feat: finish forward of ExecutorchModule

Author: chmjkb

packages/react-native-executorch/common/rnexecutorch/bindings/ExecutorchModule.cpp

@@ -25,17 +25,47 @@ ExecutorchModule::ExecutorchModule(
   }
 }
 
-int ExecutorchModule::forward(std::vector<JsiTensorView> tensorViewVec) {
-  auto currTensor = tensorViewVec[0];
-  auto myTensor =
-      make_tensor_ptr(currTensor.shape, currTensor.dataPtr, ScalarType::Float);
-  auto result = module->forward(myTensor);
+std::vector<std::shared_ptr<OwningArrayBuffer>>
+ExecutorchModule::forward(std::vector<JsiTensorView> tensorViewVec) {
+  std::vector<executorch::runtime::EValue> evalues;
+  evalues.reserve(tensorViewVec.size());
+  // Because EValue doesn't hold to the dynamic data and metadata from
+  // TensorPtr, we need to make sure that the TensorPtr for each EValue is valid
+  // as long as that EValue is in use. Therefore we create a vec solely for
+  // keeping references to the TensorPtr
+  std::vector<TensorPtr> tensorPtrs;
+  tensorPtrs.reserve(evalues.size());
+
+  for (size_t i = 0; i < tensorViewVec.size(); i++) {
+    const auto &currTensorView = tensorViewVec[i];
+    auto tensorPtr = make_tensor_ptr(currTensorView.shape,
+                                     currTensorView.dataPtr, ScalarType::Float);
+    tensorPtrs.emplace_back(tensorPtr);
+    evalues.emplace_back(*tensorPtr); // Dereference TensorPtr to get Tensor,
+                                      // which implicitly converts to EValue
+  }
+
+  auto result = module->forward(evalues);
   if (!result.ok()) {
-    std::string errorStr = std::to_string(static_cast<int>(result.error()));
-    log(LOG_LEVEL::Debug, errorStr.c_str());
-    throw std::runtime_error("Failed to run forward! Error: " + errorStr);
+    throw std::runtime_error("Forward error: " +
+                             std::to_string(static_cast<int>(result.error())));
+  }
+
+  auto &outputs = result.get();
+  std::vector<std::shared_ptr<OwningArrayBuffer>> output;
+  output.reserve(outputs.size());
+
+  // Convert ET outputs to a vector of ArrayBuffers which are later
+  // converted to JSI array via JsiConversions.h
+  for (size_t i = 0; i < outputs.size(); i++) {
+    auto &outputTensor = outputs[i].toTensor();
+
+    size_t bufferSize = outputTensor.numel() * outputTensor.element_size();
+    auto buffer = std::make_shared<OwningArrayBuffer>(bufferSize);
+    std::memcpy(buffer->data(), outputTensor.const_data_ptr(), bufferSize);
+    output.emplace_back(buffer);
   }
-  return 1;
+  return output;
 }
 
 std::vector<int32_t> ExecutorchModule::getInputShape(std::string method_name,