git subrepo clone https://github.com/Atmosphere-NX/Atmosphere-libs libraries

subrepo:
  subdir:   "libraries"
  merged:   "07af583b"
upstream:
  origin:   "https://github.com/Atmosphere-NX/Atmosphere-libs"
  branch:   "master"
  commit:   "07af583b"
git-subrepo:
  version:  "0.4.0"
  origin:   "https://github.com/ingydotnet/git-subrepo"
  commit:   "5d6aba9"

libraries/libstratosphere/source/rnd/rnd_api.cpp

@@ -0,0 +1,129 @@
+/*
+ * 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 <random>
+#include <stratosphere.hpp>
+
+namespace ams::rnd {
+
+    namespace {
+
+        /* Generator type. */
+        /* Official HOS uses TinyMT. This is high effort. Let's just use XorShift. */
+        /* https://en.wikipedia.org/wiki/Xorshift */
+        class XorShiftGenerator {
+            public:
+                using ResultType = uint32_t;
+                using result_type = ResultType;
+                static constexpr ResultType (min)() { return std::numeric_limits<ResultType>::min(); }
+                static constexpr ResultType (max)() { return std::numeric_limits<ResultType>::max(); }
+                static constexpr size_t SeedSize = 4;
+            private:
+                ResultType random_state[SeedSize];
+            public:
+
+                explicit XorShiftGenerator() {
+                    /* Seed using process entropy. */
+                    u64 val = 0;
+                    for (size_t i = 0; i < SeedSize; i++) {
+                        R_ASSERT(svcGetInfo(&val, InfoType_RandomEntropy, INVALID_HANDLE, i));
+                        this->random_state[i] = ResultType(val);
+                    }
+                }
+
+                explicit XorShiftGenerator(std::random_device &rd) {
+                    for (size_t i = 0; i < SeedSize; i++) {
+                        this->random_state[i] = ResultType(rd());
+                    }
+                }
+
+                ResultType operator()() {
+                    ResultType s, t = this->random_state[3];
+                    t ^= t << 11;
+                    t ^= t >> 8;
+                    this->random_state[3] = this->random_state[2]; this->random_state[2] = this->random_state[1]; this->random_state[1] = (s = this->random_state[0]);
+                    t ^= s;
+                    t ^= s >> 19;
+                    this->random_state[0] = t;
+                    return t;
+                }
+
+                void discard(size_t n) {
+                    for (size_t i = 0; i < n; i++) {
+                        operator()();
+                    }
+                }
+        };
+
+        /* Generator global. */
+        XorShiftGenerator g_rnd_generator;
+
+        /* Templated helpers. */
+        template<typename T>
+        T GenerateRandom(T max = std::numeric_limits<T>::max()) {
+            std::uniform_int_distribution<T> rnd(std::numeric_limits<T>::min(), max);
+            return rnd(g_rnd_generator);
+        }
+
+    }
+
+    void GenerateRandomBytes(void* _out, size_t size) {
+        uintptr_t out = reinterpret_cast<uintptr_t>(_out);
+        uintptr_t end = out + size;
+
+        /* Force alignment. */
+        if (out % sizeof(u16) && out < end) {
+            *reinterpret_cast<u8 *>(out) = GenerateRandom<u8>();
+            out += sizeof(u8);
+        }
+        if (out % sizeof(u32) && out < end) {
+            *reinterpret_cast<u16 *>(out) = GenerateRandom<u16>();
+            out += sizeof(u16);
+        }
+        if (out % sizeof(u64) && out < end) {
+            *reinterpret_cast<u32 *>(out) = GenerateRandom<u32>();
+            out += sizeof(u32);
+        }
+
+        /* Perform as many aligned writes as possible. */
+        while (out + sizeof(u64) <= end) {
+            *reinterpret_cast<u64 *>(out) = GenerateRandom<u64>();
+            out += sizeof(u64);
+        }
+
+        /* Do remainder writes. */
+        if (out + sizeof(u32) <= end) {
+            *reinterpret_cast<u32 *>(out) = GenerateRandom<u32>();
+            out += sizeof(u32);
+        }
+        if (out + sizeof(u16) <= end) {
+            *reinterpret_cast<u16 *>(out) = GenerateRandom<u16>();
+            out += sizeof(u16);
+        }
+        if (out + sizeof(u8) <= end) {
+            *reinterpret_cast<u8 *>(out) = GenerateRandom<u8>();
+            out += sizeof(u8);
+        }
+    }
+
+    u32  GenerateRandomU32(u32 max) {
+        return GenerateRandom<u32>(max);
+    }
+
+    u64  GenerateRandomU64(u64 max) {
+        return GenerateRandom<u64>(max);
+    }
+
+}