[GitHub] spark pull request #21440: [SPARK-24307][CORE] Support reading remote cached...

[vanzin <gi...@git.apache.org>]

Github user vanzin commented on a diff in the pull request:

    https://github.com/apache/spark/pull/21440#discussion_r198636259
  
    --- Diff: core/src/main/scala/org/apache/spark/util/io/ChunkedByteBufferFileRegion.scala ---
    @@ -0,0 +1,103 @@
    +/*
    + * 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.io
    +
    +import java.nio.channels.WritableByteChannel
    +
    +import io.netty.channel.FileRegion
    +import io.netty.util.AbstractReferenceCounted
    +
    +import org.apache.spark.internal.Logging
    +
    +
    +/**
    + * This exposes a ChunkedByteBuffer as a netty FileRegion, just to allow sending > 2gb in one netty
    + * message.   This is because netty cannot send a ByteBuf > 2g, but it can send a large FileRegion,
    + * even though the data is not backed by a file.
    + */
    +private[io] class ChunkedByteBufferFileRegion(
    +    val chunkedByteBuffer: ChunkedByteBuffer,
    +    val ioChunkSize: Int) extends AbstractReferenceCounted with FileRegion with Logging {
    +
    +  private var _transferred: Long = 0
    +  // this duplicates the original chunks, so we're free to modify the position, limit, etc.
    +  private val chunks = chunkedByteBuffer.getChunks()
    +  private val cumLength = chunks.scanLeft(0L) { _ + _.remaining()}
    --- End diff --
    
    Use `foldLeft(0) { blah }` + avoid the intermediate `val`?


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