michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.sync;
michael@0: 
michael@0: import org.mozilla.gecko.background.common.log.Logger;
michael@0: 
michael@0: /**
michael@0:  * A little class to allow us to maintain a count of extant
michael@0:  * things (in our case, callbacks that need to fire), and
michael@0:  * some work that we want done when that count hits 0.
michael@0:  *
michael@0:  * @author rnewman
michael@0:  *
michael@0:  */
michael@0: public class DelayedWorkTracker {
michael@0:   private static final String LOG_TAG = "DelayedWorkTracker";
michael@0:   protected Runnable workItem = null;
michael@0:   protected int outstandingCount = 0;
michael@0: 
michael@0:   public int incrementOutstanding() {
michael@0:     Logger.trace(LOG_TAG, "Incrementing outstanding.");
michael@0:     synchronized(this) {
michael@0:       return ++outstandingCount;
michael@0:     }
michael@0:   }
michael@0:   public int decrementOutstanding() {
michael@0:     Logger.trace(LOG_TAG, "Decrementing outstanding.");
michael@0:     Runnable job = null;
michael@0:     int count;
michael@0:     synchronized(this) {
michael@0:       if ((count = --outstandingCount) == 0 &&
michael@0:           workItem != null) {
michael@0:         job = workItem;
michael@0:         workItem = null;
michael@0:       } else {
michael@0:         return count;
michael@0:       }
michael@0:     }
michael@0:     job.run();
michael@0:     // In case it's changed.
michael@0:     return getOutstandingOperations();
michael@0:   }
michael@0:   public int getOutstandingOperations() {
michael@0:     synchronized(this) {
michael@0:       return outstandingCount;
michael@0:     }
michael@0:   }
michael@0:   public void delayWorkItem(Runnable item) {
michael@0:     Logger.trace(LOG_TAG, "delayWorkItem.");
michael@0:     boolean runnableNow = false;
michael@0:     synchronized(this) {
michael@0:       Logger.trace(LOG_TAG, "outstandingCount: " + outstandingCount);
michael@0:       if (outstandingCount == 0) {
michael@0:         runnableNow = true;
michael@0:       } else {
michael@0:         if (workItem != null) {
michael@0:           throw new IllegalStateException("Work item already set!");
michael@0:         }
michael@0:         workItem = item;
michael@0:       }
michael@0:     }
michael@0:     if (runnableNow) {
michael@0:       Logger.trace(LOG_TAG, "Running item now.");
michael@0:       item.run();
michael@0:     }
michael@0:   }
michael@0: }