Cache.java — netty Source File

Source Code

/*
 * Copyright 2018 The Netty Project
 *
 * The Netty Project 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:
 *
 *   https://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.netty.resolver.dns;

import io.netty.channel.EventLoop;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.Delayed;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

import static java.util.Collections.singletonList;

/**
 * Abstract cache that automatically removes entries for a hostname once the TTL for an entry is reached.
 *
 * @param <E>
 */
abstract class Cache<E> {
    private static final AtomicReferenceFieldUpdater<Cache.Entries, ScheduledFuture> FUTURE_UPDATER =
            AtomicReferenceFieldUpdater.newUpdater(Cache.Entries.class, ScheduledFuture.class, "expirationFuture");

    private static final ScheduledFuture<?> CANCELLED = new ScheduledFuture<Object>() {

        @Override
        public boolean cancel(boolean mayInterruptIfRunning) {
            return false;
        }

        @Override
        public long getDelay(TimeUnit unit) {
            // We ignore unit and always return the minimum value to ensure the TTL of the cancelled marker is
            // the smallest.
            return Long.MIN_VALUE;
        }

        @Override
        public int compareTo(Delayed o) {
// ... (233 more lines)