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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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/*
 * 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.activemq.artemis.utils;

import io.netty.buffer.ByteBuf;
import io.netty.util.internal.MathUtil;

/**
 * Thread-safe {@code } interner.
 * 
 * Differently from {@link String#intern()} it contains a fixed amount of entries and
 * when used by concurrent threads it doesn't ensure the uniqueness of the entries ie
 * the same entry could be allocated multiple times by concurrent calls.
 */
public abstract class AbstractPool {

   public static final int DEFAULT_POOL_CAPACITY = 32;

   private final O[] entries;
   private final int mask;
   private final int shift;

   public AbstractPool() {
      this(DEFAULT_POOL_CAPACITY);
   }

   public AbstractPool(final int capacity) {
      entries = (O[]) new Object[MathUtil.findNextPositivePowerOfTwo(capacity)];
      mask = entries.length - 1;
      //log2 of entries.length
      shift = 31 - Integer.numberOfLeadingZeros(entries.length);
   }

   /**
    * Create a new entry.
    */
   protected abstract O create(I value);

   /**
    * Returns {@code true} if the {@code entry} content is equal to {@code value};
    */
   protected abstract boolean isEqual(O entry, I value);

   protected int hashCode(I value) {
      return value.hashCode();
   }

   /**
    * Returns and interned entry if possible, a new one otherwise.
    * 
    * The {@code byteBuf}'s {@link ByteBuf#readerIndex()} is incremented by {@code length} after it.
    */
   public final O getOrCreate(final I value) {
      if (value == null) {
         return null;
      }
      final int hashCode = hashCode(value);
      //fast % operation with power of 2 entries.length
      final int firstIndex = hashCode & mask;
      final O firstEntry = entries[firstIndex];
      if (isEqual(firstEntry, value)) {
         return firstEntry;
      }
      final int secondIndex = (hashCode >> shift) & mask;
      final O secondEntry = entries[secondIndex];
      if (isEqual(secondEntry, value)) {
         return secondEntry;
      }
      final O internedEntry = create(value);
      final int entryIndex = firstEntry == null ? firstIndex : secondIndex;
      entries[entryIndex] = internedEntry;
      return internedEntry;
   }
}