1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.bcel.generic;
18
19 import java.io.DataOutputStream;
20 import java.io.IOException;
21
22 /**
23 * GOTO - Branch always (to relative offset, not absolute address)
24 */
25 public class GOTO extends GotoInstruction implements VariableLengthInstruction {
26
27 /**
28 * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
29 */
30 GOTO() {
31 }
32
33 public GOTO(final InstructionHandle target) {
34 super(org.apache.bcel.Const.GOTO, target);
35 }
36
37 /**
38 * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
39 * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
40 *
41 * @param v Visitor object
42 */
43 @Override
44 public void accept(final Visitor v) {
45 v.visitVariableLengthInstruction(this);
46 v.visitUnconditionalBranch(this);
47 v.visitBranchInstruction(this);
48 v.visitGotoInstruction(this);
49 v.visitGOTO(this);
50 }
51
52 /**
53 * Dump instruction as byte code to stream out.
54 *
55 * @param out Output stream
56 */
57 @Override
58 public void dump(final DataOutputStream out) throws IOException {
59 super.setIndex(getTargetOffset());
60 final short opcode = getOpcode();
61 if (opcode == org.apache.bcel.Const.GOTO) {
62 super.dump(out);
63 } else { // GOTO_W
64 super.setIndex(getTargetOffset());
65 out.writeByte(opcode);
66 out.writeInt(super.getIndex());
67 }
68 }
69
70 /**
71 * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to
72 * variable length instructions.
73 *
74 * @param offset additional offset caused by preceding (variable length) instructions
75 * @param maxOffset the maximum offset that may be caused by these instructions
76 * @return additional offset caused by possible change of this instruction's length
77 */
78 @Override
79 protected int updatePosition(final int offset, final int maxOffset) {
80 final int i = getTargetOffset(); // Depending on old position value
81 setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
82 if (Math.abs(i) >= Short.MAX_VALUE - maxOffset) { // to large for short (estimate)
83 super.setOpcode(org.apache.bcel.Const.GOTO_W);
84 final short oldLength = (short) super.getLength();
85 super.setLength(5);
86 return super.getLength() - oldLength;
87 }
88 return 0;
89 }
90 }