Preview: node_handle.h
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//opt/rh/gcc-toolset-14/root/usr/include/c++/14/bits/node_handle.h
// Node handles for containers -*- C++ -*-
// Copyright (C) 2016-2024 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file bits/node_handle.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly.
* @headername{map,set,unordered_map,unordered_set}
*/
#ifndef _NODE_HANDLE
#define _NODE_HANDLE 1
#pragma GCC system_header
#include <bits/version.h>
#ifdef __glibcxx_node_extract // C++ >= 17 && HOSTED
#include <new>
#include <bits/alloc_traits.h>
#include <bits/ptr_traits.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @defgroup node_handles Node handles
* @ingroup associative_containers
* @since C++17
*
* The associative containers (`map`, `set`, `multimap` and `multiset`)
* support extracting and re-inserting nodes from the container. Those
* operations use the container's `node_handle` type, which is an alias
* for a `_Node_handle<...>` type. You should always use the container's
* `node_handle` type (e.g. `std::set<int>::node_handle`) to refer to
* these types, not the non-standard internal `_Node_handle` names.
*
* @{
*/
/// Base class for node handle types of maps and sets.
template<typename _Val, typename _NodeAlloc>
class _Node_handle_common
{
using _AllocTraits = allocator_traits<_NodeAlloc>;
public:
using allocator_type = __alloc_rebind<_NodeAlloc, _Val>;
allocator_type
get_allocator() const noexcept
{
__glibcxx_assert(!this->empty());
return allocator_type(_M_alloc._M_alloc);
}
explicit operator bool() const noexcept { return _M_ptr != nullptr; }
[[nodiscard]] bool empty() const noexcept { return _M_ptr == nullptr; }
/// @cond undocumented
protected:
constexpr _Node_handle_common() noexcept : _M_ptr() { }
~_Node_handle_common()
{
if (!empty())
_M_reset();
}
_Node_handle_common(_Node_handle_common&& __nh) noexcept
: _M_ptr(__nh._M_ptr)
{
if (_M_ptr)
_M_move(std::move(__nh));
}
_Node_handle_common&
operator=(_Node_handle_common&& __nh) noexcept
{
if (empty())
{
if (!__nh.empty())
_M_move(std::move(__nh));
}
else if (__nh.empty())
_M_reset();
else
{
// Free the current node before replacing the allocator.
_AllocTraits::destroy(*_M_alloc, _M_ptr->_M_valptr());
_AllocTraits::deallocate(*_M_alloc, _M_ptr, 1);
_M_alloc = __nh._M_alloc.release(); // assigns if POCMA
_M_ptr = __nh._M_ptr;
__nh._M_ptr = nullptr;
}
return *this;
}
_Node_handle_common(typename _AllocTraits::pointer __ptr,
const _NodeAlloc& __alloc)
: _M_ptr(__ptr), _M_alloc(__alloc)
{
__glibcxx_assert(__ptr != nullptr);
}
void
_M_swap(_Node_handle_common& __nh) noexcept
{
if (empty())
{
if (!__nh.empty())
_M_move(std::move(__nh));
}
else if (__nh.empty())
__nh._M_move(std::move(*this));
else
{
using std::swap;
swap(_M_ptr, __nh._M_ptr);
_M_alloc.swap(__nh._M_alloc); // swaps if POCS
}
}
private:
// Moves the pointer and allocator from __nh to *this.
// Precondition: empty() && !__nh.empty()
// Postcondition: !empty() && __nh.empty()
void
_M_move(_Node_handle_common&& __nh) noexcept
{
::new (std::__addressof(_M_alloc)) _NodeAlloc(__nh._M_alloc.release());
_M_ptr = __nh._M_ptr;
__nh._M_ptr = nullptr;
}
// Deallocates the node, destroys the allocator.
// Precondition: !empty()
// Postcondition: empty()
void
_M_reset() noexcept
{
_NodeAlloc __alloc = _M_alloc.release();
_AllocTraits::destroy(__alloc, _M_ptr->_M_valptr());
_AllocTraits::deallocate(__alloc, _M_ptr, 1);
_M_ptr = nullptr;
}
// Destroys the allocator. Does not deallocate or destroy the node.
// Precondition: !empty()
// Postcondition: empty()
void
release() noexcept
{
_M_alloc.release();
_M_ptr = nullptr;
}
protected:
typename _AllocTraits::pointer _M_ptr;
private:
// A simplified, non-copyable std::optional<_NodeAlloc>.
// Call release() before destruction iff the allocator member is active.
union _Optional_alloc
{
_Optional_alloc() { }
~_Optional_alloc() { }
_Optional_alloc(_Optional_alloc&&) = delete;
_Optional_alloc& operator=(_Optional_alloc&&) = delete;
_Optional_alloc(const _NodeAlloc& __alloc) noexcept
: _M_alloc(__alloc)
{ }
// Precondition: _M_alloc is the active member of the union.
void
operator=(_NodeAlloc&& __alloc) noexcept
{
using _ATr = _AllocTraits;
if constexpr (_ATr::propagate_on_container_move_assignment::value)
_M_alloc = std::move(__alloc);
else if constexpr (!_AllocTraits::is_always_equal::value)
__glibcxx_assert(_M_alloc == __alloc);
}
// Precondition: _M_alloc is the active member of both unions.
void
swap(_Optional_alloc& __other) noexcept
{
using std::swap;
if constexpr (_AllocTraits::propagate_on_container_swap::value)
swap(_M_alloc, __other._M_alloc);
else if constexpr (!_AllocTraits::is_always_equal::value)
__glibcxx_assert(_M_alloc == __other._M_alloc);
}
// Precondition: _M_alloc is the active member of the union.
