Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/5234#discussion_r27619485
--- Diff:
network/common/src/main/java/org/apache/spark/network/protocol/MessageWithHeader.java
---
@@ -0,0 +1,106 @@
+/*
+ * 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.protocol;
+
+import java.io.IOException;
+import java.nio.channels.WritableByteChannel;
+
+import com.google.common.base.Preconditions;
+import com.google.common.primitives.Ints;
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.FileRegion;
+import io.netty.util.AbstractReferenceCounted;
+import io.netty.util.ReferenceCountUtil;
+
+/**
+ * A wrapper message that holds two separate pieces (a header and a body)
to avoid
+ * copying the body's content.
+ */
+class MessageWithHeader extends AbstractReferenceCounted implements
FileRegion {
+
+ private final ByteBuf header;
+ private final int headerLength;
+ private final Object body;
+ private final long bodyLength;
+ private long totalBytesTransferred;
+
+ MessageWithHeader(ByteBuf header, Object body, long bodyLength) {
+ Preconditions.checkArgument(body instanceof ByteBuf || body instanceof
FileRegion,
+ "Body must be a ByteBuf or a FileRegion.");
+ this.header = header;
+ this.headerLength = header.readableBytes();
+ this.body = body;
+ this.bodyLength = bodyLength;
+ }
+
+ @Override
+ public long count() {
+ return headerLength + bodyLength;
+ }
+
+ @Override
+ public long position() {
+ return 0;
+ }
+
+ @Override
+ public long transfered() {
+ return totalBytesTransferred;
+ }
+
+ @Override
+ public long transferTo(WritableByteChannel target, long position) throws
IOException {
+ Preconditions.checkArgument(position == totalBytesTransferred,
"Invalid position.");
+ long written = 0;
+
+ if (position < headerLength) {
+ written += copyByteBuf(header, target);
+ if (header.readableBytes() > 0) {
+ totalBytesTransferred += written;
+ return written;
+ }
+ }
+
+ if (body instanceof FileRegion) {
+ // Adjust the position. If the write is happening as part of the
same call where the header
+ // (or some part of it) is written, `position` will be less than the
header size, so we want
+ // to start from position 0 in the FileRegion object. Otherwise, we
start from the position
+ // requested by the caller.
+ long bodyPos = position > headerLength ? position - headerLength : 0;
+ written += ((FileRegion)body).transferTo(target, bodyPos);
+ } else if (body instanceof ByteBuf) {
+ written += copyByteBuf((ByteBuf) body, target);
+ }
+
+ totalBytesTransferred += written;
+ return written;
+ }
+
+ @Override
+ protected void deallocate() {
+ header.release();
+ ReferenceCountUtil.release(body);
+ }
+
+ private int copyByteBuf(ByteBuf buf, WritableByteChannel target) throws
IOException {
+ int written = target.write(buf.nioBuffer());
--- End diff --
ah nvm i thougth this was a ManagedBuffer
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