org.basinmc.plunger.mapping.mcp.VariableTableConstructionBytecodeTransformer Maven / Gradle / Ivy

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/*
 * Copyright 2018 Johannes Donath 
 * and other copyright owners as documented in the project's IP log.
 *
 * Licensed 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.basinmc.plunger.mapping.mcp;

import edu.umd.cs.findbugs.annotations.NonNull;
import java.nio.file.Path;
import java.util.Optional;
import org.basinmc.plunger.bytecode.transformer.BytecodeTransformer;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

/**
 * Replaces the variable table with comprehensive names (e.g. numbers them based on  their index).
 *
 * @author Johannes Donath
 */
public class VariableTableConstructionBytecodeTransformer implements BytecodeTransformer {

  /**
   * {@inheritDoc}
   */
  @Override
  public Optional createTransformer(@NonNull Context context, @NonNull Path source,
      @NonNull ClassVisitor nextVisitor) {
    return Optional.of(new VariableTableConstructionClassVisitor(nextVisitor));
  }

  private static class VariableTableConstructionClassVisitor extends ClassVisitor {

    private VariableTableConstructionClassVisitor(ClassVisitor classVisitor) {
      super(Opcodes.ASM6, classVisitor);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public MethodVisitor visitMethod(int access, String name, String descriptor, String signature,
        String[] exceptions) {
      MethodVisitor visitor = super.visitMethod(access, name, descriptor, signature, exceptions);

      if (visitor == null) {
        return null;
      }

      return new VariableTableConstructionMethodVisitor(visitor);
    }
  }

  private static final class VariableTableConstructionMethodVisitor extends MethodVisitor {

    private VariableTableConstructionMethodVisitor(@NonNull MethodVisitor methodVisitor) {
      super(Opcodes.ASM6, methodVisitor);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void visitLocalVariable(String name, String descriptor, String signature, Label start,
        Label end, int index) {
      if (name.charAt(0) == '☃') {
        name = "var" + index;
      }

      super.visitLocalVariable(name, descriptor, signature, start, end, index);
    }
  }
}