#!/usr/bin/perl -w
use strict;
use warnings;

# Call the script using
# perl mpxcrc.pl fileofinterest.log
# reveng.exe must be in the same directory
# http://reveng.sourceforge.net/
# Expects input file to look like:
#
#15 00
#09 f3 84 f3 84 f3 84 c2 
#0a 00 00 f3 84 f3 84 7a 
#88 f3 84 f3 84 f3 84 68 
#3b 01
#01 f6 8e f6 8e f6 8e b6 
#02 00 00 f6 8e f6 8e 58 
#80 f6 e1 f6 e1 f6 dc ff 
#etc...
 
my $length=0;
my $crctest="";
my $rfchannel;
my $packet;
my $lineno=0;


foreach my $line (<>)
	{

	$lineno++;
	my $length=length($line);
	
	if ($length==7)
		{
		if ($crctest ne "") 
			{
			my $poly;
			my $init;
			
			# Sometimes with the data provided there are multiple possible poly and init values.
			# We read them all until we find a poly equal to 0x31 we use this one as we assume it to be correct
			# (Assumed because it gets the most hits)
			# If there isn't a match on 0x31 we save the last guess
			open(REVENG,"./reveng.exe -w 8 -s ".$crctest." |") || die "Open reveng failed: $! \n";
			while (<REVENG>)
				{
				chomp;
				#print $rfchannel." ".$_."\n";
				($poly, $init) = (/^width=8  poly=0x(..)  init=0x(..)/);
				last if ($poly eq "31")
				}
			close(REVENG);	
			# Print results
			print "lineno=".($lineno-4).",rfchan=".$rfchannel.",poly=0x".$poly.",init=0x".$init."\n";	
				
			}	
		$rfchannel = substr($line,0, 2);
		$packet="";
		$crctest="";
		}
	else # ($length != 7)
		{
		$packet = trim($line);
		$crctest.= $packet." ";
		}
		
	
	}

exit;

sub  trim { my $s = shift; $s =~ s/\s+//g; return $s };