random: use TinyMT instead of XorShift

libraries/libstratosphere/source/os/os_random.cpp

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2018-2019 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>
+#include "impl/os_random_impl.hpp"
+
+namespace ams::os {
+
+    namespace {
+
+        util::TinyMT g_random;
+        os::Mutex g_random_mutex;
+        bool g_initialized_random;
+
+        template<typename T>
+        inline T GenerateRandomTImpl(T max) {
+            static_assert(std::is_integral<T>::value && std::is_unsigned<T>::value);
+            const T EffectiveMax = (std::numeric_limits<T>::max() / max) * max;
+            T cur_rnd;
+            while (true) {
+                os::GenerateRandomBytes(&cur_rnd, sizeof(T));
+                if (cur_rnd < EffectiveMax) {
+                    return cur_rnd % max;
+                }
+            }
+        }
+
+    }
+
+    void GenerateRandomBytes(void *dst, size_t size) {
+        std::scoped_lock lk(g_random_mutex);
+
+        if (!g_initialized_random) {
+            impl::InitializeRandomImpl(&g_random);
+            g_initialized_random = true;
+        }
+
+        g_random.GenerateRandomBytes(dst, size);
+    }
+
+    u32 GenerateRandomU32(u32 max) {
+        return GenerateRandomTImpl<u32>(max);
+    }
+
+    u64 GenerateRandomU64(u64 max) {
+        return GenerateRandomTImpl<u64>(max);
+    }
+
+}