Add HLG decoding for streaming CTC models (#731)

sherpa-onnx/csrc/offline-ctc-fst-decoder-config.cc

@@ -7,6 +7,9 @@
 #include <sstream>
 #include <string>
 
+#include "sherpa-onnx/csrc/file-utils.h"
+#include "sherpa-onnx/csrc/macros.h"
+
 namespace sherpa_onnx {
 
 std::string OfflineCtcFstDecoderConfig::ToString() const {
@@ -29,4 +32,12 @@ void OfflineCtcFstDecoderConfig::Register(ParseOptions *po) {
              "Decoder max active states.  Larger->slower; more accurate");
 }
 
+bool OfflineCtcFstDecoderConfig::Validate() const {
+  if (!graph.empty() && !FileExists(graph)) {
+    SHERPA_ONNX_LOGE("graph: %s does not exist", graph.c_str());
+    return false;
+  }
+  return true;
+}
+
 }  // namespace sherpa_onnx