public static void ParsePacket(byte[] packet, out byte command, out byte[] payload)
{
var headerBytes = new ArraySegment <byte>(packet, 0, HEADER_SIZE).ToArray();
HeaderStruct header = StructInterop.ByteArrayToStruct <HeaderStruct>(headerBytes);
// Payload
if (header.length > 0)
{
payload = new ArraySegment <byte>(packet, HEADER_SIZE, header.length).ToArray();
}
else
{
payload = null;
}
var footerBytes = new ArraySegment <byte>(packet, HEADER_SIZE + header.length, FOOTER_SIZE).ToArray();
FooterStruct footer = StructInterop.ByteArrayToStruct <FooterStruct>(footerBytes);
// Detect protocol errors
if (header.command == CMD_ERROR)
{
if (payload != null && payload.Length > 0)
{
throw HLDCProtocolException.FromCode(payload[0]);
}
else
{
throw new HLDCException("Protocol malformed error message");
}
}
command = header.command;
}
public static byte[] CreatePacket(byte command, byte[] payload = null)
{
List <byte> packetBuilder = new List <byte>();
if (payload != null && payload.Length > MAX_PAYLOAD_LEN)
{
throw new Exception("HLDC payload too large");
}
packetBuilder.Add(HLDC_FRAME_DELIMITER);
// Build the packet header
HeaderStruct header = new HeaderStruct()
{
command = command,
length = (byte)((payload != null) ? payload.Length : 0)
};
packetBuilder.AddRange(EscapeBytes(StructInterop.StructToByteArray <HeaderStruct>(header)));
// Build the packet payload
UInt16 crc = 0;
if (payload != null)
{
byte[] escapedPayload = EscapeBytes(payload);
packetBuilder.AddRange(escapedPayload);
crc = CalculateCrc(escapedPayload);
}
// BUild the packet footer
FooterStruct footer = new FooterStruct()
{
crc = crc,
};
packetBuilder.AddRange(EscapeBytes(StructInterop.StructToByteArray <FooterStruct>(footer)));
packetBuilder.Add(HLDC_FRAME_DELIMITER);
if (packetBuilder.Count > MAX_PACKET_LEN)
{
throw new Exception("HLDC packet too large");
}
return(packetBuilder.ToArray());
}
public static void ParsePacket(byte[] packet, out byte command, out byte[] payload)
{
// NOTE: Assumes packet has a complete HLDC frame (excluding the SOF/EOF bytes)
// Use the HLDCFramer helper class to receive a complete HLDC frame
var headerBytes = new ArraySegment <byte>(packet, 0, HEADER_SIZE).ToArray();
HeaderStruct header = StructInterop.ByteArrayToStruct <HeaderStruct>(headerBytes);
// Payload
if (header.length > 0)
{
payload = new ArraySegment <byte>(packet, HEADER_SIZE, header.length).ToArray();
}
else
{
payload = null;
}
var footerBytes = new ArraySegment <byte>(packet, HEADER_SIZE + header.length, FOOTER_SIZE).ToArray();
FooterStruct footer = StructInterop.ByteArrayToStruct <FooterStruct>(footerBytes);
// Detect protocol errors
if (header.command == CMD_ERROR)
{
if (payload != null && payload.Length > 0)
{
throw HLDCProtocolException.FromCode(payload[0]);
}
else
{
throw new HLDCException("HLDC Malformed Error Message");
}
}
command = header.command;
}