#!/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.

# Dump the file if it is really in TSS ASCII format.
# TSS ASCII stores three 8 bit characters per 24-bit double word:
# aaaaaaaabbbb bbbbcccccccc
# Theoretically, any file content could be interpreted as characters.
# However, in practice, mark parity is used.  So, we recognise here
# files which contain only bytes with the high bit set, making an
# exception for NUL, which was sometimes used for leader/trailer.

# Pick a block size (in words!)
$bsize = 128;
$upack = "S$bsize";

# Process the argument(s).  The -q option toggles quiet mode, in which the
# FOCAL text is not output.
$quiet = 0;
for $file (@ARGV) {
  if ($file =~ /-q/i) {
    $quiet = !$quiet;
    next;
  }

  # Open the file
  open(INPUT, $file) || die "$file: $!";
  binmode(INPUT);

  #
  # Read in each block.
  @buf = ();
  for ($block = 0; ; $block++) {
      read(INPUT, $buf, 2*$bsize) || last;
      push(@buf, unpack($upack, $buf));
  }

  #
  # Check for a valid ASCII file.  Accumulate the text.
  $fail = 0;
  $text = "";
  while (@buf) {
    $word1 = shift @buf;
    # An odd number of words rules out ASC format.
    $fail unless @buf;
    $word2 = shift @buf;
    $word1 = ($word1 << 12) + $word2;
    $c1 = $word1 >> 16;
    $c2 = ($word1 >> 8) & 0377;
    $c3 = $word1 & 0377;
    if ($c1 & 0177) {
      $fail = 1 unless $c1 & 0200;
      $text .= pack("C", $c1 & 0177);
    }
    if ($c2 & 0177) {
      $fail = 1 unless $c2 & 0200;
      $text .= pack("C", $c2 & 0177);
    }
    if ($c3 & 0177) {
      $fail = 1 unless $c3 & 0200;
      $text .= pack("C", $c3 & 0177);
    }
    last if $fail;
  }
  warn "$file: not an ASC file\n" if $fail;

# warn "$file:\n";
  $quiet = 1 if $fail;
  print $text unless $quiet;
}
exit 0;