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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.cache.query.internal;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import com.gemstone.gemfire.CopyHelper;
import com.gemstone.gemfire.cache.query.SelectResults;
import com.gemstone.gemfire.cache.query.Struct;
import com.gemstone.gemfire.cache.query.internal.types.StructTypeImpl;
import com.gemstone.gemfire.cache.query.types.CollectionType;
import com.gemstone.gemfire.cache.query.types.ObjectType;

/**
 * Class that wraps any SelectResults and performs copy on read when iterating through the results
 * This should only be used when the cache itself has set copy-on-read to true
 * This will save space in that we do not need to copy all results until they are actually accessed
 * through iterator.next().  
 * This wrapper will only be used for queries executed locally
 * PartitionedRegion queries that are executed on the local node will already have been copied 
 * and will be treated as remote queries, so will not use this class
 * 
 * The downside is that we may actually make two copies of the data if the cached data is actually 
 * a serialized byte array.
 * toSet, toList, toArray and toArray(Object[] a) will create new structures that will iterate through
 * the results using a SelectResultsCopyOnReadIterator.  The new structures will then have a copy of the values.
 * 
 * @author jhuynh
 * @since 7.5
 */
public class ResultsCollectionCopyOnReadWrapper implements SelectResults {
  SelectResults results;
  
  public ResultsCollectionCopyOnReadWrapper(SelectResults results) {
    this.results = results;
  }
  
  @Override
  public Iterator iterator() {
    return new SelectResultsCopyOnReadIterator(results.iterator());
  }
  
  private class SelectResultsCopyOnReadIterator implements Iterator {

    Iterator iterator;
    
    SelectResultsCopyOnReadIterator(Iterator iterator) {
     this.iterator = iterator; 
    }
    
    @Override
    public boolean hasNext() {
      return iterator.hasNext();
    }

    @Override
    public Object next() {
      Object object = iterator.next();
      if (object instanceof Struct) {
        Struct struct = (Struct) object;
        Object[] values = struct.getFieldValues();
        Object[] newValues = new Object[values.length];
        int length = values.length;
        for (int i = 0; i < length; i++) {
          newValues[i] = CopyHelper.copy(values[i]);
        }
        return new StructImpl((StructTypeImpl) struct.getStructType(), newValues);
      }
      else {
        return CopyHelper.copy(object);
      }
    }

    @Override
    public void remove() {
      iterator.remove();
    }
  }
  
  
  //All other methods are pass throughs and won't actually be used.
  @Override
  public boolean add(Object e) {
    return results.add(e);
  }



  @Override
  public boolean addAll(Collection c) {
    return results.addAll(c);
  }



  @Override
  public void clear() {
    results.clear();
  }



  @Override
  public boolean contains(Object o) {
    return results.contains(o);
  }



  @Override
  public boolean containsAll(Collection c) {
    return results.containsAll(c);
  }



  @Override
  public boolean isEmpty() {
    return results.isEmpty();
  }

  @Override
  public boolean remove(Object o) {
    return results.remove(o);
  }



  @Override
  public boolean removeAll(Collection c) {
    return results.removeAll(c);
  }



  @Override
  public boolean retainAll(Collection c) {
    return results.retainAll(c);
  }



  @Override
  public int size() {
    return results.size();
  }



  @Override
  public Object[] toArray() {
    return new ArrayList(this).toArray();
  }



  @Override
  public Object[] toArray(Object[] a) {
    return new ArrayList(this).toArray(a);
  }



  @Override
  public boolean isModifiable() {
    return results.isModifiable();
  }



  @Override
  public int occurrences(Object element) {
    return results.occurrences(element);
  }



  @Override
  public Set asSet() {
    return new HashSet(this);
  }



  @Override
  public List asList() {
    return new ArrayList(this);
  }



  @Override
  public CollectionType getCollectionType() {
    return results.getCollectionType();
  }



  @Override
  public void setElementType(ObjectType elementType) {
    results.setElementType(elementType);
  }

}