range.hxx

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#ifndef PQXX_H_RANGE
#define PQXX_H_RANGE
 
#if !defined(PQXX_HEADER_PRE)
#  error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
#endif
 
#include <optional>
#include <utility>
#include <variant>
 
#include "pqxx/internal/array-composite.hxx"
#include "pqxx/internal/concat.hxx"
 
namespace pqxx
{

struct no_bound
{
  template<typename TYPE>
  constexpr bool extends_down_to(TYPE const &) const noexcept
  {
    return true;
  }
  template<typename TYPE>
  constexpr bool extends_up_to(TYPE const &) const noexcept
  {
    return true;
  }
};
 


template<typename TYPE> class inclusive_bound
{
  // (Putting private section first to work around bug in gcc < 10: see #665.)
private:
  TYPE m_value;
 
public:
  inclusive_bound() = delete;
  constexpr explicit inclusive_bound(TYPE const &value) : m_value{value}
  {
    if (is_null(value))
      throw argument_error{"Got null value as an inclusive range bound."};
  }
 
  [[nodiscard]] constexpr TYPE const &get() const & noexcept
  {
    return m_value;
  }

  [[nodiscard]] constexpr bool extends_down_to(TYPE const &value) const
    noexcept(noexcept(value < m_value))
  {
    return not(value < m_value);
  }

  [[nodiscard]] constexpr bool extends_up_to(TYPE const &value) const
    noexcept(noexcept(value < m_value))
  {
    return not(m_value < value);
  }
};
 


template<typename TYPE> class exclusive_bound
{
  // (Putting private section first to work around bug in gcc < 10: see #665.)
private:
  TYPE m_value;
 
public:
  exclusive_bound() = delete;
  constexpr explicit exclusive_bound(TYPE const &value) : m_value{value}
  {
    if (is_null(value))
      throw argument_error{"Got null value as an exclusive range bound."};
  }
 
  [[nodiscard]] constexpr TYPE const &get() const & noexcept
  {
    return m_value;
  }

  [[nodiscard]] constexpr bool extends_down_to(TYPE const &value) const
    noexcept(noexcept(m_value < value))
  {
    return m_value < value;
  }

  [[nodiscard]] constexpr bool extends_up_to(TYPE const &value) const
    noexcept(noexcept(value < m_value))
  {
    return value < m_value;
  }
};
 


template<typename TYPE> class range_bound
{
  // (Putting private section first to work around bug in gcc < 10: see #665.)
private:
  std::variant<no_bound, inclusive_bound<TYPE>, exclusive_bound<TYPE>> m_bound;
 
public:
  range_bound() = delete;
  constexpr range_bound(no_bound) noexcept : m_bound{} {}
 
  constexpr range_bound(inclusive_bound<TYPE> const &bound) noexcept(
    noexcept(inclusive_bound<TYPE>{bound})) :
          m_bound{bound}
  {}
 
  constexpr range_bound(exclusive_bound<TYPE> const &bound) noexcept(
    noexcept(exclusive_bound{bound})) :
          m_bound{bound}
  {}
 
  constexpr range_bound(range_bound const &) noexcept(
    noexcept(inclusive_bound<TYPE>{
      std::declval<inclusive_bound<TYPE> const &>()}) and
    noexcept(exclusive_bound<TYPE>{
      std::declval<exclusive_bound<TYPE> const &>()})) = default;
 
  constexpr range_bound(range_bound &&) = default;
 
  constexpr bool operator==(range_bound const &rhs) const
    noexcept(noexcept(*this->value() == *rhs.value()))
  {
    if (this->is_limited())
      return (
        rhs.is_limited() and (this->is_inclusive() == rhs.is_inclusive()) and
        (*this->value() == *rhs.value()));
    else
      return not rhs.is_limited();
  }
 
  constexpr bool operator!=(range_bound const &rhs) const
    noexcept(noexcept(*this == rhs))
  {
    return not(*this == rhs);
  }
  range_bound &operator=(range_bound const &) = default;
  range_bound &operator=(range_bound &&) = default;

  constexpr bool is_limited() const noexcept
  {
    return not std::holds_alternative<no_bound>(m_bound);
  }

  constexpr bool is_inclusive() const noexcept
  {
    return std::holds_alternative<inclusive_bound<TYPE>>(m_bound);
  }

  constexpr bool is_exclusive() const noexcept
  {
    return std::holds_alternative<exclusive_bound<TYPE>>(m_bound);
  }

  constexpr bool extends_down_to(TYPE const &value) const
  {
    return std::visit(
      [&value](auto const &bound) noexcept(noexcept(bound.extends_down_to(
        value))) { return bound.extends_down_to(value); },
      m_bound);
  }

  constexpr bool extends_up_to(TYPE const &value) const
  {
    return std::visit(
      [&value](auto const &bound) noexcept(noexcept(
        bound.extends_up_to(value))) { return bound.extends_up_to(value); },
      m_bound);
  }

