Support streaming conformer CTC models from wenet (#427)

sherpa-onnx/csrc/online-ctc-model.h

@@ -0,0 +1,67 @@
+// sherpa-onnx/csrc/online-ctc-model.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+#ifndef SHERPA_ONNX_CSRC_ONLINE_CTC_MODEL_H_
+#define SHERPA_ONNX_CSRC_ONLINE_CTC_MODEL_H_
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "onnxruntime_cxx_api.h"  // NOLINT
+#include "sherpa-onnx/csrc/online-model-config.h"
+
+namespace sherpa_onnx {
+
+class OnlineCtcModel {
+ public:
+  virtual ~OnlineCtcModel() = default;
+
+  static std::unique_ptr<OnlineCtcModel> Create(
+      const OnlineModelConfig &config);
+
+#if __ANDROID_API__ >= 9
+  static std::unique_ptr<OnlineCtcModel> Create(
+      AAssetManager *mgr, const OnlineModelConfig &config);
+#endif
+
+  // Return a list of tensors containing the initial states
+  virtual std::vector<Ort::Value> GetInitStates() const = 0;
+
+  /**
+   *
+   * @param x A 3-D tensor of shape (N, T, C). N has to be 1.
+   * @param states  It is from GetInitStates() or returned from this method.
+   *
+   * @return Return a list of tensors
+   *    - ans[0] contains log_probs, of shape (N, T, C)
+   *    - ans[1:] contains next_states
+   */
+  virtual std::vector<Ort::Value> Forward(
+      Ort::Value x, std::vector<Ort::Value> states) const = 0;
+
+  /** Return the vocabulary size of the model
+   */
+  virtual int32_t VocabSize() const = 0;
+
+  /** Return an allocator for allocating memory
+   */
+  virtual OrtAllocator *Allocator() const = 0;
+
+  // The model accepts this number of frames before subsampling as input
+  virtual int32_t ChunkLength() const = 0;
+
+  // Similar to frame_shift in feature extractor, after processing
+  // ChunkLength() frames, we advance by ChunkShift() frames
+  // before we process the next chunk.
+  virtual int32_t ChunkShift() const = 0;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_CTC_MODEL_H_