Add RNN LM rescore for offline ASR with modified_beam_search (#125)

sherpa-onnx/csrc/offline-transducer-model.cc

@@ -95,6 +95,30 @@ class OfflineTransducerModel::Impl {
       std::copy(begin, end, p);
       p += context_size;
     }
+
+    return decoder_input;
+  }
+
+  Ort::Value BuildDecoderInput(const std::vector<Hypothesis> &results,
+                               int32_t end_index) const {
+    assert(end_index <= results.size());
+
+    int32_t batch_size = end_index;
+    int32_t context_size = ContextSize();
+    std::array<int64_t, 2> shape{batch_size, context_size};
+
+    Ort::Value decoder_input = Ort::Value::CreateTensor<int64_t>(
+        Allocator(), shape.data(), shape.size());
+    int64_t *p = decoder_input.GetTensorMutableData<int64_t>();
+
+    for (int32_t i = 0; i != batch_size; ++i) {
+      const auto &r = results[i];
+      const int64_t *begin = r.ys.data() + r.ys.size() - context_size;
+      const int64_t *end = r.ys.data() + r.ys.size();
+      std::copy(begin, end, p);
+      p += context_size;
+    }
+
     return decoder_input;
   }
 
@@ -234,4 +258,9 @@ Ort::Value OfflineTransducerModel::BuildDecoderInput(
   return impl_->BuildDecoderInput(results, end_index);
 }
 
+Ort::Value OfflineTransducerModel::BuildDecoderInput(
+    const std::vector<Hypothesis> &results, int32_t end_index) const {
+  return impl_->BuildDecoderInput(results, end_index);
+}
+
 }  // namespace sherpa_onnx