#!/usr/bin/perl
# 
# Copyright © 2015-2020 by Vincent Slyngstad
# 
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
# 
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS LISTED ABOVE BE LIABLE
# FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
# CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
# 
# Except as contained in this notice, the names of the authors above
# shall not be used in advertising or otherwise to promote the sale, use
# or other dealings in this Software without prior written authorization
# from those authors.

#
# Given a BIN format image, expand it to the three ROM images
# needed by the DECmate II.
#

#
# First, read in the BINary.
#
# Issue: Many of the DEC tapes have the location bit set in
# their checksums, so we allow that.
open(INPUT, $ARGV[0]) || die "$ARGV[0]: $!";
binmode(INPUT);
@core1 = (); $loc = $store = undef;
$sum = $add = $field = 0;
while (read(INPUT, $top, 1)) {
  $top = unpack("C", $top);
  next if $top == 0200;	# Leader or Trailer
  last if $top == 0232; # End of file
  # It isn't trailer.  That implies time to store the previous word
  # if any.
  if (defined($store)) {
    $core1[$field*4096+$loc] = $store;
    $max = $field*4096+$loc unless $max > $field*4096+$loc;
    $store = undef;
    $loc = ($loc + 1) & 07777;
    $sum += $add;
    $fortran = 0;
  }
  if ($top & 0200) { # Better be field setting!
    die "$ARGV[0]: Invalid field setting" unless $top >= 0300;
    die "$ARGV[0]: Invalid field setting" if $top & 0007;
    $fortran = 1 if $top == 0340;
    $field = ($top & 070) >> 3;
    next;
  }
  # Read and verify the format of the bottom half.
  read(INPUT, $bot, 1) || die "$ARGV[0] read: $!";
  $bot = unpack("c", $bot);
  die "$ARGV[0]: ".$bot." not in bin format ". tell(INPUT) unless $bot <= 077;
  # Assemble the word, and figure out the checksum update.
  $word = ($top << 6) + $bot;
  $add = $top + $bot; # Update checksum
  # If the word has the 010000 bit set, it's a location setting.
  if ($word > 07777) {
    #
    # Change location counter
    $loc = $word & 07777;
#printf "Loc == %04o\n", $loc;
    $sum += $add;
  } else {
    die "$ARGV[0]: no location counter" unless defined($loc);
    $store = $word;
  }
}
close(INPUT);
if ($fortran) {
  die "$ARGV[0]: 4K Fortran Binary\n" if $fortran;
  $sum += 0640; # 4K Fortran loader counts 0300 and 0340
}
if (!defined($store)) {
  # This is that weird case where the checksum has location bit set!
  $store = $loc;
  $sum -= $add;
}
$sum &= 07777;
printf "$ARGV[0]: Checksum is %04o, not %04o\n", $sum, $store if $sum != $store;
#printf STDERR "$ARGV[0]: Checksum is %04o, not %04o\n", $sum, $store if $sum != $store;

#
# Check for loading outside the ROMs!
#
for ($loc = 000000; $loc < 070000; $loc++) {
  next unless defined $core1[$loc];
  printf "%05o)%04o is outside ROM\n", $loc, $core[$loc];
  $status = 1;
}

#
# At this point @core1 contains the program.
# Dump the ROMs in an appropriate format..
#
$status = 0;
open(ROM1, ">$ARGV[1]") || die "$ARGV[1]: $!"; binmode(ROM1);
open(ROM2, ">$ARGV[2]") || die "$ARGV[2]: $!"; binmode(ROM2);
open(ROM3, ">$ARGV[3]") || die "$ARGV[3]: $!"; binmode(ROM3);

for ($loc = 070000; $loc < 074000; $loc++) {
  # First ROM has high 0000-3777.
  $core1[$loc+00000] = 0377 unless defined $core1[$loc+00000];
  printf ROM1 "%c", $core1[$loc+00000] >> 4;
  # Second ROM has high 04000-07777.
  $core1[$loc+04000] = 0377 unless defined $core1[$loc+04000];
  printf ROM2 "%c", $core1[$loc+04000] >> 4;
  # Third ROM alternates low nibble bits.
  $n1 = $core1[$loc+00000] & 017;
  $n2 = $core1[$loc+04000] & 017;
  $byte = (($n1 & 010) << 4)
        + (($n1 & 004) << 3)
        + (($n1 & 002) << 2)
        + (($n1 & 001) << 1)
        + (($n2 & 010) << 3)
        + (($n2 & 004) << 2)
        + (($n2 & 002) << 1)
        +  ($n2 & 001);
  printf ROM3 "%c", $byte;
}
exit $status;

__END__
:endofperl