[common] introduce new random header with convience wrapper around std::random dists

dune/stuff/common/random.hh

+#ifndef DUNE_STUFF_RANDOM_HH
+#define DUNE_STUFF_RANDOM_HH
+
+#include <random>
+#include <boost/assign/list_of.hpp>
+
+namespace Dune {
+namespace Stuff {
+namespace Common {
+namespace Math {
+
+template <typename T, bool = std::is_integral<T>::value>
+struct UniformDistributionSelector
+{
+};
+
+template <typename T>
+struct UniformDistributionSelector<T, true>
+{
+  typedef std::uniform_int_distribution<T> type;
+};
+template <typename T>
+struct UniformDistributionSelector<T, false>
+{
+  typedef std::uniform_real_distribution<T> type;
+};
+
+template <class T, class DistributionImp, class EngineImp>
+struct RNG
+{
+  typedef DistributionImp DistributionType;
+  typedef EngineImp EngineType;
+  EngineType generator;
+  DistributionType distribution;
+  RNG(EngineType g, DistributionType d)
+    : generator(g)
+    , distribution(d)
+  {
+  }
+
+  T operator()()
+  {
+    return distribution(generator);
+  }
+};
+
+template <class T>
+class DefaultRNG : public RNG<T, typename UniformDistributionSelector<T>::type, std::default_random_engine>
+{
+  typedef RNG<T, typename UniformDistributionSelector<T>::type, std::default_random_engine> BaseType;
+
+public:
+  DefaultRNG(T min = std::numeric_limits<T>::min(), T max = std::numeric_limits<T>::max())
+    : BaseType(std::default_random_engine(std::random_device()()),
+               typename UniformDistributionSelector<T>::type(min, max))
+  {
+  }
+};
+
+namespace {
+const std::string alphanums("abcdefghijklmnopqrstuvwxyz"
+                            "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                            "1234567890");
+const std::string other_printables("!@#$%^&*()"
+                                   "`~-_=+[{]{\\|;:'\",<.>/? ");
+}
+
+class RandomStrings : public RNG<std::string, std::uniform_int_distribution<int>, std::mt19937>
+{
+  typedef RNG<std::string, std::uniform_int_distribution<int>, std::mt19937> BaseType;
+  const int length;
+
+public:
+  RandomStrings(int l)
+    : BaseType(std::mt19937(std::random_device()()), std::uniform_int_distribution<int>(0, alphanums.size() - 1))
+    , length(l)
+  {
+  }
+
+  std::string operator()()
+  {
+    std::string ret(length, '\0');
+    std::generate(std::begin(ret), std::end(ret), [=]() { return alphanums[distribution(generator)]; });
+    return ret;
+  }
+};
+
+
+} // namespace Math
+} // namespace Common
+} // namespace Stuff
+} // namespace Dune
+
+#endif // DUNE_STUFF_RANDOM_HH
+
+/** Copyright (c) 2012, Rene Milk
+   * All rights reserved.
+   *
+   * Redistribution and use in source and binary forms, with or without
+   * modification, are permitted provided that the following conditions are met:
+   *
+   * 1. Redistributions of source code must retain the above copyright notice, this
+   *    list of conditions and the following disclaimer.
+   * 2. Redistributions in binary form must reproduce the above copyright notice,
+   *    this list of conditions and the following disclaimer in the documentation
+   *    and/or other materials provided with the distribution.
+   *
+   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+   *
+   * The views and conclusions contained in the software and documentation are those
+   * of the authors and should not be interpreted as representing official policies,
+   * either expressed or implied, of the FreeBSD Project.
+   **/