sdks/java/core/src/main/java/org/apache/beam/sdk/coders/FloatCoder.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.beam.sdk.coders;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UTFDataFormatException;
import org.apache.beam.sdk.values.TypeDescriptor;

/** A {@link FloatCoder} encodes {@link Float} values in 8 bytes using Java serialization. */
public class FloatCoder extends AtomicCoder<Float> {

  public static FloatCoder of() {
    return INSTANCE;
  }

  /////////////////////////////////////////////////////////////////////////////

  private static final FloatCoder INSTANCE = new FloatCoder();
  private static final TypeDescriptor<Float> TYPE_DESCRIPTOR = new TypeDescriptor<Float>() {};

  private FloatCoder() {}

  @Override
  public void encode(Float value, OutputStream outStream) throws IOException, CoderException {
    if (value == null) {
      throw new CoderException("cannot encode a null Float");
    }
    new DataOutputStream(outStream).writeFloat(value);
  }

  @Override
  public Float decode(InputStream inStream) throws IOException, CoderException {
    try {
      return new DataInputStream(inStream).readFloat();
    } catch (EOFException | UTFDataFormatException exn) {
      // These exceptions correspond to decoding problems, so change
      // what kind of exception they're branded as.
      throw new CoderException(exn);
    }
  }

  /**
   * {@inheritDoc}
   *
   * @throws NonDeterministicException always. Floating-point operations are not guaranteed to be
   *     deterministic, even if the storage format might be, so floating point representations are
   *     not recommended for use in operations that require deterministic inputs.
   */
  @Override
  public void verifyDeterministic() throws NonDeterministicException {
    throw new NonDeterministicException(
        this, "Floating point encodings are not guaranteed to be deterministic.");
  }

  /**
   * {@inheritDoc}
   *
   * @return {@code true}. This coder is injective.
   */
  @Override
  public boolean consistentWithEquals() {
    return true;
  }

  /**
   * {@inheritDoc}
   *
   * @return {@code true}. {@link FloatCoder#getEncodedElementByteSize} returns a constant.
   */
  @Override
  public boolean isRegisterByteSizeObserverCheap(Float value) {
    return true;
  }

  @Override
  public TypeDescriptor<Float> getEncodedTypeDescriptor() {
    return TYPE_DESCRIPTOR;
  }

  /**
   * {@inheritDoc}
   *
   * @return {@code 4}, the byte size of a {@link Float} encoded using Java serialization.
   */
  @Override
  protected long getEncodedElementByteSize(Float value) throws Exception {
    if (value == null) {
      throw new CoderException("cannot encode a null Float");
    }
    return 4;
  }
}