Day 15 – Building a (little) Spacecraft with Perl 6

Showing off long ears

In the previous post, we have encountered some kind of special elves’ magic:

enum Fuel <Solid Liquid Gas>;

class SpeedChoice does ASNChoice {
    method ASN-choice { { mph => (1 => Int), kmph => (0 => Int) } }
}

class Rocket does ASNSequence {
    has Str $.name is UTF8String;
    has Str $.message is default-value("Hello World") is UTF8String;
    has Fuel $.fuel;
    has SpeedChoice $.speed is optional;
    has Str @.payload is UTF8String;

    method ASN-order { <$!name $!message $!fuel $!speed @!payload> }
}

my $rocket = Rocket.new(
    name => 'Falcon',
    fuel => Solid,
    speed => SpeedChoice.new((mph => 18000)),
    payload => [ "Car", "GPS" ]);

my $rocket-bytes = ASN::Serializer.serialize($rocket, :mode(Implicit));

#`[ Result:
      Blob.new(
          0x30, 0x1B, # Outermost SEQUENCE
          0x0C, 0x06, 0x46, 0x61, 0x6C, 0x63, 0x6F, 0x6E, # NAME, MESSAGE is missing
          0x0A, 0x01, 0x00, # ENUMERATED
          0x81, 0x02, 0x46, 0x50, # CHOICE
          0x30, 0x0A, # SEQUENCE OF UTF8String
              0x0C, 0x03, 0x43, 0x61, 0x72,  # UTF8String
              0x0C, 0x03, 0x47, 0x50, 0x53); # UTF8String
]

say ASN::Parser.new(:type(Rocket)).parse($rocket-bytes) eqv $rocket; # Certainly true!

However, as an elf I know once quoted, ‘It’s hard to tell the difference between mastered technique and magic’. So the mystery can be resolved? Let’s glance over the way it all works.

Day 14 – Designing a (little) Spacecraft with Perl 6

Looking for a common point

Greetings!

Those days I am spending some of my time working on foundation parts for, revealing a possible surprise, a LDAP (Lightweight Directory Access Protocol) implementation for Perl 6.

However, it is yet too early to talk about this one, so I will have some mystery blanket covering this topic for now, as we have another one – spacecrafts!

And a common point between spacecrafts and LDAP is: LDAP specification uses a notation called ASN.1, which allows one to define an abstract type, using a specific textual syntax, and, with a help of ASN.1 compilers, create a type definition for particular programming language and what’s more: encoder and decoder for values of this type, which can serialize your value into some data which, for example, can be send over network and parsed nicely on another computer.