Utilities/interface/Span.h

0001 #ifndef FWCore_Utilities_Span_h
0002 #define FWCore_Utilities_Span_h
0003
0004 #include <cstddef>
0005
0006 namespace edm {
0007   /*
0008       *An edm::Span wraps begin() and end() iterators to a contiguous sequence
0009       of objects with the first element of the sequence at position zero,
0010       In other words the iterators should refer to random-access containers.
0011
0012       To be replaced with std::Span in C++20.
0013       */
0014
0015   template <class T>
0016   class Span {
0017   public:
0018     Span(T begin, T end) : begin_(begin), end_(end) {}
0019
0020     T begin() const { return begin_; }
0021     T end() const { return end_; }
0022
0023     bool empty() const { return begin_ == end_; }
0024     auto size() const { return end_ - begin_; }
0025
0026     auto const& operator[](std::size_t idx) const { return *(begin_ + idx); }
0027
0028     auto const& front() const { return *begin_; }
0029     auto const& back() const { return *(end_ - 1); }
0030
0031   private:
0032     const T begin_;
0033     const T end_;
0034   };
0035 };  // namespace edm
0036
0037 #endif