/**
 * Copyright 2019 Huawei Technologies Co., Ltd
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef MINDSPORE_CCSRC_MINDDATA_DATASET_CORE_TENSOR_H_
#define MINDSPORE_CCSRC_MINDDATA_DATASET_CORE_TENSOR_H_

#include <deque>
#include <memory>
#include <string>
#include <vector>
#include "./securec.h"
#include "utils/log_adapter.h"
#if defined(_WIN32) || defined(_WIN64)
#undef HAVE_STDDEF_H
#undef HAVE_STDLIB_H
#endif

#ifdef ENABLE_PYTHON
#include "pybind11/numpy.h"
#include "pybind11/pybind11.h"
#include "pybind11/stl.h"
#endif

#include "utils/ms_utils.h"
#include "minddata/dataset/core/constants.h"
#include "minddata/dataset/core/data_type.h"
#include "minddata/dataset/core/tensor_shape.h"
#include "minddata/dataset/util/status.h"
#ifndef ENABLE_ANDROID
#include "proto/example.pb.h"
#else
#include "minddata/dataset/include/de_tensor.h"
#endif

#ifdef ENABLE_PYTHON
namespace py = pybind11;
#endif
namespace mindspore {
#ifdef ENABLE_ANDROID
namespace tensor {
class DETensor;
}  // namespace tensor
#endif
namespace dataset {
class Tensor;
template <typename T>
class Allocator;

using CharAllocPtr = std::unique_ptr<Allocator<unsigned char>>;
using TensorAllocPtr = std::shared_ptr<Allocator<Tensor>>;  // An allocator shared_ptr for Tensors
using offset_t = uint32_t;                                  // type of offset values to store strings locations
using TensorPtr = std::shared_ptr<Tensor>;

class Tensor {
 public:
  Tensor() = delete;
  Tensor(const Tensor &other) = delete;
  Tensor &operator=(const Tensor &other) = delete;

  /// Create a tensor using shape and type. This constructor should not be used directly, use CreateFromTensor instead
  /// \note The shape and type information should be known and valid
  /// \note The constructor does not allocate data
  /// \param shape TensorShape
  /// \param type DataType
  Tensor(const TensorShape &shape, const DataType &type);

  /// Move constructor
  /// \param other Tensor to be moved
  Tensor(Tensor &&other) noexcept;

  /// Move assigment operator
  /// \param other Tensor to be moved
  Tensor &operator=(Tensor &&other) noexcept;

  /// Create a numeric tensor with type and shape. Items of the tensor would be uninitialized.
  /// \param[in] shape shape of the output tensor
  /// \param[in] type type of the output tensor
  /// \param[out] out Generated tensor
  /// \return Status code
  static Status CreateEmpty(const TensorShape &shape, const DataType &type, TensorPtr *out);

  /// Create a numeric tensor from a pointer in memory. Length of the source data is determined from the shape and type.
  /// Data will be copied into the new created tensor.
  /// \param[in] shape shape of the output tensor
  /// \param[in] type type of the output tensor
  /// \param[in] src pointer to the source data
  /// \param[out] out Generated tensor
  /// \return Status code
  static Status CreateFromMemory(const TensorShape &shape, const DataType &type, const uchar *src, TensorPtr *out);

  /// Create a tensor from a pointer in memory and length. Data will be copied into the new created tensor.
  /// \param[in] shape shape of the output tensor
  /// \param[in] type type of the output tensor
  /// \param[in] src pointer to the source data
  /// \param[in] length length of the src data
  /// \param[out] out Generated tensor
  /// \return Status code
  static Status CreateFromMemory(const TensorShape &shape, const DataType &type, const uchar *src,
                                 const dsize_t &length, TensorPtr *out);

  /// Create a copy of the input tensor
  /// \param[in] in original tensor to be copied
  /// \param[out] out output tensor to be generated
  /// \return Status
  static Status CreateFromTensor(const TensorPtr &in, TensorPtr *out) {
    return CreateFromMemory(in->shape(), in->type(), in->GetBuffer(), in->SizeInBytes(), out);
  }

