ceph/src/boost/libs/log/example/doc/attr_value_visitation.cpp

   1 /*
   2  *          Copyright Andrey Semashev 2007 - 2015.
   3  * Distributed under the Boost Software License, Version 1.0.
   4  *    (See accompanying file LICENSE_1_0.txt or copy at
   5  *          http://www.boost.org/LICENSE_1_0.txt)
   6  */
   7
   8 #include <cstddef>
   9 #include <string>
  10 #include <iostream>
  11 #include <boost/mpl/vector.hpp>
  12 #include <boost/log/attributes/value_visitation.hpp>
  13 #include <boost/log/attributes/attribute_value_impl.hpp>
  14 #include <boost/log/utility/functional/save_result.hpp>
  15
  16 namespace logging = boost::log;
  17 namespace attrs = boost::log::attributes;
  18
  19 //[ example_attr_value_visitation
  20 // Our attribute value visitor
  21 struct print_visitor
  22 {
  23     typedef void result_type;
  24
  25     result_type operator() (int val) const
  26     {
  27         std::cout << "Visited value is int: " << val << std::endl;
  28     }
  29
  30     result_type operator() (std::string const& val) const
  31     {
  32         std::cout << "Visited value is string: " << val << std::endl;
  33     }
  34 };
  35
  36 void print_value(logging::attribute_value const& attr)
  37 {
  38     // Define the set of expected types of the stored value
  39     typedef boost::mpl::vector< int, std::string > types;
  40
  41     // Apply our visitor
  42     logging::visitation_result result = logging::visit< types >(attr, print_visitor());
  43
  44     // Check the result
  45     if (result)
  46         std::cout << "Visitation succeeded" << std::endl;
  47     else
  48         std::cout << "Visitation failed" << std::endl;
  49 }
  50 //]
  51
  52 //[ example_attr_value_visitation_with_retval
  53 struct hash_visitor
  54 {
  55     typedef std::size_t result_type;
  56
  57     result_type operator() (int val) const
  58     {
  59         std::size_t h = val;
  60         h = (h << 15) + h;
  61         h ^= (h >> 6) + (h << 7);
  62         return h;
  63     }
  64
  65     result_type operator() (std::string const& val) const
  66     {
  67         std::size_t h = 0;
  68         for (std::string::const_iterator it = val.begin(), end = val.end(); it != end; ++it)
  69             h += *it;
  70
  71         h = (h << 15) + h;
  72         h ^= (h >> 6) + (h << 7);
  73         return h;
  74     }
  75 };
  76
  77 void hash_value(logging::attribute_value const& attr)
  78 {
  79     // Define the set of expected types of the stored value
  80     typedef boost::mpl::vector< int, std::string > types;
  81
  82     // Apply our visitor
  83     std::size_t h = 0;
  84     logging::visitation_result result = logging::visit< types >(attr, logging::save_result(hash_visitor(), h));
  85
  86     // Check the result
  87     if (result)
  88         std::cout << "Visitation succeeded, hash value: " << h << std::endl;
  89     else
  90         std::cout << "Visitation failed" << std::endl;
  91 }
  92 //]
  93
  94 #if 0
  95 //[ example_attr_value_visitation_with_retval_rec
  96 void hash_value(logging::record_view const& rec, logging::attribute_name name)
  97 {
  98     // Define the set of expected types of the stored value
  99     typedef boost::mpl::vector< int, std::string > types;
 100
 101     // Apply our visitor
 102     std::size_t h = 0;
 103     logging::visitation_result result = logging::visit< types >(name, rec, logging::save_result(hash_visitor(), h));
 104
 105     // Check the result
 106     if (result)
 107         std::cout << "Visitation succeeded, hash value: " << h << std::endl;
 108     else
 109         std::cout << "Visitation failed" << std::endl;
 110 }
 111 //]
 112 #endif
 113
 114 int main(int, char*[])
 115 {
 116     print_value(attrs::make_attribute_value(10));
 117     print_value(attrs::make_attribute_value(std::string("Hello")));
 118
 119     hash_value(attrs::make_attribute_value(10));
 120     hash_value(attrs::make_attribute_value(std::string("Hello")));
 121
 122     return 0;
 123 }