public static MemoryBuffer SliceShortProtectedPacketBytes(
MemoryCursor cursor,
IAead aead,
ICipher cipher,
int startPacketOffset,
PacketFirstByte firstByte,
PacketNumber largestAcknowledgedPacketNumber,
out PacketNumber packetNumber)
{
var startPacketNumberOffset = cursor.AsOffset();
cursor.Move(SkipToSampleLength);
var sample = cursor.Move(SampleLength);
var mask = cipher.CreateMask(sample.Span);
cursor.Set(startPacketOffset);
firstByte.Mask(mask).Write(cursor);
cursor.Set(startPacketNumberOffset);
var packetNumberBytes = firstByte.Mask(mask).SlicePacketNumberBytes(cursor);
var headerLength = cursor - startPacketOffset;
var headerBytes = cursor.Peek(-headerLength);
var startPayloadOffset = cursor.AsOffset();
cursor.MoveEnd();
var tagBytes = cursor.Move(-aead.TagLength);
var payloadLength = cursor - startPayloadOffset;
var payloadBytes = cursor.Peek(-payloadLength);
var payload = cursor.Slice(-payloadLength);
var encodedPacketNumber = PacketNumber.Parse(packetNumberBytes.Span, mask);
encodedPacketNumber.Fill(packetNumberBytes.Span);
packetNumber = encodedPacketNumber.DecodeByLargestAcknowledged(largestAcknowledgedPacketNumber);
packetNumber.Decrypt(aead, payloadBytes.Span, tagBytes.Span, headerBytes.Span);
cursor.MoveEnd();
return(payload);
}
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);
}
