From c04406d75aa5db9e1f969416f3904e8fef06b8ae Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Sun, 19 Feb 2017 09:54:57 -0800
Subject: [PATCH] Clean shutdown+join of FLITE synthesis threads.

use a marker value to wake the blocking queue, and allow the thread
loop to terminate cleanly, before calling join() from the parent
thread.
---
 src/Sound/VoiceSynthesizer.cxx | 25 ++++++++++++++++++++++---
 src/Sound/VoiceSynthesizer.hxx |  4 ++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/Sound/VoiceSynthesizer.cxx b/src/Sound/VoiceSynthesizer.cxx
index 5871716d0..ef51c3b5b 100644
--- a/src/Sound/VoiceSynthesizer.cxx
+++ b/src/Sound/VoiceSynthesizer.cxx
@@ -23,7 +23,8 @@
 #include <simgear/debug/logstream.hxx>
 #include <simgear/sound/readwav.hxx>
 #include <simgear/misc/sg_path.hxx>
-#include <OpenThreads/Thread>
+#include <simgear/threads/SGThread.hxx>
+
 #include <flite_hts_engine.h>
 
 using std::string;
@@ -33,7 +34,8 @@ static const char * VOICE_FILES[] = {
   "cstr_uk_female-1.0.htsvoice"
 };
 
-class FLITEVoiceSynthesizer::WorkerThread: public OpenThreads::Thread {
+class FLITEVoiceSynthesizer::WorkerThread : public SGThread
+{
 public:
   WorkerThread(FLITEVoiceSynthesizer * synthesizer)
       : _synthesizer(synthesizer)
@@ -48,6 +50,13 @@ void FLITEVoiceSynthesizer::WorkerThread::run()
 {
   for (;;) {
     SynthesizeRequest request = _synthesizer->_requests.pop();
+
+    // marker value indicating termination requested
+    if ((request.speed < 0.0) && (request.volume < 0.0)) {
+      SG_LOG(SG_SOUND, SG_INFO, "FLITE synthesis thread exiting");
+      return;
+    }
+
     if ( NULL != request.listener) {
       SGSharedPtr<SGSoundSample> sample = _synthesizer->synthesize(request.text, request.volume, request.speed, request.pitch);
       request.listener->SoundSampleReady( sample );
@@ -55,6 +64,14 @@ void FLITEVoiceSynthesizer::WorkerThread::run()
   }
 }
 
+SynthesizeRequest SynthesizeRequest::cancelThreadRequest()
+{
+  SynthesizeRequest marker;
+  marker.volume = -999.0;
+  marker.speed = -999.0;
+  return marker;
+}
+
 string FLITEVoiceSynthesizer::getVoicePath( voice_t voice )
 {
   if( voice < 0 || voice >= VOICE_UNKNOWN ) return string("");
@@ -86,8 +103,10 @@ FLITEVoiceSynthesizer::FLITEVoiceSynthesizer(const std::string & voice)
 
 FLITEVoiceSynthesizer::~FLITEVoiceSynthesizer()
 {
-  _worker->cancel();
+  // push the special marker value
+  _requests.push(SynthesizeRequest::cancelThreadRequest());
   _worker->join();
+  SG_LOG(SG_SOUND, SG_INFO, "FLITE synthesis thread joined OK");
   Flite_HTS_Engine_clear(_engine);
 }
 
diff --git a/src/Sound/VoiceSynthesizer.hxx b/src/Sound/VoiceSynthesizer.hxx
index 246085d9b..cce9da2be 100644
--- a/src/Sound/VoiceSynthesizer.hxx
+++ b/src/Sound/VoiceSynthesizer.hxx
@@ -64,6 +64,10 @@ struct SynthesizeRequest {
     return *this;
   }
 
+  // return a special marker request used to indicate the synthesis thread
+  // should be exited.
+  static SynthesizeRequest cancelThreadRequest();
+
   std::string text;
   double speed;
   double volume;