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 signature
The 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::MorseSignals
Tests 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.
