The LogContext is created at a point in the application code and filled in with details about that log point, such as the file and line number, and the function name of the containing function, and the log level of that log point, such as LOGGER_DEBUG or LOGGER_ERROR. More...

#include <Logger.h>

Public Member Functions
	LogContext (int level, const char file, const char function, int line, const char *tags=0)
	The LogContext constructor initializes all the static context information, adds this context to the global registry of log points, then sets the active() status according to the current log configuration. More...

	~LogContext ()

bool	active () const
	Return true if log messages from this context would be accepted. More...

const char *	filename () const

const char *	function () const

int	line () const

int	level () const

const char *	tags () const

std::string	threadName () const
	Return the name of the thread which created this context. More...

std::string	levelName () const

void	log (const std::string &msg) const
	Convenience method which writes the given message to the current Logger instance, passing this object as the LogContext instance. More...

LogMessage	log () const
	Return a LogMessage associated with this LogContext, so the message will be logged through this context when the LogMessage goes out of scope. More...

Private Member Functions
	LogContext (const LogContext &)
	No copying. More...

LogContext &	operator= (const LogContext &)
	No assignment. More...

Private Attributes
int	_level

const char *	_file

const char *	_function

int	_line

const char *	_tags

bool	_active

pthread_t	_threadId

Friends
class	nidas::util::Logger

class	nidas::util::LoggerPrivate

Detailed Description

The LogContext is created at a point in the application code and filled in with details about that log point, such as the file and line number, and the function name of the containing function, and the log level of that log point, such as LOGGER_DEBUG or LOGGER_ERROR.

Except for the log level and tags, the rest of the LogContext can be filled in with CPP macros and predefined compiler symbols like PRETTY_FUNCTION. The LogContext holds its own active state, so a simple, inline boolean test determines whether a log point has been activated and thus needs to generate and log its message. Otherwise the log point can be skipped with minimal time overhead. Where further discrimination of log points is needed, a log point can be associated with a string of tags, and a LogConfig can match the log point by one of its tags. The tags string is empty unless specified at creation.

The LogContext effectively stashes context info for a log point so that info can be used in the log message output, and so that info can be used as criteria for selecting which messages are logged. Thus a LogContext registers itself with the Logger class, and the Logger class can enable or disable a log point according to the current configuration scheme, Logging Configuration Schemes. The LogContext contains a flag which is false if the log point is not active, meaning almost all overhead of generating a log message can be avoided by testing the active() flag first. The typical usage of a LogContext will be as a static object, and the log macros DLOG, ELOG, and so on test the active() flag before passing a message.

The ultimate goal is to make all log messages always available in the runtime while incurring as little performance overhead as possible when they are not needed, and without requiring alternate compile configurations. However, if it should ever be necessary, then the log macros can still be defined as completely empty.

See LogContext::log() for using a LogContext instance to enclose more complicated blocks of logging output.

A LogContext has no support for concurrency. If it might be shared among multiple threads, then it should be guarded with a lock or created in thread-local storage. However, a LogContext does record the thread which created it, and the name of that thread is returned by the threadName() method.

Constructor & Destructor Documentation

LogContext::LogContext	(	int	level,
		const char *	file,
		const char *	function,
		int	line,
		const char *	tags = `0`
	)

The LogContext constructor initializes all the static context information, adds this context to the global registry of log points, then sets the active() status according to the current log configuration.

The constructor also records the ID of the current thread, so if this LogContext is instantiated in thread-local storage, all messages logged through it will be associated with the correct thread name.

References _active, current_scheme, nidas::util::LoggerPrivate::get_active_flag(), nidas::util::LogScheme::getShowLogPoints(), log_points, nidas::util::Logger::mutex, and nidas::util::LogScheme::show_log_point().

LogContext::~LogContext ( )

References log_points, and nidas::util::Logger::mutex.

nidas::util::LogContext::LogContext ( const LogContext & )

private

No copying.

Member Function Documentation

bool nidas::util::LogContext::active ( ) const

inline

Return true if log messages from this context would be accepted.

If this returns false, then there is no point in generating and submitting a log message.

References _active.

Referenced by nidas::core::SampleTracer::active(), nidas::dynld::raf::SyncRecordSource::allocateRecord(), nidas::dynld::StatisticsCruncher::computeStats(), nidas::core::SamplePipeline::connect(), nidas::dynld::raf::TwoD_USB::countParticle(), nidas::dynld::StatisticsCruncher::createCombinations(), nidas::core::BadSampleFilter::invalidSampleHeader(), nidas::util::Logger::log(), nidas::util::Logger::msg_locked(), nidas::core::NidasApp::parseInputs(), NidsMerge::parseRunstring(), StatsProcess::parseRunstring(), nidas::dynld::raf::SyncRecordSource::preLoadCalibrations(), nidas::dynld::raf::TwoD64_USB::process(), nidas::dynld::iss::TiltSensor::process(), nidas::dynld::isff::Wind2D::process(), nidas::dynld::raf::TwoD64_USB::processImageRecord(), nidas::core::CalFile::readCFInclude(), nidas::dynld::StatisticsCruncher::receive(), nidas::util::SocketImpl::receive(), DataPrep::run(), nidas::core::SampleSorter::run(), nidas::dynld::SampleInputStream::sampleFromHeader(), nidas::core::CharacterSensor::searchSampleScanners(), nidas::dynld::raf::SyncRecordSource::sendSyncRecord(), nidas::util::LogScheme::show_log_point(), nidas::dynld::isff::NCAR_TRH::validate(), and nidas::dynld::SampleOutputStream::write().

const char* nidas::util::LogContext::filename ( ) const

inline

References _file.

Referenced by nidas::util::LogConfig::matches(), nidas::util::Logger::msg_locked(), and nidas::util::LogScheme::show_log_point().

const char* nidas::util::LogContext::function ( ) const

inline

References _function.

Referenced by nidas::util::LogConfig::matches(), nidas::util::Logger::msg_locked(), and nidas::util::LogScheme::show_log_point().

int nidas::util::LogContext::level ( ) const

inline

References _level.

Referenced by nidas::util::LogConfig::matches(), and nidas::util::Logger::msg_locked().

std::string nidas::util::LogContext::levelName ( ) const

inline

References _level, and nidas::util::logLevelToString().

Referenced by nidas::util::Logger::msg_locked(), and nidas::util::LogScheme::show_log_point().

int nidas::util::LogContext::line ( ) const

inline

References _line.

Referenced by nidas::util::LogConfig::matches(), nidas::util::Logger::msg_locked(), and nidas::util::LogScheme::show_log_point().

LogContext& nidas::util::LogContext::operator= ( const LogContext & )

private

No assignment.

const char* nidas::util::LogContext::tags ( ) const

inline

References _tags.

Referenced by nidas::util::LogConfig::matches(), and nidas::util::LogScheme::show_log_point().

std::string LogContext::threadName ( ) const

Return the name of the thread which created this context.

This is not necessarily the name of the currently running thread, so it may not be the same as the thread named in a log message when LogScheme::ThreadField is enabled in the LogScheme.

References _threadId, nidas::util::Thread::getName(), and nidas::util::Thread::lookupThread().