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/*!
 *  Copyright (c) 2016 by Contributors
 * \file array_view.h
 * \brief Read only data structure to reference array
 */
#ifndef DMLC_ARRAY_VIEW_H_
#define DMLC_ARRAY_VIEW_H_

#include <vector>
#include <array>

namespace dmlc {

/*!
 * \brief Read only data structure to reference continuous memory region of array.
 * Provide unified view for vector, array and C style array.
 * This data structure do not guarantee aliveness of referenced array.
 *
 * Make sure do not use array_view to record data in async function closures.
 * Also do not use array_view to create reference to temporary data structure.
 *
 * \tparam ValueType The value
 *
 * \code
 *  std::vector<int> myvec{1,2,3};
 *  dmlc::array_view<int> view(myvec);
 *  // indexed visit to the view.
 *  LOG(INFO) << view[0];
 *
 *  for (int v : view) {
 *     // visit each element in the view
 *  }
 * \endcode
 */
template<typename ValueType>
class array_view {
 public:
  /*! \brief default constructor */
  array_view() = default;
  /*!
   * \brief default copy constructor
   * \param other another array view.
   */
  array_view(const array_view<ValueType> &other) = default;  // NOLINT(*)
#ifndef _MSC_VER
  /*!
   * \brief default move constructor
   * \param other another array view.
   */
  array_view(array_view<ValueType>&& other) = default; // NOLINT(*)
#else
  /*!
  * \brief default move constructor
  * \param other another array view.
  */
  array_view(array_view<ValueType>&& other) { // NOLINT(*)
    begin_ = other.begin_;
    size_ = other.size_;
    other.begin_ = nullptr;
  }
#endif
  /*!
   * \brief default assign constructor
   * \param other another array view.
   * \return self.
   */
  array_view<ValueType>& operator=(const array_view<ValueType>& other) = default; // NOLINT(*)
  /*!
   * \brief construct array view std::vector
   * \param other vector container
   */
  array_view(const std::vector<ValueType>& other) {  // NOLINT(*)
    if (other.size() != 0) {
      begin_ = &other[0]; size_ = other.size();
    }
  }
  /*!