Add CTC HLG decoding using OpenFst (#349)

sherpa-onnx/csrc/offline-zipformer-ctc-model-config.cc

@@ -0,0 +1,35 @@
+// sherpa-onnx/csrc/offline-zipformer-ctc-model-config.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/offline-zipformer-ctc-model-config.h"
+
+#include "sherpa-onnx/csrc/file-utils.h"
+#include "sherpa-onnx/csrc/macros.h"
+
+namespace sherpa_onnx {
+
+void OfflineZipformerCtcModelConfig::Register(ParseOptions *po) {
+  po->Register("zipformer-ctc-model", &model, "Path to zipformer CTC model");
+}
+
+bool OfflineZipformerCtcModelConfig::Validate() const {
+  if (!FileExists(model)) {
+    SHERPA_ONNX_LOGE("zipformer CTC model file %s does not exist",
+                     model.c_str());
+    return false;
+  }
+
+  return true;
+}
+
+std::string OfflineZipformerCtcModelConfig::ToString() const {
+  std::ostringstream os;
+
+  os << "OfflineZipformerCtcModelConfig(";
+  os << "model=\"" << model << "\")";
+
+  return os.str();
+}
+
+}  // namespace sherpa_onnx