Main.kt

import java.net.InetSocketAddress
import java.nio.ByteBuffer
import java.nio.ByteOrder
import java.nio.channels.FileChannel
import java.nio.channels.SocketChannel
import java.nio.file.Files
import java.nio.file.Path
import java.nio.file.StandardOpenOption.*

fun main(args: Array<String>) {
    val (dir) = args
    Files
        .list(Path.of(dir))
        .use { paths ->
            paths.forEach { path ->
                SocketChannel.open(InetSocketAddress(8888)).use { socketChannel ->
                    FileChannel.open(path, READ)
                        .use { inputFileChannel ->
                            FileChannel.open(
                                Path.of(path.toFile().name.replaceFirst("in", "out")),
                                CREATE,
                                APPEND,
                                WRITE
                            )
                                .use { outputChannel ->
                                    val start = System.currentTimeMillis()
                                    var counter = 0
                                    val buffer = ByteBuffer.allocate(2)
                                    while (true) {
                                        val position = inputFileChannel.position()
                                        val readBytes = inputFileChannel.read(buffer)
                                        if (readBytes < buffer.capacity()) {
                                            break
                                        }
                                        val size = buffer.flip().order(ByteOrder.BIG_ENDIAN).short.toLong()
                                        buffer.clear()
                                        val transferBytes =
                                            inputFileChannel.transferTo(position, size + readBytes, socketChannel)
                                        inputFileChannel.position(position + transferBytes)
                                        if (transferBytes < size) {
                                            break
                                        }
                                        val readResponseBytes = socketChannel.read(buffer)
                                        if (readResponseBytes < buffer.capacity()) {
                                            break
                                        }
                                        val outputPosition = outputChannel.position()
                                        val responseSize = buffer.flip().order(ByteOrder.BIG_ENDIAN).short.toLong()
                                        buffer.clear()
                                        val transferResponseBytes = outputChannel.transferFrom(
                                            socketChannel,
                                            outputChannel.position(),
                                            responseSize
                                        )
                                        outputChannel.position(outputPosition + transferResponseBytes)
                                        counter++
                                    }
                                    println("${System.currentTimeMillis() - start} ms for $counter transactions")
                                }
                        }
                }
            }
        }
}