iterator.h

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#include <array>
 
namespace AmpGen {
  template <class stored_type, class store_type, unsigned simd_size, bool modifiable> class scatter_iterator {
    store_type *m_store;
    std::array<stored_type, simd_size> m_buffer;
    size_t m_pos{0};
 
  public:
    int pos() const { return m_pos; }
    scatter_iterator(const size_t &pos, store_type *store) : m_store(store), m_pos(pos) {
      if(m_store != nullptr && pos < m_store->aligned_size()) m_buffer = m_store->scatter(pos / simd_size);
    }
    stored_type *operator->() const { return &(m_buffer)[m_pos % simd_size]; }
    stored_type operator*() const { return m_buffer[m_pos % simd_size]; }
    stored_type &operator*() { return m_buffer[m_pos % simd_size]; }
    scatter_iterator &operator++() {
      m_pos++;
      if(m_pos % simd_size == 0) {
        if constexpr(modifiable == true) m_store->gather(m_buffer, (m_pos - 1) / simd_size);
        m_buffer = m_store->scatter(m_pos);
      }
      return *this;
    }
    ~scatter_iterator() {
      if constexpr(modifiable == true) {
        if(m_store != nullptr && m_pos % simd_size != 0) { m_store->gather(m_buffer, m_pos / simd_size); }
      }
    }
    bool operator==(const scatter_iterator &rhs) const { return m_pos == rhs.m_pos; }
    bool operator!=(const scatter_iterator &rhs) const { return m_pos != rhs.m_pos; }
    friend int operator-(const scatter_iterator &lhs, const scatter_iterator &rhs) { return lhs.pos() - rhs.pos(); }
  };
  template <unsigned simd_size, bool modifiable = false, class store_type> auto make_scatter_iterator(const unsigned &pos, store_type *store) {
    return scatter_iterator<typename store_type::value_type, store_type, simd_size, modifiable>(pos, store);
  }
}