content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * 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
   *
   * 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 org.apache.calcite.avatica.util;
  
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  /**
   * Implementation of {@link org.apache.calcite.avatica.util.Cursor}
   * on top of an {@link Iterator} that
   * returns a record for each row. The returned record is cached to avoid
   * multiple computations of current row.
   *
   * @param <E> Element type
   */
  public abstract class IteratorCursor<E> extends PositionedCursor<E> {
    private Position position = Position.BEFORE_START;
    private final Iterator<E> iterator;
    private E current = null;
  
    /**
     * Creates an {@code IteratorCursor}.
     *
     * @param iterator input iterator
     */
    protected IteratorCursor(Iterator<E> iterator) {
      this.iterator = iterator;
    }
  
    public boolean next() {
      if (iterator.hasNext()) {
        current = iterator.next();
        position = Position.OK;
        return true;
      }
      current = null;
      position = Position.AFTER_END;
      return false;
    }
  
    public void close() {
      current = null;
      position = Position.CLOSED;
      if (iterator instanceof AutoCloseable) {
        try {
          ((AutoCloseable) iterator).close();
        } catch (RuntimeException e) {
          throw e;
        } catch (Exception e) {
          throw new RuntimeException(e);
        }
      }
    }
  
    protected E current() {
      if (position != Position.OK) {
        throw new NoSuchElementException("Expecting cursor position to be Position." + Position.OK
                + ", actual is Position." + position);
      }
      return current;
    }
  
    /** Are we positioned on a valid row? */
    private enum Position {
      CLOSED,
      BEFORE_START,
      OK,
      AFTER_END
    }
  }
  
  // End IteratorCursor.java
  