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// Copyright 2021 The Tint Authors.
//
// 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.
#ifndef FUZZERS_TINT_AST_FUZZER_PROBABILITY_CONTEXT_H_
#define FUZZERS_TINT_AST_FUZZER_PROBABILITY_CONTEXT_H_
#include <utility>
#include <vector>
#include "fuzzers/random_generator.h"
namespace tint {
namespace fuzzers {
namespace ast_fuzzer {
/// This class is intended to be used by the `MutationFinder`s to introduce some
/// variance to the mutation process.
class ProbabilityContext {
public:
/// Initializes this instance with a random number generator.
/// @param generator - must not be a `nullptr`. Must remain in scope as long
/// as this
/// instance exists.
explicit ProbabilityContext(RandomGenerator* generator);
/// Get random bool with even odds
/// @returns true 50% of the time and false %50 of time.
bool RandomBool() { return generator_->GetBool(); }
/// Get random bool with weighted odds
/// @param percentage - likelihood of true being returned
/// @returns true |percentage|% of the time, and false (100 - |percentage|)%
/// of the time.
bool ChoosePercentage(uint32_t percentage) {
return generator_->GetWeightedBool(percentage);
}
/// Returns a random value in the range `[0; arr.size())`.
/// @tparam T - type of the elements in the vector.
/// @param arr - may not be empty.
/// @return the random index in the `arr`.
template <typename T>
size_t GetRandomIndex(const std::vector<T>& arr) {
return static_cast<size_t>(generator_->GetUInt64(arr.size()));
}
/// @return the probability of replacing some identifier with some other one.
uint32_t GetChanceOfReplacingIdentifiers() const {
return chance_of_replacing_identifiers_;
}
private:
/// @param range - a pair of integers `a` and `b` s.t. `a <= b`.
/// @return an random number in the range `[a; b]`.
uint32_t RandomFromRange(std::pair<uint32_t, uint32_t> range);
RandomGenerator* generator_;
uint32_t chance_of_replacing_identifiers_;
};
} // namespace ast_fuzzer
} // namespace fuzzers
} // namespace tint
#endif // FUZZERS_TINT_AST_FUZZER_PROBABILITY_CONTEXT_H_