content: /*******************************************************************************
   * Copyright (c) 2009, 2019 Mountainminds GmbH & Co. KG and Contributors
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *    Evgeny Mandrikov - initial API and implementation
   *
   *******************************************************************************/
  package org.jacoco.core.internal.analysis.filter;
  
  import org.objectweb.asm.Opcodes;
  import org.objectweb.asm.tree.MethodNode;
  
  /**
   * Filters empty enum constructors.
   *
   * Constructor of enum is invoked from static initialization block to create
   * instance of each enum constant. So it won't be executed if number of enum
   * constants is zero. Such enums are sometimes used as alternative to classes
   * with static utilities and private empty constructor. Implicit constructor of
   * enum created by compiler doesn't have a synthetic flag and refers to a line
   * of enum definition. Therefore in order to not have partial coverage of enum
   * definition line in enums without enum constants and similarly to
   * {@link PrivateEmptyNoArgConstructorFilter filter of private empty
   * constructors} - empty constructor in enums without additional parameters
   * should be filtered out even if it is not implicit.
   */
  public final class EnumEmptyConstructorFilter implements IFilter {
  
  	private static final String CONSTRUCTOR_NAME = "<init>";
  	private static final String CONSTRUCTOR_DESC = "(Ljava/lang/String;I)V";
  
  	private static final String ENUM_TYPE = "java/lang/Enum";
  
  	public void filter(final MethodNode methodNode,
  			final IFilterContext context, final IFilterOutput output) {
  		if (ENUM_TYPE.equals(context.getSuperClassName())
  				&& CONSTRUCTOR_NAME.equals(methodNode.name)
  				&& CONSTRUCTOR_DESC.equals(methodNode.desc)
  				&& new Matcher().match(methodNode)) {
  			output.ignore(methodNode.instructions.getFirst(),
  					methodNode.instructions.getLast());
  		}
  	}
  
  	private static class Matcher extends AbstractMatcher {
  		private boolean match(final MethodNode methodNode) {
  			firstIsALoad0(methodNode);
  			nextIs(Opcodes.ALOAD);
  			nextIs(Opcodes.ILOAD);
  			nextIsInvoke(Opcodes.INVOKESPECIAL, ENUM_TYPE, CONSTRUCTOR_NAME,
  					CONSTRUCTOR_DESC);
  			nextIs(Opcodes.RETURN);
  			return cursor != null;
  		}
  	}
  
  }
  