Add srb2::MobjList, similar to std::forward_list

src/mobj_list.hpp

@@ -0,0 +1,86 @@
+// DR. ROBOTNIK'S RING RACERS
+//-----------------------------------------------------------------------------
+// Copyright (C) 2023 by James Robert Roman
+//
+// This program is free software distributed under the
+// terms of the GNU General Public License, version 2.
+// See the 'LICENSE' file for more details.
+//-----------------------------------------------------------------------------
+
+#ifndef mobj_list_hpp
+#define mobj_list_hpp
+
+#include <type_traits>
+
+#include "cxxutil.hpp"
+#include "mobj.hpp"
+#include "mobj_list_view.hpp"
+
+namespace srb2
+{
+
+// Requires:
+//   void T::next(T*)
+//   T*   T::next() const
+template <typename T, mobj_t*& Head>
+struct MobjList
+{
+	static_assert(std::is_convertible_v<T, mobj_t>);
+
+	MobjList() {}
+
+	T* front() const { return static_cast<T*>(Head); }
+	bool empty() const { return !front(); }
+
+	void push_front(T* ptr)
+	{
+		ptr->next(front());
+		front(ptr);
+	}
+
+	void erase(T* node)
+	{
+		if (front() == node)
+		{
+			front(node->next());
+			node->next(nullptr);
+			return;
+		}
+
+		auto view = this->view();
+		auto end = view.end();
+		auto it = view.begin();
+
+		SRB2_ASSERT(it != end);
+
+		for (;;)
+		{
+			T* prev = *it;
+
+			it++;
+
+			if (it == end)
+			{
+				break;
+			}
+
+			if (*it == node)
+			{
+				prev->next(node->next());
+				node->next(nullptr);
+				break;
+			}
+		}
+	}
+
+	auto begin() const { return view().begin(); }
+	auto end() const { return view().end(); }
+
+private:
+	void front(T* ptr) { Mobj::ManagedPtr {Head} = ptr; }
+	auto view() const { return MobjListView(front(), [](T* node) { return node->next(); }); }
+};
+
+}; // namespace srb2
+
+#endif/*mobj_list_hpp*/