chore: import upstream snapshot with attribution

csrc/utils/tensor_cast.cpp

@@ -0,0 +1,26 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0
+
+// DeepSpeed Team
+
+#include "tensor_cast.h"
+
+at::Tensor cast_to_byte_tensor(at::Tensor& src_tensor)
+{
+    if (src_tensor.nbytes() <= 1) return src_tensor;
+
+    auto options = torch::TensorOptions()
+                       .dtype(torch::kUInt8)
+                       .layout(src_tensor.layout())
+                       .device(src_tensor.device());
+    return at::from_blob(
+        src_tensor.data_ptr(), static_cast<long int>(src_tensor.nbytes()), options);
+}
+
+std::vector<at::Tensor> cast_to_byte_tensor(std::vector<at::Tensor>& tensor_list)
+{
+    std::vector<at::Tensor> byte_tensors;
+    for (auto src_tensor : tensor_list) { byte_tensors.push_back(cast_to_byte_tensor(src_tensor)); }
+
+    return byte_tensors;
+}