The following function would be nice to have

ByteReadChannel.readTo(sink: RawSink, byteCount: Long) [io.ktor.utils.io]

It would allow to store directly into a file (instead of copying data inbetween

so something like this

@OptIn(InternalAPI::class)
suspend fun ByteReadChannel.readTo(sink: RawSink, byteCount: Long) {

var remaining = byteCount

while (remaining > 0 && !isClosedForRead) {
    if (readBuffer.exhausted()) awaitContent()

    val size = minOf(remaining.toLong(), readBuffer.remaining)
    readBuffer.readTo(sink, size)
    remaining -= size.toInt()
}

}

Not sure if it is working (not tested)