add endpointing for online websocket server (#294)

sherpa-onnx/csrc/online-recognizer-transducer-impl.h

@@ -26,7 +26,8 @@ namespace sherpa_onnx {
 static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
                                       const SymbolTable &sym_table,
                                       int32_t frame_shift_ms,
-                                      int32_t subsampling_factor) {
+                                      int32_t subsampling_factor,
+                                      int32_t segment) {
   OnlineRecognizerResult r;
   r.tokens.reserve(src.tokens.size());
   r.timestamps.reserve(src.tokens.size());
@@ -44,6 +45,8 @@ static OnlineRecognizerResult Convert(const OnlineTransducerDecoderResult &src,
     r.timestamps.push_back(time);
   }
 
+  r.segment = segment;
+
   return r;
 }
 
@@ -192,7 +195,8 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
     // TODO(fangjun): Remember to change these constants if needed
     int32_t frame_shift_ms = 10;
     int32_t subsampling_factor = 4;
-    return Convert(decoder_result, sym_, frame_shift_ms, subsampling_factor);
+    return Convert(decoder_result, sym_, frame_shift_ms, subsampling_factor,
+                   s->GetCurrentSegment());
   }
 
   bool IsEndpoint(OnlineStream *s) const override {
@@ -213,6 +217,15 @@ class OnlineRecognizerTransducerImpl : public OnlineRecognizerImpl {
   }
 
   void Reset(OnlineStream *s) const override {
+    {
+      // segment is incremented only when the last
+      // result is not empty
+      const auto &r = s->GetResult();
+      if (!r.tokens.empty() && r.tokens.back() != 0) {
+        s->GetCurrentSegment() += 1;
+      }
+    }
+
     // we keep the decoder_out
     decoder_->UpdateDecoderOut(&s->GetResult());
     Ort::Value decoder_out = std::move(s->GetResult().decoder_out);