util: LockFreeAtomicType (for time)

libraries/libstratosphere/include/stratosphere/util.hpp

@@ -19,3 +19,4 @@
 #include <stratosphere/util/util_compression.hpp>
 #include <stratosphere/util/util_ini.hpp>
 #include <stratosphere/util/util_singleton_traits.hpp>
+#include <stratosphere/util/util_lock_free_atomic_type.hpp>

libraries/libstratosphere/include/stratosphere/util/util_lock_free_atomic_type.hpp

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#pragma once
+#include <vapours.hpp>
+#include <stratosphere/os/os_memory_fence_api.hpp>
+
+namespace ams::util {
+
+    template<typename T>
+    struct LockFreeAtomicType {
+        volatile u32 _counter;
+        T _value[2];
+    };
+
+    template<typename T>
+    void StoreToLockFreeAtomicType(LockFreeAtomicType<T> *p, const T &value) {
+        /* Get the current counter. */
+        auto counter = p->_counter;
+
+        /* Increment the counter. */
+        ++counter;
+
+        /* Store the updated value. */
+        p->_value[counter % 2] = value;
+
+        /* Fence memory. */
+        os::FenceMemoryStoreStore();
+
+        /* Set the updated counter. */
+        p->_counter = counter;
+    }
+
+    template<typename T>
+    T LoadFromLockFreeAtomicType(const LockFreeAtomicType<T> *p) {
+        while (true) {
+            /* Get the counter. */
+            auto counter = p->_counter;
+
+            /* Get the value. */
+            auto value = p->_value[counter % 2];
+
+            /* Fence memory. */
+            os::FenceMemoryLoadLoad();
+
+            /* Check that the counter matches. */
+            if (counter == p->_counter) {
+                return value;
+            }
+        }
+    }
+
+}