/// <summary>
/// Unmarshals the data stored in the specified <paramref name="buffer"/> into this
/// <see cref="NcomPacket"/>. If no marshalled NCOM packet can be found,
/// <see langword="false"/> is returned.
/// </summary>
/// <param name="buffer">The byte array containing the marshalled NCOM packet.</param>
/// <param name="offset">
/// The zero-based index indicating the location in the buffer to start looking for a sync
/// byte from.
/// </param>
/// <returns>
/// <see langword="false"/> if no marshalled NCOM packet can be found, otherwise
/// <see langword="true"/>.
/// </returns>
/// <exception cref="ArgumentNullException">
/// When the <paramref name="buffer"/> is null.
/// </exception>
/// <exception cref="IndexOutOfRangeException">
/// When the <paramref name="offset"/> is less than <c>0</c>.
/// </exception>
/// <remarks>
/// <para>
/// If the first byte of the buffer is not <see cref="SyncByte"/> then the method will look
/// for the first occurance of the sync byte.
/// </para>
/// <para>
/// The <paramref name="offset"/> can be greater than the length of the
/// <paramref name="buffer"/> without throwing an exception, returning
/// <see langword="false"/>. This allows for easy unmarshalling of multiple consecutive
/// packets, e.g. <see langword="while" /> loops.
/// </para>
/// </remarks>
public virtual bool Unmarshal(byte[] buffer, int offset)
{
// Check that the buffer is not null
if (buffer == null)
{
throw new ArgumentNullException(nameof(buffer));
}
// Check that the offset is in the expected range
if (offset < 0)
{
throw new IndexOutOfRangeException("Offset in buffer can not be less than zero");
}
// Seek the sync byte
while (offset <= buffer.Length - PacketLength)
{
// Have we found the sync byte?
if (buffer[offset++] == SyncByte)
{
// packet found. offset now points to [1]
// Get navigation status byte
NavigationStatus = ByteHandling.ParseEnum(buffer[offset + 20], NavigationStatus.Unknown);
// Calculate Checksum 3
Checksum3 = CalculateChecksum(buffer, offset, 70) == buffer[offset + PacketLength - 2];
// Unmarshalled OK, return true
return(true);
}
}
// Couldn't find packet, return false;
return(false);
}
/// <summary>
/// Unmarshals the data stored in the specified <paramref name="buffer" /> into this
/// <see cref="NcomPacket" />. If no marshalled NCOM packet can be found,
/// <see langword="false" /> is returned.
/// </summary>
/// <param name="buffer">The byte array containing the marshalled NCOM packet.</param>
/// <param name="offset">The zero-based index indicating the location in the buffer to start looking for a sync
/// byte from.</param>
/// <returns>
/// <see langword="false" /> if no marshalled NCOM packet can be found, otherwise
/// <see langword="true" />.
/// </returns>
/// <remarks>
/// <para>
/// If the first byte of the buffer is not <see cref="NcomPacket.SyncByte" /> then the method will look
/// for the first occurance of the sync byte.
/// </para>
/// <para>
/// The <paramref name="offset" /> can be greater than the length of the
/// <paramref name="buffer" /> without throwing an exception, returning
/// <see langword="false" />. This allows for easy unmarshalling of multiple consecutive
/// packets, e.g. <see langword="while" /> loops.
/// </para>
/// </remarks>
public override bool Unmarshal(byte[] buffer, int offset)
{
// Check that the buffer is not null
if (buffer == null)
{
throw new ArgumentNullException(nameof(buffer));
}
// Check that the offset is in the expected range
if (offset < 0)
{
throw new IndexOutOfRangeException("Offset in buffer can not be less than zero");
}
// Seek the sync byte
while (offset <= buffer.Length - PacketLength)
{
// Have we found the sync byte?
