#perl
#
######################################################################
# This is file changes.pl. 
#
# Determine the changed pages between 2 dvi files using dvii and diff
#

use strict ; 

my $version = "0.02 (17 August 2002)" ;

# CHANGE these two values (if needed) to point to the dvii and diff 
# executables. 
our $DVII = "dvii" ; 
our $DIFF = "diff" ; 

use Getopt::Std ;

my $usage_string = 
"changes.pl $version
USAGE: changes.pl [options] dvi_file1 dvi_file2
\n" ;

my $number_of_args = $#ARGV ; 

# Check that there are at least three arguments. 
if ($number_of_args < 1) 
{
  print STDOUT $usage_string ; 
  exit 0 ; 
}

# Get the 2 filenames
my $dvifile1 = $ARGV[0] ; 
my $dvifile2 = $ARGV[1] ; 

# ERROR CHECKING.
# Check that these two files exist.
 
if (!(-f $dvifile1))
{
  # Maybe we need to append a .dvi
  if (-f "$dvifile1.dvi")
  {
    $dvifile1 = "$ARGV[0]" . ".dvi" ; 
  }
  else
  {
    print "ERROR. Cannot find file $dvifile1 or $dvifile1.dvi. Exiting.\n" ;
    exit 1 ;
  }
}

if (!(-f $dvifile2))
{
  # Maybe we need to append a .dvi
  if (-f "$dvifile2.dvi")
  {
    $dvifile2 = "$ARGV[1]" . ".dvi" ; 
  }
  else
  {
    print "ERROR. Cannot find file $dvifile2 or $dvifile2.dvi. Exiting.\n" ;
    exit 1 ;
  }
}

# Check that these two files are in fact dvi files. 
if (is_dvii_file($dvifile1) < 0)
{
  print "ERROR. $dvifile1 is not a valid .dvi file. Exiting.\n" ;
  exit 1 ;
}

if (is_dvii_file($dvifile2) < 0)
{
  print "ERROR. $dvifile2 is not a valid .dvi file. Exiting.\n" ;
  exit 1 ;
}

my $mdfile1 = tempfilename() ; 
my $mdfile2 = tempfilename() ; 

# Set up to erase the files at end of script

END 
{ 
  if (-e $mdfile1) 
  {
    unlink($mdfile1) or die "Couldn't unlink $mdfile1 : $!" ;
  }
  if (-e $mdfile2) 
  {
    unlink($mdfile2) or die "Couldn't unlink $mdfile2 : $!" ;
  }
}


# At this point we have two valid .dvi files. Compute their message digests. 
my ($cmd1, $cmd2, $cmd, $rv) ; 
$cmd1 = "$DVII -M1 $dvifile1 > $mdfile1" ;
$cmd2 = "$DVII -M1 $dvifile2 > $mdfile2" ;
$rv = `$cmd1` ; 
$rv = `$cmd2` ; 


# Do the diff
$cmd = "$DIFF $mdfile1 $mdfile2" ; 
$rv = `$cmd` ; 
print "$rv\n" ; 

exit 0 ; 


######################################################################

sub tempfilename
{
  my ($tempfile_name) ;

  # Need both of these:
  use Fcntl;
  use POSIX qw(tmpnam);

  no strict 'subs' ;
  # Loop until we get a name that we can open.
  do { $tempfile_name = tmpnam() }
  until sysopen(TMPFH, $tempfile_name, O_RDWR|O_CREAT|O_EXCL);

  # Close the file handle.
  close(TMPFH) ;

  # Return the filename
  return $tempfile_name ;
}


sub is_dvii_file
{
  my ($file, $rv) ; 

  my $file = $_[0] ; 

  $rv = `$DVII -C $file` ;
 
  if (!($rv =~ /passed/))
  {
    return -1 ;
  }
  else
  {
    return 0 ; 
  }

}