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      1 /*
      2  * Copyright (C) 2017 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package dexfuzz.program.mutators;
     18 
     19 import dexfuzz.MutationStats;
     20 import dexfuzz.program.MInsn;
     21 import dexfuzz.program.Mutation;
     22 import dexfuzz.rawdex.Opcode;
     23 import java.util.List;
     24 import java.util.Random;
     25 
     26 public class RandomBranchChanger extends IfBranchChanger {
     27 
     28   private static final Opcode[] EQUALITY_CMP_OP_LIST = {
     29     Opcode.IF_EQ,
     30     Opcode.IF_NE,
     31     Opcode.IF_LT,
     32     Opcode.IF_GE,
     33     Opcode.IF_GT,
     34     Opcode.IF_LE
     35   };
     36 
     37   private static final Opcode[] ZERO_CMP_OP_LIST = {
     38     Opcode.IF_EQZ,
     39     Opcode.IF_NEZ,
     40     Opcode.IF_LTZ,
     41     Opcode.IF_GEZ,
     42     Opcode.IF_GTZ,
     43     Opcode.IF_LEZ
     44   };
     45 
     46   public RandomBranchChanger(Random rng, MutationStats stats, List<Mutation> mutations) {
     47     super(rng, stats, mutations);
     48     likelihood = 30;
     49   }
     50 
     51   @Override
     52   protected Opcode getModifiedOpcode(MInsn mInsn) {
     53     Opcode opcode = mInsn.insn.info.opcode;
     54     if (Opcode.isBetween(opcode, Opcode.IF_EQ, Opcode.IF_LE)) {
     55       int index = opcode.ordinal() - Opcode.IF_EQ.ordinal();
     56       int length = EQUALITY_CMP_OP_LIST.length;
     57       return EQUALITY_CMP_OP_LIST[(index + 1 + rng.nextInt(length - 1)) % length];
     58     } else if (Opcode.isBetween(opcode, Opcode.IF_EQZ, Opcode.IF_LEZ)) {
     59       int index = opcode.ordinal() - Opcode.IF_EQZ.ordinal();
     60       int length = ZERO_CMP_OP_LIST.length;
     61       return ZERO_CMP_OP_LIST[(index + 1 + rng.nextInt(length - 1)) % length];
     62     }
     63     return opcode;
     64   }
     65 
     66   @Override
     67   protected String getMutationTag() {
     68     return "random";
     69   }
     70 }