public static FrameIHeader Read(ReadOnlySpan <byte> buffer, int apduLength)
{
var sendSeqNo = (ushort)Bytes.GetNFromBytes(buffer[0], buffer[1]);
var recieveSeqNo = (ushort)Bytes.GetNFromBytes(buffer[2], buffer[3]);
var bAsduTypeId = buffer[4];
var asduTypeId = Enum.IsDefined(typeof(AsduTypeId), bAsduTypeId)
? (AsduTypeId)bAsduTypeId
: AsduTypeId.Unknown;
var(isSequence, infoObjectsCount) = ReadByte7(buffer[5]);
var(isTest, isNegative, cot) = ReadByte8(buffer[6]);
var org = buffer[7];
var ushortLE = new UshortLittleEndian {
LSB = buffer[8], MSB = buffer[9]
};
var ca = ushortLE.V;
return(new FrameIHeader(sendSeqNo, recieveSeqNo, asduTypeId, isSequence, isTest, isNegative, cot, org, ca, infoObjectsCount, apduLength));
}
public int TryWrite(Span <byte> buffer)
{
// :0 start byte
buffer[0] = Constants.StartByte;
// :1 length of APDU
buffer[1] = (byte)ApduLength;
// APCI (4 bytes)
var(b2, b3) = Bytes.GetBytesFromN(SendSeqNo);
var(b4, b5) = Bytes.GetBytesFromN(RecieveSeqNo);
buffer[2] = b2;
buffer[3] = b3;
buffer[4] = b4;
buffer[5] = b5;
// ASDU
// :6 type identification
buffer[6] = (byte)AsduTypeId;
// :7 SQ | number of information objects
buffer[7] = CreateByte7(IsSequence, InfoObjectsCount);
// :8 T | P/N | COT
buffer[8] = CreateByte8(IsTest, IsNegativeConfirmation, CauseOfTransmission);
// :9 ORG
buffer[9] = OriginatorAddress;
// :10-11 CA (2 bytes)
var ca = new UshortLittleEndian {
V = CommonAddress
};
buffer[10] = ca.LSB;
buffer[11] = ca.MSB;
return(Constants.FrameIHeaderLength);
}
