Added ability to set the total workload, then get the current progress -- without blocking

src/dorkbox/util/ParallelProcessor.java

@@ -18,6 +18,7 @@ package dorkbox.util;
 import java.util.ArrayList;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.slf4j.Logger;
 
@@ -39,11 +40,19 @@ class ParallelProcessor<T extends Runnable> {
     private final ArrayBlockingQueue<Object> queue;
     private final CountDownLatch latch;
 
+    private int totalWorkload = 0;
+    private AtomicInteger currentProgress = new AtomicInteger(0);
+
     public
     ParallelProcessor() {
         this(OS.getOptimumNumberOfThreads(), null);
     }
 
+    public
+    ParallelProcessor(final int numberOfThreads) {
+        this(numberOfThreads, null);
+    }
+
     public
     ParallelProcessor(final int numberOfThreads, final Logger logger) {
         latch = new CountDownLatch(numberOfThreads);
@@ -98,6 +107,7 @@ class ParallelProcessor<T extends Runnable> {
                             }
                         } finally {
                             if (taken instanceof Runnable) {
+                                currentProgress.getAndIncrement();
                                 // Return object to the pool, waking the threads that have blocked during take()
                                 ParallelProcessor.this.workerPool.offer((T) taken);
                             }
@@ -128,10 +138,12 @@ class ParallelProcessor<T extends Runnable> {
     public abstract
     void workComplete(T worker);
 
-
+    /**
+     * Returns true if there are workers immediately available for work.
+     */
     public
-    ParallelProcessor(final int numberOfThreads) {
-        this(numberOfThreads, null);
+    boolean hasAvailableWorker() {
+        return !this.workerPool.isEmpty();
     }
 
     /**
@@ -154,6 +166,19 @@ class ParallelProcessor<T extends Runnable> {
         queue.put(work);
     }
 
+    /**
+     * Notifies the threads that no more work will be queued after this is called.
+     *
+     * @throws InterruptedException if the current thread is interrupted while waiting
+     */
+    public
+    void doneQueueingTasks() throws InterruptedException {
+        for (int i = 0; i < threads.size(); i++) {
+            // this tells out threads that we have finished work and can exit
+            queue.put(SENTINEL);
+        }
+    }
+
     /**
      * Waits for the results to finish processing. No more work should be queued after this is called.
      *
@@ -161,11 +186,37 @@ class ParallelProcessor<T extends Runnable> {
      */
     public
     void waitUntilDone() throws InterruptedException {
-        for (int i = 0; i < threads.size(); i++) {
-            // this tells out threads that we have finished work and can exit
-            queue.put(SENTINEL);
-        }
+        doneQueueingTasks();
 
         latch.await();
     }
+
+    /**
+     * Sets the total amount of work to be performed. Also resets the count for the amount of work done.
+     */
+    public
+    void setTotalWorkload(int totalWorkload) {
+        currentProgress.set(0);
+        this.totalWorkload = totalWorkload;
+    }
+
+    /**
+     * Gets the amount of progress made, between 0-1
+     * <p>
+     * If this returns 0, it is safe to call {@link ParallelProcessor#waitUntilDone()}. It will block, but only until the processing
+     * threads shutdown (which is quick)
+     */
+    public
+    float getProgress() {
+        int i = currentProgress.get();
+
+        if (i == 0) {
+            return 0.0f;
+        }
+        if (i == totalWorkload) {
+            return 1.0f;
+        }
+
+        return (float) i / (float) totalWorkload;
+    }
 }