/*
 * 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.iceberg.transforms;

import java.io. ObjectStreamException;
import java.io. Serializable;

/**
 * Stand-in classes for expression classes in Java Serialization. 
 * <p>
 * These are used so that transform classes can be singletons and use identical equality. 
 */
class SerializationProxies {
  private SerializationProxies() {
  }

  static class VoidTransformProxy implements Serializable {
    private static final VoidTransformProxy INSTANCE = new VoidTransformProxy();

    static VoidTransformProxy get() {
      return INSTANCE;
    }

    /**
     * Constructor for Java serialization. 
     */
    VoidTransformProxy() {
    }

    Object readResolve() throws ObjectStreamException {
      return VoidTransform.get();
    }
  }
}
