Update the random_device implementation so that it:

* Supports more platforms optimally, for example CloudABI, OpenBSD, and Windows UWP
* Is easier to maintain as each platform's implementation is in a separate file
* Removes the library dependency on Boost.System
* Is header-only, and thus makes Boost.Random header-only
* Is well-tested for happy and sad paths

Adds a new exception "entropy_error" to handle errors getting entropy.

Removed the detail auto_link implementation inside Boost.Random as it is no longer
necessary - the one in Boost.Config is sufficient.

Also added a top-level Jamfile that builds the example subdirectory with each
build, as one of the examples needed to be updated in order to build.  This will
prevent rot in the example directory.

Note: Other libraries that link against Boost.Random (like Boost.Uuid) will fail
to build until they stop trying to link against Boost.Random.

This fixes boostorg#20
This fixes boostorg#22

.gitignore

@@ -1,3 +1,4 @@
 /doc/html
 /doc/reference.xml
-/test/rng.saved
+/example/rng.saved
+**/rng.saved

Jamfile

@@ -0,0 +1,30 @@
+#  Boost.Random Library Jamfile
+#
+#  Copyright (c) 2017 James E. King, III
+#
+#  Use, modification, and distribution are subject to the
+#  Boost Software License, Version 1.0. (See accompanying file
+#  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+project libs/random
+    : requirements
+
+      <warnings>all
+
+      <toolset>clang:<cxxflags>-Wextra
+      <toolset>clang:<cxxflags>-ansi
+#     <toolset>clang:<cxxflags>-pedantic
+      <toolset>clang:<cxxflags>-Wno-c++11-long-long
+
+      <toolset>gcc:<cxxflags>-Wextra
+      <toolset>gcc:<cxxflags>-ansi
+#     <toolset>gcc:<cxxflags>-pedantic
+      <toolset>gcc:<cxxflags>-Wno-long-long
+    ;
+
+# pedantic mode disabled due to issue in multiprecision
+# https://github.com/boostorg/multiprecision/issues/34
+
+# please order by name to ease maintenance
+build-project example ;
+build-project test ;

example/Jamfile.v2

@@ -7,6 +7,21 @@
 # accompanying file LICENSE_1_0.txt or copy at
 # http://www.boost.org/LICENSE_1_0.txt)
 
+project libs/random/example
+    : requirements
+
+      # boost.jam defines BOOST_ALL_NO_LIB for builds 
+      # which cannot be undefined?
+      <toolset>msvc:<define>BOOST_RANDOM_FORCE_AUTO_LINK
+      <toolset>gcc-mingw:<linkflags>"-lbcrypt"
+
+      # boost::random needs this setting for a warning free build:
+      <toolset>msvc:<define>_SCL_SECURE_NO_WARNINGS
+
+      # link static for easier debugging - uncomment if you need to debug...
+      # <link>static
+;
+
 run die.cpp ;
 run weighted_die.cpp ;
-run password.cpp /boost//random ;
+run password.cpp ;

example/password.cpp

@@ -16,9 +16,9 @@
     password.
  */
 
-
 #include <boost/random/random_device.hpp>
 #include <boost/random/uniform_int_distribution.hpp>
+#include <iostream>
 
 int main() {
     /*<< We first define the characters that we're going

include/boost/random/detail/generator_seed_seq.hpp

@@ -1,4 +1,4 @@
-/* boost random/mersenne_twister.hpp header file
+/* boost random/detail/generator_seed_seq.hpp header file
  *
  * Copyright Jens Maurer 2000-2001
  * Copyright Steven Watanabe 2010

