content: /*
   * Copyright 1999-2101 Alibaba Group.
   *
   * 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 com.alibaba.fastjson.util;
  
  /**
   * for concurrent IdentityHashMap
   * 
   * @author wenshao<szujobs@hotmail.com>
   */
  @SuppressWarnings("unchecked")
  public class IdentityHashMap<K, V> {
  
      public static final int     DEFAULT_TABLE_SIZE = 1024;
  
      private final Entry<K, V>[] buckets;
      private final int           indexMask;
  
      public IdentityHashMap(){
          this(DEFAULT_TABLE_SIZE);
      }
  
      public IdentityHashMap(int tableSize){
          this.indexMask = tableSize - 1;
          this.buckets = new Entry[tableSize];
      }
  
      public final V get(K key) {
          final int hash = System.identityHashCode(key);
          final int bucket = hash & indexMask;
  
          for (Entry<K, V> entry = buckets[bucket]; entry != null; entry = entry.next) {
              if (key == entry.key) {
                  return (V) entry.value;
              }
          }
  
          return null;
      }
  
      public boolean put(K key, V value) {
          final int hash = System.identityHashCode(key);
          final int bucket = hash & indexMask;
  
          for (Entry<K, V> entry = buckets[bucket]; entry != null; entry = entry.next) {
              if (key == entry.key) {
                  entry.value = value;
                  return true;
              }
          }
  
          Entry<K, V> entry = new Entry<K, V>(key, value, hash, buckets[bucket]);
          buckets[bucket] = entry;  // 并发是处理时会可能导致缓存丢失，但不影响正确性
  
          return false;
      }
  
      public int size() {
          int size = 0;
          for (int i = 0; i < buckets.length; ++i) {
              for (Entry<K, V> entry = buckets[i]; entry != null; entry = entry.next) {
                  size++;
              }
          }
          return size;
      }
  
      protected static final class Entry<K, V> {
  
          public final int   hashCode;
          public final K     key;
          public V     value;
  
          public final Entry<K, V> next;
  
          public Entry(K key, V value, int hash, Entry<K, V> next){
              this.key = key;
              this.value = value;
              this.next = next;
              this.hashCode = hash;
          }
      }
  
  }
  