use strict;
use warnings;

use vars qw($XOR $BLOCKSIZE $HEADERSIZE $CRYPT_MAGIC_1 $CRYPT_MAGIC_2
     $size $mode $line $Fingerprint $file $block
    ) ;

$XOR   = 'Perl' ;
$BLOCKSIZE       = length $XOR ;
$HEADERSIZE      = 2 ;
$CRYPT_MAGIC_1   = 0xff ;
$CRYPT_MAGIC_2   = 0x00 ;

$Fingerprint     = pack ("C*",$CRYPT_MAGIC_1,$CRYPT_MAGIC_2) ;

die "Usage: encrypt file...\n"
  unless @ARGV ;

# Loop throught each file in turn.
foreach $file (@ARGV)
{

    if (! -T $file)
    {
 print "Skipping directory $file\n" if -d $file ;
 print "Skipping non-text $file\n" if ! -d $file ;
 next ;
    }

    open (F,"<$file") or die "Cannot open $file: $!\n" ;
    open (O,">${file}.pe") or die "Cannot open ${file}.pe: $!\n" ;
    binmode O;

    # Get the mode
    $mode = (stat F)[2] ;

    # Check for "#!perl" line
    $line = <F> ;

    if ( $line =~ /^#!/ )
      { print O $line }
    else
      { seek F,0 }
   
    print O "use Filter::decrypt ;\n" ;
    print O $Fingerprint ;

    $block = '';
    while ($size = read(F,$block,$BLOCKSIZE) )
    {
        print O ($block ^ substr($XOR,length $block)) ;
    }

    close F ;
    close O ;

    unlink ($file)
 or die "Could not remove '$file': $!\n" ;

    rename ("${file}.pe",$file)
 or die "Could not rename $file.pe to $file: $!\n" ;

    chmod $mode,$file unless $^O eq 'MSWin32' ;

    print "encrypted $file\n" ; }