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 public GOTO(final InstructionHandle target) {
36 super(org.apache.bcel.Const.GOTO, target);
37 }
38
39 /**
40 * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
41 * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
42 *
43 * @param v Visitor object
44 */
45 @Override
46 public void accept(final Visitor v) {
47 v.visitVariableLengthInstruction(this);
48 v.visitUnconditionalBranch(this);
49 v.visitBranchInstruction(this);
50 v.visitGotoInstruction(this);
51 v.visitGOTO(this);
52 }
53
54 /**
55 * Dump instruction as byte code to stream out.
56 *
57 * @param out Output stream
58 */
59 @Override
60 public void dump(final DataOutputStream out) throws IOException {
61 super.setIndex(getTargetOffset());
62 final short opcode = getOpcode();
63 if (opcode == org.apache.bcel.Const.GOTO) {
64 super.dump(out);
65 } else { // GOTO_W
66 super.setIndex(getTargetOffset());
67 out.writeByte(opcode);
68 out.writeInt(super.getIndex());
69 }
70 }
71
72 /**
73 * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to
74 * variable length instructions.
75 *
76 * @param offset additional offset caused by preceding (variable length) instructions
77 * @param maxOffset the maximum offset that may be caused by these instructions
78 * @return additional offset caused by possible change of this instruction's length
79 */
80 @Override
81 protected int updatePosition(final int offset, final int maxOffset) {
82 final int i = getTargetOffset(); // Depending on old position value
83 setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
84 if (Math.abs(i) >= Short.MAX_VALUE - maxOffset) { // to large for short (estimate)
85 super.setOpcode(org.apache.bcel.Const.GOTO_W);
86 final short oldLength = (short) super.getLength();
87 super.setLength(5);
88 return super.getLength() - oldLength;
89 }
90 return 0;
91 }
92 }