bgfx/3rdparty/spirv-tools/source/fuzz/fuzzer_context.cpp

// Copyright (c) 2019 Google LLC
//
// 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 "source/fuzz/fuzzer_context.h"

#include <cmath>

namespace spvtools {
namespace fuzz {

namespace {
// Default probabilities for applying various transformations.
// All values are percentages.
// Keep them in alphabetical order.

const uint32_t kDefaultChanceOfAddingDeadBreak = 20;
const uint32_t kDefaultChanceOfAddingDeadContinue = 20;
const uint32_t kDefaultChanceOfCopyingObject = 20;
const uint32_t kDefaultChanceOfMovingBlockDown = 25;
const uint32_t kDefaultChanceOfObfuscatingConstant = 20;
const uint32_t kDefaultChanceOfSplittingBlock = 20;

// Default functions for controlling how deep to go during recursive
// generation/transformation. Keep them in alphabetical order.

const std::function<bool(uint32_t, RandomGenerator*)>
    kDefaultGoDeeperInConstantObfuscation =
        [](uint32_t current_depth, RandomGenerator* random_generator) -> bool {
  double chance = 1.0 / std::pow(3.0, static_cast<float>(current_depth + 1));
  return random_generator->RandomDouble() < chance;
};

}  // namespace

FuzzerContext::FuzzerContext(RandomGenerator* random_generator,
                             uint32_t min_fresh_id)
    : random_generator_(random_generator),
      next_fresh_id_(min_fresh_id),
      chance_of_adding_dead_break_(kDefaultChanceOfAddingDeadBreak),
      chance_of_adding_dead_continue_(kDefaultChanceOfAddingDeadContinue),
      chance_of_copying_object_(kDefaultChanceOfCopyingObject),
      chance_of_moving_block_down_(kDefaultChanceOfMovingBlockDown),
      chance_of_obfuscating_constant_(kDefaultChanceOfObfuscatingConstant),
      chance_of_splitting_block_(kDefaultChanceOfSplittingBlock),
      go_deeper_in_constant_obfuscation_(
          kDefaultGoDeeperInConstantObfuscation) {}

FuzzerContext::~FuzzerContext() = default;

uint32_t FuzzerContext::GetFreshId() { return next_fresh_id_++; }

bool FuzzerContext::ChooseEven() { return random_generator_->RandomBool(); }

bool FuzzerContext::ChoosePercentage(uint32_t percentage_chance) {
  assert(percentage_chance <= 100);
  return random_generator_->RandomPercentage() < percentage_chance;
}

}  // namespace fuzz
}  // namespace spvtools