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日志类封装日志类封装日志类封装日志类封装日志类封装日志类封装

The Log is not instantiated directly but a reference to a Log object
is obtained through a call to one of the static getLog() methods.

Each log has 6 builtin LogStreams each of which recieve messages at
a different LogLevel. In this way different LogStreams can be turned
on or off at will.

The five primary builtin LogStreams are:

 Log.debug
 Log.info
 Log.warn
 Log.error
 Log.fatal

In addition to these five the Log object itself is also an LogStream.

Usage: In order to use the log the client program sends a message to
one of the Log objects LogStream objects.
Eg.

 log("Final statistics follow:");
 log.debug("Entering loop:");
 log.warn("Value to delete does not exist.");
 

In addition to treating the builtin LogStream objects as methods they
can also be used like traditional C++ streams (which they are).
Eg.

 log << "Vat = " << vatPercent << "%" << std::endl;
 log.debug << "value = " << value << std::endl;
 log.error << "This should never happen at line " << __LINE__;
 log.error << ", file " << __FILE__ << std::endl;
 log.fatal << "Bad vibes, exiting..." << std::endl; exit(10);
 

Both the above approaches can be mixed. Eg.

 log("Total annual income = ") << lowIncomeValue << std::endl; 
 log.debug("variable dv = ") << dv << std::endl;
 

On top of all this additional LogStream objects can be added to the Log
using the addLogStream() method. Eg.

 log.addLogStream("report");
 

This can be subsequently accessed thus:

 log.to("report", "Temperature guage initialization.");
 log.to("report") << "Temperature of core: " << coreTemp << std::endl;
 

Different levels of reporting can be achieved by setting the LogMask of
the Log. Each LogStream operates at a specific LogLevel and the LogLevel
of each of the builtin ones is set such that they may be enabled or
disabled in a hirarchal manner. For example if you wanted to receive only
'error' and 'fatal' messages you could set the LogMask thus:

 log.setLogMask(log.error.getLogLevel());
 

This sets the LogMask of the Log to a value such that all LogStream objects
operating below the level of 'error' will be turned off.

You may wish your Log to send its output to more than one place. This can
be achieved by adding std::ostream objects to the Log.
Eg.

 // Send the logging over a network.
 std::ostream* os = socket->get_output();
 log.addOStream(*os);
 

This output may subsequently be removed with:

 log.delOStream(*os);