content: /*
   * 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.beam.sdk.coders;
  
  import java.io.InputStream;
  import java.io.OutputStream;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /** A {@link Coder} for {@link Void}. Uses zero bytes per {@link Void}. */
  public class VoidCoder extends AtomicCoder<@Nullable Void> {
  
    public static VoidCoder of() {
      return INSTANCE;
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    private static final VoidCoder INSTANCE = new VoidCoder();
    private static final TypeDescriptor<Void> TYPE_DESCRIPTOR = new TypeDescriptor<Void>() {};
    private static final Object STRUCTURAL_VOID_VALUE = new Object();
  
    private VoidCoder() {}
  
    @Override
    public void encode(Void value, OutputStream outStream) {
      // Nothing to write!
    }
  
    @Override
    public @Nullable Void decode(InputStream inStream) {
      // Nothing to read!
      return null;
    }
  
    @Override
    public void verifyDeterministic() {}
  
    @Override
    public Object structuralValue(Void value) {
      return STRUCTURAL_VOID_VALUE;
    }
  
    /**
     * {@inheritDoc}
     *
     * @return {@code true}. {@link VoidCoder#getEncodedElementByteSize} runs in constant time.
     */
    @Override
    public boolean isRegisterByteSizeObserverCheap(Void value) {
      return true;
    }
  
    @Override
    public TypeDescriptor<Void> getEncodedTypeDescriptor() {
      return TYPE_DESCRIPTOR;
    }
  
    @Override
    protected long getEncodedElementByteSize(Void value) throws Exception {
      return 0;
    }
  }
  