Add Pool type

Author: danngreen

util/pool.hh

@@ -0,0 +1,59 @@
+#pragma once
+#include <array>
+#include <cstddef>
+
+namespace cpputil
+{
+
+// Hold static memory for a maximum number of objects of a given type T
+// Default constructs one when asked to create()
+template<typename T, size_t MaxEntries>
+struct Pool {
+
+	struct Entry {
+		T data;
+		bool used = false;
+	};
+	std::array<Entry, MaxEntries> entries{};
+
+	Pool() = default;
+
+	// Returns ptr to a default-constructed T
+	// Returns nullptr if none available
+	T *create() {
+		for (auto &entry : entries) {
+			if (!entry.used) {
+				entry.used = true;
+				entry.data = T{};
+				return &entry.data;
+			}
+		}
+
+		return nullptr;
+	}
+
+	// Returns ptr to a T in an unspecificed state
+	// Returns nullptr if none available
+	T *create_for_overwrite() {
+		for (auto &entry : entries) {
+			if (!entry.used) {
+				entry.used = true;
+				return &entry.data;
+			}
+		}
+
+		return nullptr;
+	}
+
+	// Returns whether item was found
+	bool destroy(T *item) {
+		for (auto &entry : entries) {
+			if (entry.used && item == &entry.data) {
+				entry.used = false;
+				return true;
+			}
+		}
+		return false;
+	}
+};
+} // namespace cpputil