#ifdef ENABLE_PYTHON
  /// Create a Tensor from a given py::array
  /// \param[in] arr py::array
  /// \param[out] out Created tensor
  /// \return Status Code
  static Status CreateFromNpArray(const py::array &arr, TensorPtr *out);
#endif

#ifndef ENABLE_ANDROID
  /// Create a tensor of type DE_STRING from a BytesList.
  /// \param[in] bytes_list protobuf's Bytelist
  /// \param[in] shape shape of the outout tensor
  /// \param[out] out created Tensor
  /// \return Status Code
  static Status CreateFromByteList(const dataengine::BytesList &bytes_list, const TensorShape &shape, TensorPtr *out);

  /// Create a tensor of type UINT8 or INT8 from a BytesList.
  /// The tensor will be padded with ' ' to reach the required pad_size.
  /// \param[in] bytes_list protobuf's Bytelist
  /// \param[in] shape shape of the output tensor
  /// \param[in] type type of created tensor. Should be DE_UINT8 or INT8
  /// \param[in] pad_size The size of the tensor after padding
  /// \param[out] out created Tensor
  /// \return Status Code
  static Status CreateFromByteList(const dataengine::BytesList &bytes_list, const TensorShape &shape,
                                   const DataType &type, dsize_t pad_size, TensorPtr *out);
#endif

  /// Create a Tensor from a given list of values.
  /// \tparam type of the values to be inserted.
  /// \param[in] items elements of the tensor
  /// \param[in] shape shape of the output tensor
  /// \param[out] out output argument to hold the created Tensor
  /// \return Status Code
  template <typename T>
  static Status CreateFromVector(const std::vector<T> &items, const TensorShape &shape, TensorPtr *out) {
    CHECK_FAIL_RETURN_UNEXPECTED(
      items.size() == shape.NumOfElements(),
      "Number of elements in the vector does not match the number of elements of the shape required");
    DataType type = DataType::FromCType<T>();
    // if items is empty, items_ptr would be nullptr. CreateFromMemory will handle this case.
    auto items_ptr = reinterpret_cast<const uchar *>(&items[0]);
    return CreateFromMemory(shape, type, items_ptr, out);
  }

  /// Create a 1D Tensor from a given list of values.
  /// \tparam type of the values to be inserted.
  /// \param[in] items elements of the tensor
  /// \param[out] out output argument to hold the created Tensor
  /// \return Status Code
  template <typename T>
  static Status CreateFromVector(const std::vector<T> &items, TensorPtr *out) {
    return CreateFromVector(items, TensorShape({static_cast<dsize_t>(items.size())}), out);
  }

  /// Create a numeric scalar Tensor from the given value.
  /// \tparam T type of value
  /// \param[in] item value
  /// \param[out] out Created tensor
  /// \return Status code
  template <typename T>
  static Status CreateScalar(const T &item, TensorPtr *out) {
    DataType type = DataType::FromCType<T>();
    auto item_ptr = reinterpret_cast<const uchar *>(&item);
    return CreateFromMemory(TensorShape::CreateScalar(), type, item_ptr, out);
  }

  /// Create a tensor from a binary file on disk.
  /// \param[in] path file to be read
  /// \param[out] out Created Tensor
  /// \return Status code
  static Status CreateFromFile(const std::string &path, TensorPtr *out);

  /// Destruct the tensor and release the memory using the allocator
  virtual ~Tensor();

  /// Equality operator. compares tensor shape, type and data
  /// \param[in] rhs Tensor to be compared with
  /// \return bool
  bool operator==(const Tensor &rhs) const;

  bool operator!=(const Tensor &rhs) const { return !((*this) == rhs); }

  /// Get item located at `index`, caller needs to provide the type.
  /// \tparam T
  /// \param[in] index vector<dsize_t>
  /// \return return the item specified at index
  template <typename T>
  Status GetItemAt(T *o, const std::vector<dsize_t> &index) const;

  /// Get string located at `index`.
  /// \param[in] index vector<dsize_t>
  /// \return return std::string_view specified at index
  Status GetItemAt(std::string_view *o, const std::vector<dsize_t> &index) const;

  template <typename T>
  Status GetUnsignedIntAt(T *o, const std::vector<dsize_t> &index) const;

  template <typename T>
  Status GetSignedIntAt(T *o, const std::vector<dsize_t> &index) const;

  template <typename T>
  Status GetFloatAt(T *o, const std::vector<dsize_t> &index) const;