_NodeAlloc& operator*() noexcept { return _M_alloc; }
// Precondition: _M_alloc is the active member of the union.
_NodeAlloc release() noexcept
{
_NodeAlloc __tmp = std::move(_M_alloc);
_M_alloc.~_NodeAlloc();
return __tmp;
}
[[__no_unique_address__]] _NodeAlloc _M_alloc;
};
[[__no_unique_address__]] _Optional_alloc _M_alloc;
template<typename _Key2, typename _Value2, typename _KeyOfValue,
typename _Compare, typename _ValueAlloc>
friend class _Rb_tree;
template<typename _Key2, typename _Value2, typename _ValueAlloc,
typename _ExtractKey, typename _Equal,
typename _Hash, typename _RangeHash, typename _Unused,
typename _RehashPolicy, typename _Traits>
friend class _Hashtable;
/// @endcond
};
/// Node handle type for maps.
template<typename _Key, typename _Value, typename _NodeAlloc>
class _Node_handle : public _Node_handle_common<_Value, _NodeAlloc>
{
public:
constexpr _Node_handle() noexcept = default;
~_Node_handle() = default;
_Node_handle(_Node_handle&&) noexcept = default;
_Node_handle&
operator=(_Node_handle&&) noexcept = default;
using key_type = _Key;
using mapped_type = typename _Value::second_type;
key_type&
key() const noexcept
{
__glibcxx_assert(!this->empty());
return *_M_pkey;
}
mapped_type&
mapped() const noexcept
{
__glibcxx_assert(!this->empty());
return *_M_pmapped;
}
void
swap(_Node_handle& __nh) noexcept
{
this->_M_swap(__nh);
using std::swap;
swap(_M_pkey, __nh._M_pkey);
swap(_M_pmapped, __nh._M_pmapped);
}
friend void
swap(_Node_handle& __x, _Node_handle& __y)
noexcept(noexcept(__x.swap(__y)))
{ __x.swap(__y); }
private:
using _AllocTraits = allocator_traits<_NodeAlloc>;
_Node_handle(typename _AllocTraits::pointer __ptr,
const _NodeAlloc& __alloc)
: _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc)
{
if (__ptr)
{
auto& __key = const_cast<_Key&>(__ptr->_M_valptr()->first);
_M_pkey = _S_pointer_to(__key);
_M_pmapped = _S_pointer_to(__ptr->_M_valptr()->second);
}
else
{
_M_pkey = nullptr;
_M_pmapped = nullptr;
}
}
template<typename _Tp>
using __pointer
= __ptr_rebind<typename _AllocTraits::pointer,
remove_reference_t<_Tp>>;
__pointer<_Key> _M_pkey = nullptr;
__pointer<typename _Value::second_type> _M_pmapped = nullptr;
template<typename _Tp>
__pointer<_Tp>
_S_pointer_to(_Tp& __obj)
{ return pointer_traits<__pointer<_Tp>>::pointer_to(__obj); }
const key_type&
_M_key() const noexcept { return key(); }
template<typename _Key2, typename _Value2, typename _KeyOfValue,
typename _Compare, typename _ValueAlloc>
friend class _Rb_tree;
template<typename _Key2, typename _Value2, typename _ValueAlloc,
typename _ExtractKey, typename _Equal,
typename _Hash, typename _RangeHash, typename _Unused,
typename _RehashPolicy, typename _Traits>
friend class _Hashtable;
};
/// Node handle type for sets.
template<typename _Value, typename _NodeAlloc>
class _Node_handle<_Value, _Value, _NodeAlloc>
: public _Node_handle_common<_Value, _NodeAlloc>
{
public:
constexpr _Node_handle() noexcept = default;
~_Node_handle() = default;
_Node_handle(_Node_handle&&) noexcept = default;
_Node_handle&
operator=(_Node_handle&&) noexcept = default;
using value_type = _Value;
value_type&
value() const noexcept
{
__glibcxx_assert(!this->empty());
return *this->_M_ptr->_M_valptr();
}
void
swap(_Node_handle& __nh) noexcept
{ this->_M_swap(__nh); }
friend void
swap(_Node_handle& __x, _Node_handle& __y)
noexcept(noexcept(__x.swap(__y)))
{ __x.swap(__y); }
private:
using _AllocTraits = allocator_traits<_NodeAlloc>;
_Node_handle(typename _AllocTraits::pointer __ptr,
const _NodeAlloc& __alloc)
: _Node_handle_common<_Value, _NodeAlloc>(__ptr, __alloc) { }
const value_type&
_M_key() const noexcept { return value(); }
template<typename _Key, typename _Val, typename _KeyOfValue,
typename _Compare, typename _Alloc>
friend class _Rb_tree;
template<typename _Key2, typename _Value2, typename _ValueAlloc,
typename _ExtractKey, typename _Equal,
typename _Hash, typename _RangeHash, typename _Unused,
typename _RehashPolicy, typename _Traits>
friend class _Hashtable;
};
/// Return type of insert(node_handle&&) on unique maps/sets.
template<typename _Iterator, typename _NodeHandle>
struct _Node_insert_return
{
_Iterator position = _Iterator();
bool inserted = false;
_NodeHandle node;
};
/// @}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // __glibcxx_node_extract
#endif
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