/// <summary>Decode BER encoded SNMP version 1 trap packet</summary>
/// <param name="buffer">BER encoded buffer</param>
/// <param name="offset">Offset in the packet to start decoding from</param>
/// <returns>Buffer position after the decoded value.</returns>
/// <exception cref="SnmpException">Invalid SNMP Pdu type received. Not an SNMP version 1 Trap PDU.</exception>
/// <exception cref="SnmpException">Invalid Variable Binding list encoding.</exception>
public override int Decode(byte[] buffer, int offset)
{
byte asnType = ParseHeader(buffer, ref offset, out int headerLength);
if (asnType != (byte)PduType.Trap)
{
throw new SnmpException("Invalid PDU type.");
}
if (headerLength > buffer.Length - offset)
{
throw new OverflowException("Packet is too short.");
}
offset = _enterprise.Decode(buffer, offset);
offset = _agentAddr.Decode(buffer, offset);
offset = _generic.Decode(buffer, offset);
offset = _specific.Decode(buffer, offset);
offset = _timeStamp.Decode(buffer, offset);
// clean out the current variables
VbList.Clear();
offset = VbList.Decode(buffer, offset);
return(offset);
}
/// <summary>Decode BER encoded variable binding.</summary>
/// <param name="buffer">BER encoded buffer</param>
/// <param name="offset">
/// Offset in the data buffer from where to start decoding. Offset is
/// passed by reference and will contain the offset of the byte immediately after the parsed
/// variable binding.
/// </param>
/// <returns>Buffer position after the decoded value</returns>
public override int Decode(byte[] buffer, int offset)
{
byte asnType = ParseHeader(buffer, ref offset, out int headerLength);
if (asnType != Type)
{
throw new SnmpException(string.Format("Invalid ASN.1 type. Expected 0x{0:x2} received 0x{1:x2}", Type, asnType));
}
// verify the length
if ((buffer.Length - offset) < headerLength)
{
throw new OverflowException("Buffer underflow error");
}
oid = new Oid();
offset = oid.Decode(buffer, offset);
int saveOffset = offset;
// Look ahead in the header to see the data type we need to parse
asnType = ParseHeader(buffer, ref saveOffset, out headerLength);
value = SnmpConstants.GetSyntaxObject(asnType);
if (value == null)
{
throw new SnmpDecodingException(string.Format("Invalid ASN.1 type encountered 0x{0:x2}. Unable to continue decoding.", asnType));
}
offset = value.Decode(buffer, offset);
return(offset);
}