TH_CLEAN_3: Use of non-blocking try_pop() when possible,

AudioThread concurrent access hardening and simplified,
and misc.

src/demod/DemodulatorPreThread.cpp

@@ -210,12 +210,11 @@ void DemodulatorPreThread::run() {
 
         inp->decRefCount();
 
-        if (!stopping && !workerResults->empty()) {
-            while (!workerResults->empty()) {
-                DemodulatorWorkerThreadResult result;
-                workerResults->pop(result);
-
-                switch (result.cmd) {
+        DemodulatorWorkerThreadResult result;
+        //process all worker results until 
+        while (!stopping && workerResults->try_pop(result)) {
+              
+            switch (result.cmd) {
                 case DemodulatorWorkerThreadResult::DEMOD_WORKER_THREAD_RESULT_FILTERS:
                     if (result.iqResampler) {
                         if (iqResampler) {
@@ -258,20 +257,19 @@ void DemodulatorPreThread::run() {
                     break;
                 default:
                     break;
-                }
             }
-        }
+        } //end while
         
         if ((cModem != nullptr) && modemSettingsChanged.load()) {
             cModem->writeSettings(modemSettingsBuffered);
             modemSettingsBuffered.clear();
             modemSettingsChanged.store(false);
         }
-    }
+    } //end while stopping
 
-    while (!iqOutputQueue->empty()) {
-        DemodulatorThreadPostIQData *tmp;
-        iqOutputQueue->pop(tmp);
+    DemodulatorThreadPostIQData *tmp;
+    while (iqOutputQueue->try_pop(tmp)) {
+        
         tmp->decRefCount();
     }
     buffers.purge();

src/demod/DemodulatorThread.cpp

@@ -250,43 +250,45 @@ void DemodulatorThread::run() {
             }
         }
         
-        if (!threadQueueControl->empty()) {
-            while (!threadQueueControl->empty()) {
-                DemodulatorThreadControlCommand command;
-                threadQueueControl->pop(command);
-                
-                switch (command.cmd) {
-                    case DemodulatorThreadControlCommand::DEMOD_THREAD_CMD_CTL_SQUELCH_ON:
-                        squelchEnabled = true;
-                        break;
-                    case DemodulatorThreadControlCommand::DEMOD_THREAD_CMD_CTL_SQUELCH_OFF:
-                        squelchEnabled = false;
-                        break;
-                    default:
-                        break;
-                }
+        DemodulatorThreadControlCommand command;
+        
+        //empty command queue, execute commands
+        while (threadQueueControl->try_pop(command)) {
+                       
+            switch (command.cmd) {
+                case DemodulatorThreadControlCommand::DEMOD_THREAD_CMD_CTL_SQUELCH_ON:
+                    squelchEnabled = true;
+                    break;
+                case DemodulatorThreadControlCommand::DEMOD_THREAD_CMD_CTL_SQUELCH_OFF:
+                    squelchEnabled = false;
+                    break;
+                default:
+                    break;
             }
         }
         
+        
         inp->decRefCount();
     }
     // end while !stopping
     
-    // Purge any unused inputs
-    while (!iqInputQueue->empty()) {
-        DemodulatorThreadPostIQData *ref;
-        iqInputQueue->pop(ref);
+    // Purge any unused inputs, with a non-blocking pop
+    DemodulatorThreadPostIQData *ref;
+    while (iqInputQueue->try_pop(ref)) {
+        
         if (ref) {  // May have other consumers; just decrement
             ref->decRefCount();
         }
     }
-    while (!audioOutputQueue->empty()) {
-        AudioThreadInput *ref;
-        audioOutputQueue->pop(ref);
-        if (ref) { // Originated here; set RefCount to 0
-            ref->setRefCount(0);
+
+    AudioThreadInput *ref_audio;
+    while (audioOutputQueue->try_pop(ref_audio)) {
+      
+        if (ref_audio) { // Originated here; set RefCount to 0
+            ref_audio->setRefCount(0);
         }
     }
+
     outputBuffers.purge();
     
 //    std::cout << "Demodulator thread done." << std::endl;

src/demod/DemodulatorWorkerThread.cpp

@@ -24,8 +24,12 @@ void DemodulatorWorkerThread::run() {
         DemodulatorWorkerThreadCommand command;
 
         bool done = false;
+        //Beware of the subtility here,
+        //we are waiting for the first command to show up (blocking!)
+        //then consuming the commands until done. 
         while (!done) {
             commandQueue->pop(command);
+
             switch (command.cmd) {
                 case DemodulatorWorkerThreadCommand::DEMOD_WORKER_THREAD_CMD_BUILD_FILTERS:
                     filterChanged = true;