atom.hpp

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#pragma once
 
#include "llvm/ADT/StringSet.h"
#include <string>
 
namespace yume {
/// `Atom`s represent strings in a string pool.
/** This means two atoms created with the same string value will contain
 * identical pointers to that string. Thus, comparing `Atom`s is extremely cheap, as it only consists of a pointer
 * equality check.
 */
class Atom {
  std::string_view m_str;
 
public:
  constexpr Atom() = delete;
  explicit constexpr Atom(std::string_view str) : m_str{str} {}
 
  /* implicit */ operator std::string_view() const { return m_str; }
  explicit operator std::string() const { return std::string(m_str); }
  auto constexpr operator<=>(const Atom& other) const noexcept = default;
 
  static auto inline make_atom(std::string_view value) noexcept -> Atom {
    const auto& data = Atom::interned.insert(value).first->first();
    return Atom{data};
  }
 
private:
  static inline llvm::StringSet interned{}; // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
};
 
/// Create an `Atom` with the given string content.
/// \sa atom_literal::operator""_a
auto inline make_atom(std::string_view value) noexcept -> Atom { return Atom::make_atom(value); }
 
auto inline operator""_a(const char* value, std::size_t len) noexcept -> Atom {
  return make_atom(std::string_view(value, len));
}
} // namespace yume