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   /*
    * Copyright 2018 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.buffer;
  
  import org.openjdk.jmh.annotations.Benchmark;
  import org.openjdk.jmh.annotations.Measurement;
  import org.openjdk.jmh.annotations.Param;
  import org.openjdk.jmh.annotations.Setup;
  import org.openjdk.jmh.annotations.TearDown;
  import org.openjdk.jmh.annotations.Warmup;
  
  import io.netty.microbench.util.AbstractMicrobenchmark;
  
  import static io.netty.buffer.Unpooled.wrappedBuffer;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  
  @Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
  @Measurement(iterations = 12, time = 1, timeUnit = TimeUnit.SECONDS)
  public class CompositeByteBufWriteOutBenchmark extends AbstractMicrobenchmark {
  
      public enum ByteBufType {
          SMALL_CHUNKS {
              @Override
              ByteBuf[] sourceBuffers(int length) {
                  return makeSmallChunks(length);
              }
          },
          LARGE_CHUNKS {
              @Override
              ByteBuf[] sourceBuffers(int length) {
                  return makeLargeChunks(length);
              }
          };
          abstract ByteBuf[] sourceBuffers(int length);
      }
  
      @Override
      protected String[] jvmArgs() {
          // Ensure we minimize the GC overhead by sizing the heap big enough.
          return new String[] { "-XX:MaxDirectMemorySize=2g", "-Xmx4g", "-Xms4g", "-Xmn3g" };
      }
  
      @Param({ "64", "1024", "10240", "102400", "1024000" })
      public int size;
  
      @Param
      public ByteBufType bufferType;
  
      private ByteBuf targetBuffer;
  
      private ByteBuf[] sourceBufs;
  
      @Setup
      public void setup() {
          targetBuffer = PooledByteBufAllocator.DEFAULT.directBuffer(size + 2048);
          sourceBufs = bufferType.sourceBuffers(size);
      }
  
      @TearDown
      public void teardown() {
          targetBuffer.release();
      }
  
      @Benchmark
      public int writeCBB() {
          ByteBuf cbb = Unpooled.wrappedBuffer(Integer.MAX_VALUE, sourceBufs); // CompositeByteBuf
          return targetBuffer.clear().writeBytes(cbb).readableBytes();
      }
  
      @Benchmark
      public int writeFCBB() {
          ByteBuf cbb = Unpooled.wrappedUnmodifiableBuffer(sourceBufs); // FastCompositeByteBuf
          return targetBuffer.clear().writeBytes(cbb).readableBytes();
      }
  
      private static ByteBuf[] makeSmallChunks(int length) {
  
          List<ByteBuf> buffers = new ArrayList<ByteBuf>(((length + 1) / 48) * 9);
          for (int i = 0; i < length + 48; i += 48) {
              for (int j = 4; j <= 12; j++) {
                  buffers.add(wrappedBuffer(new byte[j]));
              }
          }
 
         return buffers.toArray(new ByteBuf[0]);
     }
 
     private static ByteBuf[] makeLargeChunks(int length) {
 
         List<ByteBuf> buffers = new ArrayList<ByteBuf>((length + 1) / 768);
         for (int i = 0; i < length + 1536; i += 1536) {
             buffers.add(wrappedBuffer(new byte[512]));
             buffers.add(wrappedBuffer(new byte[1024]));
         }
 
         return buffers.toArray(new ByteBuf[0]);
     }
 }