#!/usr/bin/perl

# MFD: <acct>  <pass1> <pass2> <next> <0.012> <cputime> <devtime> <frib>
# UFD: <name1> <name2> <name3> <next> <ext.prot> <size> <date>    <frib>
# <next> and <frib> are offsets within this block.
# <size> is in blocks.  There's no smaller resolution.

# TSS/8 <ext.prot>:
# ext.prot&7700	EXTENSION
# 0000		[NONE]
# 0200		.ASC
# 0400		.SAV
# 0600		.BIN
# 1000		.BAS
# 1200		.BAC
# 1400		.FCL
# 1600		.TMP
# 2000		[NONE]
# 2200		.DAT
# 2400		.LST
# 2600		.PAL
@ext = ("", ".ASC", ".SAV", ".BIN", ".BAS", ".BAC", ".FCL", ".TMP", "", ".DAT", ".LST", ".PAL");
$binary{".SAV"} = 1;
$binary{".BIN"} = 1;
$binary{".BAC"} = 1;
$binary{".TMP"} = 1;
$binary{".DAT"} = 1;
sub ext {
  return $ext[($_[0]&07700)/2];
}
# ext.prot & 077: <NC uw gw gr ow or> where a set bit prohibits the action.
# There seems to be no way to prevent one from reading his own files.
# The default permission is 012; "group write" and "all write" are prohibited.
# Permissions where u<g, u<o, or g<o are probably silly, but are allowed.
@prot = (0666, 0662, 0664, 0660, 0626, 0622, 0624, 0620,
         0646, 0642, 0644, 0640, 0606, 0602, 0604, 0600,
         0446, 0442, 0444, 0440, 0406, 0402, 0404, 0400);

#
# This flavor of sixbit encodes "A" as 041 (not 001)..
sub sixbit {
  return ord($_[0])-040;
}
sub asc {
  return chr($_[0]+040);
}

#
# The date is not optional in TSS directories.
# DATE FORMAT: <mmmm><ddddd><yyy>  Year is yyy+74.
$epoch = 1974; # Or should it be 1964, per the User's Guide?
@month = ("0",  "JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL",
	 "AUG", "SEP", "OCT", "NOV", "DEC", "13",  "14",  "15");

open(INPUT, $ARGV[0]) || die "$ARGV[0]: $!";
binmode(INPUT);

#
# An OS/8 directory starts in block 1, but the TSS MFD 
# location depends on the number of users.  There are 
# 4K each for SIP, FIP, INIT, then 8K for the RM.
# That's 20K of fixed overhead, followed by the swap
# area, 4K per user.
$mfbase = 0;
for ($users = 20; $users < 32; $users++) {
    $link = (20 + 4*$users) * 4; # 1K == 4 blocks
    #
    # Attempt to find the MFD at the next proposed spot.
    # The block should start with 8 dummy words, a 0010 
    # being in the fourth word.  This should be followed
    # by the MFD: 0001 <pw1> <pw2> 0012 <cpu> <dev> <frb>
    # and then the FRB: 0000 0001 <s2> <s3> <s4> <s5> <s6> <s7>
    # Example: The MFD has been found at offset 0620020,
    # following a dummy block at 0620000.  Each 4K is 
    # 20000, so that corresponds to 031 or 25 core images.
    # Five core images are not part of swap, so the system
    # Has a maxximum of 20 users.
    seek(INPUT, $link*01000, 0) || die "directory seek: $!";
    read(INPUT, $mfd, 01000) || die "directory read: $!";
    @mfd = unpack("S*", $mfd);
    #
    # @mfd starts with an MFD.
    next unless $mfd[003] == 0010;
#   next unless $mfd[014] == 0012;
    next if $mfd[014] & 07700;
    next unless $mfd[017] == 0020;
    next unless $mfd[020] == 0000;
    warn "users = $users\n";
    $mfbase = $link*01000;
    $mfbase -= 512; # Work around first "block is block 1".
    last;
}
exit 1 unless $mfbase;
#warn "mfbase is $mfbase\n";