include/boost/random/detail/random_provider.hpp

@@ -0,0 +1,75 @@
+//
+// Copyright (c) 2017 James E. King III
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+//   http://www.boost.org/LICENCE_1_0.txt)
+//
+// Platform-specific random entropy provider
+//
+
+#ifndef BOOST_RANDOM_DETAIL_RANDOM_PROVIDER_HPP
+#define BOOST_RANDOM_DETAIL_RANDOM_PROVIDER_HPP
+
+#include <boost/core/noncopyable.hpp>
+#include <boost/cstdint.hpp>
+#include <boost/limits.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/type_traits/is_integral.hpp>
+#include <boost/type_traits/is_unsigned.hpp>
+#include <boost/random/entropy_error.hpp>
+#include <iterator>
+
+// Detection of the platform is separated from inclusion of the correct
+// header to facilitate mock testing of the provider implementations.
+
+#include <boost/random/detail/random_provider_detect_platform.hpp>
+#include <boost/random/detail/random_provider_include_platform.hpp>
+
+
+namespace boost {
+namespace random {
+namespace detail {
+
+//! \brief Contains code common to all random_provider implementations.
+//! \note  random_provider_base is required to provide this method:
+//!        void get_random_bytes(void *buf, size_t siz);
+//! \note  noncopyable because of some base implementations so
+//!        this makes it uniform across platforms to avoid any  
+//!        porting surprises
+class random_provider
+    : public detail::random_provider_base,
+      public noncopyable
+{
+public:
+    //! Leverage the provider as a SeedSeq for
+    //! PseudoRandomNumberGeneration seeding
+    //! \note: See Boost.Random documentation for more details
+    template<class Iter>
+    void generate(Iter first, Iter last)
+    {
+        typedef typename std::iterator_traits<Iter>::value_type value_type;
+        BOOST_STATIC_ASSERT(is_integral<value_type>::value);
+        BOOST_STATIC_ASSERT(is_unsigned<value_type>::value);
+        BOOST_STATIC_ASSERT(sizeof(value_type) * CHAR_BIT >= 32);
+
+        for (; first != last; ++first)
+        {
+            get_random_bytes(&*first, sizeof(*first));
+            *first &= (std::numeric_limits<boost::uint32_t>::max)();
+        }
+    }
+
+    //! Return the name of the selected provider
+    const char * name() const
+    {
+        return BOOST_RANDOM_PROVIDER_STRINGIFY(BOOST_RANDOM_PROVIDER_NAME);
+    }
+};
+
+} // detail
+} // random
+} // boost
+
+#endif // BOOST_RANDOM_DETAIL_RANDOM_PROVIDER_HPP
+

include/boost/random/detail/random_provider_arc4random.ipp

@@ -0,0 +1,32 @@
+//
+// Copyright (c) 2017 James E. King III
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+//   http://www.boost.org/LICENCE_1_0.txt)
+//
+// "A Replacement Call for Random"
+// https://man.openbsd.org/arc4random.3
+//
+
+#include <stdlib.h> 
+
+namespace boost {
+namespace random {
+namespace detail {
+
+class random_provider_base
+{
+  public:
+    //! Obtain entropy and place it into a memory location
+    //! \param[in]  buf  the location to write entropy
+    //! \param[in]  siz  the number of bytes to acquire
+    void get_random_bytes(void *buf, size_t siz)
+    {
+        arc4random_buf(buf, siz);
+    }
+};
+
+} // detail
+} // random
+} // boost

include/boost/random/detail/random_provider_bcrypt.ipp

@@ -0,0 +1,78 @@
+//
+// Copyright (c) 2017 James E. King III
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+//   http://www.boost.org/LICENCE_1_0.txt)
+//
+// BCrypt provider for entropy
+//
+
+#include <boost/core/ignore_unused.hpp>
+#include <boost/throw_exception.hpp>
+#include <boost/winapi/bcrypt.hpp>
+#include <boost/winapi/get_last_error.hpp>
+
+#if defined(BOOST_RANDOM_FORCE_AUTO_LINK) || (!defined(BOOST_ALL_NO_LIB) && !defined(BOOST_RANDOM_NO_LIB))
+#   define BOOST_LIB_NAME "bcrypt"
+#   define BOOST_AUTO_LINK_NOMANGLE
+#   include <boost/config/auto_link.hpp>
+#   undef BOOST_AUTO_LINK_NOMANGLE
+#endif
+
+namespace boost {
+namespace random {
+namespace detail {
+
+class random_provider_base
+{
+  public:
+    random_provider_base()
+      : hProv_(NULL)
+    {
+        boost::winapi::NTSTATUS_ status =
+            boost::winapi::BCryptOpenAlgorithmProvider(
+                &hProv_, 
+                boost::winapi::BCRYPT_RNG_ALGORITHM_,
+                NULL,
+                0);
+
+        if (status)
+        {
+            BOOST_THROW_EXCEPTION(entropy_error(status, "BCryptOpenAlgorithmProvider"));
+        }
+    }
+
+    ~random_provider_base() BOOST_NOEXCEPT
+    {
+        if (hProv_)
+        {
+            ignore_unused(boost::winapi::BCryptCloseAlgorithmProvider(hProv_, 0));
+        }
+    }
+
+    //! Obtain entropy and place it into a memory location
+    //! \param[in]  buf  the location to write entropy
+    //! \param[in]  siz  the number of bytes to acquire
+    void get_random_bytes(void *buf, size_t siz)
+    {
+        boost::winapi::NTSTATUS_ status =
+            boost::winapi::BCryptGenRandom(
+                hProv_,
+                static_cast<boost::winapi::PUCHAR_>(buf),
+                siz,
+                0);
+
+        if (status)
+        {
+            BOOST_THROW_EXCEPTION(entropy_error(status, "BCryptGenRandom"));
+        }
+    }
+
+  private:
+    boost::winapi::BCRYPT_ALG_HANDLE_ hProv_;
+};
+
+} // detail
+} // random
+} // boost

