Implement support for parsing/interacting with NCAs. (#942)

* fs: implement support for interacting with ncas.

* spl: extend to use virtual keyslots

libraries/libstratosphere/include/stratosphere/fssystem/dbm/fssystem_dbm_utils.hpp

@@ -0,0 +1,43 @@
+/*
+ * 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 <vapours.hpp>
+
+namespace ams::fssystem::dbm {
+
+    namespace {
+
+        constexpr inline s32 CountLeadingZeros(u32 val) {
+            return util::CountLeadingZeros(val);
+        }
+
+        constexpr inline s32 CountLeadingOnes(u32 val) {
+            return CountLeadingZeros(~val);
+        }
+
+        inline u32 ReadU32(const u8 *buf, size_t index) {
+            u32 val;
+            std::memcpy(std::addressof(val), buf + index, sizeof(u32));
+            return val;
+        }
+
+        inline void WriteU32(u8 *buf, size_t index, u32 val) {
+            std::memcpy(buf + index, std::addressof(val), sizeof(u32));
+        }
+
+    }
+
+}