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 /**
20 * BranchHandle is returned by specialized InstructionList.append() whenever a BranchInstruction is appended. This is
21 * useful when the target of this instruction is not known at time of creation and must be set later via setTarget().
22 *
23 * @see InstructionHandle
24 * @see Instruction
25 * @see InstructionList
26 */
27 public final class BranchHandle extends InstructionHandle {
28
29 /**
30 * Factory method.
31 */
32 static BranchHandle getBranchHandle(final BranchInstruction i) {
33 return new BranchHandle(i);
34 }
35
36 // This is also a cache in case the InstructionHandle#swapInstruction() method is used
37 // See BCEL-273
38 private BranchInstruction bi; // An alias in fact, but saves lots of casts
39
40 private BranchHandle(final BranchInstruction i) {
41 super(i);
42 bi = i;
43 }
44
45 /*
46 * Override InstructionHandle methods: delegate to branch instruction. Through this overriding all access to the private
47 * i_position field should be prevented.
48 */
49 @Override
50 public int getPosition() {
51 return bi.getPosition();
52 }
53
54 /**
55 * @return target of instruction.
56 */
57 public InstructionHandle getTarget() {
58 return bi.getTarget();
59 }
60
61 /**
62 * Sets new contents. Old instruction is disposed and may not be used anymore.
63 */
64 @Override // This is only done in order to apply the additional type check; could be merged with super impl.
65 public void setInstruction(final Instruction i) { // TODO could be package-protected?
66 super.setInstruction(i);
67 if (!(i instanceof BranchInstruction)) {
68 throw new ClassGenException("Assigning " + i + " to branch handle which is not a branch instruction");
69 }
70 bi = (BranchInstruction) i;
71 }
72
73 @Override
74 void setPosition(final int pos) {
75 // Original code: i_position = bi.position = pos;
76 bi.setPosition(pos);
77 super.setPosition(pos);
78 }
79
80 /**
81 * Pass new target to instruction.
82 */
83 public void setTarget(final InstructionHandle ih) {
84 bi.setTarget(ih);
85 }
86
87 @Override
88 protected int updatePosition(final int offset, final int maxOffset) {
89 final int x = bi.updatePosition(offset, maxOffset);
90 super.setPosition(bi.getPosition());
91 return x;
92 }
93
94 /**
95 * Update target of instruction.
96 */
97 public void updateTarget(final InstructionHandle oldIh, final InstructionHandle newIh) {
98 bi.updateTarget(oldIh, newIh);
99 }
100 }