spark CompletionIterator 源码
spark CompletionIterator 代码
文件路径：/core/src/main/scala/org/apache/spark/util/CompletionIterator.scala
/*
* 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.util
/**
* Wrapper around an iterator which calls a completion method after it successfully iterates
* through all the elements.
*/
private[spark]
abstract class CompletionIterator[ +A, +I <: Iterator[A]](sub: I) extends Iterator[A] {
private[this] var completed = false
private[this] var iter = sub
def next(): A = iter.next()
def hasNext: Boolean = {
val r = iter.hasNext
if (!r && !completed) {
completed = true
// reassign to release resources of highly resource consuming iterators early
iter = Iterator.empty.asInstanceOf[I]
completion()
}
r
}
def completion(): Unit
}
private[spark] object CompletionIterator {
def apply[A, I <: Iterator[A]](sub: I, completionFunction: => Unit) : CompletionIterator[A, I] = {
new CompletionIterator[A, I](sub) {
def completion(): Unit = completionFunction
}
}
}
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