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   * 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.
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  package org.apache.cassandra.test.microbench;
  
  import com.google.common.hash.Hasher;
  import com.google.common.hash.Hashing;
  import com.google.common.primitives.Longs;
  import org.apache.cassandra.utils.ChecksumType;
  import org.openjdk.jmh.annotations.Benchmark;
  import org.openjdk.jmh.annotations.BenchmarkMode;
  import org.openjdk.jmh.annotations.Fork;
  import org.openjdk.jmh.annotations.Measurement;
  import org.openjdk.jmh.annotations.Mode;
  import org.openjdk.jmh.annotations.OutputTimeUnit;
  import org.openjdk.jmh.annotations.Param;
  import org.openjdk.jmh.annotations.Scope;
  import org.openjdk.jmh.annotations.Setup;
  import org.openjdk.jmh.annotations.State;
  import org.openjdk.jmh.annotations.Threads;
  import org.openjdk.jmh.annotations.Warmup;
  import org.xerial.snappy.PureJavaCrc32C;
  
  import java.security.NoSuchAlgorithmException;
  import java.util.Random;
  import java.util.concurrent.TimeUnit;
  
  @BenchmarkMode(Mode.AverageTime)
  @OutputTimeUnit(TimeUnit.NANOSECONDS)
  @Warmup(iterations = 3, time = 1, timeUnit = TimeUnit.SECONDS)
  @Measurement(iterations = 5, time = 2, timeUnit = TimeUnit.SECONDS)
  @Threads(4) // make sure this matches the number of _physical_cores_
  @State(Scope.Benchmark)
  public class ChecksumBench
  {
      private static final Random random = new Random(12345678);
  
      // intentionally not on power-of-2 values
      @Param({ "31", "131", "517", "2041" })
      private int bufferSize;
  
      private byte[] array;
  
      @Setup
      public void setup() throws NoSuchAlgorithmException
      {
          array = new byte[bufferSize];
          random.nextBytes(array);
      }
  
      @Benchmark
      @Fork(value = 1, jvmArgsAppend = { "-Xmx512M", "-Djmh.executor=CUSTOM",
              "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor",
      })
      public byte[] benchCrc32()
      {
          return Longs.toByteArray(ChecksumType.CRC32.of(array, 0, array.length));
      }
  
      @Benchmark
      @Fork(value = 1, jvmArgsAppend = { "-Xmx512M", "-Djmh.executor=CUSTOM",
              "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor",
              "-XX:+UnlockDiagnosticVMOptions", "-XX:-UseCRC32Intrinsics",
      })
      public byte[] benchCrc32NoIntrinsic()
      {
          return Longs.toByteArray(ChecksumType.CRC32.of(array, 0, array.length));
      }
  
      @Benchmark
      @Fork(value = 1, jvmArgsAppend = { "-Xmx512M", "-Djmh.executor=CUSTOM",
              "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor",
      })
      public byte[] benchHasherCrc32c()
      {
          Hasher crc32cHasher = Hashing.crc32c().newHasher();
          crc32cHasher.putBytes(array);
          return crc32cHasher.hash().asBytes();
      }
  
      @Benchmark
      @Fork(value = 1, jvmArgsAppend = { "-Xmx512M", "-Djmh.executor=CUSTOM",
              "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor",
      })
      public byte[] benchPureJavaCrc32c()
      {
          PureJavaCrc32C pureJavaCrc32C = new PureJavaCrc32C();
          pureJavaCrc32C.update(array, 0, array.length);
          return Longs.toByteArray(pureJavaCrc32C.getValue());
      }
  
      // Below benchmarks are commented because CRC32C is unavailable in Java 8.
  //    @Benchmark
  //    @Fork(value = 1, jvmArgsAppend = { "-Xmx512M", "-Djmh.executor=CUSTOM",
  //            "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor",
  //    })
  //    public byte[] benchCrc32c()
  //    {
  //        CRC32C crc32C = new CRC32C();
  //        crc32C.update(array);
  //        return Longs.toByteArray(crc32C.getValue());
  //    }
  //
  //    @Benchmark
  //    @Fork(value = 1, jvmArgsAppend = { "-Xmx512M", "-Djmh.executor=CUSTOM",
  //            "-Djmh.executor.class=org.apache.cassandra.test.microbench.FastThreadExecutor",
  //            "-XX:+UnlockDiagnosticVMOptions", "-XX:-UseCRC32CIntrinsics",
  //    })
  //    public byte[] benchCrc32cNoIntrinsic()
  //    {
  //        CRC32C crc32C = new CRC32C();
  //        crc32C.update(array);
  //        return Longs.toByteArray(crc32C.getValue());
  //    }
  }
  