public static PacketPayload.CursorWritingContext StartWriting(MemoryCursor cursor,
PacketVersion version,
PacketConnectionId destinationConnectionId,
PacketConnectionId sourceConnectionId,
PacketNumber packetNumber,
PacketToken token)
{
var startOffset = cursor.AsOffset();
var firstByte = new PacketFirstByte()
.SetInitial()
.SetMaxPacketNumberLength();
firstByte.Write(cursor);
version.WriteBytes(cursor);
destinationConnectionId.WriteBytes(cursor);
sourceConnectionId.WriteBytes(cursor);
token.WriteBytes(cursor);
var context = PacketPayload.StartPacketWriting(cursor, startOffset);
var packetNumberBytes = firstByte.SlicePacketNumberBytes(cursor);
packetNumber.Fill(packetNumberBytes.Span);
return(context);
}
public static PacketPayload.CursorWritingContext StartWriting(MemoryCursor cursor,
PacketVersion version,
PacketConnectionId destinationConnectionId,
PacketConnectionId sourceConnectionId,
PacketNumber largestAcknowledgedPacketNumber,
PacketNumber packetNumber)
{
var startOffset = cursor.AsOffset();
var firstByte = new PacketFirstByte()
.SetHandshake()
.SetMaxPacketNumberLength();
firstByte.Write(cursor);
version.WriteBytes(cursor);
destinationConnectionId.WriteBytes(cursor);
sourceConnectionId.WriteBytes(cursor);
var context = PacketPayload.StartPacketWriting(cursor, startOffset);
var packetNumberBytes = firstByte.SlicePacketNumberBytes(cursor);
packetNumber
.EncodeByLargestAcknowledged(largestAcknowledgedPacketNumber)
.Fill(packetNumberBytes.Span);
return(context);
}
public void Dispose()
{
var payloadLength = cursor - startPayloadOffset;
var payload = cursor.Peek(-payloadLength);
Span <byte> payloadBuffer = stackalloc byte[payloadLength];
Span <byte> tagBuffer = stackalloc byte[aead.TagLength];
payload.Span.CopyTo(payloadBuffer);
packetFirstByte.SlicePacketNumberBytes(cursor);
var packetLength = cursor - startPacketOffset;
cursor.Set(startPayloadOffset);
cursor.EncodeVariable32(packetLength);
var packetNumberBytes = packetFirstByte.SlicePacketNumberBytes(cursor);
var encodedPacketNumber = largestAcknowledgedPacketNumber.HasValue
? packetNumber.EncodeByLargestAcknowledged(largestAcknowledgedPacketNumber.Value)
: packetNumber;
encodedPacketNumber.Fill(packetNumberBytes.Span);
var headerLength = cursor - startPacketOffset;
var header = cursor.Peek(-headerLength);
packetNumber.Encrypt(aead, payloadBuffer, tagBuffer, header.Span);
payloadBuffer.CopyTo(cursor);
tagBuffer.CopyTo(cursor);
var endPacketOffset = cursor.AsOffset();
var encryptedLength = payloadBuffer.Length + tagBuffer.Length;
var encryptedData = cursor.Peek(-encryptedLength);
var sample = encryptedData.Slice(0, SampleLength);
var mask = cipher.CreateMask(sample.Span);
encodedPacketNumber.Fill(packetNumberBytes.Span, mask);
cursor.Set(startPacketOffset);
packetFirstByte.Mask(mask).Write(cursor);
cursor.Set(endPacketOffset);
}
public static MemoryBuffer SlicePacketBytes(
MemoryCursor cursor,
PacketFirstByte firstByte,
int startPacketOffset,
PacketNumber?largestAcknowledgedPacketNumber,
out PacketNumber packetNumber)
{
var readLength = cursor - startPacketOffset;
var packetLength = cursor.DecodeVariable32();
var packetNumberBytes = firstByte.SlicePacketNumberBytes(cursor);
var payloadLength = packetLength - readLength - packetNumberBytes.Length;
packetNumber = PacketNumber.Parse(packetNumberBytes.Span);
if (largestAcknowledgedPacketNumber.HasValue)
{
packetNumber = packetNumber.DecodeByLargestAcknowledged(largestAcknowledgedPacketNumber.Value);
}
return(cursor.Slice(payloadLength));
}