| /* |
| * 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 |