erpt: reimplement the sysmodule (#875)

* erpt: reimplement the sysmodule

* fatal: update for latest bindings

* erpt: amend logic for culling orphan attachments

libraries/libstratosphere/source/time/impl/util/time_impl_util_api.cpp

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2019-2020 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/>.
+ */
+#include <stratosphere.hpp>
+
+namespace ams::time::impl::util {
+
+    Result GetSpanBetween(s64 *out, const SteadyClockTimePoint &from, const SteadyClockTimePoint &to) {
+        AMS_ASSERT(out != nullptr);
+
+        R_UNLESS(out != nullptr,                 time::ResultInvalidPointer());
+        R_UNLESS(from.source_id == to.source_id, time::ResultNotComparable());
+
+        const bool no_overflow = (from.value >= 0 ? (to.value >= std::numeric_limits<s64>::min() + from.value)
+                                                  : (to.value <= std::numeric_limits<s64>::max() + from.value));
+        R_UNLESS(no_overflow, time::ResultOverflowed());
+
+        *out = to.value - from.value;
+        return ResultSuccess();
+    }
+
+}