XML::SAX::Tap - Tap a pipeline of SAX processors

    use XML::SAX::Machines qw( Pipeline Tap ) ;

    my $m = Pipeline(
        "UpstreamFilter",
        Tap( "My::Reformatter", \*STDERR ),
        "DownstreamFilter",
    );

    my $m = Pipeline(
        "UpstreamFilter",
        Tap( "| xmllint --format -" ),
        "DownstreamFilter",
    );

XML::SAX::Tap is a SAX machine that passes each event it receives on to a brach handler and then on down to it's main handler. This allows debugging output, logging output, validators, and other processors (and machines, of course) to be placed in a pipeline. This differs from XML::Filter::Tee, XML::Filter::SAXT and XML::SAX::Distributer in that a tap is also a pipeline; it contains the processoring that handles the tap.

It's like XML::Filter::Tee in that the events are not buffered; each event is sent first to the tap, and then to the branch (this is different from XML::SAX::Dispatcher, which buffers the events).

It's like XML::SAX::Pipeline in that it contains a series of processors in a pipeline; these comprise the "tapping" processors:

            +----------------------------------------------+
            |                  Tap instance                |
            |                                              |
            |  Intake                                      |
            |  +-----+    +---------+        +---------+   |
 upstream --+->| Tee |--->| Stage_0 |--...-->| Stage_N |   |
            |  +-----+    +---------+        +---------+   |
            |         \                                    |
            |          \                          Exhaust  |
            |           +----------------------------------+--> downstream
            |                                              |
            +----------------------------------------------+

The events are not copied, since they may be data structures that are difficult or impossibly to copy properly, like parts of a C-based DOM implementation.

Events go to the tap first so that you can validate events using a tap that throws exceptions and they will be acted on before the tap's handler sees them.

This machine has no Exhaust port (see XML::SAX::Machine for details about Intake and Exhaust ports).

new

    my $tap = XML::SAX::Tap->new( @tap_processors, \%options );

    Barrie Slaymaker <barries@slaysys.com>

    Copyright 2002, Barrie Slaymaker, All Rights Reserved

You may use this module under the terms of the Artistic, GNU Public, or BSD licenses, as you choose.