  /// set item at location specified by index
  /// \tparam `T`
  /// \param[in] index
  /// \param[in] value of type `T`
  template <typename T>
  Status SetItemAt(const std::vector<dsize_t> &index, const T &value) {
    T *ptr = nullptr;
    RETURN_IF_NOT_OK(GetItemPtr<T>(&ptr, index));
    *ptr = value;
    return Status::OK();
  }

  /// set string item at location specified by index
  /// \param[in] index
  /// \param[in] value of type std::string
  Status SetItemAt(const std::vector<dsize_t> &index, const std::string &value) {
    RETURN_UNEXPECTED_IF_NULL(data_);
    uchar *ptr = nullptr;
    offset_t length = 0;
    RETURN_IF_NOT_OK(GetItemPtr(&ptr, index, &length));
    if (value.length() != length) {
      RETURN_STATUS_UNEXPECTED("Length of the new string does not match the item.");
    }
    memcpy_s(reinterpret_cast<char *>(ptr), length, value.c_str(), length);

    return Status::OK();
  }

  /// fill tensor with Zeros. Does not support strings.
  Status Zero() {
    CHECK_FAIL_RETURN_UNEXPECTED(type_ != DataType::DE_STRING, "Cannot use Zero on tensor of strings..");
    dsize_t size = SizeInBytes();
    CHECK_FAIL_RETURN_UNEXPECTED(memset_sp(GetMutableBuffer(), size, 0, size) == 0,
                                 "Failed to fill tensor with zeroes.");
    return Status::OK();
  }

  /// Fill all elements in the Tensor with the given value of type `T`.  Does not support strings.
  /// \tparam T
  /// \param value[in]
  template <typename T>
  Status Fill(const T &value) {
    CHECK_FAIL_RETURN_UNEXPECTED(type_ != DataType::DE_STRING, "Cannot use fill on tensor of strings.");
    int64_t cellSize = type_.SizeInBytes();
    if ((data_ != nullptr) && type_.IsCompatible<T>()) {
      for (dsize_t i = 0; i < Size(); i++) {
        CHECK_FAIL_RETURN_UNEXPECTED(memcpy_s((data_ + i * cellSize), cellSize, &value, cellSize) == 0, "memcpy err");
      }
      return Status::OK();
    } else {
      std::string err;
      err += (data_ == nullptr) ? "data_ is nullptr \t" : "";
      err += type_.IsCompatible<T>() ? "data type not compatible\t" : "";
      return Status(StatusCode::kUnexpectedError, err);
    }
  }

  /// Getter function for shape
  /// \return
  const TensorShape &shape() const { return shape_; }

  /// Check if tensor has data
  /// \return bool - true if tensor is empty
  bool HasData() const { return data_ != nullptr; }

  /// Reshape the tensor. The given shape should have the same number of elements in the Tensor
  /// \param shape
  virtual Status Reshape(const TensorShape &shape);

  /// \return number of elements in this tensor
  dsize_t Size() const { return shape().NumOfElements(); }

  /// \return the number of bytes this tensor is needs
  dsize_t SizeInBytes() const {
    if (data_end_ == nullptr) return type_.SizeInBytes() * shape_.NumOfElements();
    return data_end_ - data_;
  }

  /// \return the rank of the tensor
  dsize_t Rank() const { return shape().Rank(); }

  /// Get the starting memory address as a constant for the data of the tensor.  This potentially
  /// drives an allocation if the data area.
  /// \return const unsigned char*
  const unsigned char *GetBuffer() const { return data_; }

  /// Getter of the type
  /// \return
  DataType type() const { return type_; }

  /// Provide stream operator for displaying it
  /// \param output stream
  /// \param so the Tensor object to be printed
  /// \return output stream
  friend std::ostream &operator<<(std::ostream &out, const Tensor &so) {
    so.Print(out);
    return out;
  }

  /// Invalidate this Tensor by setting the type and shape to unknown and MData to null.
  /// Calling this method will make the Tensor and its data inaccessible, use it with caution.
  void Invalidate();

