your_scenario.cpp

This usage:

• You have several loggers
• You have one filter, which can be turned on or off
• You want to format the message before it's written
• Each logger has several log destinations
• The logger and filter are specified using the boost::logging::scenario namespace
  • the filter is always accurate (but slow)
  • the filter does not use levels
  • the logger favors speed (on a dedicated thread)
  • the logger is initialized once, when only one thread is running

Optimizations:

• use a cache string (from optimize namespace), in order to make formatting the message faster

Logs:

• Error messages go into err.txt file
  • formatting - prefix each message by time, index, and append newline
• Info output goes to console, and a file called out.txt
  • formatting - prefix each message by time and append newline
• Debug messages go to the debug output window, and the console
  • formatting - prefix each message by time, and append newline

Here's how the output will look like:

The debug output window:

18:59.24 this is so cool 1
18:59.24 this is so cool again 2

The console:

18:59.24 this is so cool 1
18:59.24 this is so cool again 2
18:59.24 hello, world
18:59.24 good to be back ;) 4

The out.txt file:

18:59.24 hello, world
18:59.24 good to be back ;) 4

The err.txt file

18:59.24 [1] first error 3
18:59.24 [2] second error 5

#include <boost/logging/format_fwd.hpp>

BOOST_LOG_FORMAT_MSG( optimize::cache_string_one_str<> )

#include <boost/logging/format_ts.hpp>
#include <boost/thread/xtime.hpp>
using namespace boost::logging;

using namespace boost::logging::scenario::usage;
typedef use<
        //  the filter is always accurate (but slow)
        filter_::change::always_accurate, 
        //  filter does not use levels
        filter_::level::no_levels, 
        // the logger is initialized once, when only one thread is running
        logger_::change::set_once_when_one_thread, 
        // the logger favors speed (on a dedicated thread)
        logger_::favor::speed> finder;

BOOST_DECLARE_LOG_FILTER(g_log_filter, finder::filter ) 
BOOST_DECLARE_LOG(g_log_err, finder::logger ) 
BOOST_DECLARE_LOG(g_log_app, finder::logger )
BOOST_DECLARE_LOG(g_log_dbg, finder::logger )

#define LDBG_ BOOST_LOG_USE_LOG_IF_FILTER(g_log_dbg(), g_log_filter()->is_enabled() ) 
#define LERR_ BOOST_LOG_USE_LOG_IF_FILTER(g_log_err(), g_log_filter()->is_enabled() )
#define LAPP_ BOOST_LOG_USE_LOG_IF_FILTER(g_log_app(), g_log_filter()->is_enabled() ) 

BOOST_DEFINE_LOG_FILTER(g_log_filter, finder::filter ) 
BOOST_DEFINE_LOG(g_log_err, finder::logger )
BOOST_DEFINE_LOG(g_log_app, finder::logger )
BOOST_DEFINE_LOG(g_log_dbg, finder::logger )

void do_sleep(int ms) {
    using namespace boost;
    xtime next;
    xtime_get( &next, TIME_UTC);
    next.nsec += (ms % 1000) * 1000000;

    int nano_per_sec = 1000000000;
    next.sec += next.nsec / nano_per_sec;
    next.sec += ms / 1000;
    next.nsec %= nano_per_sec;
    thread::sleep( next);
}

void your_scenario_example() {
    //         add formatters and destinations
    //         That is, how the message is to be formatted and where should it be written to

    // Err log
    g_log_err()->writer().add_formatter( formatter::idx(), "[%] "  );
    g_log_err()->writer().add_formatter( formatter::time("$hh:$mm.$ss ") );
    g_log_err()->writer().add_formatter( formatter::append_newline() );
    g_log_err()->writer().add_destination( destination::file("err.txt") );

    // App log
    g_log_app()->writer().add_formatter( formatter::time("$hh:$mm.$ss ") );
    g_log_app()->writer().add_formatter( formatter::append_newline() );
    g_log_app()->writer().add_destination( destination::file("out.txt") );
    g_log_app()->writer().add_destination( destination::cout() );

    // Debug log
    g_log_dbg()->writer().add_formatter( formatter::time("$hh:$mm.$ss ") );
    g_log_dbg()->writer().add_formatter( formatter::append_newline() );
    g_log_dbg()->writer().add_destination( destination::dbg_window() );
    g_log_dbg()->writer().add_destination( destination::cout() );
    g_log_app()->mark_as_initialized();
    g_log_err()->mark_as_initialized();
    g_log_dbg()->mark_as_initialized();

    int i = 1;
    LDBG_ << "this is so cool " << i++;
    LDBG_ << "this is so cool again " << i++;
    LERR_ << "first error " << i++;

    std::string hello = "hello", world = "world";
    LAPP_ << hello << ", " << world;

    g_log_filter()->set_enabled(false);
    LDBG_ << "this will not be written anywhere";
    LAPP_ << "this won't be written anywhere either";
    LERR_ << "this error is not logged " << i++;

    g_log_filter()->set_enabled(true);
    LAPP_ << "good to be back ;) " << i++;
    LERR_ << "second error " << i++;

    // just so that we can see the output to the console as well (the messages are written no a different thread)...
    do_sleep(1000);
}




int main() {
    your_scenario_example();
}


// End of file

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Copyright John Torjo © 2007
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