#!/usr/bin/perl
# whatsthis
# read an id off the tape and display it to the user

# This file is part of chiark backup, a system for backing up GNU/Linux and
# other UN*X-compatible machines, as used on chiark.greenend.org.uk.
#
# chiark backup is:
#  Copyright (C) 1997-1998,2000-2001 Ian Jackson <ian@chiark.greenend.org.uk>
#  Copyright (C) 1999 Peter Maydell <pmaydell@chiark.greenend.org.uk>
#
# This is free software; you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation; either version 2, or (at your option) any later version.
#
# This is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
# details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

# First rough hack; mostly just code nabbed from full. 
# --list assumes the dump type was 'zafio', which is a bit bogus.

# whatsthis   : no args => just print tapeid
# whatsthis --list [n] : print tapeid then list archive n (if n omitted,
# 0 is assumed.) Note that archives are numbered from zero!

sub rewind();
sub stopandsay(@);

$etc='/etc/chiark-backup';
require "$etc/settings.pl";
require 'backuplib.pl';

$| = 1;

# This isn't intended to be run automatically, so don't bother 
# with setting status.

# If we are run with the argument --list then list the backup to 
# stdout. Otherwise just print the tape ID.
$listing = 0;  # default : don't list
$listing = 1 if ($ARGV[0] eq '--list');
$listarchive = 0;
$listarchive = $ARGV[1] if defined $ARGV[1];

print "Trying to read tape ID from currently inserted tape...\n";

unlink 'TAPEID';
system "mt -f $ntape setblk $blocksizebytes"; $? and die $?;
system "dd if=$ntape bs=${blocksize}b count=10 | tar -b$blocksize -vvxf - TAPEID";
$? and stopandsay "Failed to read TAPEID.\n";

if (!open(T, "TAPEID"))
{
  stopandsay "Tape has no ID label.\n";
}

# OK, there's a TAPEID file, read the ID and check for sanity.
chomp($tapeid= <T>);
if ($tapeid =~ m/[^0-9a-zA-Z]/)
{
   stopandsay "Tape has a bad (non-alphanumeric) TAPEID ($&).\n";
}
elsif (! $tapeid =~ m/[0-9a-zA-Z]/)
{
   stopandsay "Empty TAPEID.\n";
}

print "TAPEID is $tapeid.\n";
close T;

# If we aren't listing the tape contents, we can just rewind the tape
# and exit.
if (!$listing)
{
   rewind();
   exit;
}

# List the contents of archive $listarchive on the tape.
# We are already at the right place for the first archive
# (after the TAPEID). 
# For any other archive, we skip forwards to the start of that archive.
if ($listarchive)
{
   system "mt -f $ntape fsf $listarchive";
   $? and stopandsay "Couldn't skip forward to archive $listarchive.";
}

# Use file to figure out what the archive type is
# This doesn't seem to work too well, so I'm disabling it -- PMM 
#$ftype = `dd if=$ntape ibs=$blocksizebytes | file -`;
#$? and stopandsay "couldn't determine file type: $?";
$ftype = 'POSIX tar';

# What we want to do here is roughly:
# dd if=$ntape ibs=$blocksizebytes | readbuffer | afio ???
#
# where the afio options are such as to list an archive created with
# afio -b $softblocksizebytes -Zvo

if ($ftype =~ /POSIX tar/) {
   # POSIX tar archive; we read it with cpio
   $reader = "cpio -it -C$softblocksizebytes -Hustar";
} elsif ($ftype =~ /ASCII cpio/) {
   $reader = "afio -b $softblocksizebytes -Zt -";
} elsif ($ftype =~ /dump file/) {
   stopandsay "sorry: can't list dump files yet";
} else {
   stopandsay "listing failed: unknown archive type";
}

# Now back up so we can read the file again properly
#system "mt -f $ntape bsf 1"; $? and stopandsay "couldn't backspace tape: $?";

system "dd if=$ntape ibs=$blocksizebytes | readbuffer | $reader";
$? and stopandsay "listing failed: $?";

# All's well, stop here.
print "Listing complete.\n";
rewind();
exit;


# Rewind the tape.
sub rewind ()
{
   system "mt -f $tape rewind"; $? and die $?;
}

# Print the given message, rewind the tape and exit failure.
sub stopandsay(@)
{
   print @_;
   rewind();
   exit(1);
}