Add C++ runtime for *streaming* faster conformer transducer from NeMo. (#889)

Co-authored-by: sangeet2020 <15uec053@gmail.com>

sherpa-onnx/csrc/online-transducer-greedy-search-nemo-decoder.h

@@ -0,0 +1,40 @@
+// sherpa-onnx/csrc/online-transducer-greedy-search-nemo-decoder.h
+//
+// Copyright (c)  2024  Xiaomi Corporation
+// Copyright (c)  2024  Sangeet Sagar
+
+#ifndef SHERPA_ONNX_CSRC_ONLINE_TRANSDUCER_GREEDY_SEARCH_NEMO_DECODER_H_
+#define SHERPA_ONNX_CSRC_ONLINE_TRANSDUCER_GREEDY_SEARCH_NEMO_DECODER_H_
+
+#include <vector>
+#include "sherpa-onnx/csrc/online-transducer-decoder.h"
+#include "sherpa-onnx/csrc/online-transducer-nemo-model.h"
+
+namespace sherpa_onnx {
+
+class OnlineTransducerGreedySearchNeMoDecoder {
+ public:
+  OnlineTransducerGreedySearchNeMoDecoder(OnlineTransducerNeMoModel *model,
+                                          float blank_penalty)
+      : model_(model),
+      blank_penalty_(blank_penalty) {}
+
+  OnlineTransducerDecoderResult GetEmptyResult() const;
+  void UpdateDecoderOut(OnlineTransducerDecoderResult *result) {}
+  void StripLeadingBlanks(OnlineTransducerDecoderResult * /*r*/) const {}
+  
+  std::vector<Ort::Value> Decode(
+    Ort::Value encoder_out, 
+    std::vector<Ort::Value> decoder_states, 
+    std::vector<OnlineTransducerDecoderResult> *result,
+    OnlineStream **ss = nullptr, int32_t n = 0);
+
+ private:
+  OnlineTransducerNeMoModel *model_;  // Not owned
+  float blank_penalty_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_TRANSDUCER_GREEDY_SEARCH_NEMO_DECODER_H_
+