use constant NUM_BITS = $Config{ivsize} * 8;
use constant SIGN_BIT = 1 << ( NUM_BITS - 1 );
use constant ALL_BITS = -1;

sub sr_signed {
   my ($p, $q) = @_;
   if ($p & SIGN_BIT) {
      return ($p >> $q) | ($ALL_BITS << (NUM_BITS - $q));
   } else {
      return $p >> $q;
   }
}