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