1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * https://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.bcel.generic;
20
21 import java.io.DataOutputStream;
22 import java.io.IOException;
23
24 /**
25 * GOTO - Branch always (to relative offset, not absolute address)
26 */
27 public class GOTO extends GotoInstruction implements VariableLengthInstruction {
28
29 /**
30 * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
31 */
32 GOTO() {
33 }
34
35 /**
36 * Constructs a GOTO instruction.
37 *
38 * @param target the target instruction.
39 */
40 public GOTO(final InstructionHandle target) {
41 super(org.apache.bcel.Const.GOTO, target);
42 }
43
44 /**
45 * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
46 * methods according to the class hierarchy in descending order, that is, the most specific visitXXX() call comes last.
47 *
48 * @param v Visitor object.
49 */
50 @Override
51 public void accept(final Visitor v) {
52 v.visitVariableLengthInstruction(this);
53 v.visitUnconditionalBranch(this);
54 v.visitBranchInstruction(this);
55 v.visitGotoInstruction(this);
56 v.visitGOTO(this);
57 }
58
59 /**
60 * Dumps instruction as byte code to stream out.
61 *
62 * @param out Output stream.
63 */
64 @Override
65 public void dump(final DataOutputStream out) throws IOException {
66 super.setIndex(getTargetOffset());
67 final short opcode = getOpcode();
68 if (opcode == org.apache.bcel.Const.GOTO) {
69 super.dump(out);
70 } else { // GOTO_W
71 super.setIndex(getTargetOffset());
72 out.writeByte(opcode);
73 out.writeInt(super.getIndex());
74 }
75 }
76
77 /**
78 * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to
79 * variable length instructions.
80 *
81 * @param offset additional offset caused by preceding (variable length) instructions.
82 * @param maxOffset the maximum offset that may be caused by these instructions.
83 * @return additional offset caused by possible change of this instruction's length.
84 */
85 @Override
86 protected int updatePosition(final int offset, final int maxOffset) {
87 final int i = getTargetOffset(); // Depending on old position value
88 setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
89 if (Math.abs(i) >= Short.MAX_VALUE - maxOffset) { // to large for short (estimate)
90 super.setOpcode(org.apache.bcel.Const.GOTO_W);
91 final short oldLength = (short) super.getLength();
92 super.setLength(5);
93 return super.getLength() - oldLength;
94 }
95 return 0;
96 }
97 }