util.hxx

/* Various utility definitions for libpqxx.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/util 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_UTIL
#define PQXX_H_UTIL

#if !defined(PQXX_HEADER_PRE)
#  error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
#endif

#include <cctype>
#include <cstdio>
#include <functional>
#include <iterator>
#include <limits>
#include <memory>
#include <stdexcept>
#include <string>
#include <string_view>
#include <type_traits>
#include <typeinfo>
#include <utility>
#include <vector>

#if __has_include(<version>)
#  include <version>
#endif

#include "pqxx/except.hxx"
#include "pqxx/internal/encodings.hxx"
#include "pqxx/types.hxx"
#include "pqxx/version.hxx"


namespace pqxx
{}

#include <pqxx/internal/libpq-forward.hxx>


namespace pqxx::internal
{


// C++20: Retire wrapper.
template<typename LEFT, typename RIGHT>
inline constexpr bool cmp_less(LEFT lhs, RIGHT rhs) noexcept
{
#if defined(PQXX_HAVE_CMP)
  return std::cmp_less(lhs, rhs);
#else
  // We need a variable just because lgtm.com gives off a false positive
  // warning when we compare the values directly.  It considers that a
  // "self-comparison."
  constexpr bool left_signed{std::is_signed_v<LEFT>};
  if constexpr (left_signed == std::is_signed_v<RIGHT>)
    return lhs < rhs;
  else if constexpr (std::is_signed_v<LEFT>)
    return (lhs <= 0) ? true : (std::make_unsigned_t<LEFT>(lhs) < rhs);
  else
    return (rhs <= 0) ? false : (lhs < std::make_unsigned_t<RIGHT>(rhs));
#endif
}


// C++20: Retire wrapper.
template<typename LEFT, typename RIGHT>
inline constexpr bool cmp_greater(LEFT lhs, RIGHT rhs) noexcept
{
#if defined(PQXX_HAVE_CMP)
  return std::cmp_greater(lhs, rhs);
#else
  return cmp_less(rhs, lhs);
#endif
}


// C++20: Retire wrapper.
template<typename LEFT, typename RIGHT>
inline constexpr bool cmp_less_equal(LEFT lhs, RIGHT rhs) noexcept
{
#if defined(PQXX_HAVE_CMP)
  return std::cmp_less_equal(lhs, rhs);
#else
  return not cmp_less(rhs, lhs);
#endif
}


// C++20: Retire wrapper.
template<typename LEFT, typename RIGHT>
inline constexpr bool cmp_greater_equal(LEFT lhs, RIGHT rhs) noexcept
{
#if defined(PQXX_HAVE_CMP)
  return std::cmp_greater_equal(lhs, rhs);
#else
  return not cmp_less(lhs, rhs);
#endif
}



[[nodiscard]] inline std::string cat2(std::string_view x, std::string_view y)
{
  std::string buf;
  auto const xs{std::size(x)}, ys{std::size(y)};
  buf.resize(xs + ys);
  x.copy(std::data(buf), xs);
  y.copy(std::data(buf) + xs, ys);
  return buf;
}
} // namespace pqxx::internal


namespace pqxx
{
using namespace std::literals;

template<typename... T> inline constexpr void ignore_unused(T &&...) noexcept
{}



template<typename TO, typename FROM>
inline TO check_cast(FROM value, std::string_view description)
{
  static_assert(std::is_arithmetic_v<FROM>);
  static_assert(std::is_arithmetic_v<TO>);
  static_assert(std::is_integral_v<FROM> == std::is_integral_v<TO>);

  // The rest of this code won't quite work for bool, but bool is trivially
  // convertible to other arithmetic types as far as I can see.
  if constexpr (std::is_same_v<FROM, bool>)
    return static_cast<TO>(value);

  // Depending on our "if constexpr" conditions, this parameter may not be
  // needed.  Some compilers will warn.
  ignore_unused(description);

  using from_limits = std::numeric_limits<decltype(value)>;
  using to_limits = std::numeric_limits<TO>;
  if constexpr (std::is_signed_v<FROM>)
  {
    if constexpr (std::is_signed_v<TO>)
    {
      if (value < to_limits::lowest())
        throw range_error{internal::cat2("Cast underflow: "sv, description)};
    }
    else
    {
      // FROM is signed, but TO is not.  Treat this as a special case, because
      // there may not be a good broader type in which the compiler can even
      // perform our check.
      if (value < 0)
        throw range_error{internal::cat2(
          "Casting negative value to unsigned type: "sv, description)};
    }
  }
  else
  {
    // No need to check: the value is unsigned so can't fall below the range
    // of the TO type.
  }

