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119 lines
3.8 KiB
C++
119 lines
3.8 KiB
C++
/** Internal wrapper for SQL cursors. Supports higher-level cursor classes.
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*
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* DO NOT INCLUDE THIS FILE DIRECTLY. Other headers include it for you.
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*
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* Copyright (c) 2000-2022, Jeroen T. Vermeulen.
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*
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* See COPYING for copyright license. If you did not receive a file called
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* COPYING with this source code, please notify the distributor of this
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* mistake, or contact the author.
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*/
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#ifndef PQXX_H_SQL_CURSOR
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#define PQXX_H_SQL_CURSOR
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namespace pqxx::internal
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{
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/// Cursor with SQL positioning semantics.
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/** Thin wrapper around an SQL cursor, with SQL's ideas of positioning.
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*
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* SQL cursors have pre-increment/pre-decrement semantics, with on either end
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* of the result set a special position that does not repesent a row. This
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* class models SQL cursors for the purpose of implementing more C++-like
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* semantics on top.
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*
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* Positions of actual rows are numbered starting at 1. Position 0 exists but
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* does not refer to a row. There is a similar non-row position at the end of
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* the result set.
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*
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* Don't use this at home. You deserve better. Use the stateles_cursor
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* instead.
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*/
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class PQXX_LIBEXPORT sql_cursor : public cursor_base
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{
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public:
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sql_cursor(
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transaction_base &t, std::string_view query, std::string_view cname,
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cursor_base::access_policy ap, cursor_base::update_policy up,
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cursor_base::ownership_policy op, bool hold);
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sql_cursor(
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transaction_base &t, std::string_view cname,
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cursor_base::ownership_policy op);
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~sql_cursor() noexcept { close(); }
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result fetch(difference_type rows, difference_type &displacement);
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result fetch(difference_type rows)
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{
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difference_type d = 0;
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return fetch(rows, d);
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}
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difference_type move(difference_type rows, difference_type &displacement);
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difference_type move(difference_type rows)
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{
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difference_type d = 0;
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return move(rows, d);
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}
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/// Current position, or -1 for unknown
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/**
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* The starting position, just before the first row, counts as position zero.
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*
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* Position may be unknown if (and only if) this cursor was adopted, and has
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* never hit its starting position (position zero).
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*/
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difference_type pos() const noexcept { return m_pos; }
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/// End position, or -1 for unknown
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/**
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* Returns the final position, just after the last row in the result set. The
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* starting position, just before the first row, counts as position zero.
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*
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* End position is unknown until it is encountered during use.
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*/
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difference_type endpos() const noexcept { return m_endpos; }
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/// Return zero-row result for this cursor.
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result const &empty_result() const noexcept { return m_empty_result; }
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void close() noexcept;
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private:
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difference_type adjust(difference_type hoped, difference_type actual);
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static std::string stridestring(difference_type);
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/// Initialize cached empty result. Call only at beginning or end!
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void init_empty_result(transaction_base &);
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/// Connection in which this cursor lives.
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connection &m_home;
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/// Zero-row result from this cursor (or plain empty one if cursor is
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/// adopted)
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result m_empty_result;
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result m_cached_current_row;
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/// Is this cursor adopted (as opposed to created by this cursor object)?
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bool m_adopted;
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/// Will this cursor object destroy its SQL cursor when it dies?
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cursor_base::ownership_policy m_ownership;
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/// At starting position (-1), somewhere in the middle (0), or past end (1)
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int m_at_end;
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/// Position, or -1 for unknown
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difference_type m_pos;
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/// End position, or -1 for unknown
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difference_type m_endpos = -1;
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};
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PQXX_LIBEXPORT result_size_type obtain_stateless_cursor_size(sql_cursor &);
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PQXX_LIBEXPORT result stateless_cursor_retrieve(
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sql_cursor &, result::difference_type size,
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result::difference_type begin_pos, result::difference_type end_pos);
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} // namespace pqxx::internal
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#endif
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