llerror.h

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#ifndef LL_LLERROR_H
#define LL_LLERROR_H

#include <sstream>
#include <typeinfo>

#include "llerrorlegacy.h"


/* Error Logging Facility

        Information for most users:
        
        Code can log messages with constuctions like this:
        
                llinfos << "request to fizzbip agent " << agent_id
                        << " denied due to timeout" << llendl;
                
        Messages can be logged to one of four increasing levels of concern,
        using one of four "streams":

                lldebugs        - debug messages that are normally supressed
                llinfos         - informational messages that are normall shown
                llwarns         - warning messages that singal a problem
                llerrs          - error messages that are major, unrecoverable failures
                
        The later (llerrs) automatically crashes the process after the message
        is logged.
        
        Note that these "streams" are actually #define magic.  Rules for use:
                * they cannot be used as normal streams, only to start a message
                * messages written to them MUST be terminated with llendl
                * between the opening and closing, the << operator is indeed
                  writing onto a std::ostream, so all conversions and stream
                  formating are available
        
        These messages are automatically logged with function name, and (if enabled)
        file and line of the message.  (Note: Existing messages that already include
        the function name don't get name printed twice.)
        
        If you have a class, adding LOG_CLASS line to the declaration will cause
        all messages emitted from member functions (normal and static) to be tagged
        with the proper class name as well as the function name:
        
                class LLFoo
                {
                        LOG_CLASS(LLFoo);
                public:
                        ...
                };
        
                void LLFoo::doSomething(int i)
                {
                        if (i > 100)
                        {
                                llwanrs << "called with a big value for i: " << i << llendl; 
                        }
                        ...
                }
        
        will result in messages like:
        
                WARN: LLFoo::doSomething: called with a big value for i: 283
        
        Which messages are logged and which are supressed can be controled at run
        time from the live file logcontrol.xml based on function, class and/or 
        source file.  See etc/logcontrol-dev.xml for details.
        
        Lastly, logging is now very efficient in both compiled code and execution
        when skipped.  There is no need to wrap messages, even debugging ones, in
        #ifdef _DEBUG constructs.  lldebugs messages are compiled into all builds,
        even release.  Which means you can use them to help debug even when deployed
        to a real grid.
*/

namespace LLError
{
        enum ELevel
        {
                LEVEL_ALL = 0,
                        // used to indicate that all messagess should be logged
                        
                LEVEL_DEBUG = 0,
                LEVEL_INFO = 1,
                LEVEL_WARN = 2,
                LEVEL_ERROR = 3,        // used to be called FATAL
                
                LEVEL_NONE = 4
                        // not really a level
                        // used to indicate that no messages should be logged
        };
        
        /*      Macro support
                The classes CallSite and Log are used by the logging macros below.
                They are not intended for general use.
        */
        
        class CallSite;
        
        class Log
        {
        public:
                static bool shouldLog(CallSite&);
                static std::ostringstream* out();
                static void flush(std::ostringstream*, const CallSite&);
        };
        
        class CallSite
        {
                // Represents a specific place in the code where a message is logged
                // This is public because it is used by the macros below.  It is not
                // intended for public use.
        public:
                CallSite(ELevel, const char* file, int line,
                                const std::type_info& class_info, const char* function);
                                                
                bool shouldLog()
                        { return mCached ? mShouldLog : Log::shouldLog(*this); }
                        // this member function needs to be in-line for efficiency
                
                void invalidate();
                
        private:
                // these describe the call site and never change
                const ELevel                    mLevel;
                const char* const               mFile;
                const int                               mLine;
                const std::type_info&   mClassInfo;
                const char* const               mFunction;
                
                // these implement a cache of the call to shouldLog()
                bool mCached;
                bool mShouldLog;
                
                friend class Log;
        };
        
        
        class End { };
        inline std::ostream& operator<<(std::ostream& s, const End&)
                { return s; }
                // used to indicate the end of a message
                
        class NoClassInfo { };
                // used to indicate no class info known for logging
}



/*
        Class type information for logging
 */

#define LOG_CLASS(s)    typedef s _LL_CLASS_TO_LOG
        // Declares class to tag logged messages with.
        // See top of file for example of how to use this
        
typedef LLError::NoClassInfo _LL_CLASS_TO_LOG;
        // Outside a class declartion, or in class without LOG_CLASS(), this
        // typedef causes the messages to not be associated with any class.





/*
        Error Logging Macros
        See top of file for common usage.       
*/

#define lllog(level) \
        { \
                static LLError::CallSite _site( \
                        level, __FILE__, __LINE__, typeid(_LL_CLASS_TO_LOG), __FUNCTION__);\
                if (_site.shouldLog()) \
                { \
                        std::ostringstream* _out = LLError::Log::out(); \
                        (*_out)
        
#define llendl \
                        LLError::End(); \
                        LLError::Log::flush(_out, _site); \
                } \
        }

#define llinfos         lllog(LLError::LEVEL_INFO)
#define lldebugs        lllog(LLError::LEVEL_DEBUG)
#define llwarns         lllog(LLError::LEVEL_WARN)
#define llerrs          lllog(LLError::LEVEL_ERROR)

#define llcont          (*_out)
        /*
                Use this construct if you need to do computation in the middle of a
                message:
                
                        llinfos << "the agent " << agend_id;
                        switch (f)
                        {
                                case FOP_SHRUGS:        llcont << "shrugs";                             break;
                                case FOP_TAPS:          llcont << "points at " << who;  break;
                                case FOP_SAYS:          llcont << "says " << message;   break;
                        }
                        llcont << " for " << t << " seconds" << llendl;
                
                Such computation is done iff the message will be logged.
        */


#endif // LL_LLERROR_H

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