optimized message drop when log file set to /dev/null

Author: sy-c

include/Common/SimpleLog.h

@@ -23,7 +23,7 @@ class SimpleLog
 
   // Set (or change) the log file name. Previous file used is closed. New file is appended when already existing.
   // Optionnaly, an automatic log rotation can be defined. Older files are renamed, appending .1, .2, .3, etc.
-  // \param logFilePath Path to log file. If NULL, using stdout/stderr.
+  // \param logFilePath Path to log file. If NULL, using stdout/stderr. If /dev/null, messages are completely dropped.
   // \param rotateMaxBytes Maximum file size, after which a new file is created. If zero, no limit.
   // \param rotateMaxFiles Maximum number of files to keep (including the "current" file). If zero, no limit.
   // \param rotateNow If non-zero, the file is immediately rotated (independently of its size), otherwise it is appended.

src/SimpleLog.cxx

@@ -36,6 +36,7 @@ class SimpleLog::Impl
   int formatOptions;
   int fdStdout;
   int fdStderr;
+  bool disableOutput = 0; // when set, messages completely dropped (logfile=/dev/null)
 
   // log rotation settings
   unsigned long rotateMaxBytes = 0;
@@ -65,6 +66,11 @@ SimpleLog::Impl::~Impl()
 
 int SimpleLog::Impl::logV(SimpleLog::Impl::Severity s, const char* message, va_list ap)
 {
+  // immediate return if output disabled
+  if (disableOutput) {
+    return 0;
+  }
+  
   char buffer[1024] = "";
   size_t len = sizeof(buffer) - 2;
   size_t ix = 0;
@@ -167,21 +173,25 @@ SimpleLog::~SimpleLog()
 int SimpleLog::setLogFile(const char* logFilePath, unsigned long rotateMaxBytes, unsigned int rotateMaxFiles, unsigned int rotateNow)
 {
   pImpl->closeLogFile();
+  pImpl->logFilePath = "";
+  pImpl->rotateMaxFiles = 0;
+  pImpl->rotateMaxBytes = 0;
+  pImpl->logFileSize = 0;
+  pImpl->disableOutput = 0;
   if (logFilePath != NULL) {
-    pImpl->rotateMaxBytes = rotateMaxBytes;
-    pImpl->rotateMaxFiles = rotateMaxFiles;
     pImpl->logFilePath = logFilePath;
+    if (!strcmp(logFilePath,"/dev/null")) {
+      pImpl->disableOutput = 1;
+      return 0;
+    }
+    pImpl->rotateMaxBytes = rotateMaxBytes;
+    pImpl->rotateMaxFiles = rotateMaxFiles;    
     if (rotateNow) {
       pImpl->rotate();
     }
     if (pImpl->openLogFile()) {
       return -1;
     }
-  } else {
-    pImpl->logFilePath = "";
-    pImpl->rotateMaxFiles = 0;
-    pImpl->rotateMaxBytes = 0;
-    pImpl->logFileSize = 0;
   }
   return 0;
 }