span.hxx

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#ifndef INCLUDED_O3TL_SPAN_HXX
#define INCLUDED_O3TL_SPAN_HXX
 
#include <sal/config.h>
 
#include <config_global.h>
 
#if HAVE_CPP_SPAN
 
#include <span>
 
namespace o3tl { using std::span; }
 
#else
 
#include <cassert>
#include <cstddef>
#include <iterator>
#include <type_traits>
#include <vector>
 
namespace o3tl {
 
template<typename T>
class span {
public:
    using value_type = T;
    using pointer = value_type *;
    using const_pointer = value_type const *;
    using reference = value_type &;
    using const_reference = value_type const &;
    using const_iterator = const_pointer;
    using iterator = pointer;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using size_type = std::size_t;
    using difference_type = std::ptrdiff_t;
 
    constexpr span() noexcept : data_(nullptr), size_(0) {}
 
    template<std::size_t N>
    constexpr span (T (&a)[N]) noexcept : data_(a), size_(N) {}
 
    constexpr span (T *a, size_type len) noexcept
        : data_(a), size_(len)
    {
        // not terribly sure about this, might need to strengthen it
        assert(a != nullptr || len == 0);
    }
 
    template<typename T2>
    constexpr span(const std::vector<T2>& vec)
        : data_(vec.data()), size_(vec.size()) {}
 
    constexpr span (const span<typename std::remove_const<T>::type>& other) noexcept
        : data_(other.data()), size_(other.size()) {}
 
    constexpr bool empty() const noexcept { return size_ == 0; }
 
    constexpr iterator begin() const noexcept { return data_; }
    constexpr iterator end() const noexcept { return begin() + size(); }
 
    reverse_iterator rbegin() const noexcept
    { return reverse_iterator(end()); }
    reverse_iterator rend() const noexcept
    { return reverse_iterator(begin()); }
 
    constexpr size_type size() const noexcept { return size_; }
 
    constexpr reference operator [](size_type pos) const {
        assert(pos < size());
        return data_[pos];
    }
 
    constexpr pointer data() const noexcept { return data_; }
 
private:
    pointer    data_;
    size_type size_;
};
 
} // namespace o3tl
 
#endif
 
#endif
 
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