add online-recognizer (#29)

sherpa-onnx/csrc/online-recognizer.h

@@ -0,0 +1,65 @@
+// sherpa-onnx/csrc/online-recognizer.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_ONLINE_RECOGNIZER_H_
+#define SHERPA_ONNX_CSRC_ONLINE_RECOGNIZER_H_
+
+#include <memory>
+#include <string>
+
+#include "sherpa-onnx/csrc/features.h"
+#include "sherpa-onnx/csrc/online-stream.h"
+#include "sherpa-onnx/csrc/online-transducer-model-config.h"
+
+namespace sherpa_onnx {
+
+struct OnlineRecognizerResult {
+  std::string text;
+};
+
+struct OnlineRecognizerConfig {
+  FeatureExtractorConfig feat_config;
+  OnlineTransducerModelConfig model_config;
+  std::string tokens;
+
+  std::string ToString() const;
+};
+
+class OnlineRecognizer {
+ public:
+  explicit OnlineRecognizer(const OnlineRecognizerConfig &config);
+  ~OnlineRecognizer();
+
+  /// Create a stream for decoding.
+  std::unique_ptr<OnlineStream> CreateStream() const;
+
+  /**
+   * Return true if the given stream has enough frames for decoding.
+   * Return false otherwise
+   */
+  bool IsReady(OnlineStream *s) const;
+
+  /** Decode a single stream. */
+  void DecodeStream(OnlineStream *s) {
+    OnlineStream *ss[1] = {s};
+    DecodeStreams(ss, 1);
+  }
+
+  /** Decode multiple streams in parallel
+   *
+   * @param ss Pointer array containing streams to be decoded.
+   * @param n Number of streams in `ss`.
+   */
+  void DecodeStreams(OnlineStream **ss, int32_t n);
+
+  OnlineRecognizerResult GetResult(OnlineStream *s);
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_RECOGNIZER_H_