content: /*
   * Copyright (C) 2014 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package dexfuzz.program.mutators;
  
  import dexfuzz.Log;
  import dexfuzz.MutationStats;
  import dexfuzz.program.MInsn;
  import dexfuzz.program.MutatableCode;
  import dexfuzz.program.Mutation;
  import dexfuzz.rawdex.EncodedField;
  import dexfuzz.rawdex.Instruction;
  import dexfuzz.rawdex.Opcode;
  import dexfuzz.rawdex.formats.ContainsPoolIndex;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Random;
  
  public class FieldFlagChanger extends CodeMutator {
    /**
     * Every CodeMutator has an AssociatedMutation, representing the
     * mutation that this CodeMutator can perform, to allow separate
     * generateMutation() and applyMutation() phases, allowing serialization.
     */
    public static class AssociatedMutation extends Mutation {
      public int fieldInsnIdx;
      public boolean setVolatile;
  
      @Override
      public String getString() {
        StringBuilder builder = new StringBuilder();
        builder.append(fieldInsnIdx).append(" ");
        builder.append(setVolatile);
        return builder.toString();
      }
  
      @Override
      public void parseString(String[] elements) {
        fieldInsnIdx = Integer.parseInt(elements[2]);
        setVolatile = Boolean.parseBoolean(elements[3]);
      }
    }
  
    // The following two methods are here for the benefit of MutationSerializer,
    // so it can create a CodeMutator and get the correct associated Mutation, as it
    // reads in mutations from a dump of mutations.
    @Override
    public Mutation getNewMutation() {
      return new AssociatedMutation();
    }
  
    public FieldFlagChanger() { }
  
    public FieldFlagChanger(Random rng, MutationStats stats, List<Mutation> mutations) {
      super(rng, stats, mutations);
      likelihood = 40;
    }
  
    // A cache that should only exist between generateMutation() and applyMutation(),
    // or be created at the start of applyMutation(), if we're reading in mutations from
    // a file.
    private List<MInsn> fieldInsns = null;
  
    private void generateCachedFieldInsns(MutatableCode mutatableCode) {
      if (fieldInsns != null) {
        return;
      }
  
      fieldInsns = new ArrayList<MInsn>();
  
      for (MInsn mInsn : mutatableCode.getInstructions()) {
        if (isFileDefinedFieldInstruction(mInsn, mutatableCode)) {
          fieldInsns.add(mInsn);
        }
      }
    }
  
    @Override
    protected boolean canMutate(MutatableCode mutatableCode) {
      for (MInsn mInsn : mutatableCode.getInstructions()) {
        if (isFileDefinedFieldInstruction(mInsn, mutatableCode)) {
          return true;
        }
      }
  
      Log.debug("No field instructions in method, skipping...");
      return false;
    }
  
    @Override
    protected Mutation generateMutation(MutatableCode mutatableCode) {
      generateCachedFieldInsns(mutatableCode);
  
      int fieldInsnIdx = rng.nextInt(fieldInsns.size());
  
      Instruction insn = fieldInsns.get(fieldInsnIdx).insn;
      ContainsPoolIndex containsPoolIndex = (ContainsPoolIndex) insn.info.format;
      int fieldIdx = containsPoolIndex.getPoolIndex(insn);
      EncodedField encodedField = mutatableCode.program.getEncodedField(fieldIdx);
  
      boolean setVolatile = false;
      if (!encodedField.isVolatile()) {
        setVolatile = true;
      }
      // TODO: Flip more flags?
  
      AssociatedMutation mutation = new AssociatedMutation();
      mutation.setup(this.getClass(), mutatableCode);
      mutation.fieldInsnIdx = fieldInsnIdx;
      mutation.setVolatile = setVolatile;
      return mutation;
    }
  
    @Override
    protected void applyMutation(Mutation uncastMutation) {
      // Cast the Mutation to our AssociatedMutation, so we can access its fields.
      AssociatedMutation mutation = (AssociatedMutation) uncastMutation;
      MutatableCode mutatableCode = mutation.mutatableCode;
  
      generateCachedFieldInsns(mutatableCode);
  
      Instruction insn = fieldInsns.get(mutation.fieldInsnIdx).insn;
      ContainsPoolIndex containsPoolIndex = (ContainsPoolIndex) insn.info.format;
      int fieldIdx = containsPoolIndex.getPoolIndex(insn);
      EncodedField encodedField = mutatableCode.program.getEncodedField(fieldIdx);
  
      if (mutation.setVolatile) {
        encodedField.setVolatile(true);
        Log.info("Set field idx " + fieldIdx + " as volatile");
      } else {
        encodedField.setVolatile(false);
        Log.info("Set field idx " + fieldIdx + " as not volatile");
      }
  
      stats.incrementStat("Changed volatility of field");
  
      // Clear cache.
      fieldInsns = null;
    }
  
    private boolean isFileDefinedFieldInstruction(MInsn mInsn, MutatableCode mutatableCode) {
      Opcode opcode = mInsn.insn.info.opcode;
      if (Opcode.isBetween(opcode, Opcode.IGET, Opcode.SPUT_SHORT)) {
        Instruction insn = mInsn.insn;
        ContainsPoolIndex containsPoolIndex = (ContainsPoolIndex) insn.info.format;
        int fieldIdx = containsPoolIndex.getPoolIndex(insn);
        if (mutatableCode.program.getEncodedField(fieldIdx) != null) {
          return true;
        }
      }
      return false;
    }
  }
  