Fixes #216: Size of SpscGrowableArrayQueue can exceeds max capacity

jctools-core/src/main/java/org/jctools/queues/SpscGrowableArrayQueue.java

@@ -114,7 +114,7 @@ final boolean offerColdPath(
                     long currConsumerIndex = lvConsumerIndex();
                     // use lookAheadStep to store the consumer distance from final buffer
                     this.lookAheadStep = -(index - currConsumerIndex);
-                    producerBufferLimit = currConsumerIndex + maxCapacity - 1;
+                    producerBufferLimit = currConsumerIndex + maxCapacity;
                 }
                 else
                 {

jctools-core/src/main/java/org/jctools/queues/atomic/SpscGrowableAtomicArrayQueue.java

@@ -106,7 +106,7 @@ final boolean offerColdPath(final AtomicReferenceArray<E> buffer, final long mas
                     long currConsumerIndex = lvConsumerIndex();
                     // use lookAheadStep to store the consumer distance from final buffer
                     this.lookAheadStep = -(index - currConsumerIndex);
-                    producerBufferLimit = currConsumerIndex + maxCapacity - 1;
+                    producerBufferLimit = currConsumerIndex + maxCapacity;
                 } else {
                     producerBufferLimit = index + producerMask - 1;
                     adjustLookAheadStep(newCapacity);

jctools-core/src/test/java/org/jctools/queues/QueueSanityTestSpscGrowable.java

@@ -2,13 +2,17 @@
 
 import org.jctools.queues.spec.ConcurrentQueueSpec;
 import org.jctools.queues.spec.Ordering;
+import org.junit.Assert;
+import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Queue;
 
+import static org.hamcrest.Matchers.is;
+
 @RunWith(Parameterized.class)
 public class QueueSanityTestSpscGrowable extends QueueSanityTest
 {
@@ -27,4 +31,30 @@ public static Collection<Object[]> parameters()
         return list;
     }
 
+    @Test
+    public void testSizeNeverExceedCapacity()
+    {
+        final SpscGrowableArrayQueue<Integer> q = new SpscGrowableArrayQueue<>(8, 16);
+        final Integer v = 0;
+        final int capacity = q.capacity();
+        for (int i = 0; i < capacity; i++)
+        {
+            Assert.assertTrue(q.offer(v));
+        }
+        Assert.assertFalse(q.offer(v));
+        Assert.assertThat(q.size(), is(capacity));
+        for (int i = 0; i < 6; i++)
+        {
+            Assert.assertEquals(v, q.poll());
+        }
+        //the consumer is left in the chunk previous the last and biggest one
+        Assert.assertThat(q.size(), is(capacity - 6));
+        for (int i = 0; i < 6; i++)
+        {
+            q.offer(v);
+        }
+        Assert.assertThat(q.size(), is(capacity));
+        Assert.assertFalse(q.offer(v));
+    }
+
 }