

COPYRIGHT

    Copyright 2002, Barrie Slaymaker, All Rights Reserved.

You may use this module under the terms of the Artistic, GNU Public, or BSD licenses, your choice.