lru_iterative_replacement_algorithm.cpp

#include <numeric>

#include "../include/lru_iterative_replacement_algorithm.h"

auto lru_iterative_replacement_algorithm::make_initial_state() const -> std::unique_ptr<state>
{
	return std::make_unique<state>();
}

auto lru_iterative_replacement_algorithm::run_step(const state& current_state, const input& all_input,
                                                   const input_const_iter& current_input) const -> run_step_result
{
	auto table = current_state;
	const auto is_hit = std::find(table.cbegin(), table.cend(), *current_input) != table.cend();

	if (!is_hit)
	{
		if (current_state.size() == page_table_size)
		{
			const auto least_recently_used = std::accumulate(table.cbegin(), table.cend(),
			                                                 std::make_reverse_iterator(current_input),
			                                                 [&](const auto& least, const auto& page)
			                                                 {
				                                                 const auto last_use = std::find(
					                                                 std::make_reverse_iterator(current_input), all_input.crend(),
					                                                 page);
				                                                 return std::max(least, last_use);
			                                                 });
			table.erase(*least_recently_used);
		}

		table.insert(*current_input);
	}

	const auto vector = std::vector<int>{table.cbegin(), table.cend()};
	return {std::make_unique<state>(std::move(table)), {is_hit, vector}};
}

lru_iterative_replacement_algorithm::
lru_iterative_replacement_algorithm(const int page_table_size) : iterative_replacement_algorithm<lru_state>(
	"Least Recently Used", page_table_size)
{
}