# subroutine to check little or big-endian byte ordering
# returns 0 if little, 1 if big

sub endiancheck
{
    my ($x, $y);
    $x = pack("i",65); # pack 'A' as an signed 32bit int
    # now $x can be considered a 4-byte string
    $y = substr($x,3,1); #extract last byte
    if (ord($y)==65) {return 1;} # big endian
    return 0;  # little endian
}

# subroutines to convert from host to network byte ordering
# note that they must be called prior to unpack.
sub htons
{
    my $x = shift;
    if ($byteorder==1) { return $x; } # no need to do anything
    # switch bytes
    my ($a,$b);
    $a = substr($x,0,1);
    $b = substr($x,1,1);
    $x = pack("CC",ord($b),ord($a));
    return $x;
}

sub htonl
{
    my $x = shift;
    if ($byteorder==1) { return $x; }
    # switch
    my @a;
    $a[0] = substr($x,0,1);
    $a[1] = substr($x,1,1);
    $a[2] = substr($x,2,1);
    $a[3] = substr($x,3,1);
    $x = pack("CCCC",ord($a[3]),ord($a[2]),ord($a[1]),ord($a[0]));
    return $x;
}

sub htond
{
    my $x = shift;
    if ($byteorder==1) { return $x; }
    # switch
    my @a;
    $a[0] = substr($x,0,1);
    $a[1] = substr($x,1,1);
    $a[2] = substr($x,2,1);
    $a[3] = substr($x,3,1);
    $a[4] = substr($x,4,1);
    $a[5] = substr($x,5,1);
    $a[6] = substr($x,6,1);
    $a[7] = substr($x,7,1);
    $x = pack("CCCCCCCC",ord($a[7]),ord($a[6]),ord($a[5]),ord($a[4]),ord($a[3]),ord($a[2]),ord($a[1]),ord($a[0]));
    return $x;
}

sub ntohs { htons($_[0]); }
sub ntohl { htonl($_[0]); }
sub ntohd { htond($_[0]); }

$byteorder = endiancheck();
1;