content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  // Includes work from:
  /*
   * Copyright 2010 Google Inc. All Rights Reserved.
   *
   * Licensed 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 io.opentelemetry.instrumentation.api.internal.cache.concurrentlinkedhashmap;
  
  import java.io.Serializable;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * A common set of {@link Weigher} and {@link EntryWeigher} implementations.
   *
   * @author ben.manes@gmail.com (Ben Manes)
   * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/">
   *     http://code.google.com/p/concurrentlinkedhashmap/</a>
   */
  public final class Weighers {
  
    private Weighers() {
      throw new AssertionError();
    }
  
    /**
     * A entry weigher backed by the specified weigher. The weight of the value determines the weight
     * of the entry.
     *
     * @param weigher the weigher to be "wrapped" in a entry weigher.
     * @return A entry weigher view of the specified weigher.
     */
    public static <K, V> EntryWeigher<K, V> asEntryWeigher(final Weigher<? super V> weigher) {
      return (weigher == singleton())
          ? Weighers.<K, V>entrySingleton()
          : new EntryWeigherView<>(weigher);
    }
  
    /**
     * A weigher where an entry has a weight of <tt>1</tt>. A map bounded with this weigher will evict
     * when the number of key-value pairs exceeds the capacity.
     *
     * @return A weigher where a value takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <K, V> EntryWeigher<K, V> entrySingleton() {
      return (EntryWeigher<K, V>) SingletonEntryWeigher.INSTANCE;
    }
  
    /**
     * A weigher where a value has a weight of <tt>1</tt>. A map bounded with this weigher will evict
     * when the number of key-value pairs exceeds the capacity.
     *
     * @return A weigher where a value takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <V> Weigher<V> singleton() {
      return (Weigher<V>) SingletonWeigher.INSTANCE;
    }
  
    /**
     * A weigher where the value is a byte array and its weight is the number of bytes. A map bounded
     * with this weigher will evict when the number of bytes exceeds the capacity rather than the
     * number of key-value pairs in the map. This allows for restricting the capacity based on the
     * memory-consumption and is primarily for usage by dedicated caching servers that hold the
     * serialized data.
     *
     * <p>A value with a weight of <tt>0</tt> will be rejected by the map. If a value with this weight
     * can occur then the caller should eagerly evaluate the value and treat it as a removal
     * operation. Alternatively, a custom weigher may be specified on the map to assign an empty value
     * a positive weight.
     *
     * @return A weigher where each byte takes one unit of capacity.
     */
    public static Weigher<byte[]> byteArray() {
      return ByteArrayWeigher.INSTANCE;
    }
  
    /**
     * A weigher where the value is a {@link Iterable} and its weight is the number of elements. This
     * weigher only should be used when the alternative {@link #collection()} weigher cannot be, as
     * evaluation takes O(n) time. A map bounded with this weigher will evict when the total number of
     * elements exceeds the capacity rather than the number of key-value pairs in the map.
     *
     * <p>A value with a weight of <tt>0</tt> will be rejected by the map. If a value with this weight
     * can occur then the caller should eagerly evaluate the value and treat it as a removal
     * operation. Alternatively, a custom weigher may be specified on the map to assign an empty value
     * a positive weight.
     *
     * @return A weigher where each element takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <E> Weigher<? super Iterable<E>> iterable() {
      return (Weigher<Iterable<E>>) (Weigher<?>) IterableWeigher.INSTANCE;
    }
  
    /**
     * A weigher where the value is a {@link Collection} and its weight is the number of elements. A
     * map bounded with this weigher will evict when the total number of elements exceeds the capacity
     * rather than the number of key-value pairs in the map.
     *
     * <p>A value with a weight of <tt>0</tt> will be rejected by the map. If a value with this weight
     * can occur then the caller should eagerly evaluate the value and treat it as a removal
     * operation. Alternatively, a custom weigher may be specified on the map to assign an empty value
     * a positive weight.
     *
     * @return A weigher where each element takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <E> Weigher<? super Collection<E>> collection() {
      return (Weigher<Collection<E>>) (Weigher<?>) CollectionWeigher.INSTANCE;
    }
  