  [[nodiscard]] constexpr TYPE const *value() const & noexcept
  {
    return std::visit(
      [](auto const &bound) noexcept {
        using bound_t = std::decay_t<decltype(bound)>;
        if constexpr (std::is_same_v<bound_t, no_bound>)
          return static_cast<TYPE const *>(nullptr);
        else
          return &bound.get();
      },
      m_bound);
  }
};
 
 
// C++20: Concepts for comparisons, construction, etc.

template<typename TYPE> class range
{
  // (Putting private section first to work around bug in gcc < 10: see #665.)
private:
  range_bound<TYPE> m_lower, m_upper;
 
public:

  constexpr range(range_bound<TYPE> lower, range_bound<TYPE> upper) :
          m_lower{lower}, m_upper{upper}
  {
    if (
      lower.is_limited() and upper.is_limited() and
      (*upper.value() < *lower.value()))
      throw range_error{internal::concat(
        "Range's lower bound (", *lower.value(),
        ") is greater than its upper bound (", *upper.value(), ").")};
  }


  constexpr range() noexcept(noexcept(exclusive_bound<TYPE>{TYPE{}})) :
          m_lower{exclusive_bound<TYPE>{TYPE{}}},
          m_upper{exclusive_bound<TYPE>{TYPE{}}}
  {}
 
  constexpr bool operator==(range const &rhs) const noexcept(
    noexcept(this->lower_bound() == rhs.lower_bound()) and
    noexcept(this->upper_bound() == rhs.upper_bound()) and
    noexcept(this->empty()))
  {
    return (this->lower_bound() == rhs.lower_bound() and
            this->upper_bound() == rhs.upper_bound()) or
           (this->empty() and rhs.empty());
  }
 
  constexpr bool operator!=(range const &rhs) const
    noexcept(noexcept(*this == rhs))
  {
    return not(*this == rhs);
  }
 
  range(range const &) = default;
  range(range &&) = default;
  range &operator=(range const &) = default;
  range &operator=(range &&) = default;


  constexpr bool empty() const noexcept(
    noexcept(m_lower.is_exclusive()) and noexcept(m_lower.is_limited()) and
    noexcept(*m_lower.value() < *m_upper.value()))
  {
    return (m_lower.is_exclusive() or m_upper.is_exclusive()) and
           m_lower.is_limited() and m_upper.is_limited() and
           not(*m_lower.value() < *m_upper.value());
  }

  constexpr bool contains(TYPE value) const noexcept(
    noexcept(m_lower.extends_down_to(value)) and
    noexcept(m_upper.extends_up_to(value)))
  {
    return m_lower.extends_down_to(value) and m_upper.extends_up_to(value);
  }


  constexpr bool contains(range<TYPE> const &other) const
    noexcept(noexcept((*this & other) == other))
  {
    return (*this & other) == other;
  }
 
  [[nodiscard]] constexpr range_bound<TYPE> const &
  lower_bound() const & noexcept
  {
    return m_lower;
  }
  [[nodiscard]] constexpr range_bound<TYPE> const &
  upper_bound() const & noexcept
  {
    return m_upper;
  }


  constexpr range operator&(range const &other) const
  {
    range_bound<TYPE> lower{no_bound{}};
    if (not this->lower_bound().is_limited())
      lower = other.lower_bound();
    else if (not other.lower_bound().is_limited())
      lower = this->lower_bound();
    else if (*this->lower_bound().value() < *other.lower_bound().value())
      lower = other.lower_bound();
    else if (*other.lower_bound().value() < *this->lower_bound().value())
      lower = this->lower_bound();
    else if (this->lower_bound().is_exclusive())
      lower = this->lower_bound();
    else
      lower = other.lower_bound();
 
    range_bound<TYPE> upper{no_bound{}};
    if (not this->upper_bound().is_limited())
      upper = other.upper_bound();
    else if (not other.upper_bound().is_limited())
      upper = this->upper_bound();
    else if (*other.upper_bound().value() < *this->upper_bound().value())
      upper = other.upper_bound();
    else if (*this->upper_bound().value() < *other.upper_bound().value())
      upper = this->upper_bound();
    else if (this->upper_bound().is_exclusive())
      upper = this->upper_bound();
    else
      upper = other.upper_bound();
 
    if (
      lower.is_limited() and upper.is_limited() and
      (*upper.value() < *lower.value()))
      return {};
    else
      return {lower, upper};
  }

  template<typename DEST> operator range<DEST>() const
  {
    range_bound<DEST> lower{no_bound{}}, upper{no_bound{}};
    if (lower_bound().is_inclusive())
      lower = inclusive_bound<DEST>{*lower_bound().value()};
    else if (lower_bound().is_exclusive())
      lower = exclusive_bound<DEST>{*lower_bound().value()};
 
    if (upper_bound().is_inclusive())
      upper = inclusive_bound<DEST>{*upper_bound().value()};
    else if (upper_bound().is_exclusive())
      upper = exclusive_bound<DEST>{*upper_bound().value()};
 
