+ xoshiro256ss (copied from kalman project)

include/randomgen/random_seed.hpp

@@ -0,0 +1,70 @@
+/* @file random_seed.hpp */
+
+#include "indentlog/print/array.hpp"
+#include <iostream>
+#include <cstdint>
+#include <stdlib.h>
+
+namespace xo {
+    namespace rng {
+        /* generate a 64-bit random seed using /dev/urandom or similar source.
+         * This is relatively expensive;  at least cost of a system call
+         * + may block if host has rebooted recently
+         *
+         * Require:
+         * - T is null-constructible.
+         *
+         * return value will contain a T-instance in which representation
+         * has been populated with random bits.   Expecting T to be something
+         * like int32_t, or std::array<uint64_t, ..>
+         */
+        template<typename T>
+        void random_seed(T * p_seed) {
+            /* NOTE: arc4random_buf() works on darwin/nix;
+             *       probably need to do something else on intel linux
+             */
+            arc4random_buf(p_seed, sizeof(*p_seed));
+        } /*random_seed*/
+
+        template<typename T>
+        T random_seed() {
+            T retval;
+            random_seed(&retval);
+
+            return retval;
+        } /*random_seed*/
+
+        /* RAII-style random-number seed
+         *
+         * Usage:
+         *
+         *   Seed<xoshiro256ss> seed;
+         *
+         *   auto eng = xoshiro256ss(seed);
+         * or
+         *   auto rng = UnitIntervalGen<xoshiro256ss>::make(seed);
+         */
+        template<typename Engine>
+        struct Seed {
+            using seed_type = typename Engine::seed_type;
+
+            Seed() { random_seed(&seed_); }
+
+            operator seed_type const & () const { return seed_; }
+
+            seed_type seed_;
+        }; /*Seed*/
+
+        template<typename T>
+        inline std::ostream &
+        operator<<(std::ostream & os,
+                   Seed<T> const & x)
+        {
+            os << x.seed_;
+            return os;
+        } /*operator<<*/
+
+    } /*namespace rng*/
+} /*namespace xo*/
+
+/* end random_seed.hpp */