AsynchronousByteChannel.kt

suspend fun AsynchronousByteChannel.readInto(buffer: ByteBuffer): Int = suspendCancellableCoroutine {
    read(buffer, null, object : CompletionHandler<Int, Any?> {
        override fun completed(result: Int, attachment: Any?) { it.resume(result) }
        override fun failed(exc: Throwable, attachment: Any?) = it.resumeWithException(exc)
    })
}

suspend fun AsynchronousByteChannel.writeFrom(buffer: ByteBuffer): Int = suspendCancellableCoroutine {
    write(buffer, null, object : CompletionHandler<Int, Any?> {
        override fun completed(result: Int, attachment: Any?) = it.resume(result)
        override fun failed(exc: Throwable, attachment: Any?) = it.resumeWithException(exc)
    })
}