Github user revans2 commented on a diff in the pull request:
https://github.com/apache/storm/pull/2711#discussion_r196838549
--- Diff: storm-client/src/jvm/org/apache/storm/utils/CustomIndexArray.java
---
@@ -0,0 +1,174 @@
+/*
+ * 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 org.apache.storm.utils;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
+
+/***
+ * A fixed size array with a customizable indexing range. The index range
can have -ve lower / upper bound.
+ * Intended to be a faster alternative to HashMap<Integer, .. >. Only
applicable as a substitute if the
+ * largest & smallest indices are known at time of creation.
+ * This class does not inherit from :
+ * - Map<Integer,T> : For performance reasons. The get(Object key)
method requires key to be cast to Integer before use.
+ * - ArrayList<T> : as this class supports negative indexes & cannot
grow/shrink.
+ */
+
+public class CustomIndexArray<T> {
+
+ public final int baseIndex;
+ private final ArrayList<T> elements;
+ private final int elemCount;
+
+ /**
+ * Creates the array with (upperIndex-lowerIndex+1) elements,
initialized to null.
+ * @param lowerIndex Smallest (inclusive) valid index for the array.
Can be +ve, -ve or 0.
+ * @param upperIndex Largest (inclusive) valid index for the array.
Can be +ve, -ve or 0. Must be > lowerIndex
+ */
+ public CustomIndexArray(int lowerIndex, int upperIndex) {
+ if (lowerIndex >= upperIndex) {
+ throw new IllegalArgumentException("lowerIndex must be <
upperIndex");
+ }
+
+ this.baseIndex = lowerIndex;
+ this.elemCount = upperIndex - lowerIndex + 1;
+
+ this.elements = makeNullInitializedArray(elemCount);
+ }
+
+ private static <T> ArrayList<T> makeNullInitializedArray(int
elemCount) {
+ ArrayList<T> result = new ArrayList<T>(elemCount);
+ for (int i = 0; i < elemCount; i++) {
+ result.add(null);
+ }
+ return result;
+ }
+
+ /**
+ * Initializes the array with elements from a HashTable.
+ *
+ * @param src the source map from which to initialize
+ */
+ public CustomIndexArray(Map<Integer, T> src) {
+ Integer lowerIndex = Integer.MAX_VALUE;
+ Integer upperIndex = Integer.MIN_VALUE;
+
+ for (Map.Entry<Integer, T> entry : src.entrySet()) { // calculate
smallest & largest indexes
--- End diff --
nit: would `src.keySet()` be simpler because we don't use the values?
---