  /// Copy input tensor into self at the location index.
  /// Index is a vector of axises which can be incomplete:
  /// Ex: shape <2,3>, inserting into index {0} will replace the first row. index {1,2} will replace the last cell.
  /// \param index
  /// \param input
  /// \param partial_insert: boolean to determine if insertion along the full axis is enforced
  /// \return Status code
  Status InsertTensor(const std::vector<dsize_t> &index, const std::shared_ptr<Tensor> &input,
                      const bool partial_insert = false);

  /// Find the address of the given index. Used in InsertTensor.
  /// Example:
  ///      Tensor t= [[1,2],[3,4]] , StartAddrOfIndex({0}) -> &1
  /// \param index  incomplete index
  /// \param output: startAddrofIndex
  /// \param output: remaining
  /// \return Status code
  Status StartAddrOfIndex(std::vector<dsize_t> ind, uchar **start_addr_of_index, TensorShape *remaining);

  /// Expand the shape of the Tensor with one extra dimension.
  /// For example, if the shape is <512,512,3>:
  ///     *- ExpandDim(0) gives: <1,512,512,3>
  ///     *- ExpandDim(1) gives: <512,1,512,3>
  ///     *- ExpandDim(3) gives: <512,512,3,1>
  /// \param axis location of the dim
  virtual Status ExpandDim(const dsize_t &axis);

  virtual void Squeeze();

  /// Calculates the strides of the Tensor
  /// Ex: Tensor of shape <4,2,2> and type DE_UINT8 (1 byte)
  /// The strides will be {6,2,1}.
  /// Ex: Tensor of shape <4,2,2> and type DE_UINT32 (4 byte)
  /// The strides will be {24,8,4}.
  /// \return vector of integers
  std::vector<dsize_t> Strides() const;

  std::string ToString() {
    std::stringstream ss;
    this->Print(ss);
    return ss.str();
  }

  /// Handle negative indices.
  static inline dsize_t HandleNeg(dsize_t index, dsize_t length) { return (index < 0) ? (index + length) : index; }

  /// Slice tensor bases on the given indicies. Copy the sliced data into out tensor. Only rank1 tensors are supported.
  /// Based on the type of tensor, SliceNumeric or SliceString will be called
  /// \param[out] out Tensor
  /// \param[in] indices vector of indices
  /// \return Status error code
  Status Slice(TensorPtr *out, const std::vector<dsize_t> &indices);

  /// Slice numeric tensors.
  Status SliceNumeric(TensorPtr *out, const std::vector<dsize_t> &indices);

  /// Slice string tensors
  Status SliceString(TensorPtr *out, const std::vector<dsize_t> &indices);

#ifdef ENABLE_PYTHON
  /// Constructs numpy array from input tensor
  /// \param[in] data this data is the location of python data
  /// \return Status code
  Status GetDataAsNumpy(py::array *data);

  Status GetDataAsNumpyStrings(py::array *data);

  static Status GetBufferInfo(Tensor *t, py::buffer_info *out);
#endif

  /// TensorIterator is a linear iterator that can be used to iterate over the elements of the Tensor
  /// The order  elements  is as the memory layout (i.e., row-major) [[1,2,3],[4,5,6] --> 1,2,3,4,5,6
  /// \tparam T type of values in the Tensor Iterator
  template <typename T, bool = true>
  class TensorIterator {
   public:
    using iterator_category = std::random_access_iterator_tag;
    using value_type = T;
    using difference_type = ptrdiff_t;
    using pointer = T *;
    using reference = T &;

    explicit TensorIterator(uchar *ptr = nullptr) { ptr_ = reinterpret_cast<T *>(ptr); }

    TensorIterator(const TensorIterator<T> &raw_iterator) { ptr_ = raw_iterator.ptr_; }

    ~TensorIterator() = default;

    TensorIterator<T> &operator=(const TensorIterator<T> &rhs) {
      ptr_ = rhs.ptr_;
      return *this;
    }

