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package jdk.incubator.http.internal.common;

import java.util.concurrent.Flow;
import java.util.concurrent.atomic.AtomicBoolean;

Maintains subscription counter and provides primitives for
- accessing window
- reducing window when delivering items externally
- resume delivery when window was zero previously
Author:
mimcmah/**
 * Maintains subscription counter and provides primitives for
 * - accessing window
 * - reducing window when delivering items externally
 * - resume delivery when window was zero previously
 *
 * @author mimcmah
 */
public class SubscriptionBase implements Flow.Subscription {

    final Demand demand = new Demand();

    final SequentialScheduler scheduler; // when window was zero and is opened, run this
    final Runnable cancelAction; // when subscription cancelled, run this
    final AtomicBoolean cancelled;

    public SubscriptionBase(SequentialScheduler scheduler, Runnable cancelAction) {
        this.scheduler = scheduler;
        this.cancelAction = cancelAction;
        this.cancelled = new AtomicBoolean(false);
    }

    @Override
    public void request(long n) {
        if (demand.increase(n))
            scheduler.runOrSchedule();
    }



    @Override
    public synchronized String toString() {
        return "SubscriptionBase: window = " + demand.get() +
                " cancelled = " + cancelled.toString();
    }

    
Returns true if the window was reduced by 1. In that case
items must be supplied to subscribers and the scheduler run
externally. If the window could not be reduced by 1, then false
is returned and the scheduler will run later when the window is updated.
/**
     * Returns true if the window was reduced by 1. In that case
     * items must be supplied to subscribers and the scheduler run
     * externally. If the window could not be reduced by 1, then false
     * is returned and the scheduler will run later when the window is updated.
     */
    public boolean tryDecrement() {
        return demand.tryDecrement();
    }

    public long window() {
        return demand.get();
    }

    @Override
    public void cancel() {
        if (cancelled.getAndSet(true))
            return;
        scheduler.stop();
        cancelAction.run();
    }
}