1 files changed, 123 insertions, 0 deletions
diff --git a/comphelper/source/misc/random.cxx b/comphelper/source/misc/random.cxx
new file mode 100644
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+++ b/comphelper/source/misc/random.cxx
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * Contributor(s):
+ *   Copyright (C) 2012 Tino Kluge <tino.kluge@hrz.tu-chemnitz.de>
+ */
+
+#include <comphelper/random.hxx>
+#include <sal/log.hxx>
+#include <assert.h>
+#include <time.h>
+#include <mutex>
+#include <random>
+#include <stdexcept>
+#if defined HAVE_VALGRIND_HEADERS
+#include <valgrind/memcheck.h>
+#endif
+
+// this is nothing but a simple wrapper around
+// the std::random generators
+
+namespace comphelper::rng
+{
+// underlying random number generator
+// std::mt19937 implements the Mersenne twister algorithm which
+// is fast and has good statistical properties, it produces integers
+// in the range of [0, 2^32-1] internally
+// memory requirement: 625*sizeof(uint32_t)
+// http://en.wikipedia.org/wiki/Mersenne_twister
+#define STD_RNG_ALGO std::mt19937
+
+namespace
+{
+struct RandomNumberGenerator
+{
+    std::mutex mutex;
+    STD_RNG_ALGO global_rng;
+    RandomNumberGenerator()
+    {
+        // make RR easier to use, breaks easily without the RNG being repeatable
+        bool bRepeatable = (getenv("SAL_RAND_REPEATABLE") != nullptr) || (getenv("RR") != nullptr);
+        // valgrind on some platforms (e.g.Ubuntu16.04) does not support the new Intel RDRAND instructions,
+        // which leads to "Illegal Opcode" errors, so just turn off randomness.
+#if defined HAVE_VALGRIND_HEADERS
+        if (RUNNING_ON_VALGRIND)
+            bRepeatable = true;
+#endif
+        if (bRepeatable)
+        {
+            global_rng.seed(42);
+            return;
+        }
+
+        try
+        {
+            std::random_device rd;
+            // initialises the state of the global random number generator
+            // should only be called once.
+            // (note, a few std::variate_generator<> (like normal) have their
+            // own state which would need a reset as well to guarantee identical
+            // sequence of numbers, e.g. via myrand.distribution().reset())
+            global_rng.seed(rd() ^ time(nullptr));
+        }
+        catch (std::runtime_error& e)
+        {
+            SAL_WARN("comphelper", "Using std::random_device failed: " << e.what());
+            global_rng.seed(time(nullptr));
+        }
+    }
+};
+
+RandomNumberGenerator& GetTheRandomNumberGenerator()
+{
+    static RandomNumberGenerator RANDOM;
+    return RANDOM;
+}
+}
+
+// uniform ints [a,b] distribution
+int uniform_int_distribution(int a, int b)
+{
+    std::uniform_int_distribution<int> dist(a, b);
+    auto& gen = GetTheRandomNumberGenerator();
+    std::scoped_lock<std::mutex> g(gen.mutex);
+    return dist(gen.global_rng);
+}
+
+// uniform ints [a,b] distribution
+unsigned int uniform_uint_distribution(unsigned int a, unsigned int b)
+{
+    std::uniform_int_distribution<unsigned int> dist(a, b);
+    auto& gen = GetTheRandomNumberGenerator();
+    std::scoped_lock<std::mutex> g(gen.mutex);
+    return dist(gen.global_rng);
+}
+
+// uniform size_t [a,b] distribution
+size_t uniform_size_distribution(size_t a, size_t b)
+{
+    std::uniform_int_distribution<size_t> dist(a, b);
+    auto& gen = GetTheRandomNumberGenerator();
+    std::scoped_lock<std::mutex> g(gen.mutex);
+    return dist(gen.global_rng);
+}
+
+// uniform size_t [a,b) distribution
+double uniform_real_distribution(double a, double b)
+{
+    assert(a < b);
+    std::uniform_real_distribution<double> dist(a, b);
+    auto& gen = GetTheRandomNumberGenerator();
+    std::scoped_lock<std::mutex> g(gen.mutex);
+    return dist(gen.global_rng);
+}
+
+} // namespace
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */