From 120b57b78455a53e8fb0116ab05916a9d1de7a97 Mon Sep 17 00:00:00 2001
From: Thiago Silva <thiago@nano.org>
Date: Mon, 17 Apr 2023 22:23:55 -0300
Subject: [PATCH] Try thread-safe optional_ptr

---
 nano/lib/optional_ptr.hpp | 50 ++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 11 deletions(-)

diff --git a/nano/lib/optional_ptr.hpp b/nano/lib/optional_ptr.hpp
index 56695fc3ed..e5b3df4b61 100644
--- a/nano/lib/optional_ptr.hpp
+++ b/nano/lib/optional_ptr.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <nano/lib/locks.hpp>
 #include <nano/lib/utility.hpp>
 
 #include <cstddef>
@@ -16,28 +17,32 @@ namespace nano
  * main difference being that it's copyable.
  */
 template <typename T>
-class optional_ptr
+class optional_ptr final
 {
 	static_assert (sizeof (T) > alignof (std::max_align_t), "Use [std|boost]::optional");
 
 public:
-	optional_ptr () = default;
+	explicit optional_ptr ()
+	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
+		ptr = nullptr;
+	}
 
-	optional_ptr (T const & value) :
-		ptr (new T{ value })
+	explicit optional_ptr (T const & value)
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
+		ptr = std::make_unique<T> (value);
 	}
 
-	optional_ptr (optional_ptr const & other)
+	explicit optional_ptr (optional_ptr const & other)
 	{
-		if (other && other.ptr)
-		{
-			ptr = std::make_unique<T> (*other.ptr);
-		}
+		nano::lock_guard<nano::mutex> lock{ mutex };
+		ptr = (other && other.ptr) ? std::make_unique<T> (*other.ptr) : nullptr;
 	}
 
 	optional_ptr & operator= (optional_ptr const & other)
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		if (other && other.ptr)
 		{
 			ptr = std::make_unique<T> (*other.ptr);
@@ -45,49 +50,72 @@ class optional_ptr
 		return *this;
 	}
 
+	optional_ptr & operator= (T const & t_object)
+	{
+		auto new_ptr = std::make_unique<T> (t_object);
+		nano::lock_guard<nano::mutex> lock{ mutex };
+		ptr.swap (new_ptr);
+		return *this;
+	}
+
+	~optional_ptr ()
+	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
+		ptr.reset (nullptr);
+	}
+
 	T & operator* ()
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		return *ptr;
 	}
 
 	T const & operator* () const
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		return *ptr;
 	}
 
 	T * const operator-> ()
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		return ptr.operator-> ();
 	}
 
 	T const * const operator-> () const
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		return ptr.operator-> ();
 	}
 
 	T const * const get () const
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		debug_assert (is_initialized ());
 		return ptr.get ();
 	}
 
 	T * const get ()
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		debug_assert (is_initialized ());
 		return ptr.get ();
 	}
 
 	explicit operator bool () const
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		return static_cast<bool> (ptr);
 	}
 
-	bool is_initialized () const
+	[[nodiscard]] bool is_initialized () const
 	{
+		nano::lock_guard<nano::mutex> lock{ mutex };
 		return static_cast<bool> (ptr);
 	}
 
 private:
-	std::unique_ptr<T> ptr{ nullptr };
+	std::unique_ptr<T> ptr;
+	mutable nano::mutex mutex;
 };
 }