Github user vesense commented on a diff in the pull request:
https://github.com/apache/storm/pull/1674#discussion_r77605544
--- Diff:
storm-core/src/jvm/org/apache/storm/scheduler/blacklist/CircularBuffer.java ---
@@ -0,0 +1,182 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.storm.scheduler.blacklist;
+
+import java.io.Serializable;
+import java.util.*;
+
+public final class CircularBuffer<T extends Serializable> extends
AbstractCollection<T> implements Serializable {
+
+ // This is the largest capacity allowed by this implementation
+ private static final int MAX_CAPACITY = 1 << 30;
+ private static final int DEFAULT_CAPACITY = 1 << 8;
+
+ private int size = 0;
+ private int producerIndex = 0;
+ private int consumerIndex = 0;
+
+ // capacity must be a power of 2 at all times
+ private int capacity;
+ //private int maxCapacity;
+
+ // we mask with capacity -1. This variable caches that values
+ //private int bitmask;
+
+ private Serializable[] q;
+
+ public CircularBuffer() {
+ this(DEFAULT_CAPACITY);
+ }
+
+ // Construct a buffer which has at least the specified capacity. If
+ // the value specified is a power of two then the buffer will be
+ // exactly the specified size. Otherwise the buffer will be the
+ // first power of two which is greater than the specified value.
+ public CircularBuffer(int c) {
+
+ if (c > MAX_CAPACITY) {
+ throw new IllegalArgumentException("Capacity greater than " +
+ "allowed");
+ }
+
+ //for (capacity = 1; capacity < c; capacity <<= 1) ;
+ capacity=c;
+ //bitmask = capacity - 1;
+ q = new Serializable[capacity];
+ }
+
+ // Constructor used by clone()
+ private CircularBuffer(CircularBuffer oldBuffer) {
+ size = oldBuffer.size;
+ producerIndex = oldBuffer.producerIndex;
+ consumerIndex = oldBuffer.consumerIndex;
+ capacity = oldBuffer.capacity;
+ //bitmask = oldBuffer.bitmask;
+ q = new Serializable[oldBuffer.q.length];
+ System.arraycopy(oldBuffer.q, 0, q, 0, q.length);
+ }
+
+ private boolean isFull(){
+ return size==capacity;
+ }
+
+ public boolean add(Serializable obj) {
+ if (isFull()) {
+ remove();
+ }
+
+ size++;
+ q[producerIndex] = obj;
+
+ producerIndex = (producerIndex + 1) % capacity;
+
+ return true;
+ }
+
+ public T remove() {
+ Serializable obj;
+
+ if (size == 0) return null;
+
+ size--;
+ obj = q[consumerIndex];
+ q[consumerIndex] = null; // allow gc to collect
+
+ consumerIndex = (consumerIndex + 1) % capacity;
+
+ return (T)obj;
+ }
+
+ public boolean isEmpty() { return size == 0; }
+
+ public int size() { return size; }
+
+ public int capacity() { return capacity; }
+
+ public Serializable peek() {
+ if (size == 0) return null;
+ return q[consumerIndex];
+ }
+
+ public void clear() {
+ Arrays.fill(q, null);
+ size = 0;
+ producerIndex = 0;
+ consumerIndex = 0;
+ }
+
+ public Object clone() {
+ return new CircularBuffer(this);
+ }
+
+ public String toString() {
+ StringBuffer s = new StringBuffer(super.toString() + "' size: '" +
size() + "'");
+
+ return s.toString();
+ }
+
+ public Iterator iterator() {
+ return new Iterator<T>() {
+ private final int ci = consumerIndex;
+ private final int pi = producerIndex;
+ private int s = size;
+ private int i = ci;
+
+ public boolean hasNext() {
+ checkForModification();
+ return s > 0;
+ }
+
+ public T next() {
+ checkForModification();
+ if (s == 0) throw new NoSuchElementException();
+
+ s--;
+ T r = (T)q[i];
+ i = (i + 1) % capacity;
+
+ return r;
+ }
+
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+
+ private void checkForModification() {
+ if (ci != consumerIndex) throw new
ConcurrentModificationException();
+ if (pi != producerIndex) throw new
ConcurrentModificationException();
+ }
+ };
+ }
+
+ public static void main(String []args){
--- End diff --
move this to a unit test?
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