001/*
002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved.
003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
004 *
005 * Project and contact information: http://www.cascading.org/
006 *
007 * This file is part of the Cascading project.
008 *
009 * Licensed under the Apache License, Version 2.0 (the "License");
010 * you may not use this file except in compliance with the License.
011 * You may obtain a copy of the License at
012 *
013 *     http://www.apache.org/licenses/LICENSE-2.0
014 *
015 * Unless required by applicable law or agreed to in writing, software
016 * distributed under the License is distributed on an "AS IS" BASIS,
017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
018 * See the License for the specific language governing permissions and
019 * limitations under the License.
020 */
021
022package cascading.tuple;
023
024import java.io.Closeable;
025import java.io.IOException;
026import java.util.Iterator;
027
028/**
029 * TupleEntryChainIterator chains the given Iterators into a single Iterator.
030 * <p>
031 * As one iterator is completed, it will be closed and a new one will start.
032 */
033public class TupleEntryChainIterator extends TupleEntryIterator
034  {
035  /** Field iterator */
036  Iterator<Tuple>[] iterators;
037  int currentIterator = 0;
038
039  public TupleEntryChainIterator( Fields fields )
040    {
041    super( fields );
042    this.iterators = new Iterator[ 1 ];
043    }
044
045  public TupleEntryChainIterator( Fields fields, Iterator<Tuple> iterator )
046    {
047    this( fields );
048    this.iterators[ 0 ] = iterator;
049    }
050
051  public TupleEntryChainIterator( Fields fields, Iterator<Tuple>[] iterators )
052    {
053    super( fields );
054    this.iterators = iterators;
055    }
056
057  /**
058   * Method hasNext returns true if there is a next TupleEntry
059   *
060   * @return boolean
061   */
062  public boolean hasNext()
063    {
064    if( iterators.length < currentIterator + 1 ) // past the end
065      return false;
066
067    if( iterators[ currentIterator ].hasNext() )
068      return true;
069
070    closeCurrent();
071
072    currentIterator++;
073
074    return iterators.length != currentIterator && hasNext();
075    }
076
077  public void reset( Iterator<Tuple> iterator )
078    {
079    this.currentIterator = 0;
080    this.iterators[ 0 ] = iterator;
081    }
082
083  public void reset( Iterator<Tuple>[] iterators )
084    {
085    this.currentIterator = 0;
086    this.iterators = iterators;
087    }
088
089  /**
090   * Method next returns the next TupleEntry.
091   *
092   * @return TupleEntry
093   */
094  public TupleEntry next()
095    {
096    hasNext(); // force roll to next iterator
097
098    entry.setTuple( iterators[ currentIterator ].next() );
099
100    return entry;
101    }
102
103  /** Method remove removes the current TupleEntry from the underlying collection. */
104  public void remove()
105    {
106    iterators[ currentIterator ].remove();
107    }
108
109  /** Method close closes all underlying resources. */
110  public void close()
111    {
112    if( iterators.length != currentIterator )
113      closeCurrent();
114    }
115
116  protected void closeCurrent()
117    {
118    close( iterators[ currentIterator ] );
119    }
120
121  private void close( Iterator iterator )
122    {
123    if( iterator instanceof Closeable )
124      {
125      try
126        {
127        ( (Closeable) iterator ).close();
128        }
129      catch( IOException exception )
130        {
131        // ignore
132        }
133      }
134    }
135  }