Using Boost.Log on Android for log cats

Question

I am trying to use Boost.Log (in version 1.57) to record logs on several platforms, including Android. For the NDK code we have, I need to send log messages before __android_log_print .

After reading the documentation over and over (the whole system is quite complicated), it seems to me that I need to write my own backend for logging. Alternatively, it looks like I could use their existing backstream and write my own stream (with Boost.Iostream).

The fact is that the thread is not suitable for this if you think about it. I will not necessarily have a buffer in which I store the logs inside. I just forward them along with the above Android NDK feature.

What is the right solution here? IO or custom backend for registrar?

Answer 1

I suggest creating a custom host server that forwards log messages to the Android logging function. The following sample code implements this and uses Android log levels so that you can filter log messages based on log level. You can, of course, define your own log levels and add a mapping between your log level and androids.

You need to call boost_android_logging::init() once, then you can instantiate boost_android_logging::Logger where you need it and send log messages using BOOST_LOG_SEV .

 #include <iostream> typedef enum android_LogPriority { ANDROID_LOG_UNKNOWN = 0, ANDROID_LOG_DEFAULT, ANDROID_LOG_VERBOSE, ANDROID_LOG_DEBUG, ANDROID_LOG_INFO, ANDROID_LOG_WARN, ANDROID_LOG_ERROR, ANDROID_LOG_FATAL, ANDROID_LOG_SILENT, } android_LogPriority; int fake__android_log_print(int prio, const char *tag, const char *fmt, ...) { std::cout << prio << " " << tag << ": " << fmt << std::endl; return 0; } #include <boost/log/attributes.hpp> #include <boost/log/sources/record_ostream.hpp> #include <boost/log/core.hpp> #include <boost/log/expressions.hpp> #include <boost/log/sinks.hpp> #include <boost/log/sources/logger.hpp> #include <boost/log/utility/setup.hpp> #include <boost/log/sources/severity_logger.hpp> #include <boost/log/expressions/keyword.hpp> namespace boost_android_logging { BOOST_LOG_ATTRIBUTE_KEYWORD(severity, "Severity", android_LogPriority) BOOST_LOG_ATTRIBUTE_KEYWORD(module, "Module", std::string) namespace logging = boost::log; namespace sinks = boost::log::sinks; namespace expr = boost::log::expressions; struct android_sink_backend : public sinks::basic_sink_backend<logging::sinks::concurrent_feeding> { void consume(const logging::record_view& rec) { android_LogPriority log_sev = rec[severity].get(); const char* log_msg = rec[expr::smessage].get().c_str(); const char* log_module = "unknown"; if (rec[module]) { log_module = rec[module].get().c_str(); } // forward to actual logging function fake__android_log_print(log_sev, log_module, log_msg); } }; typedef boost::log::sources::severity_logger<android_LogPriority> Logger; void init() { logging::add_common_attributes(); typedef sinks::synchronous_sink<android_sink_backend> android_sink; boost::shared_ptr<android_sink> sink = boost::make_shared<android_sink>(); sink->set_filter(severity >= ANDROID_LOG_INFO); logging::core::get()->add_sink(sink); } void shutdown() { logging::core::get()->remove_all_sinks(); } } // namespace boost_android_logging #define SET_MODULE(logger,log_module) logger.add_attribute(boost_android_logging::module.get_name(), boost::log::attributes::constant<std::string>(#log_module)); struct Demo { Demo() { SET_MODULE(logger, Demo); BOOST_LOG_SEV(logger, ANDROID_LOG_WARN) << "this is a warning"; } void test() { BOOST_LOG_SEV(logger, ANDROID_LOG_FATAL) << "fatal error occured"; } boost_android_logging::Logger logger; }; int main() { boost_android_logging::init(); boost_android_logging::Logger logger; SET_MODULE(logger, main); BOOST_LOG_SEV(logger, ANDROID_LOG_WARN) << "this is a warning"; BOOST_LOG_SEV(logger, ANDROID_LOG_DEBUG) << "this will be filtered"; BOOST_LOG_SEV(logger, ANDROID_LOG_FATAL) << "fatal error occured"; Demo d; d.test(); boost_android_logging::shutdown(); } 

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