    /**
     * A weigher where the value is a {@link List} and its weight is the number of elements. A map
     * bounded with this weigher will evict when the total number of elements exceeds the capacity
     * rather than the number of key-value pairs in the map.
     *
     * <p>A value with a weight of <tt>0</tt> will be rejected by the map. If a value with this weight
     * can occur then the caller should eagerly evaluate the value and treat it as a removal
     * operation. Alternatively, a custom weigher may be specified on the map to assign an empty value
     * a positive weight.
     *
     * @return A weigher where each element takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <E> Weigher<? super List<E>> list() {
      return (Weigher<List<E>>) (Weigher<?>) ListWeigher.INSTANCE;
    }
  
    /**
     * A weigher where the value is a {@link Set} and its weight is the number of elements. A map
     * bounded with this weigher will evict when the total number of elements exceeds the capacity
     * rather than the number of key-value pairs in the map.
     *
     * <p>A value with a weight of <tt>0</tt> will be rejected by the map. If a value with this weight
     * can occur then the caller should eagerly evaluate the value and treat it as a removal
     * operation. Alternatively, a custom weigher may be specified on the map to assign an empty value
     * a positive weight.
     *
     * @return A weigher where each element takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <E> Weigher<? super Set<E>> set() {
      return (Weigher<Set<E>>) (Weigher<?>) SetWeigher.INSTANCE;
    }
  
    /**
     * A weigher where the value is a {@link Map} and its weight is the number of entries. A map
     * bounded with this weigher will evict when the total number of entries across all values exceeds
     * the capacity rather than the number of key-value pairs in the map.
     *
     * <p>A value with a weight of <tt>0</tt> will be rejected by the map. If a value with this weight
     * can occur then the caller should eagerly evaluate the value and treat it as a removal
     * operation. Alternatively, a custom weigher may be specified on the map to assign an empty value
     * a positive weight.
     *
     * @return A weigher where each entry takes one unit of capacity.
     */
    @SuppressWarnings({"cast", "unchecked"})
    public static <A, B> Weigher<? super Map<A, B>> map() {
      return (Weigher<Map<A, B>>) (Weigher<?>) MapWeigher.INSTANCE;
    }
  
    static final class EntryWeigherView<K, V> implements EntryWeigher<K, V>, Serializable {
      static final long serialVersionUID = 1;
      final Weigher<? super V> weigher;
  
      EntryWeigherView(Weigher<? super V> weigher) {
        ConcurrentLinkedHashMap.checkNotNull(weigher);
        this.weigher = weigher;
      }
  
      @Override
      public int weightOf(K key, V value) {
        return weigher.weightOf(value);
      }
    }
  
    enum SingletonEntryWeigher implements EntryWeigher<Object, Object> {
      INSTANCE;
  
      @Override
      public int weightOf(Object key, Object value) {
        return 1;
      }
    }
  
    enum SingletonWeigher implements Weigher<Object> {
      INSTANCE;
  
      @Override
      public int weightOf(Object value) {
        return 1;
      }
    }
  
    enum ByteArrayWeigher implements Weigher<byte[]> {
      INSTANCE;
  
      @Override
      public int weightOf(byte[] value) {
        return value.length;
      }
    }
  
    enum IterableWeigher implements Weigher<Iterable<?>> {
      INSTANCE;
  
      @Override
      public int weightOf(Iterable<?> values) {
        if (values instanceof Collection<?>) {
          return ((Collection<?>) values).size();
        }
        int size = 0;
        for (Iterator<?> i = values.iterator(); i.hasNext(); ) {
          i.next();
          size++;
        }
        return size;
      }
    }
  
    enum CollectionWeigher implements Weigher<Collection<?>> {
      INSTANCE;
  
      @Override
      public int weightOf(Collection<?> values) {
        return values.size();
      }
    }
  
    enum ListWeigher implements Weigher<List<?>> {
      INSTANCE;
  
      @Override
      public int weightOf(List<?> values) {
        return values.size();
      }
    }
  
    enum SetWeigher implements Weigher<Set<?>> {
      INSTANCE;
  
      @Override
      public int weightOf(Set<?> values) {
        return values.size();
      }
    }
  
    enum MapWeigher implements Weigher<Map<?, ?>> {
      INSTANCE;
  
      @Override
      public int weightOf(Map<?, ?> values) {
        return values.size();
      }
    }
  }
  