Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/5400#discussion_r31356558
--- Diff:
network/common/src/main/java/org/apache/spark/network/buffer/WrappedLargeByteBuffer.java
---
@@ -0,0 +1,269 @@
+/*
+* 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.network.buffer;
+
+import com.google.common.annotations.VisibleForTesting;
+import sun.nio.ch.DirectBuffer;
+
+import java.io.IOException;
+import java.nio.BufferUnderflowException;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.WritableByteChannel;
+import java.util.Arrays;
+import java.util.List;
+
+public class WrappedLargeByteBuffer implements LargeByteBuffer {
+
+ @VisibleForTesting
+ public final ByteBuffer[] underlying;
+
+ private final long size;
+ /**
+ * each sub-ByteBuffer (except for the last one) must be exactly this
size. Note that this
+ * class *really* expects this to be LargeByteBufferHelper.MAX_CHUNK.
The only reason it isn't
+ * is so that we can do tests without creating ginormous buffers.
Public methods force it to
+ * be LargeByteBufferHelper.MAX_CHUNK
+ */
+ private final int subBufferSize;
+ private long _pos;
+ @VisibleForTesting
+ int currentBufferIdx;
+ @VisibleForTesting
+ ByteBuffer currentBuffer;
+
+
+ public WrappedLargeByteBuffer(ByteBuffer[] underlying) {
+ this(underlying, LargeByteBufferHelper.MAX_CHUNK);
+ }
+
+ /**
+ * you do **not** want to call this version. It leads to a buffer which
doesn't properly
+ * support {@link #asByteBuffer}. The only reason it exists is to we
can have tests which
+ * don't require 2GB of memory
+ *
+ * @param underlying
+ * @param subBufferSize
+ */
+ @VisibleForTesting
+ WrappedLargeByteBuffer(ByteBuffer[] underlying, int subBufferSize) {
+ if (underlying.length == 0) {
+ throw new IllegalArgumentException("must wrap at least one
ByteBuffer");
+ }
+ this.underlying = underlying;
+ this.subBufferSize = subBufferSize;
+ long sum = 0L;
+ boolean startFound = false;
+ long initialPosition = -1;
+ for (int i = 0; i < underlying.length; i++) {
+ ByteBuffer b = underlying[i];
+ if (i != underlying.length -1 && b.capacity() != subBufferSize) {
+ throw new IllegalArgumentException("All buffers, except for the
final one, must have " +
+ "size = " + subBufferSize);
+ }
+ if (startFound) {
+ if (b.position() != 0) {
+ throw new IllegalArgumentException("ByteBuffers have
inconsistent positions");
+ }
+ } else if (b.position() != b.capacity()) {
+ startFound = true;
+ initialPosition = sum + b.position();
+ }
+ sum += b.capacity();
+ }
+ _pos = initialPosition;
+ currentBufferIdx = 0;
+ currentBuffer = underlying[0];
+ size = sum;
+ }
+
+ @Override
+ public void get(byte[] dest, int offset, int length) {
+ if (length > remaining()) {
+ throw new BufferUnderflowException();
+ }
+ int moved = 0;
+ while (moved < length) {
+ int toRead = Math.min(length - moved, currentBuffer.remaining());
+ currentBuffer.get(dest, offset + moved, toRead);
+ moved += toRead;
+ updateCurrentBuffer();
+ }
+ _pos += moved;
+ }
+
+ @Override
+ public LargeByteBuffer rewind() {
+ if (currentBuffer != null) {
+ currentBuffer.rewind();
+ }
+ while (currentBufferIdx > 0) {
+ currentBufferIdx -= 1;
+ currentBuffer = underlying[currentBufferIdx];
+ currentBuffer.rewind();
+ }
+ _pos = 0;
+ return this;
+ }
+
+ @Override
+ public WrappedLargeByteBuffer deepCopy() {
+ ByteBuffer[] dataCopy = new ByteBuffer[underlying.length];
+ for (int i = 0; i < underlying.length; i++) {
+ ByteBuffer b = underlying[i];
+ dataCopy[i] = ByteBuffer.allocate(b.capacity());
+ int originalPosition = b.position();
+ b.rewind();
+ dataCopy[i].put(b);
+ dataCopy[i].position(0);
+ b.position(originalPosition);
+ }
+ return new WrappedLargeByteBuffer(dataCopy, subBufferSize);
+ }
+
+ @Override
+ public byte get() {
+ byte r = currentBuffer.get();
+ _pos += 1;
+ updateCurrentBuffer();
+ return r;
+ }
+
+ private void updateCurrentBuffer() {
--- End diff --
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