Add ThreadSafePool

Author: danngreen

util/thread_safe_pool.hh

@@ -0,0 +1,59 @@
+#pragma once
+#include <array>
+#include <atomic>
+#include <cstddef>
+#include <optional>
+
+namespace cpputil
+{
+
+template<typename T, size_t MaxEntries>
+class ThreadSafePool {
+private:
+	std::array<T, MaxEntries> data;
+	std::array<std::atomic<bool>, MaxEntries> used_flags;
+
+public:
+	ThreadSafePool() = default;
+
+	// Returns index of first available entry
+	// Returns nullopt if none available
+	std::optional<size_t> create() {
+		for (size_t i = 0; auto &used : used_flags) {
+			bool expected = false;
+			if (used.compare_exchange_strong(expected, true)) {
+				return i;
+			}
+			i++;
+		}
+		return std::nullopt;
+	}
+
+	// Returns whether item was actually destroyed
+	bool destroy(size_t idx) {
+		if (idx < used_flags.size()) {
+			bool expected = true;
+			if (used_flags[idx].compare_exchange_strong(expected, false)) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	void clear() {
+		for (size_t i = 0; i < MaxEntries; i++) {
+			data[i] = T{};
+			used_flags[i].store(false, std::memory_order_acquire);
+		}
+	}
+
+	T &operator[](size_t idx) {
+		return data[idx];
+	}
+
+	T &operator[](size_t idx) const {
+		return data[idx];
+	}
+};
+
+} // namespace cpputil