Move decoder process handling to separate thread to avoid exhaustuion

commons.h

@@ -10,6 +10,7 @@
 #define JS8_USE_IHSYM      0       // compute ihsym manually instead of from symspec
 #define JS8_RING_BUFFER    1       // use a ring buffer instead of clearing the decode frames
 #define JS8_SINGLE_DECODE  0       // single submode decode per instantiation of the decoder
+#define JS8_DECODE_THREAD  1       // use a separate thread for decode process handling
 
 #ifdef QT_DEBUG
 #define JS8_DEBUG_DECODE   1       // emit debug statements for the decode pipeline

lib/decoder.f90

@@ -170,7 +170,7 @@ subroutine multimode_decoder(ss,id2,params,nfsample)
   call flush(6)
 
   ndecoded = my_js8a%decoded + my_js8b%decoded + my_js8c%decoded + my_js8e%decoded
-  call sleep_msec(3000)
+  !call sleep_msec(3000)
   write(*,1010) ndecoded
 1010 format('<DecodeFinished>',i4)
   call flush(6)

mainwindow.cpp

@@ -536,6 +536,9 @@ MainWindow::MainWindow(QDir const& temp_directory, bool multiple,
            , &m_WSPR_band_hopping, &WSPRBandHopping::set_tx_percent);
 #endif
 
+  // decoder queue handler
+  connect(this, &MainWindow::decodedLineReady, this, &MainWindow::processDecodedLine);
+
   on_EraseButton_clicked ();
 
   QActionGroup* modeGroup = new QActionGroup(this);
@@ -1603,11 +1606,21 @@ void MainWindow::initDecoderSubprocess(){
 
     if(JS8_DEBUG_DECODE) qDebug() << "decoder subprocess starting...";
 
-    auto proc = new QProcess(this);
+#if JS8_DECODE_THREAD
+    auto thread = new QThread(nullptr);
+#endif
+
+    auto proc = new QProcess(nullptr);
 
     connect(proc, &QProcess::readyReadStandardOutput, this,
             [this, proc](){
+#if JS8_DECODE_THREAD
+                while(proc->canReadLine()){
+                    emit decodedLineReady(proc->readLine());
+                }
+#else
                 readFromStdout(proc);
+#endif
             });
 
     connect(proc, static_cast<void (QProcess::*) (QProcess::ProcessError)> (&QProcess::error),
@@ -1617,8 +1630,10 @@ void MainWindow::initDecoderSubprocess(){
 
     connect(proc, static_cast<void (QProcess::*) (int, QProcess::ExitStatus)> (&QProcess::finished),
             [this, proc] (int exitCode, QProcess::ExitStatus status) {
+#if JS8_DECODE_THREAD
               proc->deleteLater();
               proc->thread()->quit();
+#endif
               subProcessFailed (proc, exitCode, status);
             });
 
@@ -1626,6 +1641,15 @@ void MainWindow::initDecoderSubprocess(){
     proc->start(QDir::toNativeSeparators (m_appDir) + QDir::separator () +
             "js8", js8_args, QIODevice::ReadWrite | QIODevice::Unbuffered);
 
+#if JS8_DECODE_THREAD
+    if(JS8_DEBUG_DECODE) qDebug() << "decoder subprocess moving to new thread...";
+    // move process handling into its own thread
+    proc->moveToThread(thread);
+    connect(thread, &QThread::finished, thread, &QObject::deleteLater);
+    thread->moveToThread(qApp->thread());
+    thread->start(QThread::HighPriority);
+#endif
+
     // create a process watcher looking for stdout read...
     // seems like we're starving the event loop or something?
     // auto watcher = new QTimer(proc);
@@ -4681,7 +4705,13 @@ void MainWindow::readFromStdout(QProcess * proc)                             //r
   }
 
   while(proc->canReadLine()) {
-      QByteArray t = proc->readLine();
+    processDecodedLine(proc->readLine());
+  }
+
+  // See MainWindow::postDecode for displaying the latest decodes
+}
+
+void MainWindow::processDecodedLine(QByteArray t){
   qDebug() << "JS8: " << QString(t);
 
   bool bAvgMsg=false;
@@ -4768,7 +4798,7 @@ void MainWindow::readFromStdout(QProcess * proc)                             //r
 
   // skip if invalid
   if(!bValidFrame) {
-          continue;
+      return;
   }
 
   ActivityDetail d = {};
@@ -5027,9 +5057,6 @@ void MainWindow::readFromStdout(QProcess * proc)                             //r
 #endif
 }
 
-  // See MainWindow::postDecode for displaying the latest decodes
-}
-
 bool MainWindow::hasExistingMessageBufferToMe(int *pOffset){
     foreach(auto offset, m_messageBuffer.keys()){
         auto buffer = m_messageBuffer[offset];

mainwindow.h

@@ -164,6 +164,7 @@ public slots:
   void tryNotify(const QString &key);
   int rxThreshold(int submode);
   int rxSnrThreshold(int submode);
+  void processDecodedLine(QByteArray t);
 
 protected:
   void keyPressEvent (QKeyEvent *) override;
@@ -430,6 +431,7 @@ private slots:
   void refreshTextDisplay();
 
 private:
+  Q_SIGNAL void decodedLineReady(QByteArray t);
   Q_SIGNAL void playNotification(const QString &name);
   Q_SIGNAL void initializeNotificationAudioOutputStream(const QAudioDeviceInfo &, unsigned, unsigned) const;
   Q_SIGNAL void initializeAudioOutputStream (QAudioDeviceInfo,