/// <summary>
/// Decode SNMP packet header. This class decodes the initial sequence and SNMP protocol version
/// number.
/// </summary>
/// <param name="buffer">BER encoded SNMP packet</param>
/// <param name="length">Packet length</param>
/// <returns>Offset position after the initial sequence header and protocol version value</returns>
/// <exception cref="SnmpDecodingException">Thrown when invalid sequence type is found at the start of the SNMP packet being decoded</exception>
public virtual int decode(byte[] buffer, int length)
{
int offset = 0;
if (length < 2)
{
// we need at least 2 bytes
throw new OverflowException("Packet too small.");
}
// make sure you get the right length buffer to be able to check for over/under flow errors
MutableByte buf = new MutableByte(buffer, length);
Sequence seq = new Sequence();
offset = seq.decode(buf, offset);
if( seq.Type != SnmpConstants.SMI_SEQUENCE )
throw new SnmpDecodingException("Invalid sequence type at the start of the SNMP packet.");
offset = _protocolVersion.decode(buf, offset);
return offset;
}