zview.hxx

/* Zero-terminated string view.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/zview instead.
 *
 * Copyright (c) 2000-2020, 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 "pqxx/compiler-public.hxx"

#include <string_view>
#include <type_traits>


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)...)
  {}

  /* implicit */
  zview(std::string const &str) : std::string_view(str) {}

  /* implicit */
  template<size_t size>
  constexpr zview(char const (&literal)[size]) : zview(literal, size - 1)
  {}

  [[nodiscard]] constexpr char const *c_str() const noexcept { return data(); }
};
} // namespace pqxx


#if defined(PQXX_HAVE_CONCEPTS)
namespace pqxx::internal
{

template<typename T>
concept ZString =
  std::is_convertible_v<T, char const *> or std::is_convertible_v<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();
}
// TODO: constexpr as of C++20.
inline char const *as_c_string(std::string const &str) noexcept
{
  return str.c_str();
}
} // namespace pqxx::internal

#endif