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 com.aliyun.odps.data;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.io.UncheckedIOException;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  import java.util.stream.Stream;
  import java.util.stream.StreamSupport;
  
  /**
   * <code>RecordReader</code>用来读取记录
   */
  public interface RecordReader extends Closeable, Iterable<Record> {
  
    /**
     * 读取一条记录
     *
     * @return 成功读到记录返回{@link Record}对象, 读取完成返回null
     * @throws IOException
     *     读取过程发生异常, 发生异常后不可重试
     */
    public Record read() throws IOException;
  
    /**
     * 提供一个迭代器来遍历所有的记录。
     * <p>
     * 默认实现会创建一个匿名的 {@link Iterator} 对象，
     * 该对象的 {@code hasNext} 和 {@code next} 方法依赖于 {@code read} 方法。
     *
     * @return 一个新的 {@link Iterator} 对象，用于遍历记录。
     */
    @Override
    default Iterator<Record> iterator() {
      return new Iterator<Record>() {
        private Record nextRecord;
  
        {
          // 初始化时尝试读取第一条记录。
          try {
            nextRecord = read();
          } catch (IOException e) {
            throw new UncheckedIOException(e);
          }
        }
  
        @Override
        public boolean hasNext() {
          // 如果 nextRecord 不为 null，则表示还有更多记录。
          return nextRecord != null;
        }
  
        @Override
        public Record next() {
          if (!hasNext()) {
            throw new NoSuchElementException();
          }
          Record current = nextRecord;
          // 在返回当前记录的同时，尝试读取下一条记录。
          try {
            nextRecord = read();
          } catch (IOException e) {
            throw new UncheckedIOException(e);
          }
          return current;
        }
      };
    }
  
    default Stream<Record> stream() {
      return StreamSupport.stream(spliterator(), false);
    }
  }
  