private byte ComputeChecksum(IoBuffer buffer)
{
buffer.Rewind();
byte checksum = 0;
for (int i = 0; i < Length - 1; i++) checksum += buffer.Get();
return checksum;
}
public MessageDecoderResult Decodable(IoSession session, IoBuffer input)
{
if (input.Remaining < MIN_PACKET_LENGTH)
return MessageDecoderResult.NeedData;
var symbol = input.GetArray(2);
if (DataPacket.True(symbol))
{
input.Skip(1);
var len = input.Get();
input.Rewind();
if (len > input.Remaining) return MessageDecoderResult.NeedData;
}
else if (!CtlPacket.True(symbol)) return MessageDecoderResult.NotOK;
return MessageDecoderResult.OK;
}
private void ManipulateIoBuffer(IoSession session, IoBuffer buffer)
{
if ((buffer.Remaining > 0) && (_removeByteProbability > _rng.Next(1000)))
{
if (log.IsInfoEnabled)
log.Info(buffer.GetHexDump());
// where to remove bytes ?
int pos = _rng.Next(buffer.Remaining);
// how many byte to remove ?
int count = _rng.Next(buffer.Remaining - pos) + 1;
if (count == buffer.Remaining)
count = buffer.Remaining - 1;
IoBuffer newBuff = IoBuffer.Allocate(buffer.Remaining - count);
for (int i = 0; i < pos; i++)
newBuff.Put(buffer.Get());
buffer.Skip(count); // hole
while (newBuff.Remaining > 0)
newBuff.Put(buffer.Get());
newBuff.Flip();
// copy the new buffer in the old one
buffer.Rewind();
buffer.Put(newBuff);
buffer.Flip();
if (log.IsInfoEnabled)
{
log.Info("Removed " + count + " bytes at position " + pos + ".");
log.Info(buffer.GetHexDump());
}
}
if ((buffer.Remaining > 0) && (_changeByteProbability > _rng.Next(1000)))
{
if (log.IsInfoEnabled)
log.Info(buffer.GetHexDump());
// how many byte to change ?
int count = _rng.Next(buffer.Remaining - 1) + 1;
byte[] values = new byte[count];
_rng.NextBytes(values);
for (int i = 0; i < values.Length; i++)
{
int pos = _rng.Next(buffer.Remaining);
buffer.Put(pos, values[i]);
}
if (log.IsInfoEnabled)
{
log.Info("Modified " + count + " bytes.");
log.Info(buffer.GetHexDump());
}
}
}
