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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