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Barrie Slaymaker > XML-SAX-Machines > XML::Filter::Tee



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Module Version: 0.1   Source   Latest Release: XML-SAX-Machines-0.46


XML::Filter::Tee - Send SAX events to multiple processor, with switching


    my $t = XML::Filter::Tee->new(
        { Handler => $h0 },
        { Handler => $h1 },
        { Handler => $h2 },

    ## Altering the handlers list:
    $t->set_handlers( $h0, $h1, $h2, $h3 );

    ## Controlling flow to a handler by number and by reference:
    $t->disable_handler( 0 );
    $t->enable_handler( 0 );

    $t->disable_handler( $h0 );
    $t->enable_handler( $h0 );

    ## Use in a SAX machine (though see L<XML::SAX::Pipeline> and
    ## L<XML::SAX::Tap> for a more convenient way to build a machine
    ## like this):
    my $m = Machine(
        [ Intake => "XML::Filter::Tee" => qw( A B ) ],
        [ A      => ">>log.xml" ],
        [ B      => \*OUTPUT ],


XML::Filter::Tee is a SAX filter that passes each event it receives on to a list of downstream handlers.

It's like XML::Filter::SAXT 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). Unlike XML::Filter::SAXT, it allows it's list of handlers to be reconfigured (via "set_handlers") and it allows control over which handlers are allowed to receive events. These features are designed to make XML::Filter::Tee instances more useful with SAX machines, but they to add some overhead relative to XML::Filter::SAXT.

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. This means that the handlers must not alter the events or later handlers will see the alterations.


    my $t = XML::Filter::Tee->new(
        { Handler => $h0 },
        { Handler => $h1 },
        { Handler => $h2 },
    $t->set_handlers( $h0, $h1, $h2 );
    $t->set_handlers( {
            Handler => $h0,
            Handler => $h1,

Replaces the current list of handlers with new ones.

Can also name handlers to make enabling/disabling them by name easier:

    $m->set_handlers( {
            Handler => $validator,
            Name    => "Validator",
            Handler => $outputer,

    $m->disable_handler( "Validator" );
    $t->disable_handler( 0 );            ## By location
    $t->disable_handler( "Validator" );  ## By name
    $t->disable_handler( $h0 );          ## By reference

Stops sending events to the indicated handler.

    $t->enable_handler( 0 );            ## By location
    $t->enable_handler( "Validator" );  ## By name
    $t->enable_handler( $h0 );          ## By reference

Stops sending events to the indicated handler.


    Barrie Slaymaker <>


    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.

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