content: /*
   * 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.cassandra.test.microbench.btree;
  
  import java.util.function.IntFunction;
  
  import org.apache.cassandra.utils.BulkIterator;
  import org.apache.cassandra.utils.btree.UpdateFunction;
  import org.apache.cassandra.utils.caching.TinyThreadLocalPool;
  
  public class Megamorphism
  {
      // All functionallity noops,
      public enum UpdateF { SIMPLE, SIMPLE_MEGAMORPH, UNSIMPLE }
  
      private static final UpdateFunction SIMPLE_KEEP_OLD_1 = UpdateFunction.noOp();
      private static final UpdateFunction SIMPLE_KEEP_OLD_2 = UpdateFunction.Simple.of((a, b) -> a);
      private static final UpdateFunction SIMPLE_KEEP_OLD_3 = UpdateFunction.Simple.of((a, b) -> a);
  
      private static final UpdateFunction SIMPLE_KEEP_NEW_1 = UpdateFunction.Simple.of((a, b) -> b);
      private static final UpdateFunction SIMPLE_KEEP_NEW_2 = UpdateFunction.Simple.of((a, b) -> b);
      private static final UpdateFunction SIMPLE_KEEP_NEW_3 = UpdateFunction.Simple.of((a, b) -> b);
  
      private static final UpdateFunction UNSIMPLE_KEEP_OLD = new UpdateFunction()
      {
          @Override
          public Object merge(Object replacing, Object update) { return replacing; }
          @Override
          public void onAllocatedOnHeap(long heapSize) { }
          @Override
          public Object insert(Object v) { return v; }
      };
  
      private static final UpdateFunction UNSIMPLE_KEEP_NEW = new UpdateFunction()
      {
          @Override
          public Object merge(Object replacing, Object update) { return update; }
          @Override
          public void onAllocatedOnHeap(long heapSize) { }
          @Override
          public Object insert(Object v) { return v; }
      };
  
      static <V> IntFunction<UpdateFunction<V, V>> updateFGetter(boolean keepOld, BTreeBench.UpdateF updateF)
      {
          switch (updateF)
          {
              case SIMPLE: return keepOld ? i -> SIMPLE_KEEP_OLD_1 : i -> SIMPLE_KEEP_NEW_1;
              case UNSIMPLE: return keepOld ? i -> UNSIMPLE_KEEP_OLD : i -> UNSIMPLE_KEEP_NEW;
              case SIMPLE_MEGAMORPH:
                  if (keepOld)
                  {
                      return i -> {
                          switch (i % 3)
                          {
                              case 0: return SIMPLE_KEEP_OLD_1;
                              case 1: return SIMPLE_KEEP_OLD_2;
                              case 2: return SIMPLE_KEEP_OLD_3;
                              default: throw new IllegalStateException();
                          }
                      };
                  }
                  else
                  {
                      return i -> {
                          switch (i % 3)
                          {
                              case 0: return SIMPLE_KEEP_NEW_1;
                              case 1: return SIMPLE_KEEP_NEW_2;
                              case 2: return SIMPLE_KEEP_NEW_3;
                              default: throw new IllegalStateException();
                          }
                      };
                  }
              default:
                  throw new IllegalStateException();
          }
      }
  
      static class FromArrayCopy<V> implements BulkIterator<V>, AutoCloseable
      {
          private static final TinyThreadLocalPool<FromArrayCopy> cache = new TinyThreadLocalPool<>();
  
          private Object[] from;
          private int i;
          private TinyThreadLocalPool.TinyPool<FromArrayCopy> pool;
  
          public static <V> FromArrayCopy<V> of(Object[] from)
          {
              TinyThreadLocalPool.TinyPool<FromArrayCopy> pool = cache.get();
              FromArrayCopy<V> result = pool.poll();
              if (result == null)
                  result = new FromArrayCopy<>();
              result.from = from;
              result.i = 0;
              result.pool = pool;
              return result;
          }
  
          public void close()
          {
              pool.offer(this);
              from = null;
              pool = null;
          }
  
          public void fetch(Object[] into, int offset, int count)
          {
              System.arraycopy(from, i, into, offset, count);
              i += count;
          }
  
          public V next()
          {
  
              return (V) from[i++];
          }
      }
  
      static class FromArrayCopy2<V> implements BulkIterator<V>, AutoCloseable
      {
          private static final TinyThreadLocalPool<FromArrayCopy2> cache = new TinyThreadLocalPool<>();
  
          private Object[] from;
          private int i;
          private TinyThreadLocalPool.TinyPool<FromArrayCopy2> pool;
  
          public static <V> FromArrayCopy2<V> of(Object[] from)
          {
              TinyThreadLocalPool.TinyPool<FromArrayCopy2> pool = cache.get();
              FromArrayCopy2<V> result = pool.poll();
              if (result == null)
                  result = new FromArrayCopy2<>();
              result.from = from;
              result.i = 0;
              result.pool = pool;
              return result;
          }
  
          public void close()
          {
              pool.offer(this);
              from = null;
              pool = null;
          }
  
          public void fetch(Object[] into, int offset, int count)
          {
              System.arraycopy(from, i, into, offset, count);
              i += count;
          }
  
          public V next()
          {
  
              return (V) from[i++];
          }
      }
  }
  