result.hxx

/* Definitions for the pqxx::result class and support classes.
 *
 * pqxx::result represents the set of result rows from a database query.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/result 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_RESULT
#define PQXX_H_RESULT

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

#include <functional>
#include <ios>
#include <memory>
#include <stdexcept>

#include "pqxx/except.hxx"
#include "pqxx/types.hxx"
#include "pqxx/util.hxx"
#include "pqxx/zview.hxx"

#include "pqxx/internal/encodings.hxx"


namespace pqxx::internal
{
// TODO: Make noexcept (but breaks ABI).
PQXX_LIBEXPORT void clear_result(pq::PGresult const *);
} // namespace pqxx::internal


namespace pqxx::internal::gate
{
class result_connection;
class result_creation;
class result_pipeline;
class result_row;
class result_sql_cursor;
} // namespace pqxx::internal::gate


namespace pqxx
{

class PQXX_LIBEXPORT result
{
public:
  using size_type = result_size_type;
  using difference_type = result_difference_type;
  using reference = row;
  using const_iterator = const_result_iterator;
  using pointer = const_iterator;
  using iterator = const_iterator;
  using const_reverse_iterator = const_reverse_result_iterator;
  using reverse_iterator = const_reverse_iterator;

  result() noexcept :
          m_data{make_data_pointer()},
          m_query{},
          m_encoding{internal::encoding_group::MONOBYTE}
  {}

  result(result const &rhs) noexcept = default;
  result(result &&rhs) noexcept = default;


  result &operator=(result const &rhs) noexcept = default;

  result &operator=(result &&rhs) noexcept = default;

  [[nodiscard]] bool operator==(result const &) const noexcept;
  [[nodiscard]] bool operator!=(result const &rhs) const noexcept
  {
    return not operator==(rhs);
  }


  template<typename... TYPE> auto iter() const;

  [[nodiscard]] const_reverse_iterator rbegin() const;
  [[nodiscard]] const_reverse_iterator crbegin() const;
  [[nodiscard]] const_reverse_iterator rend() const;
  [[nodiscard]] const_reverse_iterator crend() const;

  [[nodiscard]] const_iterator begin() const noexcept;
  [[nodiscard]] const_iterator cbegin() const noexcept;
  [[nodiscard]] inline const_iterator end() const noexcept;
  [[nodiscard]] inline const_iterator cend() const noexcept;

  [[nodiscard]] reference front() const noexcept;
  [[nodiscard]] reference back() const noexcept;

  [[nodiscard]] PQXX_PURE size_type size() const noexcept;
  [[nodiscard]] PQXX_PURE bool empty() const noexcept;
  [[nodiscard]] size_type capacity() const noexcept { return size(); }


  void swap(result &) noexcept;


  [[nodiscard]] row operator[](size_type i) const noexcept;

#if defined(PQXX_HAVE_MULTIDIMENSIONAL_SUBSCRIPT)
  // TODO: If C++23 will let us, also accept string for the column.
  [[nodiscard]] field
  operator[](size_type row_num, row_size_type col_num) const noexcept;
#endif

  row at(size_type) const;

  field at(size_type, row_size_type) const;


  void clear() noexcept
  {
    m_data.reset();
    m_query = nullptr;
  }

  [[nodiscard]] PQXX_PURE row_size_type columns() const noexcept;

  [[nodiscard]] row_size_type column_number(zview name) const;

  [[nodiscard]] char const *column_name(row_size_type number) const &;

  [[nodiscard]] oid column_type(row_size_type col_num) const;

  [[nodiscard]] oid column_type(zview col_name) const
  {
    return column_type(column_number(col_name));
  }

  [[nodiscard]] oid column_table(row_size_type col_num) const;

  [[nodiscard]] oid column_table(zview col_name) const
  {
    return column_table(column_number(col_name));
  }

  [[nodiscard]] row_size_type table_column(row_size_type col_num) const;

  [[nodiscard]] row_size_type table_column(zview col_name) const
  {
    return table_column(column_number(col_name));
  }

  [[nodiscard]] PQXX_PURE std::string const &query() const &noexcept;


  [[nodiscard]] PQXX_PURE oid inserted_oid() const;


  [[nodiscard]] PQXX_PURE size_type affected_rows() const;

  // C++20: Concept like std::invocable, but without specifying param types.

  template<typename CALLABLE> inline void for_each(CALLABLE &&func) const;

private:
  using data_pointer = std::shared_ptr<internal::pq::PGresult const>;

  data_pointer m_data;

  static data_pointer
  make_data_pointer(internal::pq::PGresult const *res = nullptr) noexcept
  {
    return {res, internal::clear_result};
  }

  friend class pqxx::internal::gate::result_pipeline;
  PQXX_PURE std::shared_ptr<std::string const> query_ptr() const noexcept
  {
    return m_query;
  }

  std::shared_ptr<std::string const> m_query;

  internal::encoding_group m_encoding;

  static std::string const s_empty_string;

  friend class pqxx::field;
  // TODO: noexcept.  Breaks ABI.
  PQXX_PURE char const *get_value(size_type row, row_size_type col) const;
  // TODO: noexcept.  Breaks ABI.
  PQXX_PURE bool get_is_null(size_type row, row_size_type col) const;
  PQXX_PURE
  field_size_type get_length(size_type, row_size_type) const noexcept;

  friend class pqxx::internal::gate::result_creation;
  result(
    internal::pq::PGresult *rhs, std::shared_ptr<std::string> query,
    internal::encoding_group enc);

  PQXX_PRIVATE void check_status(std::string_view desc = ""sv) const;

  friend class pqxx::internal::gate::result_connection;
  friend class pqxx::internal::gate::result_row;
  bool operator!() const noexcept { return m_data.get() == nullptr; }
  operator bool() const noexcept { return m_data.get() != nullptr; }

  [[noreturn]] PQXX_PRIVATE void
  throw_sql_error(std::string const &Err, std::string const &Query) const;
  PQXX_PRIVATE PQXX_PURE int errorposition() const;
  PQXX_PRIVATE std::string status_error() const;

  friend class pqxx::internal::gate::result_sql_cursor;
  PQXX_PURE char const *cmd_status() const noexcept;
};
} // namespace pqxx
#endif