public int Decrypt(Internal.CommunicationStream message, int offset = 0, int length = int.MaxValue)
{
length = Math.Min(length, (int)message.Length - offset);
length -= length % BlockSize;
int i = offset;
while (i < offset + length)
{
message.Position = i;
uint v0 = message.ReadUnsignedInt();
uint v1 = message.ReadUnsignedInt();
uint delta = 0x61C88647;
uint sum = 0xC6EF3720;
for (int r = 0; r < 32; r++)
{
v1 -= (v0 << 4 ^ v0 >> 5) + v0 ^ sum + _key[sum >> 11 & 3];
sum += delta;
v0 -= (v1 << 4 ^ v1 >> 5) + v1 ^ sum + _key[sum & 3];
}
message.Position -= BlockSize;
message.WriteUnsignedInt(v0);
message.WriteUnsignedInt(v1);
i += BlockSize;
}
message.Position = offset;
int payloadLength = message.ReadUnsignedShort();
int messageLength = payloadLength + Internal.Connection.PacketLengthSize;
int lengthDelta = messageLength - length;
if (lengthDelta > 0 || -lengthDelta > length)
{
return(0);
}
message.SetLength(message.Length + lengthDelta);
return(length);
}