//returns true if a new packet could be obtained
private SSH2Packet ConstructPacket()
{
SSH2Packet packet = null;
if (_event != null && !_event.WaitOne(3000, false))
{
throw new Exception("waithandle timed out");
}
if (_cipher == null)
{
if (_writeOffset - _readOffset < 4)
{
return(null);
}
int len = SSHUtil.ReadInt32(_buffer, _readOffset);
if (_writeOffset - _readOffset < 4 + len)
{
return(null);
}
packet = SSH2Packet.FromPlainStream(_buffer, _readOffset);
_readOffset += 4 + len;
_sequence++;
}
else
{
if (_head == null)
{
if (_writeOffset - _readOffset < _cipher.BlockSize)
{
return(null);
}
_head = new byte[_cipher.BlockSize];
byte[] eh = new byte[_cipher.BlockSize];
Array.Copy(_buffer, _readOffset, eh, 0, eh.Length);
_readOffset += eh.Length;
_cipher.Decrypt(eh, 0, eh.Length, _head, 0);
}
int len = SSHUtil.ReadInt32(_head, 0);
if (_writeOffset - _readOffset < len + 4 - _head.Length + _mac.Size)
{
return(null);
}
packet = SSH2Packet.FromDecryptedHead(_head, _buffer, _readOffset, _cipher, _sequence++, _mac);
_readOffset += 4 + len - _head.Length + _mac.Size;
_head = null;
}
return(packet);
}
