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 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
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 * 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
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package org.apache.lucene.queries.intervals;

import java.io.IOException;

import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.search.TwoPhaseIterator;

A DocIdSetIterator that also allows iteration over matching intervals in a document. Once the iterator is positioned on a document by calling DocIdSetIterator.advance(int) or DocIdSetIterator.nextDoc(), intervals may be retrieved by calling nextInterval() until NO_MORE_INTERVALS is returned. The limits of the current interval are returned by start() and end(). When the iterator has been moved to a new document, but before nextInterval() has been called, both these methods return -1. Note that it is possible for a document to return NO_MORE_INTERVALS on the first call to nextInterval() /**
 * A {@link DocIdSetIterator} that also allows iteration over matching
 * intervals in a document.
 *
 * Once the iterator is positioned on a document by calling {@link #advance(int)}
 * or {@link #nextDoc()}, intervals may be retrieved by calling {@link #nextInterval()}
 * until {@link #NO_MORE_INTERVALS} is returned.
 *
 * The limits of the current interval are returned by {@link #start()} and {@link #end()}.
 * When the iterator has been moved to a new document, but before {@link #nextInterval()}
 * has been called, both these methods return {@code -1}.
 *
 * Note that it is possible for a document to return {@link #NO_MORE_INTERVALS}
 * on the first call to {@link #nextInterval()}
 */
public abstract class IntervalIterator extends DocIdSetIterator {

  
When returned from nextInterval(), indicates that there are no more matching intervals on the current document /**
   * When returned from {@link #nextInterval()}, indicates that there are no more
   * matching intervals on the current document
   */
  public static final int NO_MORE_INTERVALS = Integer.MAX_VALUE;

  
The start of the current interval Returns -1 if nextInterval() has not yet been called and NO_MORE_INTERVALS once the iterator is exhausted. /**
   * The start of the current interval
   *
   * Returns -1 if {@link #nextInterval()} has not yet been called and {@link #NO_MORE_INTERVALS}
   * once the iterator is exhausted.
   */
  public abstract int start();

  
The end of the current interval Returns -1 if nextInterval() has not yet been called and NO_MORE_INTERVALS once the iterator is exhausted. /**
   * The end of the current interval
   *
   * Returns -1 if {@link #nextInterval()} has not yet been called and {@link #NO_MORE_INTERVALS}
   * once the iterator is exhausted.
   */
  public abstract int end();

  
The number of gaps within the current interval Note that this returns the number of gaps between the immediate sub-intervals of this interval, and does not include the gaps inside those sub-intervals. Should not be called before nextInterval(), or after it has returned NO_MORE_INTERVALS /**
   * The number of gaps within the current interval
   *
   * Note that this returns the number of gaps between the immediate sub-intervals
   * of this interval, and does not include the gaps inside those sub-intervals.
   *
   * Should not be called before {@link #nextInterval()}, or after it has returned
   * {@link #NO_MORE_INTERVALS}
   */
  public abstract int gaps();

  
The width of the current interval
/**
   * The width of the current interval
   */
  public int width() {
    return end() - start() + 1;
  }

  
Advance the iterator to the next interval
Returns:
the start of the next interval, or NO_MORE_INTERVALS if there are no more intervals on the current document/**
   * Advance the iterator to the next interval
   *
   * @return the start of the next interval, or {@link IntervalIterator#NO_MORE_INTERVALS} if
   *         there are no more intervals on the current document
   */
  public abstract int nextInterval() throws IOException;

  
An indication of the average cost of iterating over all intervals in a document
See Also:
matchCost.matchCost()/**
   * An indication of the average cost of iterating over all intervals in a document
   *
   * @see TwoPhaseIterator#matchCost()
   */
  public abstract float matchCost();

  @Override
  public String toString() {
    return docID() + ":[" + start() + "->" + end() + "]";
  }

}