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.spark.sql.execution;
  
  import java.io.IOException;
  import java.util.LinkedList;
  
  import scala.collection.Iterator;
  
  import org.apache.spark.TaskContext;
  import org.apache.spark.sql.catalyst.InternalRow;
  import org.apache.spark.sql.catalyst.expressions.UnsafeRow;
  
  /**
   * An iterator interface used to pull the output from generated function for multiple operators
   * (whole stage codegen).
   */
  public abstract class BufferedRowIterator {
    protected LinkedList<InternalRow> currentRows = new LinkedList<>();
    // used when there is no column in output
    protected UnsafeRow unsafeRow = new UnsafeRow(0);
    private long startTimeNs = System.nanoTime();
  
    protected int partitionIndex = -1;
  
    public boolean hasNext() throws IOException {
      if (currentRows.isEmpty()) {
        processNext();
      }
      return !currentRows.isEmpty();
    }
  
    public InternalRow next() {
      return currentRows.remove();
    }
  
    /**
     * Returns the elapsed time since this object is created. This object represents a pipeline so
     * this is a measure of how long the pipeline has been running.
     */
    public long durationMs() {
      return (System.nanoTime() - startTimeNs) / (1000 * 1000);
    }
  
    /**
     * Initializes from array of iterators of InternalRow.
     */
    public abstract void init(int index, Iterator<InternalRow>[] iters);
  
    /**
     * Append a row to currentRows.
     */
    protected void append(InternalRow row) {
      currentRows.add(row);
    }
  
    /**
     * Returns whether `processNext()` should stop processing next row from `input` or not.
     *
     * If it returns true, the caller should exit the loop (return from processNext()).
     */
    protected boolean shouldStop() {
      return !currentRows.isEmpty();
    }
  
    /**
     * Increase the peak execution memory for current task.
     */
    protected void incPeakExecutionMemory(long size) {
      TaskContext.get().taskMetrics().incPeakExecutionMemory(size);
    }
  
    /**
     * Processes the input until have a row as output (currentRow).
     *
     * After it's called, if currentRow is still null, it means no more rows left.
     */
    protected abstract void processNext() throws IOException;
  }
  