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From: rxin <git@git.apache.org>
To: reviews@spark.apache.org
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Subject: [GitHub] spark pull request: [SPARK-6578] [core] Fix thread-safety
 issue in...
Content-Type: text/plain
Message-Id: <20150401224549.3B51FE10A2@git1-us-west.apache.org>
Date: Wed,  1 Apr 2015 22:45:49 +0000 (UTC)

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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