boost.log（七）再谈过滤

#include <string>
#include <fstream>
#include <iomanip>
#include <boost/log/core.hpp>
#include <boost/smart_ptr.hpp>
#include <boost/log/sinks.hpp>
#include <boost/log/expressions.hpp>
#include <boost/log/utility/setup.hpp>
#include <boost/log/sources/record_ostream.hpp>
#include <boost/log/sources/severity_logger.hpp>
#include <boost/log/attributes/scoped_attribute.hpp>
 
enum severity_level
{
	normal,
	notification,
	warning,
	error,
	critical
};
 
BOOST_LOG_ATTRIBUTE_KEYWORD(tag_attr, "Tag", std::string)
BOOST_LOG_ATTRIBUTE_KEYWORD(line_id, "LineID", unsigned int)
BOOST_LOG_ATTRIBUTE_KEYWORD(severity, "Severity", severity_level)
 
void init()
{
	boost::log::formatter fmt = boost::log::expressions::stream
		<< std::setw(6) << std::setfill(‘0‘) << line_id << std::setfill(‘ ‘)
		<< ": <" << severity << ">\t"
		<< boost::log::expressions::if_(boost::log::expressions::has_attr(tag_attr))
		[
			boost::log::expressions::stream << "[" << tag_attr << "] "
		]
	<< boost::log::expressions::smessage;
 
	// Initialize sinks
	typedef boost::log::sinks::synchronous_sink< boost::log::sinks::text_ostream_backend > text_sink;
	boost::shared_ptr< text_sink > sink = boost::make_shared< text_sink >();
 
	sink->locked_backend()->add_stream(boost::make_shared< std::ofstream >("full.log"));
 
	sink->set_formatter(fmt);
 
	boost::log::core::get()->add_sink(sink);
 
	sink = boost::make_shared< text_sink >();
 
	sink->locked_backend()->add_stream(boost::make_shared< std::ofstream >("important.log"));
 
	sink->set_formatter(fmt);
 
	sink->set_filter(severity >= warning || (boost::log::expressions::has_attr(tag_attr) && tag_attr == "IMPORTANT_MESSAGE"));
 
	boost::log::core::get()->add_sink(sink);
 
	// Add attributes
	boost::log::add_common_attributes();
}
 
void logging_function()
{
	boost::log::sources::severity_logger< severity_level > slg;
 
	BOOST_LOG_SEV(slg, normal) << "A regular message";
	BOOST_LOG_SEV(slg, warning) << "Something bad is going on but I can handle it";
	BOOST_LOG_SEV(slg, critical) << "Everything crumbles, shoot me now!";
 
	{
		BOOST_LOG_SCOPED_THREAD_TAG("Tag", "IMPORTANT_MESSAGE");
		BOOST_LOG_SEV(slg, normal) << "An important message";
	}
}
 
int main(int, char*[])
{
	init();
 
	logging_function();
 
	return 0;
}