#!/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.

# Unpack every 3 TSS8 bytes into 2 words.  Output the words as a
# rudimentary file in .bin format.  Each input file is presumed to
# be a program in .sav format, designed to load starting at location 0.

# Output leader/trailer.
sub leader {
  for ($i = 0; $i < 120; $i++) {
    print OUTPUT pack("C", 0200);
  }
}

# Ouput a word and update the checksum.
sub dframe {
  local($word) = @_;
  print OUTPUT pack("CC", $word >> 6, 077 & $word);
  $checksum += $word >> 6;
  $checksum += 077 & $word;
}

foreach $f (@ARGV) {
  open(INPUT, $f) || die "$f: $!";
  binmode(INPUT);
  $of = $f; $of =~ s/[.]sav$/.svb/;
  die "$f: Expected .sav" if $f eq $of;
  open(OUTPUT, ">$of") || die "$of: $!";
  binmode(OUTPUT);
  &leader;
  print OUTPUT pack("CC", 0100, 0);
  $checksum = 0100;
  while (read(INPUT, $buf, 3) == 3) {
    ($b1, $b2, $b3) = unpack("CCC", $buf);
    $b1 = ($b1<<16) + ($b2<<8) + $b3;
    $b2 = $b1 & 07777;
    $b1 = $b1 >> 12;
    &dframe($b1);
    &dframe($b2);
  }
  &dframe(07777 & $checksum);
  &leader;
}