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 /**
22 * Equality of instructions isn't clearly to be defined. You might wish, for example, to compare whether instructions
23 * have the same meaning. E.g., whether two INVOKEVIRTUALs describe the same call.
24 * <p>
25 * The DEFAULT comparator however, considers two instructions to be equal if they have same opcode and point to the same
26 * indexes (if any) in the constant pool or the same local variable index. Branch instructions must have the same
27 * target.
28 * </p>
29 *
30 * @see Instruction
31 */
32 public interface InstructionComparator {
33
34 /**
35 * Default instruction comparator.
36 */
37 InstructionComparator DEFAULT = (i1, i2) -> {
38 if (i1.getOpcode() == i2.getOpcode()) {
39 if (i1 instanceof BranchInstruction) {
40 // BIs are never equal to make targeters work correctly (BCEL-195)
41 return false;
42 // } else if (i1 == i2) { TODO consider adding this shortcut
43 // return true; // this must be AFTER the BI test
44 }
45 if (i1 instanceof ConstantPushInstruction) {
46 return ((ConstantPushInstruction) i1).getValue().equals(((ConstantPushInstruction) i2).getValue());
47 }
48 if (i1 instanceof IndexedInstruction) {
49 return ((IndexedInstruction) i1).getIndex() == ((IndexedInstruction) i2).getIndex();
50 }
51 if (i1 instanceof NEWARRAY) {
52 return ((NEWARRAY) i1).getTypecode() == ((NEWARRAY) i2).getTypecode();
53 }
54 return true;
55 }
56 return false;
57 };
58
59 /**
60 * Compares two instructions for equality.
61 *
62 * @param i1 the first instruction.
63 * @param i2 the second instruction.
64 * @return true if the instructions are equal, false otherwise.
65 */
66 boolean equals(Instruction i1, Instruction i2);
67 }