trySeizeZones

Takes a set of zones, and answers null when some zone of it is already promised.

seizeZones with the one refusable condition turned into an answer, and the form a model wants whenever a closure lands where it lands rather than where it was told to. A zone carries one promise at a time, and by default a second asker is refused rather than queued behind the first -- ZoneOverlap.QUEUE is the opt-in for waiting instead. So a model with spills at random locations has to say what an overlap means. This is how it says it, in one call that cannot be got wrong.

inner class Spill : Entity() {
    val cleanup = process {
        val extent = aisle.zones.take(myExtent.value.toInt())
        // A spill landing where one is already being dealt with is part of that spill.
        if (trySeizeZones(system, extent, spillQ) == null) {
            myAbsorbed.increment()
            return@process
        }
        delay(myCleanupTime)
        releaseZones(system)
    }
}

Null is answered without suspending. A zone another holder already holds is not an overlap and does not answer null: that is the ordinary case, and this waits for the hold to end exactly as seizeZones would.

Parameters