/*

 * Copyright 2020 Google Inc.

 * 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.

 */

#include "libprotobuf-mutator/src/libfuzzer/libfuzzer_macro.h"

#include "png_fuzz_proto.pb.h"

template <typename Proto>

using FuzzMutatorCallback = std::function<void(Proto*, unsigned int)>;

template <typename Proto>

struct PngProtoCBRegistration

{

  PngProtoCBRegistration(FuzzMutatorCallback<Proto> const& _callback)

  {

    static protobuf_mutator::libfuzzer::PostProcessorRegistration<Proto> reg = {_callback};

  }

};

/// Custom mutation: Otherchunk unknown_type -> known_type

static PngProtoCBRegistration<OtherChunk> addCustomChunk = {

  [](OtherChunk* message, unsigned int seed)

  {

    // Mutate with a probability of roughly 1/47

    // 47 has been chosen ad-hoc

    if (seed % 47 == 0)

    {

      // If otherChunk is unknown type, mutate

      // it to known type

      if (message->has_unknown_type())

      {

        // This is our custom mutation

        // We assume (k * 47 mod N) distribute

        // uniformly, where

        //  - N is total number of known

        // chunks defined by png proto converter

        //  - k is a factor of seed

        message->set_known_type(seed);

      }

    }

  }

};