kafka TimelineObject 源码
kafka TimelineObject 代码
文件路径:/metadata/src/main/java/org/apache/kafka/timeline/TimelineObject.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF 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
*
* 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 org.apache.kafka.timeline;
import java.util.Iterator;
import java.util.Objects;
/**
* This is a mutable reference to an immutable object. It can be snapshotted.
*
* This class requires external synchronization.
*/
public class TimelineObject<T> implements Revertable {
static class ObjectContainer<T> implements Delta {
private T value;
ObjectContainer(T initialValue) {
this.value = initialValue;
}
T value() {
return value;
}
void setValue(T value) {
this.value = value;
}
@Override
public void mergeFrom(long destinationEpoch, Delta delta) {
// Nothing to do
}
}
private final SnapshotRegistry snapshotRegistry;
private final T initialValue;
private T value;
public TimelineObject(SnapshotRegistry snapshotRegistry, T initialValue) {
Objects.requireNonNull(initialValue);
this.snapshotRegistry = snapshotRegistry;
this.initialValue = initialValue;
this.value = initialValue;
snapshotRegistry.register(this);
}
public T get() {
return value;
}
public T get(long epoch) {
if (epoch == SnapshotRegistry.LATEST_EPOCH) return value;
Iterator<Snapshot> iterator = snapshotRegistry.iterator(epoch);
while (iterator.hasNext()) {
Snapshot snapshot = iterator.next();
ObjectContainer<T> container = snapshot.getDelta(TimelineObject.this);
if (container != null) return container.value();
}
return value;
}
public void set(T newValue) {
Objects.requireNonNull(newValue);
Iterator<Snapshot> iterator = snapshotRegistry.reverseIterator();
if (iterator.hasNext()) {
Snapshot snapshot = iterator.next();
ObjectContainer<T> prevContainer = snapshot.getDelta(TimelineObject.this);
if (prevContainer == null) {
prevContainer = new ObjectContainer<>(initialValue);
snapshot.setDelta(TimelineObject.this, prevContainer);
prevContainer.setValue(value);
}
}
this.value = newValue;
}
@SuppressWarnings("unchecked")
@Override
public void executeRevert(long targetEpoch, Delta delta) {
ObjectContainer<T> container = (ObjectContainer<T>) delta;
this.value = container.value();
}
@Override
public void reset() {
set(initialValue);
}
@Override
public int hashCode() {
return value.hashCode();
}
@Override
public boolean equals(Object o) {
if (!(o instanceof TimelineObject)) return false;
TimelineObject other = (TimelineObject) o;
return value.equals(other.value);
}
@Override
public String toString() {
return value.toString();
}
}
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