include/boost/random/detail/random_provider_detect_platform.hpp

@@ -0,0 +1,62 @@
+//
+// Copyright (c) 2017 James E. King III
+//
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+//   http://www.boost.org/LICENCE_1_0.txt)
+//
+// Platform-specific random entropy provider platform detection
+//
+
+#ifndef BOOST_RANDOM_DETAIL_RANDOM_PROVIDER_PLATFORM_DETECTION_HPP
+#define BOOST_RANDOM_DETAIL_RANDOM_PROVIDER_PLATFORM_DETECTION_HPP
+
+#include <boost/predef/library/c/cloudabi.h>
+#include <boost/predef/library/c/gnu.h>
+#include <boost/predef/os/bsd/open.h>
+#include <boost/predef/os/windows.h>
+
+//
+// Platform Detection - will load in the correct header and
+// will define the class <tt>random_provider_base</tt>.
+//
+
+#if BOOST_OS_BSD_OPEN >= BOOST_VERSION_NUMBER(2, 1, 0) || BOOST_LIB_C_CLOUDABI
+# define BOOST_RANDOM_PROVIDER_ARC4RANDOM
+# define BOOST_RANDOM_PROVIDER_NAME arc4random
+
+#elif BOOST_OS_WINDOWS
+# include <boost/winapi/config.hpp>
+# if BOOST_WINAPI_PARTITION_APP_SYSTEM && \
+     !defined(BOOST_RANDOM_PROVIDER_FORCE_WINCRYPT) && \
+     !defined(_WIN32_WCE) && \
+     (defined(BOOST_WINAPI_IS_MINGW_W64) || \
+        (BOOST_USE_WINAPI_VERSION >= BOOST_WINAPI_VERSION_WIN6))
+#  define BOOST_RANDOM_PROVIDER_BCRYPT
+#  define BOOST_RANDOM_PROVIDER_NAME bcrypt
+
+# elif BOOST_WINAPI_PARTITION_DESKTOP || BOOST_WINAPI_PARTITION_SYSTEM
+#  define BOOST_RANDOM_PROVIDER_WINCRYPT
+#  define BOOST_RANDOM_PROVIDER_NAME wincrypt
+# else
+#  error Unable to find a suitable windows entropy provider
+# endif
+
+#elif BOOST_LIB_C_GNU >= BOOST_VERSION_NUMBER(2, 25, 0) && !defined(BOOST_RANDOM_PROVIDER_FORCE_POSIX)
+# define BOOST_RANDOM_PROVIDER_GETENTROPY
+# define BOOST_RANDOM_PROVIDER_NAME getentropy
+
+#else
+# define BOOST_RANDOM_PROVIDER_POSIX
+# define BOOST_RANDOM_PROVIDER_NAME posix
+
+#endif
+
+#define BOOST_RANDOM_PROVIDER_STRINGIFY2(X) #X
+#define BOOST_RANDOM_PROVIDER_STRINGIFY(X) BOOST_RANDOM_PROVIDER_STRINGIFY2(X)
+
+#if defined(BOOST_RANDOM_PROVIDER_SHOW)
+#pragma message("BOOST_RANDOM_PROVIDER_NAME " BOOST_RANDOM_PROVIDER_STRINGIFY(BOOST_RANDOM_PROVIDER_NAME))
+#endif
+
+#endif // BOOST_RANDOM_DETAIL_RANDOM_PROVIDER_PLATFORM_DETECTION_HPP