Function ExportArray

cpp/src/arrow/c/dlpack.cc:69–106

}  // namespace

Result<DLManagedTensor*> ExportArray(const std::shared_ptr<Array>& arr) {
  // Define DLDevice struct and check if array type is supported
  // by the DLPack protocol at the same time. Raise TypeError if not.
  // Supported data types: int, uint, float with no validity buffer.
  ARROW_ASSIGN_OR_RAISE(auto device, ExportDevice(arr))

  // Define the DLDataType struct
  const DataType& type = *arr->type();
  std::shared_ptr<ArrayData> data = arr->data();
  ARROW_ASSIGN_OR_RAISE(auto dlpack_type, GetDLDataType(type));

  // Create ManagerCtx that will serve as the owner of the DLManagedTensor
  auto ctx = std::make_unique<ManagerCtx>();

  // Define the data pointer to the DLTensor
  // If array is of length 0, data pointer should be NULL
  if (arr->length() == 0) {
    ctx->tensor.dl_tensor.data = NULL;
  } else {
    const auto data_offset = data->offset * type.byte_width();
    ctx->tensor.dl_tensor.data =
        const_cast<uint8_t*>(data->buffers[1]->data() + data_offset);
  }

  ctx->tensor.dl_tensor.device = device;
  ctx->tensor.dl_tensor.ndim = 1;
  ctx->tensor.dl_tensor.dtype = dlpack_type;
  ctx->tensor.dl_tensor.shape = const_cast<int64_t*>(&data->length);
  ctx->tensor.dl_tensor.strides = NULL;
  ctx->tensor.dl_tensor.byte_offset = 0;

  ctx->array = std::move(data);
  ctx->tensor.manager_ctx = ctx.get();
  ctx->tensor.deleter = [](struct DLManagedTensor* self) {
    delete reinterpret_cast<ManagerCtx*>(self->manager_ctx);
  };
  return &ctx.release()->tensor;
}

Result<DLDevice> ExportDevice(const std::shared_ptr<Array>& arr) {
  // Check if array is supported by the DLPack protocol.