add stop() to logger_file

this allows to close and currently running log process, flush the content
to the file, continue logging during that time, open a new file
and write the new log entries to that new file

basically it allows to use the logger_file multiple times without
needing to destroy the object

this is used in the UE tester to write each testcase into a separate
log file

lib/include/srslte/common/logger_file.h

@@ -47,6 +47,7 @@ public:
   logger_file(std::string file);
   ~logger_file();
   void init(std::string file, int max_length = -1);
+  void stop();
   // Implementation of log_out
   void log(unique_log_str_t msg);
 

lib/src/common/logger_file.cc

@@ -33,35 +33,52 @@ logger_file::logger_file() : logfile(NULL), is_running(false), cur_length(0), ma
   pthread_cond_init(&not_empty, NULL);
 }
 
-logger_file::~logger_file() {
-  if(is_running) {
-    logger::log_char("Closing log\n");
-    pthread_mutex_lock(&mutex);
-    is_running = false;
-    pthread_cond_signal(&not_empty);  // wakeup thread and let it terminate
-    pthread_mutex_unlock(&mutex);
-    wait_thread_finish();
-    flush();
-    if (logfile) {
-      fclose(logfile);
-    }
-  }
+logger_file::~logger_file()
+{
+  stop();
   pthread_mutex_destroy(&mutex);
   pthread_cond_destroy(&not_empty);
 }
 
 void logger_file::init(std::string file, int max_length_) {
-  pthread_mutex_init(&mutex, NULL); 
-  pthread_cond_init(&not_empty, NULL);
+  if (is_running) {
+    fprintf(stderr, "Error: logger thread is already running.\n");
+    return;
+  }
+  pthread_mutex_lock(&mutex);
   max_length = (int64_t)max_length_*1024;
   name_idx = 0;
   filename = file;
   logfile = fopen(filename.c_str(), "w");
-  if(logfile == NULL) {
+  if (logfile == NULL) {
     printf("Error: could not create log file, no messages will be logged!\n");
   }
   is_running = true;
   start(-2);
+  pthread_mutex_unlock(&mutex);
+}
+
+void logger_file::stop()
+{
+  if (is_running) {
+    logger::log_char("Closing log\n");
+    pthread_mutex_lock(&mutex);
+    is_running = false;
+    pthread_cond_signal(&not_empty); // wakeup thread and let it terminate
+    pthread_mutex_unlock(&mutex);
+    wait_thread_finish();
+    pthread_mutex_lock(&mutex);
+    flush();
+    if (logfile) {
+      fclose(logfile);
+      logfile = NULL;
+    }
+    pthread_mutex_unlock(&mutex);
+  } else {
+    pthread_mutex_lock(&mutex);
+    flush(); // flush even if thread isn't running anymore
+    pthread_mutex_unlock(&mutex);
+  }
 }
 
 void logger_file::log(unique_log_str_t msg)
@@ -85,10 +102,12 @@ void logger_file::run_thread() {
     unique_log_str_t s = std::move(buffer.front());
 
     int n = 0;
-    if(logfile)
+    if (logfile) {
       n = fprintf(logfile, "%s", s->msg);
+    }
+
     buffer.pop_front();
-    pthread_mutex_unlock(&mutex);
+
     if (n > 0) {
       cur_length += (int64_t) n;
       if (cur_length >= max_length && max_length > 0) {
@@ -104,17 +123,20 @@ void logger_file::run_thread() {
         cur_length = 0;
       }
     }
+    pthread_mutex_unlock(&mutex);
   }
 }
 
-void logger_file::flush() {
+void logger_file::flush()
+{
   std::deque<unique_log_str_t>::iterator it;
-  for(it=buffer.begin();it!=buffer.end();it++)
-  {
+  for (it = buffer.begin(); it != buffer.end(); it++) {
     unique_log_str_t s = std::move(*it);
-    if(logfile)
+    if (logfile) {
       fprintf(logfile, "%s", s->msg);
+    }
   }
+  buffer.clear();
 }
 
 } // namespace srslte