Move optional to fundamental and adapt / arrange deque

rt/include/typon/deque.hpp

@@ -4,13 +4,17 @@
 #include <atomic>
 #include <cstdint>
 #include <memory>
+#include <type_traits>
 #include <utility>
 
+#include <typon/fundamental/optional.hpp>
+
 
 namespace typon
 {
 
   template <typename T>
+    requires std::is_trivially_copyable_v<T>
   struct RingBuffer
   {
     using u8 = std::uint_least8_t;
@@ -75,57 +79,16 @@ namespace typon
   };
 
 
-  template <typename T>
-  struct Optional
-  {
-    enum State : unsigned char { empty = 0, abort = 1, engaged = 2};
-
-    State _state;
-    union
-    {
-      T _value;
-    };
-
-    Optional(State state = empty) noexcept : _state(state) {}
-
-    Optional(T value) noexcept : _state(engaged), _value(value) {}
-
-    ~Optional()
-    {
-      if (_state == engaged)
-      {
-        std::destroy_at(std::addressof(_value));
-      }
-    }
-
-    operator bool() noexcept
-    {
-      return _state == engaged;
-    }
-
-    State state() noexcept
-    {
-      return _state;
-    }
-
-    T * operator->() noexcept
-    {
-      return std::addressof(_value);
-    }
-
-    T & operator*() noexcept
-    {
-      return _value;
-    }
-  };
-
-
   template <typename T>
   struct Deque
   {
     using u8 = typename RingBuffer<T>::u8;
     using u64 = typename RingBuffer<T>::u64;
     using Array = RingBuffer<T>;
+    using Pop = fdt::optional<T, 2>;
+
+    static constexpr typename Pop::template state<0> Empty {};
+    static constexpr typename Pop::template state<1> Abort {};
 
     using enum std::memory_order;
 
@@ -157,49 +120,48 @@ namespace typon
       _bottom.store(bottom + 1, relaxed);
     }
 
-    Optional<T> pop() noexcept
+    Pop pop() noexcept
     {
       u64 bottom = _bottom.load(relaxed) - 1;
       Array * array = _array.load(relaxed);
       _bottom.store(bottom, relaxed);
       std::atomic_thread_fence(seq_cst);
       u64 top = _top.load(relaxed);
-      Optional<T> x {};
-      if (top <= bottom)
+      if (top > bottom)
       {
-        x = array->get(bottom);
-        if (top == bottom)
-        {
-          if (!_top.compare_exchange_strong(top, top + 1, seq_cst, relaxed))
-          {
-            x = {};
-          }
-          _bottom.store(bottom + 1, relaxed);
+        _bottom.store(top, relaxed);
+        return { Empty };
       }
+      T x = array->get(bottom);
+      if (top < bottom)
+      {
+        return { x };
       }
-      else
+      if (!_top.compare_exchange_strong(top, top + 1, seq_cst, relaxed))
       {
-        _bottom.store(bottom + 1, relaxed);
+        _bottom.store(top + 1, relaxed);
+        return { Empty };
       }
-      return x;
+      _bottom.store(top + 1, relaxed);
+      return { x };
     }
 
-    Optional<T> steal() noexcept
+    Pop steal() noexcept
     {
       u64 top = _top.load(acquire);
       std::atomic_thread_fence(seq_cst);
       u64 bottom = _bottom.load(acquire);
-      Optional<T> x {};
       if (top < bottom)
       {
         Array * array = _array.load(consume);
-        x = array->get(top);
+        T x = array->get(top);
         if (!_top.compare_exchange_strong(top, top + 1, seq_cst, relaxed))
         {
-          return {Optional<T>::abort};
+          return { Abort };
         }
+        return { x };
       }
-      return x;
+      return { Empty };
     }
   };
 

rt/include/typon/fork.hpp

@@ -51,7 +51,7 @@ namespace typon
         {
           std::coroutine_handle<> await_suspend(std::coroutine_handle<promise_type> coroutine) noexcept
           {
-            if (Optional continuation = Scheduler::pop())
+            if (auto continuation = Scheduler::pop())
             {
               return *continuation;
             }

rt/include/typon/fundamental/optional.hpp

+#ifndef TYPON_FUNDAMENTAL_OPTIONAL_HPP_INCLUDED
+#define TYPON_FUNDAMENTAL_OPTIONAL_HPP_INCLUDED
+
+#include <type_traits>
+
+
+namespace typon::fdt
+{
+
+  template <typename T, unsigned char N>
+    requires std::is_trivially_copyable_v<T>
+  struct optional
+  {
+    static_assert(N > 0, "N must be greater than 0");
+
+    template <unsigned char I>
+      requires (I <= N)
+    using state = std::integral_constant<unsigned char, I>;
+
+    unsigned char _state;
+    union
+    {
+      T _value;
+    };
+
+    optional() noexcept : _state(0) {}
+
+    template <unsigned char I>
+      requires (I < N)
+    optional(state<I> state) noexcept : _state(state) {}
+
+    optional(T value) noexcept : _state(N), _value(value) {}
+
+    ~optional()
+    {
+      if (_state == N)
+      {
+        std::destroy_at(std::addressof(_value));
+      }
+    }
+
+    operator bool() noexcept
+    {
+      return _state == N;
+    }
+
+    template <unsigned char I>
+    bool match(state<I> state) noexcept
+    {
+      return state() == _state;
+    }
+
+    T * operator->() noexcept
+    {
+      return std::addressof(_value);
+    }
+
+    T & operator*() noexcept
+    {
+      return _value;
+    }
+  };
+
+}
+
+
+#endif // TYPON_FUNDAMENTAL_OPTIONAL_HPP_INCLUDED

rt/include/typon/scheduler.hpp

@@ -8,6 +8,7 @@
 #include <vector>
 
 #include <typon/fundamental/event_count.hpp>
+#include <typon/fundamental/optional.hpp>
 #include <typon/fundamental/random.hpp>
 
 #include <typon/continuation.hpp>
@@ -20,8 +21,8 @@ namespace typon
   struct Scheduler
   {
     using uint = unsigned int;
-    using Task = Optional<continuation_handle>;
     using Deque = Deque<continuation_handle>;
+    using Task = typename Deque::Pop;
 
     static inline thread_local uint thread_id;
 
@@ -151,7 +152,7 @@ namespace typon
       }
       auto key = _notifyer.prepare_wait();
       task = _deque.back().steal();
-      if (task.state() != Task::empty)
+      if (!task.match(Deque::Empty))
       {
         _notifyer.cancel_wait();
         if (task)