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

           Barrie Slaymaker <barries@slaysys.com>

       •   Barry Slaymaker

       •   Chris Prather <chris@prather.org>

           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.

       This software is copyright (c) 2013 by Barry Slaymaker.

       This  is  free  software;  you  can  redistribute  it and/or modify it under the same terms as the Perl 5
       programming language system itself.

perl v5.34.0                                       2022-06-28                            XML::SAX::Pipeline(3pm)

       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",
          );

       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().

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

           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 -" );

       version 0.46