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.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.UTFDataFormatException;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.joda.time.Instant;
  
  /**
   * A {@link Coder} for joda {@link Instant} that encodes it as a big endian {@link Long} shifted
   * such that lexicographic ordering of the bytes corresponds to chronological order.
   */
  public class InstantCoder extends AtomicCoder<Instant> {
    public static InstantCoder of() {
      return INSTANCE;
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    private static final InstantCoder INSTANCE = new InstantCoder();
    private static final TypeDescriptor<Instant> TYPE_DESCRIPTOR = new TypeDescriptor<Instant>() {};
  
    private InstantCoder() {}
  
    @Override
    public void encode(Instant value, OutputStream outStream) throws CoderException, IOException {
      if (value == null) {
        throw new CoderException("cannot encode a null Instant");
      }
  
      // Converts {@link Instant} to a {@code long} representing its millis-since-epoch,
      // but shifted so that the byte representation of negative values are lexicographically
      // ordered before the byte representation of positive values.
      //
      // This deliberately utilizes the well-defined underflow for {@code long} values.
      // See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.18.2
      long shiftedMillis = value.getMillis() - Long.MIN_VALUE;
      BitConverters.writeBigEndianLong(shiftedMillis, outStream);
    }
  
    @Override
    public Instant decode(InputStream inStream) throws CoderException, IOException {
      long shiftedMillis;
      try {
        shiftedMillis = BitConverters.readBigEndianLong(inStream);
      } catch (EOFException | UTFDataFormatException exn) {
        // These exceptions correspond to decoding problems, so change
        // what kind of exception they're branded as.
        throw new CoderException(exn);
      }
  
      // Produces an {@link Instant} from a {@code long} representing its millis-since-epoch,
      // but shifted so that the byte representation of negative values are lexicographically
      // ordered before the byte representation of positive values.
      //
      // This deliberately utilizes the well-defined overflow for {@code long} values.
      // See http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.18.2
      return new Instant(shiftedMillis + Long.MIN_VALUE);
    }
  
    @Override
    public void verifyDeterministic() {}
  
    /**
     * {@inheritDoc}
     *
     * @return {@code true}. This coder is injective.
     */
    @Override
    public boolean consistentWithEquals() {
      return true;
    }
  
    /**
     * {@inheritDoc}
     *
     * @return {@code true}. The byte size for a big endian long is a constant.
     */
    @Override
    public boolean isRegisterByteSizeObserverCheap(Instant value) {
      return true;
    }
  
    @Override
    protected long getEncodedElementByteSize(Instant value) throws Exception {
      if (value == null) {
        throw new CoderException("cannot encode a null Instant");
      }
      return 8;
    }
  
    @Override
    public TypeDescriptor<Instant> getEncodedTypeDescriptor() {
      return TYPE_DESCRIPTOR;
    }
  }
  