SnugLog/LibSnugLog/source/registry.cpp

#include "registry.h"
#include "disruptor.h"
#include "sl/register.h"

#include <concepts>
#include <atomic>
#include <unordered_map>
#include <functional>
#include <any>


/**
 * @brief A fast semaphore exclusion handler WITHOUT deadlock detection or yielding
 */
template<std::integral T, T default_increment, T maximum_increment>
class fast_semaphore {
	std::atomic<T> flag; //< This is our counter
public:
	fast_semaphore() = default;
	fast_semaphore(fast_semaphore&) = delete;
	fast_semaphore(fast_semaphore&&) = delete;
	
	/// 3 things may happen when trying to unlock
	enum class tristate {
		success = 1, //< The unlocking was successful
		timing = 0, //< Someone interfered with the unlocking
		error = -1 //< The unlocking would over-unlock the semaphore
	};
	
	/// We try locking until we succeed
	template<T increment = default_increment>
	void lock() {
		while(not try_lock<increment>());
	}
	
	/// For locking, we try to atomically increment the counter while maintaining it below the set limit
	template<T increment = default_increment>
	[[nodiscard]] bool try_lock() {
		T expect = flag.load(std::memory_order::acquire);
		T target = expect + increment;
		if(target > maximum_increment) return false;
		return flag.compare_exchange_strong(expect,target,std::memory_order::release);
	}
	
	/// Similarly to locking, we try unlocking until we succeed (or reach an invalid state)
	template<T increment = default_increment>
	void unlock() {
		tristate v;
		do{ v = try_unlock<increment>(); }
		while(v == tristate::timing);
		if(v != tristate::success) {
			throw std::runtime_error("Over unlocking may have happened: potential double unlocking issue");
		}
	}
	
	/// Unlocking is the reverse of locking, we have to ensure to return an error if we try to go below zero
	template<T increment = default_increment>
	[[nodiscard]] tristate try_unlock() {
		T expect = flag.load(std::memory_order::relaxed);
		T target = expect - increment;
		if(target < 0) return tristate::error;
		return flag.compare_exchange_strong(expect,target,std::memory_order::release) ? tristate::success : tristate::timing;
	}
};

using rw_lock_type = fast_semaphore<int32_t, 256, 256>;

class lock_handler_read {
	rw_lock_type& ref;
	explicit lock_handler_read(rw_lock_type& _ref) : ref(_ref) {
		while(ref.try_lock<1>());
	}
	
	~lock_handler_read() {
		while(ref.try_unlock<1>() != rw_lock_type::tristate::success);
	}
};

class lock_handler_write {
	rw_lock_type& ref;
	explicit lock_handler_write(rw_lock_type& _ref) : ref(_ref) {
		while(ref.try_lock());
	}
	
	~lock_handler_write() {
		while(ref.try_unlock() != rw_lock_type::tristate::success);
	}
};

static fast_semaphore<int32_t, 256, 256> registry_rw_lock;


struct registry_slab {
	int id;
	std::string name;
	std::function<token_t(size_t)> reserve_write;
	std::function<token_t(size_t)> reserve_write_c_align;
	std::function<void(token_t)>   conclude_write;
	std::any disruptor;
};

/**
 * @internal used because we need the pointer stability
 * @see sl_transaction
 */
static std::unordered_map<int, registry_slab> registry_map;

BufferStrategyInternal::buffer_type BufferStrategyInternal::build_buffer(size_t) {
	return {};
}

BufferStrategyShared::buffer_type BufferStrategyShared::build_buffer(size_t) {
	return {};
}

BufferStrategyExternal::buffer_type BufferStrategyExternal::build_buffer(size_t) {
	return {};
}

void SinkStrategyDirect::write(int fd, std::string_view data) {

}

void SinkStrategyFastest::write(int fd, std::string_view data) {

}

void SinkStrategyMmaped::write(int fd, std::string_view data) {

}

void SinkStrategyExternal::write(int fd, std::string_view data) {

}

void OverflowStrategyWait::wait() {

}

void OverflowStrategyContinue::wait() {

}

std::pair<std::string_view, std::string_view> OutputStrategyTimed::chunk(std::string_view) {
	return {};
}

int OutputStrategyTimed::on_write_completed_event(std::string_view, int) {
	return 0;
}

std::pair<std::string_view, std::string_view> OutputStrategySized::chunk(std::string_view) {
	return {};
}

int OutputStrategySized::on_write_completed_event(std::string_view, int) {
	return 0;
}

std::pair<std::string_view, std::string_view> OutputStrategySimple::chunk(std::string_view) {
	return {};
}

int OutputStrategySimple::on_write_completed_event(std::string_view, int) {
	return 0;
}