DefaultAttributeMap.java — netty Source File

Source Code

/*
 * Copyright 2012 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.util;

import io.netty.util.internal.ObjectUtil;

import java.util.Arrays;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

/**
 * Default {@link AttributeMap} implementation which not exibit any blocking behaviour on attribute lookup while using a
 * copy-on-write approach on the modify path.<br> Attributes lookup and remove exibit {@code O(logn)} time worst-case
 * complexity, hence {@code attribute::set(null)} is to be preferred to {@code remove}.
 */
public class DefaultAttributeMap implements AttributeMap {

    private static final AtomicReferenceFieldUpdater<DefaultAttributeMap, DefaultAttribute[]> ATTRIBUTES_UPDATER =
            AtomicReferenceFieldUpdater.newUpdater(DefaultAttributeMap.class, DefaultAttribute[].class, "attributes");
    private static final DefaultAttribute[] EMPTY_ATTRIBUTES = new DefaultAttribute[0];

    /**
     * Similarly to {@code Arrays::binarySearch} it perform a binary search optimized for this use case, in order to
     * save polymorphic calls (on comparator side) and unnecessary class checks.
     */
    private static int searchAttributeByKey(DefaultAttribute[] sortedAttributes, AttributeKey<?> key) {
        int low = 0;
        int high = sortedAttributes.length - 1;

        while (low <= high) {
            int mid = low + high >>> 1;
            DefaultAttribute midVal = sortedAttributes[mid];
            AttributeKey midValKey = midVal.key;
            if (midValKey == key) {
                return mid;
            }
            int midValKeyId = midValKey.id();
            int keyId = key.id();
            assert midValKeyId != keyId;
            boolean searchRight = midValKeyId < keyId;
            if (searchRight) {
                low = mid + 1;
            } else {
                high = mid - 1;
            }
        }

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