/*
    * 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
    *
   *   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 org.apache.bcel;
  
  import java.io.ByteArrayInputStream;
  import java.io.IOException;
  import java.util.concurrent.TimeUnit;
  import java.util.jar.JarEntry;
  import java.util.jar.JarFile;
  
  import org.apache.bcel.classfile.ClassParser;
  import org.apache.bcel.classfile.JavaClass;
  import org.apache.bcel.classfile.Method;
  import org.apache.bcel.generic.ClassGen;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.MethodGen;
  import org.apache.commons.collections4.Predicate;
  import org.apache.commons.collections4.iterators.EnumerationIterator;
  import org.apache.commons.collections4.iterators.FilterIterator;
  import org.apache.commons.collections4.iterators.IteratorIterable;
  import org.apache.commons.io.IOUtils;
  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.Threads;
  import org.openjdk.jmh.annotations.Warmup;
  import org.openjdk.jmh.infra.Blackhole;
  
  @BenchmarkMode(Mode.AverageTime)
  @Fork(value = 1, jvmArgs = "-server")
  @Threads(1)
  @Warmup(iterations = 10)
  @Measurement(iterations = 20)
  @OutputTimeUnit(TimeUnit.MILLISECONDS)
  public class BCELBenchmark {
  
      /**
       * Baseline benchmark. Read the classes but don't parse them.
       */
      @Benchmark
      public void baseline(Blackhole bh) throws IOException {
          final JarFile jar = getJarFile();
          for (JarEntry entry : getClasses(jar)) {
              final byte[] bytes = IOUtils.toByteArray(jar.getInputStream(entry));
              bh.consume(bytes);
          }
          jar.close();
      }
  
      @Benchmark
      public void generator(Blackhole bh) throws IOException {
          final JarFile jar = getJarFile();
          for (JarEntry entry : getClasses(jar)) {
              final byte[] bytes = IOUtils.toByteArray(jar.getInputStream(entry));
              final JavaClass clazz = new ClassParser(new ByteArrayInputStream(bytes), entry.getName()).parse();
              final ClassGen cg = new ClassGen(clazz);
              for (Method m : cg.getMethods()) {
                  final MethodGen mg = new MethodGen(m, cg.getClassName(), cg.getConstantPool());
                  final InstructionList il = mg.getInstructionList();
                  if (il != null) {
                      mg.getInstructionList().setPositions();
                      mg.setMaxLocals();
                      mg.setMaxStack();
                  }
                  cg.replaceMethod(m, mg.getMethod());
              }
              bh.consume(cg.getJavaClass().getBytes());
          }
          jar.close();
      }
  
      private Iterable<JarEntry> getClasses(JarFile jar) {
          return new IteratorIterable<>(new FilterIterator<>(new EnumerationIterator<>(jar.entries()), new Predicate<JarEntry>() {
              @Override
              public boolean evaluate(JarEntry entry) {
                  return entry.getName().endsWith(JavaClass.EXTENSION);
              }
          }));
      }
  
     private JarFile getJarFile() throws IOException {
         final String javaHome = System.getProperty("java.home");
         return new JarFile(javaHome + "/lib/rt.jar");
     }
 
     @Benchmark
     public void parser(final Blackhole bh) throws IOException {
         final JarFile jar = getJarFile();
         for (JarEntry entry : getClasses(jar)) {
             final byte[] bytes = IOUtils.toByteArray(jar.getInputStream(entry));
             final JavaClass clazz = new ClassParser(new ByteArrayInputStream(bytes), entry.getName()).parse();
             bh.consume(clazz);
         }
         jar.close();
     }
 }