001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 */
018 package org.apache.bcel.generic;
019
020 import java.io.DataOutputStream;
021 import java.io.IOException;
022
023 /**
024 * GOTO - Branch always (to relative offset, not absolute address)
025 *
026 * @version $Id: GOTO.java 1152072 2011-07-29 01:54:05Z dbrosius $
027 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
028 */
029 public class GOTO extends GotoInstruction implements VariableLengthInstruction {
030
031 private static final long serialVersionUID = 6106731367505145625L;
032
033
034 /**
035 * Empty constructor needed for the Class.newInstance() statement in
036 * Instruction.readInstruction(). Not to be used otherwise.
037 */
038 GOTO() {
039 }
040
041
042 public GOTO(InstructionHandle target) {
043 super(org.apache.bcel.Constants.GOTO, target);
044 }
045
046
047 /**
048 * Dump instruction as byte code to stream out.
049 * @param out Output stream
050 */
051 @Override
052 public void dump( DataOutputStream out ) throws IOException {
053 index = getTargetOffset();
054 if (opcode == org.apache.bcel.Constants.GOTO) {
055 super.dump(out);
056 } else { // GOTO_W
057 index = getTargetOffset();
058 out.writeByte(opcode);
059 out.writeInt(index);
060 }
061 }
062
063
064 /** Called in pass 2 of InstructionList.setPositions() in order to update
065 * the branch target, that may shift due to variable length instructions.
066 */
067 @Override
068 protected int updatePosition( int offset, int max_offset ) {
069 int i = getTargetOffset(); // Depending on old position value
070 position += offset; // Position may be shifted by preceding expansions
071 if (Math.abs(i) >= (32767 - max_offset)) { // to large for short (estimate)
072 opcode = org.apache.bcel.Constants.GOTO_W;
073 short old_length = length;
074 length = 5;
075 return length - old_length;
076 }
077 return 0;
078 }
079
080
081 /**
082 * Call corresponding visitor method(s). The order is:
083 * Call visitor methods of implemented interfaces first, then
084 * call methods according to the class hierarchy in descending order,
085 * i.e., the most specific visitXXX() call comes last.
086 *
087 * @param v Visitor object
088 */
089 @Override
090 public void accept( Visitor v ) {
091 v.visitVariableLengthInstruction(this);
092 v.visitUnconditionalBranch(this);
093 v.visitBranchInstruction(this);
094 v.visitGotoInstruction(this);
095 v.visitGOTO(this);
096 }
097 }