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// Copyright 2021 The Dawn & Tint Authors
//
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#ifndef SRC_TINT_FUZZERS_TINT_AST_FUZZER_PROBABILITY_CONTEXT_H_
#define SRC_TINT_FUZZERS_TINT_AST_FUZZER_PROBABILITY_CONTEXT_H_
#include <utility>
#include <vector>
#include "src/tint/fuzzers/random_generator.h"
namespace tint::fuzzers::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 binary operator with another.
uint32_t GetChanceOfChangingBinaryOperators() const {
return chance_of_changing_binary_operators_;
}
/// @return the probability of changing operator for an unary expression.
uint32_t GetChanceOfChangingUnaryOperators() const {
return chance_of_changing_unary_operators_;
}
/// @return the probability of changing operator for a binary expression.
uint32_t GetChanceOfDeletingStatements() const { return chance_of_deleting_statements_; }
/// @return the probability of replacing some identifier with some other one.
uint32_t GetChanceOfReplacingIdentifiers() const { return chance_of_replacing_identifiers_; }
/// @return the probability of wrapping an expression in a unary operator.
uint32_t GetChanceOfWrappingUnaryOperators() const {
return chance_of_wrapping_unary_operators_;
}
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_changing_binary_operators_;
uint32_t chance_of_changing_unary_operators_;
uint32_t chance_of_deleting_statements_;
uint32_t chance_of_replacing_identifiers_;
uint32_t chance_of_wrapping_unary_operators_;
};
} // namespace tint::fuzzers::ast_fuzzer
#endif // SRC_TINT_FUZZERS_TINT_AST_FUZZER_PROBABILITY_CONTEXT_H_