ceph/src/boost/libs/math/example/nonfinite_serialization_archives.cpp

   1 /** nonfinite_serialization_archives.cpp
   2 *
   3 * Copyright (c) 2011 Paul A. Bristow
   4 *
   5 * Distributed under the Boost Software License, Version 1.0.
   6 * (See accompanying file LICENSE_1_0.txt
   7 * or copy at http://www.boost.org/LICENSE_1_0.txt)
   8 *
   9 * This very simple program illustrates how to use the
  10 * `boost/math/nonfinite_num_facets.hpp' to obtain C99
  11 * representation of infinity and NaN.
  12 * From the original Floating Point  Utilities contribution by Johan Rade.
  13 * Floating Point Utility library has been accepted into Boost,
  14 * but the utilities are incorporated into Boost.Math library.
  15 *
  16 \file
  17
  18 \brief A simple example of using non_finite_num facet for
  19 C99 standard output of infinity and NaN in serialization archives.
  20
  21 \detail This example shows how to create a C99 non-finite locale,
  22 and imbue input and output streams with the non_finite_num put and get facets.
  23 This allow output and input of infinity and NaN in a Standard portable way,
  24 This permits 'loop-back' of output back into input (and portably across different system too).
  25 This is particularly useful when used with Boost.Seralization so that non-finite NaNs and infinity
  26 values in text and xml archives can be handled correctly and portably.
  27
  28 */
  29
  30
  31 #ifdef _MSC_VER
  32 #   pragma warning(disable : 4127) // conditional expression is constant.
  33 #endif
  34
  35
  36 #include <boost/archive/text_oarchive.hpp>
  37 using boost::archive::text_oarchive;
  38 #include <boost/archive/codecvt_null.hpp>
  39 using boost::archive::codecvt_null;
  40 using boost::archive::no_codecvt;
  41
  42 #include <boost/math/special_functions/nonfinite_num_facets.hpp>
  43 using boost::math::nonfinite_num_get;
  44 using boost::math::nonfinite_num_put;
  45
  46 #include <iostream>
  47 using std::cout;
  48 using std::endl;
  49 using std::cerr;
  50
  51 #include <iomanip>
  52 using std::setw;
  53 using std::left;
  54 using std::right;
  55 using std::internal;
  56
  57 #include <string>
  58 using std::string;
  59
  60 #include <sstream>
  61 using std::istringstream;
  62
  63 #include <fstream>
  64 using std::ofstream;
  65
  66 #include <limits>
  67 using std::numeric_limits;
  68
  69 #include <locale>
  70 using std::locale;
  71
  72
  73 /*
  74 Use with serialization archives.
  75
  76 It is important that the same locale is used
  77 when an archive is saved and when it is loaded.
  78 Otherwise, loading the archive may fail.
  79
  80 By default, archives are saved and loaded with a classic C locale with a
  81 `boost::archive::codecvt_null` facet added.
  82 Normally you do not have to worry about that.
  83 The constructors for the archive classes, as a side-effect,
  84 imbue the stream with such a locale.
  85
  86 However, if you want to use the facets `nonfinite_num_put` and `nonfinite_num_get`
  87 with archives,`then you have to manage the locale manually.
  88
  89 That is done by calling the archive constructor with the flag `boost::archive::no_codecvt`.
  90 Then the archive constructor will not imbue the stream with a new locale.
  91
  92 The following code shows how to use `nonfinite_num_put` with a `text_oarchive`:
  93
  94 */
  95
  96 int main()
  97 {
  98
  99   if((std::numeric_limits<double>::has_infinity == false) || (std::numeric_limits<double>::infinity() == 0))
 100   {
 101     std::cout << "Infinity not supported on this platform." << std::endl;
 102     return 0;
 103   }
 104
 105   if((std::numeric_limits<double>::has_quiet_NaN == false) || (std::numeric_limits<double>::quiet_NaN() == 0))
 106   {
 107     std::cout << "NaN not supported on this platform." << std::endl;
 108     return 0;
 109   }
 110
 111   locale default_locale(locale::classic(), new boost::archive::codecvt_null<char>);
 112   // codecvt_null so the archive constructor will not imbue the stream with a new locale.
 113
 114   locale my_locale(default_locale, new nonfinite_num_put<char>);
 115   // Add nonfinite_num_put facet to locale.
 116
 117   ofstream ofs("test.txt");
 118   ofs.imbue(my_locale);
 119
 120   boost::archive::text_oarchive oa(ofs, no_codecvt);
 121
 122   double x = numeric_limits<double>::infinity();
 123   oa & x;
 124
 125
 126 } // int main()
 127
 128
 129 /* The same method works with nonfinite_num_get  and text_iarchive.
 130
 131 If you use the trap_infinity and trap_nan flags with a serialization archive,
 132 then you must set the exception mask of the stream.
 133 Serialization archives do not check the stream state.
 134
 135
 136 */