enable loading onnx from buffer

Source/CNTKv2LibraryDll/API/CNTKLibrary.h

@@ -3613,7 +3613,8 @@ namespace CNTK
         /// Load a Function from a memory buffer
         ///
         CNTK_API static FunctionPtr Load(const char* buffer, size_t length,
-                                         const DeviceDescriptor& computeDevice = DeviceDescriptor::UseDefaultDevice());
+                                         const DeviceDescriptor& computeDevice = DeviceDescriptor::UseDefaultDevice(),
+                                         ModelFormat format = ModelFormat::CNTKv2);
 
         ///
         /// Load a Function from an istream. The legacy V1 model is not supported.

Source/CNTKv2LibraryDll/Function.cpp

@@ -531,7 +531,7 @@ namespace CNTK
         return nullptr;
     }
 
-    /*static*/ FunctionPtr Function::Load(const char *buffer, size_t length, const DeviceDescriptor& computeDevice)
+    /*static*/ FunctionPtr Function::Load(const char *buffer, size_t length, const DeviceDescriptor& computeDevice, ModelFormat format)
     {
         if ((buffer == nullptr) || (length <= 0))
             InvalidArgument("The model buffer should not be null and its length should be greater than 0");
@@ -545,15 +545,32 @@ namespace CNTK
             }
         };
 
-        if (Internal::IsLegacyModel(buffer, length))
-            InvalidArgument("Loading a legacy model from byte array is not supported.");
-        else
+        switch (format)
         {
-            modelStreamBuffer buf(buffer, length);
-            std::istream modelStream(&buf);
+        case ModelFormat::CNTKv2:
+        {
+            if (Internal::IsLegacyModel(buffer, length)) {
+                InvalidArgument("Loading a legacy model from byte array is not supported.");
+            }
+            else
+            {
+                modelStreamBuffer buf(buffer, length);
+                std::istream modelStream(&buf);
 
-            return Load(modelStream, computeDevice);
+                return Load(modelStream, computeDevice);
+            }
+            break;
         }
+
+        case ModelFormat::ONNX:
+            return ONNXFormat::Load(static_cast<const void*>(buffer), length, computeDevice);
+            break;
+
+        default:
+            InvalidArgument("unsupported ModelFormat.");
+        }
+
+        return nullptr;
     }
 
     /*static*/ FunctionPtr Function::Load(std::istream& inputStream, const DeviceDescriptor& computeDevice)

Source/CNTKv2LibraryDll/proto/onnx/ONNX.cpp

@@ -121,3 +121,23 @@ FunctionPtr ONNXFormat::Load(const std::wstring& filepath, const DeviceDescripto
     FunctionPtr cntkFunction = ONNXToCNTK::CreateGraph(&model->MainGraph(), computeDevice);
     return cntkFunction;
 }
+
+FunctionPtr ONNXFormat::Load(const void* model_data, int model_data_len, const DeviceDescriptor& computeDevice)
+{
+    InitializeLotusIR();
+
+    onnx::ModelProto model_proto;
+    const bool result = model_proto.ParseFromArray(model_data, model_data_len);
+    if (!result) {
+        LogicError("protobuf failed to parse model");
+    }
+
+    std::shared_ptr<onnxruntime::Model> model;
+    onnxruntime::common::Status loadStatus = onnxruntime::Model::Load(model_proto, model);
+
+    if (!loadStatus.IsOK())
+        LogicError("Failed to load model: '%s'", loadStatus.ErrorMessage().c_str());
+
+    FunctionPtr cntkFunction = ONNXToCNTK::CreateGraph(&model->MainGraph(), computeDevice);
+    return cntkFunction;
+}

Source/CNTKv2LibraryDll/proto/onnx/ONNX.h

@@ -16,8 +16,9 @@ namespace CNTK
     public:
         static void Save(const FunctionPtr& src, const std::wstring& filepath);
         static FunctionPtr Load(const std::wstring& filepath, const DeviceDescriptor& computeDevice = DeviceDescriptor::UseDefaultDevice());
+        static FunctionPtr Load(const void* model_data, int model_data_len, const DeviceDescriptor& computeDevice = DeviceDescriptor::UseDefaultDevice());
     private:
         static void InitializeLotusIR();
         static std::once_flag op_schema_initializer_flag_;
     };
-}
+}