public ArraySegment <byte> Encode(CoapMessage message)
{
if (message == null)
{
throw new ArgumentNullException(nameof(message));
}
ThrowIfInvalid(message);
using (var writer = new CoapMessageWriter())
{
writer.WriteBits(0x1, 2); // Version
writer.WriteBits((int)message.Type, 2); // Type
writer.WriteBits(message.Token?.Length ?? 0, 4); // Token length
var code = message.Code.Detail | message.Code.Class << 3;
writer.WriteBits(code, 8);
writer.WriteBits((byte)(message.Id >> 8), 8); // MessageId MSB
writer.WriteBits((byte)(message.Id), 8); // MessageId LSB
if (message.Token != null)
{
writer.WriteBytes(message.Token);
}
EncodeOptions(message.Options, writer);
if (message.Payload.Count > 0)
{
writer.WriteByte(0xFF);// Payload Marker
writer.WriteBytes(message.Payload);
}
return(writer.ToArray());
}
}
void EncodeOptions(IEnumerable <CoapMessageOption> options, CoapMessageWriter writer)
{
if (options == null)
{
return;
}
CoapMessageOptionNumber previousOptionNumber = 0;
foreach (var option in options.OrderBy(o => o.Number))
{
// As per RFC: Only the delta of the option number is stored.
var delta = option.Number - previousOptionNumber;
previousOptionNumber = option.Number;
byte[] value;
if (option.Value is CoapMessageOptionEmptyValue)
{
value = _emptyArray;
}
else if (option.Value is CoapMessageOptionUintValue uintValue)
{
value = EncodeUintOptioNValue(uintValue.Value);
}
else if (option.Value is CoapMessageOptionStringValue stringValue)
{
value = System.Text.Encoding.UTF8.GetBytes(stringValue.Value);
}
else if (option.Value is CoapMessageOptionOpaqueValue opaqueValue)
{
value = opaqueValue.Value;
}
else
{
throw new CoapProtocolViolationException("The specified option is not supported.");
}
var length = value.Length;
EncodeOptionValue(delta, out var deltaNibble);
writer.WriteBits(deltaNibble, 4);
EncodeOptionValue(length, out var lengthNibble);
writer.WriteBits(lengthNibble, 4);
if (deltaNibble == 13)
{
writer.WriteBits(delta - 13, 8);
}
else if (deltaNibble == 14)
{
writer.WriteBits(delta - 269, 16);
}
if (lengthNibble == 13)
{
writer.WriteBits(length - 13, 8);
}
else if (lengthNibble == 14)
{
writer.WriteBits(length - 269, 16);
}
if (value.Length > 0)
{
writer.WriteBytes(value);
}
}
}