use strict;
use warnings;
use Time::HiRes qw( time );

my $start = time();

my $input_file = $ARGV[0];

my $data = do {

    local $/ = undef;
    open (my $fh, "<", $input_file) or die "could not open $input_file: $!";
    binmode($fh);
    <$fh>;

};

my $reversed_data = pack( "v*", unpack( "n*", $data ) );

open my $output, '>', "bkpps3.swap.bin";
binmode($output);

print $output $reversed_data;

my $end = time();
my $runtime = sprintf( "%.16s", $end - $start );
print $runtime;