zview.hxx

/* Zero-terminated string view.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/zview instead.
 *
 * Copyright (c) 2000-2022, Jeroen T. Vermeulen.
 *
 * See COPYING for copyright license.  If you did not receive a file called
 * COPYING with this source code, please notify the distributor of this
 * mistake, or contact the author.
 */
#ifndef PQXX_H_ZVIEW
#define PQXX_H_ZVIEW
 
#include <string>
#include <string_view>
#include <type_traits>
 
#include "pqxx/types.hxx"
 
 
namespace pqxx
{
 
class zview : public std::string_view
{
public:
  constexpr zview() noexcept = default;
 
  constexpr zview(char const text[], std::ptrdiff_t len) :
          std::string_view{text, static_cast<std::size_t>(len)}
  {}
 
  constexpr zview(char text[], std::ptrdiff_t len) :
          std::string_view{text, static_cast<std::size_t>(len)}
  {}
 
 
  template<typename... Args>
  explicit constexpr zview(Args &&...args) :
          std::string_view(std::forward<Args>(args)...)
  {}
 
  zview(std::string const &str) : std::string_view{str.c_str(), std::size(str)}
  {}
 
 
  constexpr zview(char const str[]) : std::string_view{str} {}
 
 
  template<size_t size>
  constexpr zview(char const (&literal)[size]) : zview(literal, size - 1)
  {}
 
  [[nodiscard]] constexpr char const *c_str() const &noexcept
  {
    return data();
  }
};
 
 
 
constexpr zview operator"" _zv(char const str[], std::size_t len) noexcept
{
  return zview{str, len};
}
} // namespace pqxx
 
 
#if defined(PQXX_HAVE_CONCEPTS)
// C++20: constinit.
template<> inline constexpr bool std::ranges::enable_view<pqxx::zview>{true};
 
 
// C++20: constinit.
template<>
inline constexpr bool std::ranges::enable_borrowed_range<pqxx::zview>{true};
 
namespace pqxx::internal
{
 
template<typename T>
concept ZString = std::is_convertible_v < strip_t<T>,
char const * > or std::is_convertible_v<strip_t<T>, zview> or
  std::is_convertible_v<T, std::string const &>;
} // namespace pqxx::internal
#endif // PQXX_HAVE_CONCEPTS
 
 
namespace pqxx::internal
{
inline constexpr char const *as_c_string(char const str[]) noexcept
{
  return str;
}
template<std::size_t N>
inline constexpr char const *as_c_string(char (&str)[N]) noexcept
{
  return str;
}
inline constexpr char const *as_c_string(pqxx::zview str) noexcept
{
  return str.c_str();
}
// C++20: Make this constexpr.
inline char const *as_c_string(std::string const &str) noexcept
{
  return str.c_str();
}
} // namespace pqxx::internal
#endif