if (buffer[offset++] == SyncByte)
{
int pkt_start = offset - 1;
// offset points to pkt[1]
// Call base method
if (!base.Unmarshal(buffer, offset - 1))
{
return(false);
}
// Check the navigation status byte
if (!AllowedNavigationStatus.Contains(NavigationStatus))
{
return(false);
}
// Batch A
// --------
// Extract the time
Time = ByteHandling.UnmarshalUInt16(buffer, ref offset);
// Extract the Accelerations
AccelerationX = ByteHandling.UnmarshalInt24(buffer, ref offset) * AccelerationScaling;
AccelerationY = ByteHandling.UnmarshalInt24(buffer, ref offset) * AccelerationScaling;
AccelerationZ = ByteHandling.UnmarshalInt24(buffer, ref offset) * AccelerationScaling;
// Extract the Angular Rates
AngularRateX = ByteHandling.UnmarshalInt24(buffer, ref offset) * AngularRateScaling;
AngularRateY = ByteHandling.UnmarshalInt24(buffer, ref offset) * AngularRateScaling;
AngularRateZ = ByteHandling.UnmarshalInt24(buffer, ref offset) * AngularRateScaling;
// Skip a bit for the nav status byte
offset++;
// Extract checksum 1
Checksum1 = CalculateChecksum(buffer, pkt_start + 1, 21) == buffer[offset];
offset++;
// Batch B
// --------
// Extract Latitude, Longitude and altitude
Latitude = ByteHandling.UnmarshalDouble(buffer, ref offset);
Longitude = ByteHandling.UnmarshalDouble(buffer, ref offset);
Altitude = ByteHandling.UnmarshalSingle(buffer, ref offset);
// Extract velocities
NorthVelocity = ByteHandling.UnmarshalInt24(buffer, ref offset) * VeloityScaling;
EastVelocity = ByteHandling.UnmarshalInt24(buffer, ref offset) * VeloityScaling;
DownVelocity = ByteHandling.UnmarshalInt24(buffer, ref offset) * VeloityScaling;
// Extract Heading, Pitch and Roll
Heading = ByteHandling.UnmarshalInt24(buffer, ref offset) * OrientationScaling;
Pitch = ByteHandling.UnmarshalInt24(buffer, ref offset) * OrientationScaling;
Roll = ByteHandling.UnmarshalInt24(buffer, ref offset) * OrientationScaling;
// Extract checksum 2
Checksum2 = CalculateChecksum(buffer, pkt_start + 1, 60) == buffer[offset];
offset++;
// Batch S
// --------
// Extract status channel (and status channel byte)
byte statusChannelByte = buffer[offset++];
StatusChannel = StatusChannelFactory.Unmarshal(statusChannelByte, buffer, ref offset);
// Unmarshalled OK, return true
return(true);
}
}
// Couldn't find packet, return false;
return(false);
}
/// <summary>
/// Marshals this <see cref="NcomPacketA"/> into a byte array of length
/// <see cref="NcomPacket.PacketLength"/>.
/// </summary>
/// <returns>
/// A <see cref="byte"/> array of length equal to <see cref="NcomPacket.PacketLength"/>.
/// </returns>
public override byte[] Marshal()
{
// Call base method to get byte array to marshal into
byte[] buffer = base.Marshal();
int offset = 1;
// Batch A
// --------
// Insert Time
ByteHandling.Marshal(buffer, ref offset, (ushort)(Time % MaxTimeValue));
// Insert accelerations
ByteHandling.MarshalInt24(buffer, ref offset, (int)(AccelerationX / AccelerationScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(AccelerationY / AccelerationScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(AccelerationZ / AccelerationScaling));
// Insert Angular Rates
ByteHandling.MarshalInt24(buffer, ref offset, (int)(AngularRateX / AngularRateScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(AngularRateY / AngularRateScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(AngularRateZ / AngularRateScaling));
// Skip over nav. status
offset++;
// Calculate and insert Checksum 1
buffer[offset] = CalculateChecksum(buffer, 1, offset - 2);
offset++;
// Batch B
// --------
// Insert Latitude, Longitude and altitude
ByteHandling.Marshal(buffer, ref offset, Latitude);
ByteHandling.Marshal(buffer, ref offset, Longitude);
ByteHandling.Marshal(buffer, ref offset, Altitude);
// Insert Velocities
ByteHandling.MarshalInt24(buffer, ref offset, (int)(NorthVelocity / VeloityScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(EastVelocity / VeloityScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(DownVelocity / VeloityScaling));
// Insert Heading, Pitch and Roll
ByteHandling.MarshalInt24(buffer, ref offset, (int)(Heading / OrientationScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(Pitch / OrientationScaling));
ByteHandling.MarshalInt24(buffer, ref offset, (int)(Roll / OrientationScaling));
// Calculate and insert Checksum 2
buffer[offset] = CalculateChecksum(buffer, 1, offset - 2);
offset++;
// Batch S
// --------
// Insert Status Channel
if (StatusChannel != null)
{
buffer[offset++] = StatusChannel.StatusChannelByte;
StatusChannel.Marshal(buffer, ref offset);
}
else
{
buffer[offset++] = 0xFF;
offset += StatusChannelLength;
}
// Calculate and insert Checksum 3
buffer[offset] = CalculateChecksum(buffer, 1, offset - 2);
// Return the marshalled NCOM packet
return(buffer);
}
