InputStream to combine a Stream of other InputStream in a lazy way in Kotlin

StreamInputStream.kt

class StreamInputStream(private val source: Stream<out InputStream>) : InputStream() {

    private val iterator by lazy {
        source
                .flatMap {
                    generateSequence {
                        val result = it.read(); if (result == -1) {
                        it.close(); null
                    } else result
                    }.asStream()
                }
                .iterator()
    }

    @Throws(IOException::class)
    override fun read(): Int =
            if (!iterator.hasNext()) -1
            else iterator.next()

    @Throws(IOException::class)
    override fun close() = source.close()
}

usage.kt

var counter = 0

const val LOGLINE = "Une ligne de log pas super longue mais bon qui commence a faire un petit peu quand même, non par ce que c'est vrai qu'il faut que ce soit long mais je sais pas a quel point\n"

val generator = {
    counter++;
    if (counter < 1000) LOGLINE.repeat(1000000) else null
}

fun main() {
    val source = generateSequence(generator)
            .asStream()
            .map { it.byteInputStream() as InputStream }

    val combined = StreamInputStream(source)

    val reader = combined.bufferedReader()
    do {
        val line = reader.readLine()
        println(line)
    } while (line != null)
}