    TensorIterator<T> &operator=(T *rhs) {
      ptr_ = rhs;
      return *this;
    }

    bool operator==(const TensorIterator<T> &rhs) { return ptr_ == rhs.ptr_; }

    bool operator!=(const TensorIterator<T> &rhs) { return !(*this == rhs); }

    operator bool() const { return ptr_ != nullptr; }

    T &operator*() { return *ptr_; }

    const T &operator*() const { return *ptr_; }

    T *operator->() { return ptr_; }

    TensorIterator<T> &operator+=(const ptrdiff_t &inc) {
      ptr_ += inc;
      return *this;
    }

    TensorIterator<T> &operator-=(const ptrdiff_t &inc) {
      ptr_ -= inc;
      return *this;
    }

    TensorIterator<T> &operator++() {
      ++ptr_;
      return *this;
    }

    TensorIterator<T> &operator--() {
      --ptr_;
      return *this;
    }

    TensorIterator<T> operator++(int) {
      auto temp(*this);
      ++ptr_;
      return temp;
    }

    TensorIterator<T> operator--(int) {
      auto temp(*this);
      --ptr_;
      return temp;
    }

    TensorIterator<T> operator+(const ptrdiff_t &inc) {
      auto oldPtr = ptr_;
      ptr_ += inc;
      auto temp(*this);
      ptr_ = oldPtr;
      return temp;
    }

    TensorIterator<T> operator-(const ptrdiff_t &inc) {
      auto oldPtr = ptr_;
      ptr_ -= inc;
      auto temp(*this);
      ptr_ = oldPtr;
      return temp;
    }

   protected:
    T *ptr_;
  };

  // Specialization of TensorIterator for strings. It returns std::string_view for every item.
  // \tparam DUMMY, used to mbe able to specialize the inner class
  template <bool DUMMY>
  class TensorIterator<std::string_view, DUMMY> {
   public:
    using iterator_category = std::random_access_iterator_tag;
    using value_type = std::string_view;
    using difference_type = ptrdiff_t;
    using pointer = std::string_view *;
    using reference = std::string_view &;

    explicit TensorIterator(uchar *data = nullptr, dsize_t index = 0) {
      data_ = reinterpret_cast<const char *>(data);
      index_ = index;
    }

    TensorIterator(const TensorIterator<std::string_view, DUMMY> &raw_iterator) {
      data_ = raw_iterator.data_;
      index_ = raw_iterator.index_;
    }

    ~TensorIterator() = default;

    bool operator==(const TensorIterator<std::string_view> &rhs) { return data_ == rhs.data_ && index_ == rhs.index_; }

    bool operator!=(const TensorIterator<std::string_view> &rhs) { return !(*this == rhs); }

    operator bool() const { return data_ != nullptr; }

    std::string_view operator*() const {
      auto offset_ = reinterpret_cast<const offset_t *>(data_);
      offset_t start = offset_[index_];
      return std::string_view{data_ + start};
    }

    TensorIterator<std::string_view> &operator+=(const dsize_t &inc) {
      index_ += inc;
      return *this;
    }

    TensorIterator<std::string_view> &operator-=(const dsize_t &inc) {
      index_ -= inc;
      return *this;
    }

    TensorIterator<std::string_view> &operator++() {
      ++index_;
      return *this;
    }

    TensorIterator<std::string_view> &operator--() {
      --index_;
      return *this;
    }

    TensorIterator<std::string_view> operator++(int) {
      auto temp(*this);
      ++index_;
      return temp;
    }

    TensorIterator<std::string_view> operator--(int) {
      auto temp(*this);
      --index_;
      return temp;
    }

    TensorIterator<std::string_view> operator+(const dsize_t &inc) {
      auto oldPtr = index_;
      index_ += inc;
      auto temp(*this);
      index_ = oldPtr;
      return temp;
    }

    TensorIterator<std::string_view> operator-(const dsize_t &inc) {
      auto oldPtr = index_;
      index_ -= inc;
      auto temp(*this);
      index_ = oldPtr;
      return temp;
    }

   protected:
    dsize_t index_;
    const char *data_;
  };

  /// Return a TensorIterator that points to the start of the Tensor.
  /// It's the user responsibility to use the correct type that matches the Tensor type
  /// \tparam T The type of values in the Tensor
  /// \return TensorIterator
  template <typename T>
  TensorIterator<T> begin() {
    return TensorIterator<T>(data_);
  }

