| /** |
| * 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 |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * 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 storm.starter.tools; |
| |
| import java.io.Serializable; |
| import java.util.HashMap; |
| import java.util.HashSet; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * This class provides per-slot counts of the occurrences of objects. |
| * <p/> |
| * It can be used, for instance, as a building block for implementing sliding window counting of objects. |
| * |
| * @param <T> The type of those objects we want to count. |
| */ |
| public final class SlotBasedCounter<T> implements Serializable { |
| |
| private static final long serialVersionUID = 4858185737378394432L; |
| |
| private final Map<T, long[]> objToCounts = new HashMap<T, long[]>(); |
| private final int numSlots; |
| |
| public SlotBasedCounter(int numSlots) { |
| if (numSlots <= 0) { |
| throw new IllegalArgumentException("Number of slots must be greater than zero (you requested " + numSlots + ")"); |
| } |
| this.numSlots = numSlots; |
| } |
| |
| public void incrementCount(T obj, int slot) { |
| long[] counts = objToCounts.get(obj); |
| if (counts == null) { |
| counts = new long[this.numSlots]; |
| objToCounts.put(obj, counts); |
| } |
| counts[slot]++; |
| } |
| |
| public long getCount(T obj, int slot) { |
| long[] counts = objToCounts.get(obj); |
| if (counts == null) { |
| return 0; |
| } |
| else { |
| return counts[slot]; |
| } |
| } |
| |
| public Map<T, Long> getCounts() { |
| Map<T, Long> result = new HashMap<T, Long>(); |
| for (T obj : objToCounts.keySet()) { |
| result.put(obj, computeTotalCount(obj)); |
| } |
| return result; |
| } |
| |
| private long computeTotalCount(T obj) { |
| long[] curr = objToCounts.get(obj); |
| long total = 0; |
| for (long l : curr) { |
| total += l; |
| } |
| return total; |
| } |
| |
| /** |
| * Reset the slot count of any tracked objects to zero for the given slot. |
| * |
| * @param slot |
| */ |
| public void wipeSlot(int slot) { |
| for (T obj : objToCounts.keySet()) { |
| resetSlotCountToZero(obj, slot); |
| } |
| } |
| |
| private void resetSlotCountToZero(T obj, int slot) { |
| long[] counts = objToCounts.get(obj); |
| counts[slot] = 0; |
| } |
| |
| private boolean shouldBeRemovedFromCounter(T obj) { |
| return computeTotalCount(obj) == 0; |
| } |
| |
| /** |
| * Remove any object from the counter whose total count is zero (to free up memory). |
| */ |
| public void wipeZeros() { |
| Set<T> objToBeRemoved = new HashSet<T>(); |
| for (T obj : objToCounts.keySet()) { |
| if (shouldBeRemovedFromCounter(obj)) { |
| objToBeRemoved.add(obj); |
| } |
| } |
| for (T obj : objToBeRemoved) { |
| objToCounts.remove(obj); |
| } |
| } |
| |
| } |