ZeroTierOne/ext/libpqxx-7.7.3/include/pqxx/internal/statement_parameters.hxx

/** Common implementation for statement parameter lists.
 *
 * These are used for both prepared statements and parameterized statements.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY.  Other headers include it for you.
 *
 * 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_STATEMENT_PARAMETER
#define PQXX_H_STATEMENT_PARAMETER

#include <cstring>
#include <functional>
#include <iterator>
#include <string>
#include <vector>

#include "pqxx/binarystring.hxx"
#include "pqxx/strconv.hxx"
#include "pqxx/util.hxx"


namespace pqxx::internal
{
template<typename ITERATOR>
constexpr inline auto const iterator_identity{
  [](decltype(*std::declval<ITERATOR>()) x) { return x; }};


/// Marker type: pass a dynamically-determined number of statement parameters.
/** @deprecated Use @ref params instead.
 *
 * Normally when invoking a prepared or parameterised statement, the number
 * of parameters is known at compile time.  For instance,
 * `t.exec_prepared("foo", 1, "x");` executes statement `foo` with two
 * parameters, an `int` and a C string.
 *
 * But sometimes you may want to pass a number of parameters known only at run
 * time.  In those cases, a @ref dynamic_params encodes a dynamically
 * determined number of parameters.  You can mix these with regular, static
 * parameter lists, and you can re-use them for multiple statement invocations.
 *
 * A dynamic_params object does not store copies of its parameters, so make
 * sure they remain accessible until you've executed the statement.
 *
 * The ACCESSOR is an optional callable (such as a lambda).  If you pass an
 * accessor `a`, then each parameter `p` goes into your statement as `a(p)`.
 */
template<typename IT, typename ACCESSOR = decltype(iterator_identity<IT>)>
class dynamic_params
{
public:
  /// Wrap a sequence of pointers or iterators.
  constexpr dynamic_params(IT begin, IT end) :
          m_begin(begin), m_end(end), m_accessor(iterator_identity<IT>)
  {}

  /// Wrap a sequence of pointers or iterators.
  /** This version takes an accessor callable.  If you pass an accessor `acc`,
   * then any parameter `p` will go into the statement's parameter list as
   * `acc(p)`.
   */
  constexpr dynamic_params(IT begin, IT end, ACCESSOR &acc) :
          m_begin(begin), m_end(end), m_accessor(acc)
  {}

  /// Wrap a container.
  template<typename C>
  explicit constexpr dynamic_params(C &container) :
          dynamic_params(std::begin(container), std::end(container))
  {}

  /// Wrap a container.
  /** This version takes an accessor callable.  If you pass an accessor `acc`,
   * then any parameter `p` will go into the statement's parameter list as
   * `acc(p)`.
   */
  template<typename C>
  explicit constexpr dynamic_params(C &container, ACCESSOR &acc) :
          dynamic_params(std::begin(container), std::end(container), acc)
  {}

  constexpr IT begin() const noexcept { return m_begin; }
  constexpr IT end() const noexcept { return m_end; }

  constexpr auto access(decltype(*std::declval<IT>()) value) const
    -> decltype(std::declval<ACCESSOR>()(value))
  {
    return m_accessor(value);
  }

private:
  IT const m_begin, m_end;
  ACCESSOR m_accessor = iterator_identity<IT>;
};


/// Internal type: encode statement parameters.
/** Compiles arguments for prepared statements and parameterised queries into
 * a format that can be passed into libpq.
 *
 * Objects of this type are meant to be short-lived: a `c_params` lives and
 * dies entirely within the call to execute.  So, for example, if you pass in a
 * non-null pointer as a parameter, @ref params may simply use that pointer as
 * a parameter value, without arranging longer-term storage for the data to
 * which it points.  All values referenced by parameters must remain "live"
 * until the parameterised or prepared statement has been executed.
 */
struct PQXX_LIBEXPORT c_params
{
  c_params() = default;
  /// Copying these objects is pointless and expensive.  Don't do it.
  c_params(c_params const &) = delete;
  c_params(c_params &&) = default;

  /// Pre-allocate storage for `n` parameters.
  void reserve(std::size_t n) &;

  /// As used by libpq: pointers to parameter values.
  std::vector<char const *> values;
  /// As used by libpq: lengths of non-null arguments, in bytes.
  std::vector<int> lengths;
  /// As used by libpq: effectively boolean "is this a binary parameter?"
  std::vector<format> formats;
};
} // namespace pqxx::internal
#endif