    return {lower, upper};
  }
};
 


template<typename TYPE> struct string_traits<range<TYPE>>
{
  [[nodiscard]] static inline zview
  to_buf(char *begin, char *end, range<TYPE> const &value)
  {
    return generic_to_buf(begin, end, value);
  }
 
  static inline char *
  into_buf(char *begin, char *end, range<TYPE> const &value)
  {
    if (value.empty())
    {
      if ((end - begin) <= internal::ssize(s_empty))
        throw conversion_overrun{s_overrun.c_str()};
      char *here = begin + s_empty.copy(begin, std::size(s_empty));
      *here++ = '\0';
      return here;
    }
    else
    {
      if (end - begin < 4)
        throw conversion_overrun{s_overrun.c_str()};
      char *here = begin;
      *here++ =
        (static_cast<char>(value.lower_bound().is_inclusive() ? '[' : '('));
      TYPE const *lower{value.lower_bound().value()};
      // Convert bound (but go back to overwrite that trailing zero).
      if (lower != nullptr)
        here = string_traits<TYPE>::into_buf(here, end, *lower) - 1;
      *here++ = ',';
      TYPE const *upper{value.upper_bound().value()};
      // Convert bound (but go back to overwrite that trailing zero).
      if (upper != nullptr)
        here = string_traits<TYPE>::into_buf(here, end, *upper) - 1;
      if ((end - here) < 2)
        throw conversion_overrun{s_overrun.c_str()};
      *here++ =
        static_cast<char>(value.upper_bound().is_inclusive() ? ']' : ')');
      *here++ = '\0';
      return here;
    }
  }
 
  [[nodiscard]] static inline range<TYPE> from_string(std::string_view text)
  {
    if (std::size(text) < 3)
      throw pqxx::conversion_error{err_bad_input(text)};
    bool left_inc{false};
    switch (text[0])
    {
    case '[': left_inc = true; break;
 
    case '(': break;
 
    case 'e':
    case 'E':
      if (
        (std::size(text) != std::size(s_empty)) or
        (text[1] != 'm' and text[1] != 'M') or
        (text[2] != 'p' and text[2] != 'P') or
        (text[3] != 't' and text[3] != 'T') or
        (text[4] != 'y' and text[4] != 'Y'))
        throw pqxx::conversion_error{err_bad_input(text)};
      return {};
      break;
 
    default: throw pqxx::conversion_error{err_bad_input(text)};
    }
 
    // The field parser uses this to track which field it's parsing, and
    // when not to expect a field separator.
    std::size_t index{0};
    // The last field we expect to see.
    static constexpr std::size_t last{1};
    // Current parsing position.  We skip the opening parenthesis or bracket.
    std::size_t pos{1};
    // The string may leave out either bound to indicate that it's unlimited.
    std::optional<TYPE> lower, upper;
    // We reuse the same field parser we use for composite values and arrays.
    auto const field_parser{
      pqxx::internal::specialize_parse_composite_field<std::optional<TYPE>>(
        pqxx::internal::encoding_group::UTF8)};
    field_parser(index, text, pos, lower, last);
    field_parser(index, text, pos, upper, last);
 
    // We need one more character: the closing parenthesis or bracket.
    if (pos != std::size(text))
      throw pqxx::conversion_error{err_bad_input(text)};
    char const closing{text[pos - 1]};
    if (closing != ')' and closing != ']')
      throw pqxx::conversion_error{err_bad_input(text)};
    bool const right_inc{closing == ']'};
 
    range_bound<TYPE> lower_bound{no_bound{}}, upper_bound{no_bound{}};
    if (lower)
    {
      if (left_inc)
        lower_bound = inclusive_bound{*lower};
      else
        lower_bound = exclusive_bound{*lower};
    }
    if (upper)
    {
      if (right_inc)
        upper_bound = inclusive_bound{*upper};
      else
        upper_bound = exclusive_bound{*upper};
    }
 
    return {lower_bound, upper_bound};
  }
 
  [[nodiscard]] static inline constexpr std::size_t
  size_buffer(range<TYPE> const &value) noexcept
  {
    TYPE const *lower{value.lower_bound().value()},
      *upper{value.upper_bound().value()};
    std::size_t const lsz{
      lower == nullptr ? 0 : string_traits<TYPE>::size_buffer(*lower) - 1},
      usz{upper == nullptr ? 0 : string_traits<TYPE>::size_buffer(*upper) - 1};
 
    if (value.empty())
      return std::size(s_empty) + 1;
    else
      return 1 + lsz + 1 + usz + 2;
  }
 
private:
  static constexpr zview s_empty{"empty"_zv};
  static constexpr auto s_overrun{"Not enough space in buffer for range."_zv};

  static std::string err_bad_input(std::string_view text)
  {
    return internal::concat("Invalid range input: '", text, "'");
  }
};
 

template<typename TYPE> struct nullness<range<TYPE>> : no_null<range<TYPE>>
{};
} // namespace pqxx
#endif