From f8f3bb242188fc433fba71550ce9fba5b7e18a24 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=CE=B6eh=20Matt?= <5415177+ZehMatt@users.noreply.github.com>
Date: Thu, 17 Mar 2022 17:35:34 +0200
Subject: [PATCH] Use std::minstd_rand and split serialization from save/load

---
 apps/openmw/mwworld/worldimp.cpp |  9 +++----
 components/misc/rng.cpp          | 19 +++++++++++++++
 components/misc/rng.hpp          | 40 ++++----------------------------
 3 files changed, 27 insertions(+), 41 deletions(-)

diff --git a/apps/openmw/mwworld/worldimp.cpp b/apps/openmw/mwworld/worldimp.cpp
index fb48707a8e..6517694f15 100644
--- a/apps/openmw/mwworld/worldimp.cpp
+++ b/apps/openmw/mwworld/worldimp.cpp
@@ -342,7 +342,7 @@ namespace MWWorld
     void World::write (ESM::ESMWriter& writer, Loading::Listener& progress) const
     {
         writer.startRecord(ESM::REC_RAND);
-        writer.writeHNT("RAND", mPrng.getSeed());
+        writer.writeHNOString("RAND", Misc::Rng::serialize(mPrng));
         writer.endRecord(ESM::REC_RAND);
 
         // Active cells could have a dirty fog of war, sync it to the CellStore first
@@ -385,11 +385,8 @@ namespace MWWorld
                 return;
             case ESM::REC_RAND:
                 {
-                    Misc::Rng::Generator::result_type seed{};
-                    reader.getHNT(seed, "RAND");
-                    Log(Debug::Info) << "---- World random state: " << seed << " ----";
-                    mPrng.seed(seed);
-                    Misc::Rng::getGenerator().seed(seed);
+                    auto data = reader.getHNOString("RAND");
+                    Misc::Rng::deserialize(data, mPrng);
                 }
                 break;
             case ESM::REC_PLAY:
diff --git a/components/misc/rng.cpp b/components/misc/rng.cpp
index b44c6c2785..01044040a0 100644
--- a/components/misc/rng.cpp
+++ b/components/misc/rng.cpp
@@ -2,6 +2,7 @@
 
 #include <chrono>
 #include <random>
+#include <sstream>
 
 #include <components/debug/debuglog.hpp>
 
@@ -14,6 +15,23 @@ namespace Misc::Rng
         return sGenerator;
     }
 
+    std::string serialize(const Generator& prng)
+    {
+        std::stringstream ss;
+        ss << prng;
+
+        return ss.str();
+    }
+
+    void deserialize(std::string_view data, Generator& prng)
+    {
+        std::stringstream ss;
+        ss << data;
+
+        ss.seekg(0);
+        ss >> prng;
+    }
+
     unsigned int generateDefaultSeed()
     {
         auto res = static_cast<unsigned int>(std::chrono::high_resolution_clock::now().time_since_epoch().count());
@@ -65,4 +83,5 @@ namespace Misc::Rng
     {
         return std::uniform_real_distribution<float>(mean - deviation, mean + deviation)(prng);
     }
+
 }
diff --git a/components/misc/rng.hpp b/components/misc/rng.hpp
index 1b7831e3c6..d7ab7f3e7a 100644
--- a/components/misc/rng.hpp
+++ b/components/misc/rng.hpp
@@ -3,50 +3,20 @@
 
 #include <cassert>
 #include <random>
+#include <string_view>
 
 /*
   Provides central implementation of the RNG logic
 */
 namespace Misc::Rng
 {
-    class Generator
-    {
-        uint32_t mState{};
-
-    public:
-        using result_type = uint32_t;
-
-        constexpr Generator() = default;
-        constexpr Generator(result_type seed) : mState{ seed } {}
-        constexpr result_type operator()() noexcept
-        {
-            mState = (214013 * mState + 2531011);
-            return (mState >> 16) & max();
-        }
-
-        static constexpr result_type min() noexcept
-        {
-            return 0u;
-        }
-
-        static constexpr result_type max() noexcept
-        {
-            return 0x7FFFu;
-        }        
-        
-        void seed(result_type val) noexcept
-        {
-            mState = val;
-        }
-
-        uint32_t getSeed() const noexcept
-        {
-            return mState;
-        }
-    };
+    using Generator = std::minstd_rand;
 
     Generator& getGenerator();
 
+    std::string serialize(const Generator& prng);
+    void deserialize(std::string_view data, Generator& prng);
+
     /// returns default seed for RNG
     unsigned int generateDefaultSeed();