Jane Avriette > Net-TDMA-0.2 > Net::TDMA::Constants

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NAME ^

Net::TDMA::Constants

ABSTRACT ^

TDMA::Constants provides basic data structures and functions which may then be used by other pieces of the TDMA structure.

USAGE ^

        use Net::TDMA::Constants;
        
        Net::TDMA::Constants->frame_configure(
                {
                        add_methods => {
                                method_name => \&method_name,
                                method_name => sub { }
                        },
                        
                        serialize  => sub { }, 
                        # or ...
                        serialize  => \&serialize,
                }
        );
        
        # a practical example
        
        Net::TDMA::Constants::slot_configure(
                add_data   => {
                        jitter      => 0,  # a default
                        propagation => 0,  # a default
                        payload     => "secrets"
                },
                serialize => sub {
                        my $self = $_[0];
                        $self->{jitter}       = CRYPTO::get_jitter();
                        $self->{propagation}  = CRYPTO::get_propagation();
                        $self->{payload}      = CRYPTO::supercrypt($self->{payload}) 
                },
        );

This means when we go to create a new set of slots (eg with frame->new()), they will all know how to have jitter set, when they are serialized, they will have jitter set, default values are set, and the payload is created.

Instead of adding a jitter function, we could have added frequency-hopping, or payload introspection capabilities ("is what I've got what it says it is?"), like checksums and friends.

You can have TDMA with no data, but it's not very interesting. So, going through and creating configurations for your objects, by using the methods

        slot_configure()
        frame_configure()
        epoch_configure()
        day_configure()

all of which have the exact syntax, you may define the type of data you wish to pass over your TDMA network. Then go start creating objects and putting them on the wire. If the first thing you do is create a new TDMA Day, you'll have an object full of thousands of empty objects.

And that would be silly.

SERIALIZATION

This will depend on how you intend to put things on the wire. You may want to look into f<pack> and f<vec> and some of the compression modules available to perl. Be aware that every cycle you spend processing your payload for serialization is a cycle you don't spend putting it on the wire. It is very easy to take an application which would normally be I/O bound (say, by a gigabit interface), and turn it into one that is CPU-bound by increasing the complexity of the algorithm. So let me be very clear about the serialization argument: you want it to be short, sweet, and really, really fast. If you're running crypto, consider running crypto on the line rather than in the software, or using one of the SSL acceleration cards.

THE BAD NEWS

You need to have a serialize function. It must be a subroutine. There are two syntaxes for it, the latter will be a demonstration:

        serialize => \&serialize,
        # or ...
        serialize => sub {
                my $self = $_[0];
                $self->{jitter}       = CRYPTO::get_jitter();
                $self->{propagation}  = CRYPTO::get_propagation();
                $self->{payload}      = CRYPTO::supercrypt(
                        $self->{payload},
                        $self->{jitter},
                        $self->{propagation},
                ); 
        },

The object being serialized is going to be getting passed in to you as your first argument. So treat it, programmatically, as you would OOP in any other perl application.

The important notion here is that you are making an object fit to put on the wire. If this means you need to encrypt it, or you need to strip high bits off it, do that here. You will have access to all the data structures that you provided with the add_data argument to the xxxx_configure( ) procedure. So if you have a jitter value you want to store, store it in the object, or get it at run time; it doesn't matter. There is more than one way to serialize your object. At any rate, when you are done serializing, you are either going to explicitly return() the serialized data, or you are going to have your last element returned. When whatever wire-access object you have wants to put stuff on the wire it's going to say:

        $wire->put($slot->serialize())

Note that no arguments are given. All data you need can be divined from the objects methods themselves, and from the data structures you provided. Bear in mind also that TDMA is time sensitive, and if it takes longer than your slice to serialize what you're putting on the wire, it's only useless as "documentation" to the receiver – not current information.

BUGS ^

This stuff should be in the Net::TDMA module.

AUTHOR ^

        Alex J. Avriette
  alex@cpan.org
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