
Perl Module String::LRC
by Ralph Padron <whoelse@elitedigital.net>

This packages provides a perl module to generate a longitudinal 
redundancy check byte for a string.

Installation:
   "perl Makefile.PL"
   "make"
   "make test"
   "make install"

Requests and notices of bugs should be sent to author's aforementioned
email (no spam).

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LRC - Perl interface for longitudinal redundancy check generation

DESCRIPTION

The Longitudinal Redundancy Check (LRC) is a one byte character,
commonly used as a byte-field in data transmission over analog systems.

Most commonly, in STX-ETX bounded strings sent in financial protocols.
Following some previous experience with such protocols, I wrote 
an LRC function in perl and later decided to re-write in C
for efficiency.  The result is this module String::LRC,
which generates this aforementioned byte.

Commonly used in financial protocols as follows with ETX (ASCII 03)
appended to LRC sum and packets after the STX (ASCII 02), payload, 
and ETX chars.  

    $outboundString = chr(02) . $outboundString . chr(03)
			. lrc($outboundString . chr(03));

A init value may also been supplied in the above example.


 EXAMPLES

    use String::LRC;
    $lrc = lrc("string to get lrc of");

	# alternately you can try the LRC of a file, 
	# if you should ever need this for some reason
	# included following Soenke J. Peters' example for CRC32
	
    use String::LRC;
    $filename = "/path/to/test.file";
    if (-e $filename) {
      open(TESTFILE, $filename);
      $filelrc = lrc(*TESTFILE);
      close(TESTFILE);
    }


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AUTHOR

Ralph Padron <whoelse@elitedigital.net>

If you have any requests or bugs, send email to the above address (no spam please).

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COPYRIGHT

License to use this module/library and make use of in derivative works is is 
granted to all, freely, provided that this module is identified as "derived 
from R Padron" and notice of other contributors be provided in any material 
referencing or mentioning this module.  The author makes no representations of 
possessing full or partial copyright to the LRC code nor the algorythyms used 
in this module, as said is either public knowledge or inspired by multiple sources.

LRC algorithms taken from combination of sources:
	1. Public Specifications, EIS 1081, San Francisco, CA: 
	   Visa, 1999

	2. QWEST Communications, Inc. Tech Publication 77359, 
	   Module 5, Issue 1, October 2001. pg 36.

	3. Tanenbaum, A. S., Computer Networks,  3rd ed.  
	   pp. 186-190Amsterdam, The Netherlands: Vrije Univ., 1996.

The module is inspired by the previous uses the author has had for 
the LRC generation algorythm; Inspiration for and partial code snippets 
for initial value and lrc generation of file data provided from 
Soenke J. Peters' String::CRC32.

The author makes no representations concerning either the merchantability of this 
software or the suitability of this software for any particular purpose.  It is 
provided "as is" without express or implied warranty of any kind.

These notices must be retained in any copies of any part of this documentation 
and/or software.

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SEE ALSO OR RELATED
    
B<String::CRC>, B<String::CRC32>, L<Device::SerialPort>, L<Device::Modem>.
