Fix websocket of browser received array buffer size is 0

[myfreax]

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Subsystem Server

Motivation websocket of browser received array buffer size is 0

Solution Use ByteBuffer.array() return ByteArray can work well

[rsinukov]

Hi @myfreax Can you please explain the problem and write test for your fix?

[myfreax]

@rsinukov I try to find the reason, but I don't know why it is happening, the following code will not work correctly. But use ByteBuffer.array() return ByteArray can work well.

fun moveToByteArray(byteBuffer: ByteBuffer): ByteArray {
    val array = ByteArray(byteBuffer.remaining())
    byteBuffer.get(array)
    return array
}
fun Application.configureSockets() {
     var tcpReadChannel: ByteReadChannel? = null
     var tcpWriteChannel: ByteWriteChannel? = null
    install(WebSockets) {
        pingPeriod = Duration.ofSeconds(15)
        timeout = Duration.ofSeconds(15)
        maxFrameSize = Long.MAX_VALUE
        masking = false
    }
    CoroutineScope(Dispatchers.IO).launch {
        val socket = aSocket(ActorSelectorManager(Dispatchers.IO)).tcp().connect("127.0.0.1", port = 9002){
            this.noDelay = false
        }
        tcpReadChannel = socket.openReadChannel()
        tcpWriteChannel = socket.openWriteChannel(autoFlush = true)
    }
    routing {
        webSocket("/") {
            launch(Dispatchers.IO) {
                while (true) {
                    val byteBuffer = ByteBuffer.allocate(tcpReadChannel?.availableForRead!!)
                    val len = tcpReadChannel?.readFully(byteBuffer)
                    if (len != 0) {
                        launch {
                            val byteArray = moveToByteArray(byteBuffer)
                            outgoing.send(Frame.Binary(true, byteArray)) //byteArray.size is 0
                            //println("TCP Client Send Data To Websocket Server: ${StandardCharsets.UTF_8.decode(byteBuffer)}") //print empty string""
                        }
                    }
                }
            }
            for (frame in incoming) {
                tcpWriteChannel?.writeFully(appendCRLF(frame.buffer))
                ///println("WebSocket Server Received Data From Browser Client: ${StandardCharsets.UTF_8.decode(frame.buffer)}")
            }
        }
    }
}

Trying the following test code also works fine, but in the above scenario it works. For unknown reasons, I'm having a hard time writing tests for the above scenarios.

val byteBuffer = ByteBuffer.wrap("aa".toByteArray())
val array = ByteArray(byteBuffer.remaining())
byteBuffer.get(array)
println(array.size)

[rsinukov]

I'm closing this PR because we can't accept this change. array() function will return the backing array of ByteBuffer which will have all the future changes in the ByteBuffer.