From 83aba92c420408b0e20e2c27436f6af97c0e4f19 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Wed, 23 Sep 2020 11:00:19 +0300
Subject: [PATCH] Add PCG32 generator to pcg

---
 .../include/psemek/pcg/random/generator.hpp   | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 libs/pcg/include/psemek/pcg/random/generator.hpp

diff --git a/libs/pcg/include/psemek/pcg/random/generator.hpp b/libs/pcg/include/psemek/pcg/random/generator.hpp
new file mode 100644
index 00000000..3d58e9d1
--- /dev/null
+++ b/libs/pcg/include/psemek/pcg/random/generator.hpp
@@ -0,0 +1,66 @@
+#pragma once
+
+#include <cstdint>
+#include <limits>
+
+namespace psemek::pcg
+{
+
+	// based on www.pcg-random.org
+	struct generator
+	{
+		generator() = default;
+		generator(generator const &) = default;
+
+		generator(std::uint64_t state, std::uint64_t inc)
+			: state_{state}
+			, inc_{inc}
+		{}
+
+		template <typename RD>
+		generator(RD && rd, std::uint64_t inc)
+			: state_{gen64(rd)}
+			, inc_{inc}
+		{}
+
+		template <typename RD>
+		generator(RD && rd)
+			: state_{gen64(rd)}
+			, inc_{gen64(rd)}
+		{}
+
+		generator & operator = (generator const &) = default;
+
+		using result_type = std::uint32_t;
+
+		result_type operator()()
+		{
+			std::uint64_t oldstate = state_;
+			state_ = oldstate * 6364136223846793005ULL + (inc_ | 1);
+			std::uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
+			std::uint32_t rot = oldstate >> 59u;
+			return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
+		}
+
+		static result_type min()
+		{
+			return 0;
+		}
+
+		static result_type max()
+		{
+			return std::numeric_limits<result_type>::max();
+		}
+
+	private:
+		std::uint64_t state_;
+		std::uint64_t inc_;
+
+		template <typename RD>
+		static std::uint64_t gen64(RD & rd)
+		{
+			return (static_cast<std::uint64_t>(rd()) << 32) | rd();
+		}
+	};
+
+}