MyBenchmark.java

/*
 * Copyright (c) 2014, Oracle America, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 *  * Neither the name of Oracle nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.sample;

import java.nio.ByteBuffer;
import org.openjdk.jmh.annotations.Benchmark;

public class MyBenchmark {
    private static short getShortFromArray(final byte[] b, final int offset) {
      return (short) ((b[offset + 1] & 0xFF) | (b[offset] << 8));
    }
    private static int getIntFromArray(final byte[] b, final int offset) {
      return (b[offset + 0] & 0xFF) << 24 |
          (b[offset + 1] & 0xFF) << 16 |
          (b[offset + 2] & 0xFF) << 8 |
          (b[offset + 3] & 0xFF) << 0;
    }

    /**
     * Original implementation as used by FlatBuffers
     */
    private static class FileDesc {
      private final ByteBuffer bb;
      int bbPos;

      FileDesc(ByteBuffer bb) {
        bbPos = bb.getShort(bb.position()) + bb.position();
        this.bb = bb;
      }

      public int getVal() {
        return bb.getInt(bbPos);
      }
    }

    /**
     * Direct implementation using a byte[]
     */
    private static class FileDesc2 {
      private final byte[] bb;
      int bbPos;

      FileDesc2(byte[] bb) {
        bbPos = getShortFromArray(bb, 0);
        this.bb = bb;
      }

      public int getVal() {
        return getIntFromArray(bb, bbPos);
      }
    }

    /**
     * Implementation using a DataAccessor to wrap either a ByteBuffer
     * or a ByteArray.
     *
     * Unfortunately, it seems like escape analysis is not able to
     * do scalar replacement of this class :(
     */
    private static class FileDesc3 {
      private final DataAccessor bb;
      int bbPos;

      FileDesc3(DataAccessor bb) {
        bbPos = bb.getShort(bb.position()) + bb.position();
        this.bb = bb;
      }

      public int getVal() {
        return bb.getInt(bbPos);
      }
    }

    private interface DataAccessor {
      int position();
      int getInt(int pos);
      short getShort(int pos);
    }
    private static class ByteArrayAccessor implements DataAccessor {
      private byte[] b;
      public ByteArrayAccessor(byte[] b) {
        this.b = b;
      }
      public ByteArrayAccessor() {}
      public int position() { return 0; }
      public short getShort(int pos) {
        return getShortFromArray(b, pos);
      }
      public int getInt(int pos) {
        return getIntFromArray(b, pos);
      }

    }

    static final byte[] foo = new byte[]{0, 4,3,4,5,6,7,8,9};

    @Benchmark
    public int testWithByteBuffer() {
      return new FileDesc(ByteBuffer.wrap(foo)).getVal();
    }

    @Benchmark
    public int testWithBytes() {
      return new FileDesc2(foo).getVal();
    }

    @Benchmark
    public int testWithBytesWrappedInAccessor() {
      return new FileDesc3(new ByteArrayAccessor(foo)).getVal();
    }

    private static ThreadLocal<ByteArrayAccessor> tlAccessor =
      ThreadLocal.withInitial(() -> new ByteArrayAccessor());

    @Benchmark
    public int testWithBytesWrappedInThreadLocalAccessor() {
      ByteArrayAccessor acc = tlAccessor.get();
      acc.b = foo;
      return new FileDesc3(acc).getVal();
    }
}