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.impl;
  
  import net.openhft.chronicle.bytes.Bytes;
  import net.openhft.chronicle.bytes.RandomDataInput;
  import net.openhft.chronicle.hash.Data;
  import net.openhft.chronicle.hash.serialization.BytesWriter;
  import net.openhft.chronicle.hash.serialization.DataAccess;
  import net.openhft.chronicle.hash.serialization.SizedReader;
  import net.openhft.chronicle.wire.WireIn;
  import net.openhft.chronicle.wire.WireOut;
  import org.jetbrains.annotations.NotNull;
  import org.jetbrains.annotations.Nullable;
  
  import java.lang.reflect.Type;
  
  import static net.openhft.chronicle.hash.serialization.StatefulCopyable.copyIfNeeded;
  import static net.openhft.chronicle.hash.serialization.impl.DefaultElasticBytes.DEFAULT_BYTES_CAPACITY;
  
  public class ExternalBytesMarshallableDataAccess<T> extends InstanceCreatingMarshaller<T>
          implements DataAccess<T>, Data<T> {
  
      // Config fields
      private SizedReader<T> reader;
      private BytesWriter<? super T> writer;
  
      /**
       * Cache field
       */
      private transient Bytes bytes;
  
      /**
       * State field
       */
      private transient T instance;
  
      public ExternalBytesMarshallableDataAccess(
              Class<T> tClass, SizedReader<T> reader, BytesWriter<? super T> writer) {
          this(tClass, reader, writer, DEFAULT_BYTES_CAPACITY);
      }
  
      private ExternalBytesMarshallableDataAccess(
              Type tClass, SizedReader<T> reader, BytesWriter<? super T> writer,
              long bytesCapacity) {
          super(tClass);
          this.writer = writer;
          this.reader = reader;
          initTransients(bytesCapacity);
      }
  
      private void initTransients(long bytesCapacity) {
          bytes = DefaultElasticBytes.allocateDefaultElasticBytes(bytesCapacity);
      }
  
      @Override
      public RandomDataInput bytes() {
          return bytes.bytesStore();
      }
  
      @Override
      public long offset() {
          return 0;
      }
  
      @Override
      public long size() {
          return bytes.readRemaining();
      }
  
      @Override
      public T get() {
          return instance;
      }
  
      @Override
      public T getUsing(@Nullable T using) {
          if (using == null)
              using = createInstance();
          T result = reader.read(bytes, size(), using);
          bytes.readPosition(0);
          return result;
      }
  
      @Override
      public int hashCode() {
          return dataHashCode();
      }
  
      @Override
      public boolean equals(Object obj) {
          return dataEquals(obj);
      }
  
      @Override
      public String toString() {
          return get().toString();
      }
  
      @Override
      public Data<T> getData(@NotNull T instance) {
          this.instance = instance;
          bytes.clear();
          writer.write(bytes, instance);
          return this;
      }
  
      @Override
      public void uninit() {
          instance = null;
      }
  
      @Override
      public DataAccess<T> copy() {
          return new ExternalBytesMarshallableDataAccess<>(
                  tType(), copyIfNeeded(reader), copyIfNeeded(writer), bytes.realCapacity());
      }
  
      @Override
      public void readMarshallable(@NotNull WireIn wireIn) {
          super.readMarshallable(wireIn);
          reader = wireIn.read(() -> "reader").typedMarshallable();
          writer = wireIn.read(() -> "writer").typedMarshallable();
          initTransients(DEFAULT_BYTES_CAPACITY);
      }
  
      @Override
      public void writeMarshallable(@NotNull WireOut wireOut) {
          super.writeMarshallable(wireOut);
          wireOut.write(() -> "reader").typedMarshallable(reader);
          wireOut.write(() -> "writer").typedMarshallable(writer);
      }
  }
  