Partial commit: sys_fs

Utilities/lockless.h

@@ -103,3 +103,46 @@ public:
 		});
 	}
 };
+
+//! Simple lock-free map. Based on lf_array<>. All elements are accessible, implicitly initialized.
+template<typename K, typename T, typename Hash = value_hash<K>, std::size_t Size = 256>
+class lf_hashmap
+{
+	struct pair_t
+	{
+		// Default-constructed key means "no key"
+		atomic_t<K> key{};
+		T value{};
+	};
+
+	//
+	lf_array<pair_t, Size> m_data{};
+
+	// Value for default-constructed key
+	T m_default_key_data{};
+
+public:
+	constexpr lf_hashmap() = default;
+
+	// Access element (added implicitly)
+	T& operator [](const K& key)
+	{
+		if (UNLIKELY(key == K{}))
+		{
+			return m_default_key_data;
+		}
+		
+		// Calculate hash and array position
+		for (std::size_t pos = Hash{}(key) % Size;; pos += Size)
+		{
+			// Access the array
+			auto& pair = m_data[pos];
+
+			// Check the key value (optimistic)
+			if (LIKELY(pair.key == key) || pair.key.compare_and_swap_test(K{}, key))
+			{
+				return pair.value;
+			}
+		}
+	}
+};