span.hpp

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#pragma once
 
#include <cstddef>
#include <cstdint>
#include <type_traits>
#include <vector>
 
namespace fcb {
 
template <typename T> class span {
  public:
    span() noexcept : data_(nullptr), size_(0) {}
    span(T* data, std::size_t size) noexcept : data_(data), size_(size) {}
 
    template <typename U, typename = std::enable_if_t<std::is_same<const U, T>::value>>
    span(const std::vector<U>& v) noexcept : data_(v.data()), size_(v.size()) {}
 
    span(std::vector<std::remove_const_t<T>>& v) noexcept : data_(v.data()), size_(v.size()) {}
 
    T* data() const noexcept { return data_; }
    std::size_t size() const noexcept { return size_; }
    bool empty() const noexcept { return size_ == 0; }
 
    T& operator[](std::size_t i) const noexcept { return data_[i]; }
    T* begin() const noexcept { return data_; }
    T* end() const noexcept { return data_ + size_; }
 
    span subspan(std::size_t offset, std::size_t count) const noexcept {
        return span(data_ + offset, count);
    }
 
  private:
    T* data_;
    std::size_t size_;
};
 
using bytes_view = span<const std::uint8_t>;
 
}  // namespace fcb