util: Establish global logger object.

The object encapsulates logging configuration, and in a later commit,
set up routines will also be moved into the class.

src/logging.h

@@ -19,13 +19,7 @@ static const bool DEFAULT_LOGIPS        = false;
 static const bool DEFAULT_LOGTIMESTAMPS = true;
 extern const char * const DEFAULT_DEBUGLOGFILE;
 
-extern bool fPrintToConsole;
-extern bool fPrintToDebugLog;
-
-extern bool fLogTimestamps;
-extern bool fLogTimeMicros;
 extern bool fLogIPs;
-extern std::atomic<bool> fReopenDebugLog;
 
 extern std::atomic<uint32_t> logCategories;
 
@@ -61,7 +55,39 @@ namespace BCLog {
         LEVELDB     = (1 << 20),
         ALL         = ~(uint32_t)0,
     };
-}
+
+    class Logger
+    {
+    private:
+        /**
+         * fStartedNewLine is a state variable that will suppress printing of
+         * the timestamp when multiple calls are made that don't end in a
+         * newline.
+         */
+        std::atomic_bool fStartedNewLine{true};
+
+        std::string LogTimestampStr(const std::string& str);
+
+    public:
+        bool fPrintToConsole = false;
+        bool fPrintToDebugLog = true;
+
+        bool fLogTimestamps = DEFAULT_LOGTIMESTAMPS;
+        bool fLogTimeMicros = DEFAULT_LOGTIMEMICROS;
+
+        std::atomic<bool> fReopenDebugLog{false};
+
+        /** Send a string to the log output */
+        int LogPrintStr(const std::string &str);
+
+        /** Returns whether logs will be written to any output */
+        bool Enabled() const { return fPrintToConsole || fPrintToDebugLog; }
+    };
+
+} // namespace BCLog
+
+extern BCLog::Logger* const g_logger;
+
 /** Return true if log accepts specified category */
 static inline bool LogAcceptCategory(uint32_t category)
 {
@@ -77,9 +103,6 @@ std::vector<CLogCategoryActive> ListActiveLogCategories();
 /** Return true if str parses as a log category and set the flags in f */
 bool GetLogCategory(uint32_t *f, const std::string *str);
 
-/** Send a string to the log output */
-int LogPrintStr(const std::string &str);
-
 /** Get format string from VA_ARGS for error reporting */
 template<typename... Args> std::string FormatStringFromLogArgs(const char *fmt, const Args&... args) { return fmt; }
 
@@ -99,7 +122,7 @@ template<typename T, typename... Args> static inline void MarkUsed(const T& t, c
 #define LogPrint(category, ...) do { MarkUsed(__VA_ARGS__); } while(0)
 #else
 #define LogPrintf(...) do { \
-    if (fPrintToConsole || fPrintToDebugLog) { \
+    if (g_logger->Enabled()) { \
         std::string _log_msg_; /* Unlikely name to avoid shadowing variables */ \
         try { \
             _log_msg_ = tfm::format(__VA_ARGS__); \
@@ -107,7 +130,7 @@ template<typename T, typename... Args> static inline void MarkUsed(const T& t, c
             /* Original format string will have newline so don't add one here */ \
             _log_msg_ = "Error \"" + std::string(fmterr.what()) + "\" while formatting log message: " + FormatStringFromLogArgs(__VA_ARGS__); \
         } \
-        LogPrintStr(_log_msg_); \
+        g_logger->LogPrintStr(_log_msg_); \
     } \
 } while(0)