  /// Return a linear iterator that points to the place after the last element of the Tensor.
  /// \tparam T The type of values in the Tensor
  /// \return TensorIterator
  template <typename T>
  TensorIterator<T> end() {
    return TensorIterator<T>(data_end_);
  }

  /// Copies the last dimension at `index` from Tensor `src` to this Tensor.
  /// \param[in] src Tensor
  /// \param[in] index vector to the start of the dimension. The last dim should be 0
  /// \return Status
  Status CopyLastDimAt(const std::shared_ptr<Tensor> &src, const std::vector<dsize_t> &index);

 protected:
  /// Allocate memory for the tensor using the data_allocator
  /// \param[in] length number of bytes to be allocated
  /// \return Error Status
  Status AllocateBuffer(const dsize_t &length);

  /// Get the starting memory address for the data of the tensor.  This potentially
  /// drives an allocation if the data is null.
  /// \return unsigned char*
  unsigned char *GetMutableBuffer() { return data_; }

  /// A function that prints Tensor recursively, first called by print
  /// \param[in] out
  /// \param[in] cur_dim
  /// \param[in] cur_index
  void PrintRecursive(std::ostream &out, int32_t cur_dim, const std::vector<dsize_t> &cur_index) const;

  /// A function that prints info about the tensor
  /// \param[out] out output stream
  void Print(std::ostream &out) const;

  /// A function that print the value as specified by its index
  /// \param[in] index vector representing the index
  /// \param[out] out
  void PrintItemAt(const std::vector<dsize_t> &index, std::ostream &out) const;

  /// Get pointer to item located at `index`, caller needs to provide the type.
  /// \tparam T
  /// \param[in] index vector<dsize_t>
  /// \return return a pointer to the item specified at index of type `T`
  template <typename T>
  Status GetItemPtr(T **, const std::vector<dsize_t> &index) const;

  /// Get pointer to string located at `index` and the length of string
  /// \param[in] index vector<dsize_t>
  /// \return return a pointer to the string specified at index and the length of the string
  Status GetItemPtr(uchar **, const std::vector<dsize_t> &index, offset_t *length = nullptr) const;

  /// Given a flat index of an item string, return the start and length of the item
  /// \param[in] index flat index of the item
  /// \param[out] start address of the ths string
  /// \param[out] length of the string
  Status GetStringAt(dsize_t index, uchar **string_start, offset_t *length) const;

  /// Skip the offsets and returns the start of the buffer where the real strings is stored. Caller needs to check if
  /// the tensor's type is a string, otherwise undefined address would be returned. \return address of the first string
  /// of the tensor.
  uchar *GetStringsBuffer() const { return data_ + kOffsetSize * shape_.NumOfElements() + kOffsetSize; }

  /// all access to shape_ should be via shape
  TensorShape shape_;
  /// data type of tensor
  DataType type_;
  /// pointer to the start of the physical data
  unsigned char *data_;
  /// An allocator for data_
  CharAllocPtr data_allocator_;
  /// pointer to the end of the physical data
  unsigned char *data_end_ = nullptr;

 private:
#ifdef ENABLE_ANDROID
  friend class tensor::DETensor;
#endif
  /// Copy raw data of a array based on shape and strides to the destination pointer
  /// \param dst [out] Pointer to the destination array where the content is to be copied
  /// \param[in] src Pointer to the source of strided array to be copied
  /// \param[in] shape shape of the source array
  /// \param[in] strides strides of the source array
  /// \param[in] type_size number of bytes needed to store one array element's type
  /// \return Status Code
  static Status CopyStridedArray(unsigned char *dst, unsigned char *src, std::vector<dsize_t> shape,
                                 std::vector<dsize_t> strides, uint8_t type_size);

  /// const of the size of the offset variable
  static constexpr uint8_t kOffsetSize = sizeof(offset_t);

#ifdef ENABLE_PYTHON
  /// Helper function to create a tensor from Numpy array of strings
  /// \param[in] arr Numpy array
  /// \param[out] out Created Tensor
  /// \return Status
  static Status CreateFromNpString(py::array arr, TensorPtr *out);
#endif
};
template <>
inline Tensor::TensorIterator<std::string_view> Tensor::end<std::string_view>() {
  return TensorIterator<std::string_view>(data_, shape_.NumOfElements());
}

