make logging thread safe

lib/log/GWLog.cpp

@@ -12,27 +12,37 @@ GwLog::GwLog(int level, GwLogWriter *writer){
     logLevel=level;
     if (writer == NULL) writer=new DefaultLogWriter();
     this->writer=writer;
+    locker = xSemaphoreCreateMutex();
+}
+GwLog::~GwLog(){
+    vSemaphoreDelete(locker);
 }
 void GwLog::logString(const char *fmt,...){
-    if (! writer) return;
     va_list args;
     va_start(args,fmt);
+    xSemaphoreTake(locker, portMAX_DELAY);
     vsnprintf(buffer,99,fmt,args);
+    if (! writer) return;
     writer->write(prefix.c_str());
     writer->write(buffer);
     writer->write("\n");
+    xSemaphoreGive(locker);
 }
 void GwLog::logDebug(int level,const char *fmt,...){
     if (level > logLevel) return;
-    if (! writer) return;
     va_list args;
     va_start(args,fmt);
+    xSemaphoreTake(locker, portMAX_DELAY);
     vsnprintf(buffer,99,fmt,args);
+    if (! writer) return;
     writer->write(prefix.c_str());
     writer->write(buffer);
     writer->write("\n");
+    xSemaphoreGive(locker);
 }
 void GwLog::setWriter(GwLogWriter *writer){
+    xSemaphoreTake(locker, portMAX_DELAY);
     if (this->writer) delete this->writer;
     this->writer=writer;
+    xSemaphoreGive(locker);
 }

lib/log/GwLog.h

@@ -12,6 +12,7 @@ class GwLog{
         char buffer[100];
         int logLevel=1;
         GwLogWriter *writer;
+        SemaphoreHandle_t locker;
     public:
         static const int LOG=1;
         static const int ERROR=0;
@@ -19,6 +20,7 @@ class GwLog{
         static const int TRACE=2;
         String prefix="LOG:";
         GwLog(int level=LOG, GwLogWriter *writer=NULL);
+        ~GwLog();
         void setWriter(GwLogWriter *writer);
         void logString(const char *fmt,...);
         void logDebug(int level, const char *fmt,...);