Logging
-------

Servers and clients may contain a logger. Every logger needs to implement the
`UA_Logger` signature. An example logger that writes to stdout is provided in
the plugins folder.

Every log-message consists of a log-level, a log-category and a string
message content. The timestamp of the log-message is created within the
logger.

.. code-block:: c

   
   typedef enum {
       UA_LOGLEVEL_TRACE,
       UA_LOGLEVEL_DEBUG,
       UA_LOGLEVEL_INFO,
       UA_LOGLEVEL_WARNING,
       UA_LOGLEVEL_ERROR,
       UA_LOGLEVEL_FATAL
   } UA_LogLevel;
   
   typedef enum {
       UA_LOGCATEGORY_NETWORK,
       UA_LOGCATEGORY_SECURECHANNEL,
       UA_LOGCATEGORY_SESSION,
       UA_LOGCATEGORY_SERVER,
       UA_LOGCATEGORY_CLIENT,
       UA_LOGCATEGORY_USERLAND
   } UA_LogCategory;
   
The signature of the logger. The msg string and following varargs are
formatted according to the rules of the printf command.

Do not use the logger directly but make use of the following macros that take
the minimum log-level defined in ua_config.h into account.

.. code-block:: c

   typedef void (*UA_Logger)(UA_LogLevel level, UA_LogCategory category,
                             const char *msg, va_list args);
   
   static UA_INLINE void
   UA_LOG_TRACE(UA_Logger logger, UA_LogCategory category, const char *msg, ...) {
   #if UA_LOGLEVEL <= 100
       if(logger) {
           va_list args; va_start(args, msg);
           logger(UA_LOGLEVEL_TRACE, category, msg, args);
           va_end(args);
       }
   #endif
   }
   
   static UA_INLINE void
   UA_LOG_DEBUG(UA_Logger logger, UA_LogCategory category, const char *msg, ...) {
   #if UA_LOGLEVEL <= 200
       if(logger) {
           va_list args; va_start(args, msg);
           logger(UA_LOGLEVEL_DEBUG, category, msg, args);
           va_end(args);
       }
   #endif
   }
   
   static UA_INLINE void
   UA_LOG_INFO(UA_Logger logger, UA_LogCategory category, const char *msg, ...) {
   #if UA_LOGLEVEL <= 300
       if(logger) {
           va_list args; va_start(args, msg);
           logger(UA_LOGLEVEL_INFO, category, msg, args);
           va_end(args);
       }
   #endif
   }
   
   static UA_INLINE void
   UA_LOG_WARNING(UA_Logger logger, UA_LogCategory category, const char *msg, ...) {
   #if UA_LOGLEVEL <= 400
       if(logger) {
           va_list args; va_start(args, msg);
           logger(UA_LOGLEVEL_WARNING, category, msg, args);
           va_end(args);
       }
   #endif
   }
   
   static UA_INLINE void
   UA_LOG_ERROR(UA_Logger logger, UA_LogCategory category, const char *msg, ...) {
   #if UA_LOGLEVEL <= 500
       if(logger) {
           va_list args; va_start(args, msg);
           logger(UA_LOGLEVEL_ERROR, category, msg, args);
           va_end(args);
       }
   #endif
   }
   
   static UA_INLINE void
   UA_LOG_FATAL(UA_Logger logger, UA_LogCategory category, const char *msg, ...) {
   #if UA_LOGLEVEL <= 600
       if(logger) {
           va_list args; va_start(args, msg);
           logger(UA_LOGLEVEL_FATAL, category, msg, args);
           va_end(args);
       }
   #endif
   }
   
Convenience macros for complex types
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: c

   #define UA_PRINTF_GUID_FORMAT "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x"
   #define UA_PRINTF_GUID_DATA(GUID) (GUID).data1, (GUID).data2, (GUID).data3, \
           (GUID).data4[0], (GUID).data4[1], (GUID).data4[2], (GUID).data4[3], \
           (GUID).data4[4], (GUID).data4[5], (GUID).data4[6], (GUID).data4[7]
   
   #define UA_PRINTF_STRING_FORMAT "\"%.*s\""
   #define UA_PRINTF_STRING_DATA(STRING) (STRING).length, (STRING).data