NAME
Bit::MorseSignals - The MorseSignals protocol.
VERSION
Version 0.08
SYNOPSIS
use Bit::MorseSignals::Emitter;
use Bit::MorseSignals::Receiver;
my $deuce = Bit::MorseSignals::Emitter->new;
my $pants = Bit::MorseSignals::Receiver->new(done => sub { print $_[1], "\n" });
$deuce->post('HLAGH') for 1 .. 3;
$pants->push while defined ($_ = $deuce->pop);DESCRIPTION
In unidirectionnal communication channels (such as networking or IPC), the main issue is often to know the length of the message. Some possible solutions are fixed-length messages (which is quite cumbersome) or a special ending sequence (but it no longer can appear in the data). This module proposes another solution, by using a begin/end signature specialized for each message.
An actual implementation is also provided :
- Bit::MorseSignals::Emitter is a base class for emitters ;
- Bit::MorseSignals::Receiver is a base class for receivers.
Go to those pages if you just want the stuff done and don't care about how it gets there.
PROTOCOL
Each byte of the data string is converted into its bits sequence, with bits of lowest weight coming first. All those bits sequences are put into the same order as the characters occur in the string.
The header is composed of three bits (lowest weight coming first) :
- - The 2 first ones denote the data type : a value of 0 is used for a plain string, 1 for an UTF-8 encoded string, and 2 for a Storable object. See also the "CONSTANTS" section ;
- - The third one is reserved. For compatibility reasons, the receiver should for now enforce the message data type to plain when this bit is lit.
The emitter computes then the longuest sequence of successives 0 (say, m) and 1 (n) in the concatenation of the header and the data. A signature is then chosen :
- - If m > n, we take n+1 times 1 followed by one 0 ;
- - Otherwise, we take m+1 times 0 followed by one 1.
The signal is then formed by concatenating the signature, the header, the data bits and the reversed signature (i.e. the bits of the signature in the reverse order).
a ... a b | t0 t1 r | ... data ... | b a ... a
signature | header | data | reversed signatureThe receiver knows that the signature has been sent when it has catched at least one 0 and one 1. The signal is completely transferred when it has received for the first time the whole reversed signature.
CONSTANTS
BM_DATA_AUTO
Default for non-references messages. Try to guess if the given scalar is an UTF-8 string with Encode::is_utf8.
BM_DATA_PLAIN
Treats the data as a plain string. No extra mangling in done.
BM_DATA_UTF8
Treats the data as an UTF-8 string. The string is Encode::encode_utf8'd in a binary string before sending, and Encode::decode_utf8'd by the receiver.
BM_DATA_STORABLE
The scalar, array or hash reference given is Storable::freeze'd by the sender and Storable::thaw'd by the receiver.
EXPORT
The constants "BM_DATA_AUTO", "BM_DATA_PLAIN", "BM_DATA_UTF8" and "BM_DATA_STORABLE" are only exported on request, either by specifying their names or the ':consts' tag.
DEPENDENCIES
Carp (standard since perl 5), Encode (since perl 5.007003), Storable (idem).
SEE ALSO
Bit::MorseSignals::Emitter, Bit::MorseSignals::Receiver.
AUTHOR
Vincent Pit, <perl at profvince.com>, http://www.profvince.com.
You can contact me by mail or on irc.perl.org (vincent).
BUGS
Please report any bugs or feature requests to bug-bit-morsesignals at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Bit-MorseSignals. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc Bit::MorseSignalsTests code coverage report is available at http://www.profvince.com/perl/cover/Bit-MorseSignals.
COPYRIGHT & LICENSE
Copyright 2008 Vincent Pit, all rights reserved.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.