Support streaming zipformer CTC (#496)

* Support streaming zipformer CTC

* test online zipformer2 CTC

* Update doc of sherpa-onnx.cc

* Add Python APIs for streaming zipformer2 ctc

* Add Python API examples for streaming zipformer2 ctc

* Swift API for streaming zipformer2 CTC

* NodeJS API for streaming zipformer2 CTC

* Kotlin API for streaming zipformer2 CTC

* Golang API for streaming zipformer2 CTC

* C# API for streaming zipformer2 CTC

* Release v1.9.6

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

@@ -33,6 +33,26 @@ class OnlineCtcModel {
   // Return a list of tensors containing the initial states
   virtual std::vector<Ort::Value> GetInitStates() const = 0;
 
+  /** Stack a list of individual states into a batch.
+   *
+   * It is the inverse operation of `UnStackStates`.
+   *
+   * @param states states[i] contains the state for the i-th utterance.
+   * @return Return a single value representing the batched state.
+   */
+  virtual std::vector<Ort::Value> StackStates(
+      std::vector<std::vector<Ort::Value>> states) const = 0;
+
+  /** Unstack a batch state into a list of individual states.
+   *
+   * It is the inverse operation of `StackStates`.
+   *
+   * @param states A batched state.
+   * @return ans[i] contains the state for the i-th utterance.
+   */
+  virtual std::vector<std::vector<Ort::Value>> UnStackStates(
+      std::vector<Ort::Value> states) const = 0;
+
   /**
    *
    * @param x A 3-D tensor of shape (N, T, C). N has to be 1.
@@ -60,6 +80,9 @@ class OnlineCtcModel {
   // ChunkLength() frames, we advance by ChunkShift() frames
   // before we process the next chunk.
   virtual int32_t ChunkShift() const = 0;
+
+  // Return true if the model supports batch size > 1
+  virtual bool SupportBatchProcessing() const { return true; }
 };
 
 }  // namespace sherpa_onnx