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.runtime;
  
  import org.apache.calcite.avatica.util.PositionedCursor;
  import org.apache.calcite.linq4j.Enumerator;
  
  /**
   * Implementation of {@link org.apache.calcite.avatica.util.Cursor} on top of an
   * {@link org.apache.calcite.linq4j.Enumerator} that
   * returns a record for each row. The returned record is cached to avoid
   * multiple computations of current row.
   * For instance,
   * {@link org.apache.calcite.adapter.enumerable.EnumerableCalc}
   * computes result just in {@code current()} method, thus it makes sense to
   * cache the result and make it available for all the accessors.
   *
   * @param <T> Element type
   */
  public abstract class EnumeratorCursor<T> extends PositionedCursor<T> {
    private final Enumerator<T> enumerator;
  
    /**
     * Creates an {@code EnumeratorCursor}.
     *
     * @param enumerator input enumerator
     */
    protected EnumeratorCursor(Enumerator<T> enumerator) {
      this.enumerator = enumerator;
    }
  
    @Override protected T current() {
      return enumerator.current();
    }
  
    @Override public boolean next() {
      return enumerator.moveNext();
    }
  
    @Override public void close() {
      enumerator.close();
    }
  }
  