erpt: reimplement the sysmodule (#875)

* erpt: reimplement the sysmodule

* fatal: update for latest bindings

* erpt: amend logic for culling orphan attachments

libraries/libstratosphere/source/erpt/srv/erpt_srv_ref_count.hpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2018-2020 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 <stratosphere.hpp>
+
+namespace ams::erpt::srv {
+
+    class RefCount {
+        private:
+            static constexpr u32 MaxReferenceCount = 1000;
+            std::atomic<u32> ref_count;
+        public:
+            RefCount() : ref_count(0) { /* ... */ }
+
+            void AddReference() {
+                const auto prev = this->ref_count.fetch_add(1);
+                AMS_ABORT_UNLESS(prev <= MaxReferenceCount);
+            }
+
+            bool RemoveReference() {
+                auto prev = this->ref_count.fetch_sub(1);
+                AMS_ABORT_UNLESS(prev != 0);
+                return prev == 1;
+            }
+    };
+
+}