Add C++ API for streaming ASR. (#1455)

It is a wrapper around the C API.

sherpa-onnx/c-api/cxx-api.h

@@ -0,0 +1,179 @@
+// sherpa-onnx/c-api/cxx-api.h
+//
+// Copyright (c)  2024  Xiaomi Corporation
+
+// C++ Wrapper of the C API for sherpa-onnx
+#ifndef SHERPA_ONNX_C_API_CXX_API_H_
+#define SHERPA_ONNX_C_API_CXX_API_H_
+
+#include <string>
+#include <vector>
+
+#include "sherpa-onnx/c-api/c-api.h"
+
+namespace sherpa_onnx::cxx {
+
+struct SHERPA_ONNX_API OnlineTransducerModelConfig {
+  std::string encoder;
+  std::string decoder;
+  std::string joiner;
+};
+
+struct SHERPA_ONNX_API OnlineParaformerModelConfig {
+  std::string encoder;
+  std::string decoder;
+};
+
+struct SHERPA_ONNX_API OnlineZipformer2CtcModelConfig {
+  std::string model;
+};
+
+struct SHERPA_ONNX_API OnlineModelConfig {
+  OnlineTransducerModelConfig transducer;
+  OnlineParaformerModelConfig paraformer;
+  OnlineZipformer2CtcModelConfig zipformer2_ctc;
+  std::string tokens;
+  int32_t num_threads = 1;
+  std::string provider = "cpu";
+  bool debug = false;
+  std::string model_type;
+  std::string modeling_unit = "cjkchar";
+  std::string bpe_vocab;
+  std::string tokens_buf;
+};
+
+struct SHERPA_ONNX_API FeatureConfig {
+  int32_t sample_rate = 16000;
+  int32_t feature_dim = 80;
+};
+
+struct SHERPA_ONNX_API OnlineCtcFstDecoderConfig {
+  std::string graph;
+  int32_t max_active = 3000;
+};
+
+struct SHERPA_ONNX_API OnlineRecognizerConfig {
+  FeatureConfig feat_config;
+  OnlineModelConfig model_config;
+
+  std::string decoding_method = "greedy_search";
+
+  int32_t max_active_paths = 4;
+
+  bool enable_endpoint = false;
+
+  float rule1_min_trailing_silence = 2.4;
+
+  float rule2_min_trailing_silence = 1.2;
+
+  float rule3_min_utterance_length = 20;
+
+  std::string hotwords_file;
+
+  float hotwords_score = 1.5;
+
+  OnlineCtcFstDecoderConfig ctc_fst_decoder_config;
+  std::string rule_fsts;
+  std::string rule_fars;
+  float blank_penalty = 0;
+
+  std::string hotwords_buf;
+};
+
+struct SHERPA_ONNX_API OnlineRecognizerResult {
+  std::string text;
+  std::vector<std::string> tokens;
+  std::vector<float> timestamps;
+  std::string json;
+};
+
+struct SHERPA_ONNX_API Wave {
+  std::vector<float> samples;
+  int32_t sample_rate;
+};
+
+SHERPA_ONNX_API Wave ReadWave(const std::string &filename);
+
+template <typename Derived, typename T>
+class SHERPA_ONNX_API MoveOnly {
+ public:
+  explicit MoveOnly(const T *p) : p_(p) {}
+
+  ~MoveOnly() { Destroy(); }
+
+  MoveOnly(const MoveOnly &) = delete;
+
+  MoveOnly &operator=(const MoveOnly &) = delete;
+
+  MoveOnly(MoveOnly &&other) : p_(other.Release()) {}
+
+  MoveOnly &operator=(MoveOnly &&other) {
+    if (&other == this) {
+      return *this;
+    }
+
+    Destroy();
+
+    p_ = other.Release();
+  }
+
+  const T *Get() const { return p_; }
+
+  const T *Release() {
+    const T *p = p_;
+    p_ = nullptr;
+    return p;
+  }
+
+ private:
+  void Destroy() {
+    if (p_ == nullptr) {
+      return;
+    }
+
+    static_cast<Derived *>(this)->Destroy(p_);
+
+    p_ = nullptr;
+  }
+
+ protected:
+  const T *p_ = nullptr;
+};
+
+class SHERPA_ONNX_API OnlineStream
+    : public MoveOnly<OnlineStream, SherpaOnnxOnlineStream> {
+ public:
+  explicit OnlineStream(const SherpaOnnxOnlineStream *p);
+
+  void AcceptWaveform(int32_t sample_rate, const float *samples,
+                      int32_t n) const;
+
+  void Destroy(const SherpaOnnxOnlineStream *p) const;
+};
+
+class SHERPA_ONNX_API OnlineRecognizer
+    : public MoveOnly<OnlineRecognizer, SherpaOnnxOnlineRecognizer> {
+ public:
+  static OnlineRecognizer Create(const OnlineRecognizerConfig &config);
+
+  void Destroy(const SherpaOnnxOnlineRecognizer *p) const;
+
+  OnlineStream CreateStream() const;
+
+  OnlineStream CreateStream(const std::string &hotwords) const;
+
+  bool IsReady(const OnlineStream *s) const;
+
+  void Decode(const OnlineStream *s) const;
+
+  void Decode(const OnlineStream *ss, int32_t n) const;
+
+  OnlineRecognizerResult GetResult(const OnlineStream *s) const;
+
+ private:
+  explicit OnlineRecognizer(const SherpaOnnxOnlineRecognizer *p);
+};
+
+}  // namespace sherpa_onnx::cxx
+
+#endif  // SHERPA_ONNX_C_API_CXX_API_H_