SpanSpan.h

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/*

             *
            ***
           *****
   *********************       Mercenaries Engineering SARL
     *****************              Copyright (C) 2018
       *************
         *********        http://www.mercenaries-engineering.com
        ***********
       ****     ****
      **           **

*/
#pragma once

  namespace maquina
  {

    template<typename TIndex, typename TValue>
    class SpanSpan
    {
    public:
      SpanSpan() {}
      SpanSpan(const gsl::span<TIndex>& offsets, const gsl::span<TValue>& values) :
        _offsets(offsets),
        _values(values) {}

      size_t size() const
      {
        return _offsets.size()-1;
      }

      size_t length() const
      {
        return *_offsets.rbegin();
      }

      const gsl::span<TValue> operator[](size_t index) const
      {
        const auto begin = _offsets[index];
        return {&_values[begin], _offsets[index+1]-begin};
      }


      const gsl::span<TIndex>& offsets() const
      {
        return _offsets;
      }

      const gsl::span<TValue>& values() const
      {
        return _values;
      }

    private:
      gsl::span<TIndex> _offsets;
      gsl::span<TValue> _values;
    };
  }