public void TestDomainSlice()
{
var actual = new Domain("foo.example.com");
var expected = new Domain("example.com");
Assert.That(actual.Slice(1), Is.EqualTo(expected));
}
/**
* Returns true if the given Domain is below the current domain (i.e
* they share a common suffix)
*/
public bool IsSubdomain(Domain other)
{
var prefix_length = other.Length - this.Length;
var other_tail = other.Slice(prefix_length);
return(other_tail == this);
}
/**
* Converts a standard domain name into a series of bytes, possibly
* compressed using domains seen so far.
*/
public byte[] SerializeDomain(Domain domain)
{
var stream = new MemoryStream();
if (domain[domain.Length - 1] != "")
{
throw new InvalidDataException("Domain name must end in 0 byte segment");
}
var idx = 0;
foreach (var segment in domain)
{
Domain current_subdomain = domain.Slice(idx);
// Avoid compressing on an empty domain, since it wastes a byte
// of space and makes the decoder work harder for no reason
if (segment != "" &&
domains_seen.ContainsKey(current_subdomain))
{
// RFC specifies that top-2 bits must be 1
UInt16 compress_bits = (1 << 15) + (1 << 14);
UInt16 offset_bits = domains_seen[current_subdomain];
UInt16 compress_ptr = (UInt16)(compress_bits | offset_bits);
stream.WriteByte((byte)((compress_ptr >> 8) & 0xff));
stream.WriteByte((byte)(compress_ptr & 0xff));
MoveForward(2);
break;
}
else
{
// Record the current domain for later compression, and
// then write it out (but only if it'll fit into the
// 14 bits we have to store the pointer in)
if (offset <= (1 << 14) - 1)
{
domains_seen[current_subdomain] = offset;
}
var segment_bytes = new byte[segment.Length];
for (int i = 0; i < segment.Length; i++)
{
segment_bytes[i] = (byte)segment[i];
}
stream.WriteByte((byte)segment_bytes.Length);
stream.Write(segment_bytes, 0, segment_bytes.Length);
MoveForward((UInt16)(1 + segment_bytes.Length));
idx++;
}
}
return(stream.ToArray());
}