#
# OK, $mfbase establishes the base for block access, 
# and @ufd is the relevant directory.  That's sufficient
# to read the file, given an offset to it's first 
# frib.  @ufd is the relevant directory context, and
# $frib # is an offset into @ufd..
sub readfile {
    local(*ufd, $frib, $offset, $bytes) = @_;
    local($count, $buf, $cblk);
    $buf = "";
    while ($bytes > 0) {
      # Calculate a block number
      $block = int($offset / 256); # 256 words / block
      $count = 256 - $offset%256;
      $count = $bytes if $count > $bytes; # Last block.
      # Locate the block.
      $cblk = $block;
      $fribo = $frib;
      while ($cblk > 6) {
	# Did we fall off the end?
        die "Walked off end of frib!\n" if $fribo == 0;
#print STDERR "Got here for $block: $fribo -> $ufd[$fribo]\n";
        $fribo = $ufd[$fribo]; # Follow link
        $cblk -= 7; # Just skipped forward 7 blocks
      }
      # This is the right FRIB segment.
      $cblk++; # Skip over the frib's link
      $cblk = $ufd[$fribo+$cblk]; # Get absolute block number, not relative.
      # Stop reading if no more blocks.
      return $buf if $cblk == 0;
      # Found the next block.  Read it.
      seek(INPUT, $mfbase+$cblk*512, 0) || die "data seek: $!";
      read(INPUT, $cb, 2*$count) || die "data read: $! ($cblk)";
      $buf .= $cb;
      $offset += $count;
      $bytes -= $count;
    }
    return $buf;
}

# Since the MFD is allowed just the one RIB, we have 
# enough context now to read in the rest of the MFD.
$mfd = &readfile(*mfd, 020, 0, 4096);
@mfd = unpack("S*", $mfd);

#
# Walk the MFD, processing each UFD.
for ($link = 010; $link; $link = $next) {
    #
    # Process a user's UFD.
    $uid  = $mfd[$link+0];
    $pw1  = $mfd[$link+1];
    $pw2  = $mfd[$link+2];
    $next = $mfd[$link+3];
    $prot = $mfd[$link+4];
    $cput = $mfd[$link+5];
    $devt = $mfd[$link+6];
    $frib = $mfd[$link+7];
    # Read the directory.
    $ufd = &readfile(*mfd, $frib, 0, 4096);
    @ufd = unpack("S*", $ufd);
    # Make a pretty name for the directory.
    $dir = sprintf("[%o,%o]%s%s%s%s", $uid>>6, $uid&077, &asc($pw1>>6), &asc($pw1&077), &asc($pw2>>6), &asc($pw2&077));
    $dir =~ s/ *$//;
    print "$dir:\n";
#   next if $uid == 1;
    # Walk the directory, listing the files.
    for ($fl = $ufd[3]; $fl; $fl = $lnxt) {
        $nam1 = $ufd[$fl+0];
        $nam2 = $ufd[$fl+1];
        $nam3 = $ufd[$fl+2];
#warn "fn: $nam1 $nam2 $nam3\n";
        $lnxt = $ufd[$fl+3];
        $prot = $ufd[$fl+4];
        $size = $ufd[$fl+5];
        $date = $ufd[$fl+6];
        $day = $date % 31;
        $month = ($date / 31) % 12;
        $year = int($date / 372); # 12*31=372
        $frib = $ufd[$fl+7];
        $fn = sprintf("%s%s%s%s%s%s", &asc($nam1>>6), &asc($nam1&077), &asc($nam2>>6), &asc($nam2&077), &asc($nam3>>6), &asc($nam3&077));
        $ext = $ext[$prot>>7];
        printf "  %s%s\t%4d\t%02o\t%2d-%3s-%4d\n", $fn, $ext[$prot>>7], $size, $prot&017, $day+1, $month[$month+1], $year+$epoch;
        $file = &readfile(*ufd, $frib, 0, 4096*256);
        #
        # At this point the data is in "S*" format.
# BUGBUG: For consistency, we should repack binary 
# data too, but in "natural" format.
        # TSS uses an "unnatural" text file byte order:
        # aaaaaaaabbbb bbbbcccccccc
        # Here we unmangle this.  At the same time, 
        # we strip bit 8, making our output legible
        # on modern systems.
        if (!$binary{$ext}) {
            @file = unpack("S*", $file);
            $file = "";
            while (@file) {
                $dword = ((shift @file)<<12) + (shift @file);
                $c1 = chr(($dword >> 16) & 0177);
                $c2 = chr(($dword >> 8) & 0177);
                $c3 = chr($dword & 0177);
                $file .= $c1 . $c2 . $c3;
            }
            #print "$file\n";
        }
        # BUGBUG: Create the output file here.
    }
}
exit 0;