code: /*
   * Copyright 2012-2018 Chronicle Map Contributors
   *
   * Licensed 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 net.openhft.chronicle.hash.serialization;
  
  import net.openhft.chronicle.hash.ChronicleHash;
  import net.openhft.chronicle.hash.ChronicleHashBuilder;
  import net.openhft.chronicle.hash.Data;
  import net.openhft.chronicle.map.ChronicleMapBuilder;
  import net.openhft.chronicle.wire.Marshallable;
  import org.jetbrains.annotations.NotNull;
  
  import java.nio.ByteBuffer;
  
  /**
   * Strategy of accessing flat byte contents of objects, using a reusable {@link Data} object, cached
   * inside the {@code DataAccess} instance. This strategy interface is suitable for types of objects,
   * that are already in fact sequences of bytes ({@code byte[]}, {@link ByteBuffer}, etc.) and
   * shouldn't be serialized, and allows to avoid extra data copying. Accessed bytes should be later
   * readable by some {@link BytesReader}.
   * <p>
   * <p>Read <a href="https://github.com/OpenHFT/Chronicle-Map/blob/ea/docs/CM_Tutorial_DataAccess.adoc">{@link
   * DataAccess} and {@code SizedReader}</a> and
   * <a href="https://github.com/OpenHFT/Chronicle-Map/blob/ea/docs/CM_Tutorial.adoc#custom-serialization-checklist">custom
   * serialization checklist</a> sections in the Chronicle Map tutorial for more information on this
   * interface, how to implement and use it properly.
   *
   * @param <T> the type of objects accessed
   * @see ChronicleHashBuilder#keyReaderAndDataAccess(SizedReader, DataAccess)
   * @see ChronicleMapBuilder#valueReaderAndDataAccess(SizedReader, DataAccess)
   */
  public interface DataAccess<T> extends StatefulCopyable<DataAccess<T>>, Marshallable {
  
      /**
       * Obtain {@code Data} accessor to the bytes of the given object. Typically a {@code Data}
       * instance should be cached in a field of this {@code DataAccess}, so always the same object
       * is returned.
       *
       * @param instance the object to access bytes (serialized form) of
       * @return an accessor to the bytes of the given object
       */
      Data<T> getData(@NotNull T instance);
  
      /**
       * Clear references to the accessed object (provided in {@link #getData(Object)} method) in
       * caching fields of this {@code DataAccess} or the cached {@link Data} object, returned from
       * {@link #getData(Object)}.
       * <p>
       * {@code DataAccess} is cached itself in thread-local variables for {@link ChronicleHash}
       * instances, this method prevents leaking of accessed objects (they are not eligible for
       * garbage collection while there are some references).
       */
      void uninit();
  }
  