lf_queue: add range-for support (endless loop with waiting)

Utilities/lockless.h

@@ -401,6 +401,64 @@ public:
 
 		return count;
 	}
+
+	// Iterator that enables direct endless range-for loop: for (auto* ptr : queue) ...
+	class iterator
+	{
+		lf_queue* _this = nullptr;
+
+		lf_queue_slice<T> m_data;
+
+	public:
+		constexpr iterator() = default;
+
+		explicit iterator(lf_queue* _this)
+			: _this(_this)
+		{
+			m_data = _this->pop_all();
+		}
+
+		bool operator !=(const iterator& rhs) const
+		{
+			return _this != rhs._this;
+		}
+
+		T* operator *() const
+		{
+			return m_data ? m_data.get() : nullptr;
+		}
+
+		iterator& operator ++()
+		{
+			if (m_data)
+			{
+				m_data.pop_front();
+			}
+
+			if (!m_data)
+			{
+				m_data = _this->pop_all();
+
+				if (!m_data)
+				{
+					_this->wait();
+					m_data = _this->pop_all();
+				}
+			}
+
+			return *this;
+		}
+	};
+
+	iterator begin()
+	{
+		return iterator{this};
+	}
+
+	iterator end()
+	{
+		return iterator{};
+	}
 };
 
 // Assignable lock-free thread-safe value of any type (memory-inefficient)