trjhtr

Here's my method used for parsing a ByteArray into multiple frames of CAN interface. It works now correctly but it's somewhat ugly in my opinion.

It's written in Kotlin with use of RxJava2

private fun parseCanFrameBytes(frame: ByteArray): Observable<CanFrame> 
 return Observable.create emitter ->
 var index = 0
 while (index < frame.size) 
 val byte = frame[index]

 if(byte xor IFM_FRAME_HEADER == BYTE_ZERO) 
 try 
 val ifmIndex = index
 val length = frame[ifmIndex + 1].toInt()
 val dlc1 = length - 3
 val dlc2 = length - 5
 val command = frame[ifmIndex + 2].toInt()
 val data = frame.copyOfRange(ifmIndex + 3, ifmIndex + 2 + length)
 val isChecksumValid = frame[ifmIndex + 2 + length].toInt() == frame.copyOfRange(ifmIndex, ifmIndex + 2 + length).calculate8XorChecksum()
 if (!isChecksumValid) 
 index++
 continue
 

 val canFrame = when (command) 
 0 -> 
 val pgn = data.copyOfRange(0, 2).toHexString()
 CanFrame(
 type = "DLC1",
 pgn = pgn,
 id = pgn,
 value = data.copyOfRange(2, 2 + dlc1).toHexString(),
 ts = timestamp(),
 data = frame.copyOfRange(ifmIndex, ifmIndex + 4 + length).toHexString()
 )
 
 2 -> 
 val pgn = data.copyOfRange(0, 4).toHexString()
 CanFrame(
 type = "DLC2",
 pgn = pgn,
 id = pgn,
 value = data.copyOfRange(4, 4 + dlc2).toHexString(),
 ts = timestamp(),
 data = frame.copyOfRange(ifmIndex, ifmIndex + 4 + length).toHexString()
 )
 
 else -> null
 ?: continue

 emitter.onNext(canFrame)
 index = ifmIndex + length + 4
 catch (ex: IllegalArgumentException) 
 index++
 
 else 
 index++
 
 
 

Probably very little beautification. I would be curious to see someone beautify it and prove me wrong. Initially I thought you could use Kotlin streams on the frame ByteArray. This way you could have done something equivalent to frame.filterIndexed(..).map(it->CanFrame(..)) etc. However then I noticed you were doing random access on the ByteArray: ex: ifmIndex + length + 4 , frame.copyOfRange(ifmIndex + 3, ifmIndex + 2 + length) which would negate the purpose of streams which go one by one.