  if constexpr (std::is_integral_v<FROM>)
  {
    using unsigned_from = std::make_unsigned_t<FROM>;
    using unsigned_to = std::make_unsigned_t<TO>;
    constexpr auto from_max{static_cast<unsigned_from>((from_limits::max)())};
    constexpr auto to_max{static_cast<unsigned_to>((to_limits::max)())};
    if constexpr (from_max > to_max)
    {
      if (internal::cmp_greater(value, to_max))
        throw range_error{internal::cat2("Cast overflow: "sv, description)};
    }
  }
  else if constexpr ((from_limits::max)() > (to_limits::max)())
  {
    if (value > (to_limits::max)())
      throw range_error{internal::cat2("Cast overflow: ", description)};
  }

  return static_cast<TO>(value);
}


inline PQXX_PRIVATE void check_version() noexcept
{
  // There is no particular reason to do this here in @ref connection, except
  // to ensure that every meaningful libpqxx client will execute it.  The call
  // must be in the execution path somewhere or the compiler won't try to link
  // it.  We can't use it to initialise a global or class-static variable,
  // because a smart compiler might resolve it at compile time.
  //
  // On the other hand, we don't want to make a useless function call too
  // often for performance reasons.  A local static variable is initialised
  // only on the definition's first execution.  Compilers will be well
  // optimised for this behaviour, so there's a minimal one-time cost.
  static auto const version_ok{internal::PQXX_VERSION_CHECK()};
  ignore_unused(version_ok);
}



struct PQXX_LIBEXPORT thread_safety_model
{
  bool safe_libpq = false;


  bool safe_kerberos = false;

  std::string description;
};


[[nodiscard]] PQXX_LIBEXPORT thread_safety_model describe_thread_safety();


#if defined(PQXX_HAVE_CONCEPTS)
#  define PQXX_POTENTIAL_BINARY_ARG pqxx::potential_binary
#else
#  define PQXX_POTENTIAL_BINARY_ARG typename
#endif



template<PQXX_POTENTIAL_BINARY_ARG TYPE>
std::basic_string_view<std::byte> binary_cast(TYPE const &data)
{
  static_assert(sizeof(value_type<TYPE>) == 1);
  return {
    reinterpret_cast<std::byte const *>(
      const_cast<strip_t<decltype(*std::data(data))> const *>(
        std::data(data))),
    std::size(data)};
}


#if defined(PQXX_HAVE_CONCEPTS)
template<typename CHAR>
concept char_sized = (sizeof(CHAR) == 1);
#  define PQXX_CHAR_SIZED_ARG char_sized
#else
#  define PQXX_CHAR_SIZED_ARG typename
#endif


template<PQXX_CHAR_SIZED_ARG CHAR, typename SIZE>
std::basic_string_view<std::byte> binary_cast(CHAR const *data, SIZE size)
{
  static_assert(sizeof(CHAR) == 1);
  return {
    reinterpret_cast<std::byte const *>(data),
    check_cast<std::size_t>(size, "binary data size")};
}


constexpr oid oid_none{0};
} // namespace pqxx



namespace pqxx::internal
{
using namespace std::literals;



template<typename CHAR> inline constexpr bool is_digit(CHAR c) noexcept
{
  return (c >= '0') and (c <= '9');
}



[[nodiscard]] std::string
describe_object(std::string_view class_name, std::string_view name);



void check_unique_register(
  void const *old_guest, std::string_view old_class, std::string_view old_name,
  void const *new_guest, std::string_view new_class,
  std::string_view new_name);



void check_unique_unregister(
  void const *old_guest, std::string_view old_class, std::string_view old_name,
  void const *new_guest, std::string_view new_class,
  std::string_view new_name);



inline constexpr std::size_t size_esc_bin(std::size_t binary_bytes) noexcept
{
  return 2 + (2 * binary_bytes) + 1;
}



inline constexpr std::size_t size_unesc_bin(std::size_t escaped_bytes) noexcept
{
  return (escaped_bytes - 2) / 2;
}


// TODO: Use actual binary type for "data".

void PQXX_LIBEXPORT
esc_bin(std::basic_string_view<std::byte> binary_data, char buffer[]) noexcept;


std::string PQXX_LIBEXPORT
esc_bin(std::basic_string_view<std::byte> binary_data);


void PQXX_LIBEXPORT
unesc_bin(std::string_view escaped_data, std::byte buffer[]);


std::basic_string<std::byte>
  PQXX_LIBEXPORT unesc_bin(std::string_view escaped_data);


template<typename T> auto ssize(T const &c)
{
#if defined(__cpp_lib_ssize) && __cplusplus >= __cpp_lib_ssize
  return std::ssize(c);
#else
  using signed_t = std::make_signed_t<decltype(std::size(c))>;
  return static_cast<signed_t>(std::size(c));
#endif // __cpp_lib_ssize
}
} // namespace pqxx::internal
#endif