124 lines
3.3 KiB
C++
124 lines
3.3 KiB
C++
/*
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* Copyright Andrey Semashev 2007 - 2015.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*/
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#include <cstddef>
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#include <string>
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#include <iostream>
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#include <boost/mpl/vector.hpp>
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#include <boost/log/attributes/value_visitation.hpp>
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#include <boost/log/attributes/attribute_value_impl.hpp>
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#include <boost/log/utility/functional/save_result.hpp>
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namespace logging = boost::log;
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namespace attrs = boost::log::attributes;
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//[ example_attr_value_visitation
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// Our attribute value visitor
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struct print_visitor
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{
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typedef void result_type;
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result_type operator() (int val) const
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{
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std::cout << "Visited value is int: " << val << std::endl;
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}
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result_type operator() (std::string const& val) const
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{
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std::cout << "Visited value is string: " << val << std::endl;
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}
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};
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void print_value(logging::attribute_value const& attr)
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{
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// Define the set of expected types of the stored value
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typedef boost::mpl::vector< int, std::string > types;
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// Apply our visitor
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logging::visitation_result result = logging::visit< types >(attr, print_visitor());
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// Check the result
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if (result)
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std::cout << "Visitation succeeded" << std::endl;
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else
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std::cout << "Visitation failed" << std::endl;
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}
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//]
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//[ example_attr_value_visitation_with_retval
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struct hash_visitor
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{
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typedef std::size_t result_type;
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result_type operator() (int val) const
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{
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std::size_t h = val;
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h = (h << 15) + h;
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h ^= (h >> 6) + (h << 7);
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return h;
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}
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result_type operator() (std::string const& val) const
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{
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std::size_t h = 0;
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for (std::string::const_iterator it = val.begin(), end = val.end(); it != end; ++it)
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h += *it;
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h = (h << 15) + h;
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h ^= (h >> 6) + (h << 7);
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return h;
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}
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};
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void hash_value(logging::attribute_value const& attr)
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{
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// Define the set of expected types of the stored value
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typedef boost::mpl::vector< int, std::string > types;
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// Apply our visitor
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std::size_t h = 0;
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logging::visitation_result result = logging::visit< types >(attr, logging::save_result(hash_visitor(), h));
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// Check the result
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if (result)
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std::cout << "Visitation succeeded, hash value: " << h << std::endl;
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else
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std::cout << "Visitation failed" << std::endl;
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}
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//]
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#if 0
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//[ example_attr_value_visitation_with_retval_rec
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void hash_value(logging::record_view const& rec, logging::attribute_name name)
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{
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// Define the set of expected types of the stored value
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typedef boost::mpl::vector< int, std::string > types;
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// Apply our visitor
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std::size_t h = 0;
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logging::visitation_result result = logging::visit< types >(name, rec, logging::save_result(hash_visitor(), h));
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// Check the result
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if (result)
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std::cout << "Visitation succeeded, hash value: " << h << std::endl;
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else
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std::cout << "Visitation failed" << std::endl;
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}
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//]
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#endif
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int main(int, char*[])
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{
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print_value(attrs::make_attribute_value(10));
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print_value(attrs::make_attribute_value(std::string("Hello")));
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hash_value(attrs::make_attribute_value(10));
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hash_value(attrs::make_attribute_value(std::string("Hello")));
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return 0;
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}
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