add option to reduce dump flush buffer size to 1

src/ebusd/main.cpp

@@ -123,6 +123,7 @@ static struct options opt = {
   false,  // dump
   "/tmp/" PACKAGE "_dump.bin",  // dumpFile
   100,  // dumpSize
+  false,  // dumpFlush
 };
 
 /** the @a MessageMap instance, or nullptr. */
@@ -174,6 +175,7 @@ static const char argpdoc[] =
 #define O_RAWSIZ (O_RAWFIL+1)
 #define O_DMPFIL (O_RAWSIZ+1)
 #define O_DMPSIZ (O_DMPFIL+1)
+#define O_DMPFLU (O_DMPSIZ+1)
 
 /** the definition of the known program arguments. */
 static const struct argp_option argpoptions[] = {
@@ -242,6 +244,7 @@ static const struct argp_option argpoptions[] = {
   {"dump",           'D',      nullptr,    0, "Enable binary dump of received bytes", 0 },
   {"dumpfile",       O_DMPFIL, "FILE",     0, "Dump received bytes to FILE [/tmp/" PACKAGE "_dump.bin]", 0 },
   {"dumpsize",       O_DMPSIZ, "SIZE",     0, "Make dump file no larger than SIZE kB [100]", 0 },
+  {"dumpflush",      O_DMPFLU, nullptr,    0, "Flush each byte", 0 },
 
   {nullptr,          0,        nullptr,    0, nullptr, 0 },
 };
@@ -581,6 +584,9 @@ error_t parse_opt(int key, char *arg, struct argp_state *state) {
       return EINVAL;
     }
     break;
+  case O_DMPFLU:  // --dumpflush
+    opt->dumpFlush = true;
+    break;
 
   case ARGP_KEY_ARG:
     if (opt->injectMessages || (opt->checkConfig && opt->scanConfig)) {

src/ebusd/main.h

@@ -85,6 +85,7 @@ struct options {
   bool dump;  //!< binary dump received bytes
   const char* dumpFile;  //!< name of dump file [/tmp/ebusd_dump.bin]
   unsigned int dumpSize;  //!< maximum size of dump file in kB [100]
+  bool dumpFlush;  //!< flush each byte
 };
 
 /**

src/ebusd/mainloop.cpp

@@ -111,7 +111,7 @@ MainLoop::MainLoop(const struct options& opt, Device *device, MessageMap* messag
   }
   m_device->setListener(this);
   if (opt.dumpFile[0]) {
-    m_dumpFile = new RotateFile(opt.dumpFile, opt.dumpSize);
+    m_dumpFile = new RotateFile(opt.dumpFile, opt.dumpSize, false, opt.dumpFlush ? 1 : 16);
     m_dumpFile->setEnabled(opt.dump);
   } else {
     m_dumpFile = nullptr;

src/lib/utils/rotatefile.cpp

@@ -82,7 +82,7 @@ void RotateFile::write(const unsigned char* value, const size_t size, const bool
     fwrite(value, (streamsize)size, 1, m_stream);
     m_fileSize += size;
     m_flushSize += size;
-    if (m_flushSize > 16) {
+    if (m_flushSize >= m_flushBuffer) {
       fflush(m_stream);
       m_flushSize = 0;
     }

src/lib/utils/rotatefile.h

@@ -43,10 +43,11 @@ class RotateFile {
    * @param fileName the name of the file write to.
    * @param maxSize the maximum size of the file to write to.
    * @param textMode whether to write each byte with prefixed timestamp and direction as text.
+   * @param flushBuffer the size of the flush buffer.
    */
-  RotateFile(const string fileName, const unsigned int maxSize, const bool textMode = false)
+  RotateFile(const string fileName, const unsigned int maxSize, const bool textMode = false, const unsigned int flushBuffer = 16)
     : m_enabled(false), m_fileName(fileName), m_maxSize(maxSize), m_textMode(textMode), m_stream(), m_fileSize(0),
-      m_flushSize(0) {}
+      m_flushSize(0), m_flushBuffer(flushBuffer) {}
 
   /**
    * Destructor.
@@ -98,6 +99,9 @@ class RotateFile {
 
   /** the number of bytes written to @a m_file since the last flush. */
   uint64_t m_flushSize;
+
+  /** the size of the flush buffer. */
+  const unsigned int m_flushBuffer;
 };
 
 }  // namespace ebusd