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.Byteable;
  import net.openhft.chronicle.bytes.Bytes;
  import net.openhft.chronicle.hash.serialization.BytesReader;
  import net.openhft.chronicle.hash.serialization.SizedReader;
  import net.openhft.chronicle.hash.serialization.StatefulCopyable;
  import net.openhft.chronicle.values.Copyable;
  import net.openhft.chronicle.values.Values;
  import net.openhft.chronicle.wire.WireIn;
  import net.openhft.chronicle.wire.WireOut;
  import org.jetbrains.annotations.NotNull;
  import org.jetbrains.annotations.Nullable;
  
  public class ValueReader<T>
          implements SizedReader<T>, BytesReader<T>, StatefulCopyable<ValueReader<T>> {
  
      /**
       * Config field
       */
      private Class<T> valueType;
  
      // Cache fields
      private transient Class<? extends T> nativeClass;
      private transient Class<? extends T> heapClass;
      private transient Byteable nativeReference;
  
      public ValueReader(Class<T> valueType) {
          this.valueType = valueType;
          initTransients();
      }
  
      /**
       * Returns the interface of values deserialized.
       */
      protected Class<T> valueType() {
          return valueType;
      }
  
      protected Class<? extends T> nativeClass() {
          return nativeClass;
      }
  
      protected Class<? extends T> heapClass() {
          return heapClass;
      }
  
      private void initTransients() {
          nativeClass = Values.nativeClassFor(valueType);
          heapClass = Values.heapClassFor(valueType);
          nativeReference = (Byteable) Values.newNativeReference(valueType);
      }
  
      protected T createInstance() {
          try {
              return heapClass.newInstance();
          } catch (InstantiationException | IllegalAccessException e) {
              throw new RuntimeException(e);
          }
      }
  
      @NotNull
      @Override
      public T read(@NotNull Bytes in, long size, @Nullable T using) {
          if (size != nativeReference.maxSize())
              throw new IllegalArgumentException();
          return read(in, using);
      }
  
      @NotNull
      @Override
      public T read(Bytes in, @Nullable T using) {
          if (using != null && using.getClass() == nativeClass) {
              ((Byteable) using).bytesStore(in.bytesStore(), in.readPosition(),
                      nativeReference.maxSize());
              return using;
          }
          if (using == null)
              using = createInstance();
          nativeReference.bytesStore(in.bytesStore(), in.readPosition(),
                  nativeReference.maxSize());
          ((Copyable) using).copyFrom(nativeReference);
          return using;
      }
  
      @Override
      public ValueReader<T> copy() {
          return new ValueReader<>(valueType);
      }
  
      @Override
      public void readMarshallable(@NotNull WireIn wireIn) {
          valueType = wireIn.read(() -> "valueType").typeLiteral();
          initTransients();
      }
  
      @Override
      public void writeMarshallable(@NotNull WireOut wireOut) {
          wireOut.write(() -> "valueType").typeLiteral(valueType);
      }
  }
  