public byte[] Encode(IStunContext ctx)
{
bool useMessageIntegrity =
!string.IsNullOrEmpty(ctx?.Username) &&
!string.IsNullOrEmpty(ctx?.Password) &&
!string.IsNullOrEmpty(ctx?.Realm);
var c = (ushort)Class;
var m = (ushort)Method;
int type =
(m & 0x0f80) << 2 |
(m & 0x0070) << 1 |
(m & 0x000f) << 0 |
(c & 0x2) << 7 |
(c & 0x1) << 4;
using (var ms = new MemoryStream())
{
List <Attribute> attrs = Attributes.ToList();
if (!string.IsNullOrEmpty(ctx?.Username))
{
attrs.Add(new Username(ctx.Username));
}
if (ctx?.Nonce != null)
{
attrs.Add(new Attributes.Nonce(ctx.Nonce));
}
if (!string.IsNullOrEmpty(ctx?.Realm))
{
attrs.Add(new Realm(ctx.Realm));
}
byte[] encodedAttrs;
using (var ams = new MemoryStream())
{
foreach (Attribute attr in attrs)
{
byte[] asBytes = attr.ToByteArray(TransactionId);
ams.Write(asBytes, 0, asBytes.Length);
}
encodedAttrs = ams.ToArray();
}
// 8 bytes for Fingerprint
var messageLength =
(ushort)(encodedAttrs.Length + FingerprintBytes);
if (useMessageIntegrity)
{
messageLength += MessageIntegrityBytes;
}
ms.Write(((ushort)type).ToBytes(), 0, 2);
ms.Write(messageLength.ToBytes(), 0, 2);
ms.Write(MagicCookie, 0, MagicCookie.Length);
ms.Write(TransactionId, 0, TransactionId.Length);
ms.Write(encodedAttrs, 0, encodedAttrs.Length);
if (useMessageIntegrity)
{
var lengthWithoutFingerprint =
(ushort)(messageLength - FingerprintBytes);
byte[] toCalc = ms.ToArray();
lengthWithoutFingerprint.ToBytes().CopyTo(toCalc, 2);
MessageIntegrity mi =
MessageIntegrity.Calculate(
ctx?.Username,
ctx?.Password,
ctx?.Realm,
toCalc);
ms.Write(mi.ToByteArray(), 0, MessageIntegrityBytes);
}
Fingerprint fingerprint = Fingerprint.FromMessage(
ms.ToArray()
);
ms.Write(fingerprint.ToByteArray(), 0, FingerprintBytes);
return(ms.ToArray());
}
}
