#!/usr/bin/perl

@rem = '
@echo off
c:\perl5\bin\perl %0 %1 %2 %3 %4 %5 %6 %7 %8 %9
goto endofperl
@rem ' if @rem;

# Open the input (hex) files.
($ifile1, $ifile2) = @ARGV;
open(INPUT1, $ifile1) || die "$ifile1: $!";
open(INPUT2, $ifile2) || die "$ifile2: $!";

# Open the output file in binary mode.
$ofile = "foo.bin";
die "$ofile" if $ifile1 eq $ofile;
open(OUTPUT, ">$ofile") || die "$ofile: $!";
binmode(OUTPUT);

# Output leader/trailer.
sub trailer {
  for ($i = 0; $i < 128; $i++) {
    print OUTPUT pack("C", 0200);
  }
}
&trailer;

sub checksum {
  local($len, $addr, $hex) = @_;
  local($sum);

  $len = hex($len);
  $addr = hex($addr);
  $sum = $len + ($addr>>8) + (0xFF&$addr);
  while ($hex =~ s/^(..)//) {
    $sum += hex($1);
  }
  return 0xFF & $sum;
}

# Convert the data.
$loc = -1; # Location not set yet.
$fld = 0;
$csum = 0;
while (($i1 = <INPUT1>)) {
  $i1 =~ s/\r//g;
  # Input files must be valid.
  die "$i1" unless $i1 =~ /^:(..)(....)0[01](.*)(..)$/;
  ($l1, $a1, $h1, $c1) = ($1, $2, $3, $4);
  $i2 = <INPUT2>;
  $i2 =~ s/\r//g;
  die "$i2" unless $i2 =~ /^:(..)(....)0[01](.*)(..)$/;
  ($l2, $a2, $h2, $c2) = ($1, $2, $3, $4);
  # Input files must remain in sync.
  die "Length mismatch: $l1 vs $l2" unless $l1 eq $l2;
  die "Address mismatch: $a1 vs $a2" unless $a1 eq $a2;
  # Are we done?
  last if $l1 eq "00";
  # Verify checksum for $i1.
  $s = 0xFF & (hex($c1) + &checksum($l1, $a1, $h1));
  die "Checksum low: $s $i1" if $s;
  # Verify checksum for $i2.
  $s = 0xFF & (hex($c2) + &checksum($l2, $a2, $h2));
  die "Checksum high: $s $i2" if $s;
  if ($loc != -1) {
    if ($fld != ($loc >> 12)) {
      # Output a field setting.
      $fld = $loc >> 12;
      print OUTPUT pack("C", 0300 + ($fld<<3));
    }
  }
  # Output location settings as required.
  if ($loc != hex($a1)) {
    $loc = hex($a1);
    print OUTPUT pack("CC", 0100+($loc>>6), 077&$loc);
    $csum += 0100 + ($loc>>6) + (077&$loc);
  }
  # Assemble the words and output them.  Each byte
  # has six of the 12 bits.
  $l1 = hex($l1);
  for ($i = 0; $i < $l1; $i++) {
    die unless $h1 =~ s/^(..)//;
    $b1 = hex($1);
    die unless $h2 =~ s/^(..)//;
    $b2 = hex($1);
    print OUTPUT pack("CC", $b2, $b1);
    $csum += $b1 + $b2;
    $loc++;
  }
}
# Output the checksum.
$csum &= 07777;
print OUTPUT pack("CC", ($csum>>6), (077&$csum));
&trailer;

__END__
:endofperl