Append CRC

append-crc.perl

#!/usr/bin/perl -w

use strict;

my $TempCompFileName = shift(@ARGV);
my $OutFileName  = shift(@ARGV);

my ($start_addr, $appd_cks, $appd_len) = (0);

sub appendCks
{
    my ($fileName) = @_;
    my ($cks, $len) = (0, 0);
    
    open APPENDCKS_FH, "+<$fileName"  or die "fail to open file $fileName : $!";
    until ( eof APPENDCKS_FH ) {
        $cks = ( $cks + ord( getc( APPENDCKS_FH )) ) % 0x100 ;
        $len++ ;
    }
    
    $cks = 0xFF - $cks;
    close APPENDCKS_FH;

    printf ("append checksum  =>  file : %s,  len : 0x%X, checksum : 0x%X \n", , $fileName, $len, $cks);
    $appd_cks =$cks;
    $appd_len =$len;
}


appendCks($TempCompFileName);

# Then append Checksum (include the 4bytes starting address)  
open INS_FH, "$TempCompFileName"  or die "fail to open file $TempCompFileName : $!";
open OUT_FH, ">$OutFileName"      or die "fail to Append file $OutFileName: $!";
while (<INS_FH>)
{
   print OUT_FH $_;
}
print OUT_FH chr($appd_cks); 
close INS_FH;
close OUT_FH;

from https://forum.openwrt.org/viewtopic.php?id=39142