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 */ 018package org.apache.bcel.generic; 019 020import java.io.DataOutputStream; 021import java.io.IOException; 022 023/** 024 * GOTO - Branch always (to relative offset, not absolute address) 025 * 026 */ 027public class GOTO extends GotoInstruction implements VariableLengthInstruction { 028 029 /** 030 * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise. 031 */ 032 GOTO() { 033 } 034 035 public GOTO(final InstructionHandle target) { 036 super(org.apache.bcel.Const.GOTO, target); 037 } 038 039 /** 040 * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call 041 * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last. 042 * 043 * @param v Visitor object 044 */ 045 @Override 046 public void accept(final Visitor v) { 047 v.visitVariableLengthInstruction(this); 048 v.visitUnconditionalBranch(this); 049 v.visitBranchInstruction(this); 050 v.visitGotoInstruction(this); 051 v.visitGOTO(this); 052 } 053 054 /** 055 * Dump instruction as byte code to stream out. 056 * 057 * @param out Output stream 058 */ 059 @Override 060 public void dump(final DataOutputStream out) throws IOException { 061 super.setIndex(getTargetOffset()); 062 final short opcode = getOpcode(); 063 if (opcode == org.apache.bcel.Const.GOTO) { 064 super.dump(out); 065 } else { // GOTO_W 066 super.setIndex(getTargetOffset()); 067 out.writeByte(opcode); 068 out.writeInt(super.getIndex()); 069 } 070 } 071 072 /** 073 * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to 074 * variable length instructions. 075 * 076 * @param offset additional offset caused by preceding (variable length) instructions 077 * @param max_offset the maximum offset that may be caused by these instructions 078 * @return additional offset caused by possible change of this instruction's length 079 */ 080 @Override 081 protected int updatePosition(final int offset, final int max_offset) { 082 final int i = getTargetOffset(); // Depending on old position value 083 setPosition(getPosition() + offset); // Position may be shifted by preceding expansions 084 if (Math.abs(i) >= Short.MAX_VALUE - max_offset) { // to large for short (estimate) 085 super.setOpcode(org.apache.bcel.Const.GOTO_W); 086 final short old_length = (short) super.getLength(); 087 super.setLength(5); 088 return super.getLength() - old_length; 089 } 090 return 0; 091 } 092}