/// Create a Tensor from a given list of strings.
/// @note: The memory layout of a Tensor of strings consists of the Offset_array followed by the strings.
/// The offset array will store one extra value to find the length of the last string.
/// OFFSET_1, OFFSET_2, ..., OFFSET_n+1, STRING_1, STRING_2, ..., STRING_n
/// The value of each offset is the start index of the corresponding string
/// Offsets is of type offset_t
/// strings will ne null-terminated
/// example: Tensor(['abc', 'de'], shape={2}, type=DE_STRING)
/// |----------------------------------------------------------------|
/// |             OFFSET ARRAY           |            STRINGS        |
/// | bytes 0-3 | bytes 3-6 | bytes 7-10 | bytes 11-14 | bytes 15-17 |
/// |     11    |    15     |     18     |     abc\0   |      de\0   |
/// |----------------------------------------------------------------|
/// \param[in] items elements of the tensor
/// \param[in] shape shape of the output tensor
/// \param[out] out output argument to hold the created Tensor
/// \return Status Code
template <>
inline Status Tensor::CreateFromVector<std::string>(const std::vector<std::string> &items, const TensorShape &shape,
                                                    TensorPtr *out) {
  CHECK_FAIL_RETURN_UNEXPECTED(
    items.size() == shape.NumOfElements(),
    "Number of elements in the vector does not match the number of elements of the shape required");
  const TensorAlloc *alloc = GlobalContext::Instance()->tensor_allocator();
  *out = std::allocate_shared<Tensor>(*alloc, TensorShape({static_cast<dsize_t>(items.size())}),
                                      DataType(DataType::DE_STRING));
  if (items.size() == 0) {
    if (shape.known()) {
      return (*out)->Reshape(shape);
    }
  }
  auto length_sum = [](dsize_t sum, const std::string &s) { return s.length() + sum; };
  dsize_t total_length = std::accumulate(items.begin(), items.end(), 0, length_sum);

  // total bytes needed = offset array + strings
  // offset array needs to store one offset var per element + 1 extra to get the length of the last string.
  // strings will be null-terminated --> need 1 extra byte per element
  dsize_t num_bytes = (kOffsetSize + 1) * (*out)->shape_.NumOfElements() + kOffsetSize + total_length;

  (*out)->AllocateBuffer(num_bytes);
  auto offset_arr = reinterpret_cast<offset_t *>((*out)->data_);
  uchar *buf = (*out)->GetStringsBuffer();

  offset_t offset = buf - (*out)->data_;  // the first string will start here
  uint32_t i = 0;
  for (const auto &str : items) {
    //  insert the start index of the string.
    offset_arr[i++] = offset;
    // total bytes are reduced by kOffsetSize
    num_bytes -= kOffsetSize;
    // insert actual string
    int ret_code = memcpy_s((*out)->data_ + offset, num_bytes, common::SafeCStr(str), str.length() + 1);
    if (ret_code != 0) MS_LOG(ERROR) << "Cannot copy string into Tensor";
    //  next string will be stored right after the current one.
    offset = offset + str.length() + 1;
    // total bytes are reduced by the length of the string
    num_bytes -= str.length() + 1;
  }
  // store one more offset value so we can get the length of the last string
  // length[last_element] = offset_arr[last_element + 1] - offset_arr[last_element]
  offset_arr[i] = offset;

  (*out)->data_end_ = (*out)->data_ + offset_arr[i];

  MS_ASSERT(num_bytes == 0);
  if (shape.known()) {
    RETURN_IF_NOT_OK((*out)->Reshape(shape));
  }
  return Status::OK();
}
/// Create a string scalar Tensor from the given value.
/// \param[in] item value
/// \param[out] out Created tensor
/// \return Status code
template <>
inline Status Tensor::CreateScalar<std::string>(const std::string &item, TensorPtr *out) {
  return CreateFromVector<std::string>({item}, TensorShape::CreateScalar(), out);
}
}  // namespace dataset
}  // namespace mindspore
#endif  // MINDSPORE_CCSRC_MINDDATA_DATASET_CORE_TENSOR_H_