intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 50 insertions, 0 deletions

diff --git a/util/random/mersenne64.h b/util/random/mersenne64.h
new file mode 100644
index 0000000000..12ca43b6af
--- /dev/null
+++ b/util/random/mersenne64.h
@@ -0,0 +1,50 @@
+#pragma once
+
+#include <util/system/defaults.h>
+
+class IInputStream;
+
+namespace NPrivate {
+    class TMersenne64 {
+        static constexpr int NN = 312;
+
+    public:
+        inline TMersenne64(ui64 s = ULL(19650218))
+            : mti(NN + 1)
+        {
+            InitGenRand(s);
+        }
+
+        inline TMersenne64(const ui64* keys, size_t len) noexcept
+            : mti(NN + 1)
+        {
+            InitByArray(keys, len);
+        }
+
+        TMersenne64(IInputStream& input);
+
+        inline ui64 GenRand() noexcept {
+            if (mti >= NN) {
+                InitNext();
+            }
+
+            ui64 x = mt[mti++];
+
+            x ^= (x >> 29) & ULL(0x5555555555555555);
+            x ^= (x << 17) & ULL(0x71D67FFFEDA60000);
+            x ^= (x << 37) & ULL(0xFFF7EEE000000000);
+            x ^= (x >> 43);
+
+            return x;
+        }
+
+    private:
+        void InitNext() noexcept;
+        void InitGenRand(ui64 seed) noexcept;
+        void InitByArray(const ui64* init_key, size_t key_length) noexcept;
+
+    private:
+        ui64 mt[NN];
+        int mti;
+    };
+}