merge changes from the defunct ubot

ext/crlib/cr-random.h

@@ -0,0 +1,72 @@
+//
+// CRLib - Simple library for STL replacement in private projects.
+// Copyright © 2020 YaPB Development Team <team@yapb.ru>.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that 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.
+// 
+
+#pragma once
+
+#include <time.h>
+#include <crlib/cr-basic.h>
+
+CR_NAMESPACE_BEGIN
+
+// random number generator see: https://github.com/preshing/RandomSequence/
+class Random final : public Singleton <Random> {
+private:
+   uint32 index_, offset_;
+   uint64 divider_;
+
+public:
+   explicit Random () {
+      const auto base = static_cast <uint32> (time (nullptr));
+      const auto offset = base + 1;
+
+      index_ = premute (premute (base) + 0x682f0161);
+      offset_ = premute (premute (offset) + 0x46790905);
+      divider_ = (static_cast <uint64> (1)) << 32;
+   }
+   ~Random () = default;
+
+private:
+   uint32 premute (uint32 index) {
+      static constexpr auto prime = 4294967291u;
+
+      if (index >= prime) {
+         return index;
+      }
+      const uint32 residue = (static_cast <uint64> (index) * index) % prime;
+      return (index <= prime / 2) ? residue : prime - residue;
+   }
+
+   uint32 generate () {
+      return premute ((premute (index_++) + offset_) ^ 0x5bf03635);
+   }
+
+public:
+   template <typename U> U int_ (U low, U high) {
+      return static_cast <U> (generate () * (static_cast <double> (high) - static_cast <double> (low) + 1.0) / divider_ + static_cast <double> (low));
+   }
+
+   float float_ (float low, float high) {
+      return static_cast <float> (generate () * (static_cast <double> (high) - static_cast <double> (low)) / (divider_ - 1) + static_cast <double> (low));
+   }
+
+   template <typename U> bool chance (const U max, const U maxChance = 100) {
+      return int_ <U> (0, maxChance) < max;
+   }
+};
+
+// expose global random generator
+CR_EXPOSE_GLOBAL_SINGLETON (Random, rg);
+
+CR_NAMESPACE_END