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.runners.spark.translation;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.OutputStream;
  import java.io.Serializable;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.util.VarInt;
  import org.apache.beam.sdk.util.common.ElementByteSizeObserver;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Throwables;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.io.ByteStreams;
  
  /**
   * A holder object that lets you serialize an element with a Coder with minimal wasted space.
   * Supports both Kryo and Java serialization.
   *
   * <p>There are two different representations: a deserialized representation and a serialized
   * representation.
   *
   * <p>The deserialized representation stores a Coder and the value. To serialize the value, we write
   * a length-prefixed encoding of value, but do NOT write the Coder used.
   *
   * <p>The serialized representation just reads a byte array - the value is not deserialized fully.
   * In order to get at the deserialized value, the caller must pass the Coder used to create this
   * instance via getOrDecode(Coder). This reverts the representation back to the deserialized
   * representation.
   *
   * @param <T> element type
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public final class ValueAndCoderLazySerializable<T> implements Serializable {
    private T value;
    // Re-use a field to save space in-memory. This is either a byte[] or a Coder, depending on
    // which representation we are in.
    private Object coderOrBytes;
  
    private ValueAndCoderLazySerializable(T value, Coder<T> currentCoder) {
      this.value = value;
      this.coderOrBytes = currentCoder;
    }
  
    @SuppressWarnings("unused") // for serialization
    ValueAndCoderLazySerializable() {}
  
    public static <T> ValueAndCoderLazySerializable<T> of(T value, Coder<T> coder) {
      return new ValueAndCoderLazySerializable<>(value, coder);
    }
  
    public T getOrDecode(Coder<T> coder) {
      if (!(coderOrBytes instanceof Coder)) {
        ByteArrayInputStream bais = new ByteArrayInputStream((byte[]) this.coderOrBytes);
        try {
          value = coder.decode(bais);
        } catch (IOException e) {
          throw new IllegalStateException("Error decoding bytes for coder: " + coder, e);
        }
        this.coderOrBytes = coder;
      }
  
      return value;
    }
  
    private static class ByteSizeObserver extends ElementByteSizeObserver {
      private long observedSize = 0;
  
      @Override
      protected void reportElementSize(long elementByteSize) {
        observedSize += elementByteSize;
      }
    }
  
    void writeCommon(OutputStream out) throws IOException {
      if (!(coderOrBytes instanceof Coder)) {
        byte[] bytes = (byte[]) coderOrBytes;
        VarInt.encode(bytes.length, out);
        out.write(bytes);
      } else {
        @SuppressWarnings("unchecked")
        Coder<T> coder = (Coder<T>) coderOrBytes;
        int bufferSize = 1024;
        if (coder.isRegisterByteSizeObserverCheap(value)) {
          try {
            ByteSizeObserver observer = new ByteSizeObserver();
            coder.registerByteSizeObserver(value, observer);
            bufferSize = (int) observer.observedSize;
          } catch (Exception e) {
            Throwables.throwIfUnchecked(e);
            throw new RuntimeException(e);
          }
        }
  
        ByteArrayOutputStream bytes = new ByteArrayOutputStream(bufferSize);
        try {
          coder.encode(value, bytes);
          VarInt.encode(bytes.size(), out);
          bytes.writeTo(out);
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
      }
    }
  
    void readCommon(InputStream in) throws IOException {
      int length = VarInt.decodeInt(in);
      byte[] bytes = new byte[length];
      ByteStreams.readFully(in, bytes);
      this.coderOrBytes = bytes;
    }
  
    private void writeObject(ObjectOutputStream out) throws IOException {
      writeCommon(out);
    }
  
    private void readObject(ObjectInputStream in) throws IOException {
      readCommon(in);
    }
  }
  