array_view.h

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#ifndef DMLC_ARRAY_VIEW_H_
#define DMLC_ARRAY_VIEW_H_
 
#include <vector>
#include <array>
 
namespace dmlc {
 
template<typename ValueType>
class array_view {
 public:
  array_view() = default;
  array_view(const array_view<ValueType> &other) = default;  // NOLINT(*)
#ifndef _MSC_VER
  array_view(array_view<ValueType>&& other) = default; // NOLINT(*)
#else
  array_view(array_view<ValueType>&& other) { // NOLINT(*)
    begin_ = other.begin_;
    size_ = other.size_;
    other.begin_ = nullptr;
  }
#endif
  array_view<ValueType>& operator=(const array_view<ValueType>& other) = default; // NOLINT(*)
  array_view(const std::vector<ValueType>& other) {  // NOLINT(*)
    if (other.size() != 0) {
      begin_ = &other[0]; size_ = other.size();
    }
  }
  template<std::size_t size>
  array_view(const std::array<ValueType, size>& other) {  // NOLINT(*)
    if (size != 0) {
      begin_ = &other[0]; size_ = size;
    }
  }
  array_view(const ValueType* begin, const ValueType* end) {
    if (begin < end) {
      begin_ = begin;
      size_ = end - begin;
    }
  }
  inline size_t size() const {
    return size_;
  }
  inline const ValueType* begin() const {
    return begin_;
  }
  inline const ValueType* end() const {
    return begin_ + size_;
  }
  inline const ValueType& operator[](size_t i) const {
    return begin_[i];
  }
 
 private:
  const ValueType* begin_{nullptr};
  size_t size_{0};
};
 
}  // namespace dmlc
 
#endif  // DMLC_ARRAY_VIEW_H_