/// <summary>
/// Decodes the fields from an extended squitter from non-transponder reply (DF = 18).
/// </summary>
/// <param name="reply"></param>
private void DecodeExtendedSquitterNonTransponder(ModeSMessage reply)
{
reply.ControlField = (ControlField)_BitStream.ReadByte(3);
switch (reply.ControlField)
{
case ControlField.AdsbDeviceTransmittingIcao24:
case ControlField.AdsbRebroadcastOfExtendedSquitter:
ExtractAircraftAddress(reply);
ExtractExtendedSquitterMessage(reply);
break;
case ControlField.AdsbDeviceNotTransmittingIcao24:
reply.NonIcao24Address = (int)_BitStream.ReadUInt32(24);
ExtractExtendedSquitterMessage(reply);
break;
default:
reply.ExtendedSquitterSupplementaryMessage = ReadBytes(10);
break;
}
ExtractParityInterrogator(reply);
}
public void BitStream_ReadUInt32_Throws_If_Reading_Less_Than_One_Or_More_Than_32_Bits()
{
for (int i = -2; i < 34; ++i)
{
_BitStream.Initialise(new byte[] { 0x00, 0x00, 0x00, 0x00 });
bool expectException = i < 1 || i > 32;
bool sawException = false;
try {
_BitStream.ReadUInt32(i);
} catch (ArgumentOutOfRangeException) {
sawException = true;
}
Assert.AreEqual(expectException, sawException, "ReadUInt32 did not behave correctly when asked to read {0} bits", i);
}
}
/// <summary>
/// Decodes an aircraft status message.
/// </summary>
/// <param name="message"></param>
private void DecodeAircraftStatus(AdsbMessage message)
{
message.MessageFormat = MessageFormat.AircraftStatus;
var subMessage = message.AircraftStatus = new AircraftStatusMessage();
subMessage.AircraftStatusType = (AircraftStatusType)_BitStream.ReadByte(3);
switch (subMessage.AircraftStatusType)
{
case AircraftStatusType.EmergencyStatus:
var emergency = subMessage.EmergencyStatus = new EmergencyStatus();
emergency.EmergencyState = (EmergencyState)_BitStream.ReadByte(3);
var modeA = (short)_BitStream.ReadUInt16(13);
if (modeA != 0)
{
emergency.Squawk = ModeS.ModeATranslator.DecodeModeA(modeA);
}
break;
case AircraftStatusType.TcasResolutionAdvisoryBroadcast:
var tcas = subMessage.TcasResolutionAdvisory = new TcasResolutionAdvisory();
var araCoding = _BitStream.ReadBit();
var araValue = (short)_BitStream.ReadUInt16(13);
tcas.ResolutionAdvisoryComplement = (ResolutionAdvisoryComplement)_BitStream.ReadByte(4);
tcas.ResolutionAdvisoryTerminated = _BitStream.ReadBit();
tcas.MultipleThreatEncounter = _BitStream.ReadBit();
if (araCoding)
{
tcas.SingleThreatResolutionAdvisory = (SingleThreatResolutionAdvisory)araValue;
}
else if (tcas.MultipleThreatEncounter)
{
tcas.MultipleThreatResolutionAdvisory = (MultipleThreatResolutionAdvisory)araValue;
}
switch (_BitStream.ReadByte(2))
{
case 1:
tcas.ThreatIcao24 = (int)_BitStream.ReadUInt32(24);
break;
case 2:
var threatAltitude = _BitStream.ReadUInt16(13);
var threatRange = _BitStream.ReadByte(7);
var threatBearing = _BitStream.ReadByte(6);
var strippedAltitude = ((threatAltitude & 0x1F80) >> 2) | ((threatAltitude & 0x20) >> 1) | (threatAltitude & 0x0f);
tcas.ThreatAltitude = ModeSAltitudeConversion.LookupGillhamAltitude(strippedAltitude);
if (threatRange > 0)
{
tcas.ThreatRange = ((float)(threatRange - 1) / 10F) + 0.05F;
tcas.ThreatRangeExceeded = threatRange == 127;
}
if (threatBearing > 0 && threatBearing < 61)
{
tcas.ThreatBearing = (short)((threatBearing - 1) * 6);
}
break;
}
break;
}
}