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.MTryBlock;
  import dexfuzz.program.MutatableCode;
  import dexfuzz.program.Mutation;
  
  import java.util.List;
  import java.util.Random;
  
  public class TryBlockShifter 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 tryIdx;
      public boolean shiftingTryBlock; // false => shifting handler
      public boolean shiftingStart; // false => shifting end (try block only)
      public boolean shiftingHandlerCatchall;
      public int shiftingHandlerIdx;
      public int newShiftedInsnIdx;
  
      @Override
      public String getString() {
        String result = String.format("%d %s %s %s %d %d",
            tryIdx,
            (shiftingTryBlock ? "T" : "F"),
            (shiftingStart ? "T" : "F"),
            (shiftingHandlerCatchall ? "T" : "F"),
            shiftingHandlerIdx,
            newShiftedInsnIdx
            );
        return result;
      }
  
      @Override
      public void parseString(String[] elements) {
        tryIdx = Integer.parseInt(elements[2]);
        shiftingTryBlock = elements[3].equals("T");
        shiftingStart = elements[4].equals("T");
        shiftingHandlerCatchall = elements[5].equals("T");
        shiftingHandlerIdx = Integer.parseInt(elements[6]);
        newShiftedInsnIdx = Integer.parseInt(elements[7]);
      }
    }
  
    // 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 TryBlockShifter() { }
  
    public TryBlockShifter(Random rng, MutationStats stats, List<Mutation> mutations) {
      super(rng, stats, mutations);
      likelihood = 40;
    }
  
    @Override
    protected boolean canMutate(MutatableCode mutatableCode) {
      if (mutatableCode.triesSize > 0) {
        return true;
      }
  
      Log.debug("Method contains no tries.");
      return false;
    }
  
    @Override
    protected Mutation generateMutation(MutatableCode mutatableCode) {
      // Pick a random try.
      int tryIdx = rng.nextInt(mutatableCode.triesSize);
      MTryBlock tryBlock = mutatableCode.mutatableTries.get(tryIdx);
  
      boolean shiftingTryBlock = rng.nextBoolean();
      boolean shiftingStart = false;
      boolean shiftingHandlerCatchall = false;
      int shiftingHandlerIdx = -1;
      if (shiftingTryBlock) {
        // We're shifting the boundaries of the try block
        // determine if we shift the start or the end.
        shiftingStart = rng.nextBoolean();
      } else {
        // We're shifting the start of a handler of the try block.
        if (tryBlock.handlers.isEmpty()) {
          // No handlers, so we MUST mutate the catchall
          shiftingHandlerCatchall = true;
        } else if (tryBlock.catchAllHandler != null) {
          // There is a catchall handler, so potentially mutate it.
          shiftingHandlerCatchall = rng.nextBoolean();
        }
        // If we're not going to shift the catchall handler, then
        // pick an explicit handler to shift.
        if (!shiftingHandlerCatchall) {
          shiftingHandlerIdx = rng.nextInt(tryBlock.handlers.size());
        }
      }
  
      // Get the original instruction wherever we're shifting.
      MInsn oldInsn = null;
      if (shiftingTryBlock && shiftingStart) {
        oldInsn = tryBlock.startInsn;
      } else if (shiftingTryBlock && !(shiftingStart)) {
        oldInsn = tryBlock.endInsn;
      } else if (!(shiftingTryBlock) && shiftingHandlerCatchall) {
        oldInsn = tryBlock.catchAllHandler;
      } else if (!(shiftingTryBlock) && !(shiftingHandlerCatchall)
          && (shiftingHandlerIdx != -1)) {
        oldInsn = tryBlock.handlers.get(shiftingHandlerIdx);
      } else {
        Log.errorAndQuit("Faulty logic in TryBlockShifter!");
      }
  
      // Find the index of this instruction.
      int oldInsnIdx = mutatableCode.getInstructionIndex(oldInsn);
  
      int newInsnIdx = oldInsnIdx;
  
      int delta = 0;
  
      // Keep searching for a new index.
      while (newInsnIdx == oldInsnIdx) {
        // Vary by +/- 2 instructions.
        delta = 0;
        while (delta == 0) {
          delta = (rng.nextInt(5) - 2);
        }
  
        newInsnIdx = oldInsnIdx + delta;
  
        // Check the new index is legal.
        if (newInsnIdx < 0) {
          newInsnIdx = 0;
        } else if (newInsnIdx >= mutatableCode.getInstructionCount()) {
          newInsnIdx = mutatableCode.getInstructionCount() - 1;
        }
      }
  
      AssociatedMutation mutation = new AssociatedMutation();
      mutation.setup(this.getClass(), mutatableCode);
      mutation.tryIdx = tryIdx;
      mutation.shiftingTryBlock = shiftingTryBlock;
      mutation.shiftingStart = shiftingStart;
      mutation.shiftingHandlerCatchall = shiftingHandlerCatchall;
      mutation.shiftingHandlerIdx = shiftingHandlerIdx;
      mutation.newShiftedInsnIdx = newInsnIdx;
      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;
  
      MTryBlock tryBlock = mutatableCode.mutatableTries.get(mutation.tryIdx);
  
      MInsn newInsn =
          mutatableCode.getInstructionAt(mutation.newShiftedInsnIdx);
  
      // Find the right mutatable instruction in try block, and point it at the new instruction.
      if (mutation.shiftingTryBlock && mutation.shiftingStart) {
        tryBlock.startInsn = newInsn;
        Log.info("Shifted the start of try block #" + mutation.tryIdx
            + " to be at " + newInsn);
      } else if (mutation.shiftingTryBlock && !(mutation.shiftingStart)) {
        tryBlock.endInsn = newInsn;
        Log.info("Shifted the end of try block #" + mutation.tryIdx
            + " to be at " + newInsn);
      } else if (!(mutation.shiftingTryBlock) && mutation.shiftingHandlerCatchall) {
        tryBlock.catchAllHandler = newInsn;
        Log.info("Shifted the catch all handler of try block #" + mutation.tryIdx
            + " to be at " + newInsn);
      } else if (!(mutation.shiftingTryBlock) && !(mutation.shiftingHandlerCatchall)
          && (mutation.shiftingHandlerIdx != -1)) {
        tryBlock.handlers.set(mutation.shiftingHandlerIdx, newInsn);
        Log.info("Shifted handler #" + mutation.shiftingHandlerIdx
            + " of try block #" + mutation.tryIdx + " to be at " + newInsn);
      } else {
        Log.errorAndQuit("faulty logic in TryBlockShifter");
      }
  
      stats.incrementStat("Shifted boundary in a try block");
    }
  }
  