/*
* 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;
}
}
}