Prepare fuzzing engine

src/fuzzing-engine/input_generator.cpp

@@ -0,0 +1,93 @@
+#include "input_generator.hpp"
+
+namespace fuzzer
+{
+	namespace
+	{
+		constexpr size_t MAX_TOP_SCORER = 20;
+
+		void mutate_input(random_generator& rng, std::vector<uint8_t>& input)
+		{
+			if (input.empty() || rng.get(10) == 0)
+			{
+				const auto new_bytes = rng.get_geometric<size_t>() + 1;
+				input.resize(input.size() + new_bytes);
+			}
+			else if (rng.get(10) == 0)
+			{
+				const auto remove_bytes = rng.get_geometric<size_t>() % input.size();
+				input.resize(input.size() - remove_bytes);
+			}
+
+			const auto mutations = (rng.get_geometric<size_t>() + 1) % input.size();
+
+
+			for (size_t i = 0; i < mutations; ++i)
+			{
+				const auto index = rng.get<size_t>(input.size());
+				input[index] = rng.get<uint8_t>();
+			}
+		}
+	}
+
+	input_generator::input_generator() = default;
+
+	std::vector<uint8_t> input_generator::generate_next_input()
+	{
+		std::vector<uint8_t> input{};
+		std::unique_lock lock{this->mutex_};
+
+		if (!this->top_scorer_.empty())
+		{
+			const auto index = this->rng.get<size_t>() % this->top_scorer_.size();
+			input = this->top_scorer_[index].data;
+		}
+
+		mutate_input(this->rng, input);
+
+		return input;
+	}
+
+	void input_generator::access_input(const std::function<input_handler>& handler)
+	{
+		auto next_input = this->generate_next_input();
+		const auto score = handler(next_input);
+		this->store_input_entry({std::move(next_input), score});
+	}
+
+	void input_generator::store_input_entry(input_entry entry)
+	{
+		std::unique_lock lock{this->mutex_};
+
+		if (entry.score < this->lowest_score && this->rng.get(40) != 0)
+		{
+			return;
+		}
+
+		const auto score = entry.score;
+
+		if (this->top_scorer_.size() < MAX_TOP_SCORER)
+		{
+			this->top_scorer_.emplace_back(std::move(entry));
+		}
+		else
+		{
+			const auto index = this->rng.get<size_t>() % this->top_scorer_.size();
+			this->top_scorer_[index] = std::move(entry);
+		}
+
+		this->lowest_score = score;
+		if (score < this->lowest_score)
+		{
+			return;
+		}
+
+		for (const auto& e : this->top_scorer_)
+		{
+			if (e.score < this->lowest_score)
+			{
+				this->lowest_score = e.score;
+			}
+		}
+	}
+}