Github user jerryshao commented on a diff in the pull request: https://github.com/apache/spark/pull/21440#discussion_r203251175 --- Diff: core/src/main/scala/org/apache/spark/util/io/ChunkedByteBufferFileRegion.scala --- @@ -0,0 +1,86 @@ +/* + * 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 +import org.apache.spark.network.util.AbstractFileRegion + + +/** + * 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( + private val chunkedByteBuffer: ChunkedByteBuffer, + private val ioChunkSize: Int) extends AbstractFileRegion { + + 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 size = chunks.foldLeft(0L) { _ + _.remaining() } + + protected def deallocate: Unit = {} + + override def count(): Long = size + + // this is the "start position" of the overall Data in the backing file, not our current position + override def position(): Long = 0 + + override def transferred(): Long = _transferred + + private var currentChunkIdx = 0 + + def transferTo(target: WritableByteChannel, position: Long): Long = { + assert(position == _transferred) + if (position == size) return 0L + var keepGoing = true + var written = 0L + var currentChunk = chunks(currentChunkIdx) + while (keepGoing) { + while (currentChunk.hasRemaining && keepGoing) { + val ioSize = Math.min(currentChunk.remaining(), ioChunkSize) + val originalLimit = currentChunk.limit() + currentChunk.limit(currentChunk.position() + ioSize) + val thisWriteSize = target.write(currentChunk) + currentChunk.limit(originalLimit) + written += thisWriteSize + if (thisWriteSize < ioSize) { --- End diff -- I see, thanks for explain.
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