stl_list.h

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// List implementation -*- C++ -*-

// Copyright (C) 2001, 2002, 2003, 2004 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 2, 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996,1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file stl_list.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef _LIST_H
#define _LIST_H 1

#include <bits/concept_check.h>

namespace _GLIBCXX_STD
{
    // Supporting structures are split into common and templated types; the
    // latter publicly inherits from the former in an effort to reduce code
    // duplication.  This results in some "needless" static_cast'ing later on,
    // but it's all safe downcasting.

    /// @if maint Common part of a node in the %list.  @endif
    struct _List_node_base
    {
        _List_node_base* _M_next;   ///< Self-explanatory
        _List_node_base* _M_prev;   ///< Self-explanatory

        static void
            swap(_List_node_base& __x, _List_node_base& __y);

        void
            transfer(_List_node_base * const __first,
                    _List_node_base * const __last);

        void
            reverse();

        void
            hook(_List_node_base * const __position);

        void
            unhook();
    };

    /// @if maint An actual node in the %list.  @endif
    template<typename _Tp>
        struct _List_node : public _List_node_base
    {
        _Tp _M_data;                ///< User's data.
    };

    /**
     *  @brief A list::iterator.
     *
     *  @if maint
     *  All the functions are op overloads.
     *  @endif
     */
    template<typename _Tp>
        struct _List_iterator
        {
            typedef _List_iterator<_Tp>           _Self;
            typedef _List_node<_Tp>               _Node;

            typedef ptrdiff_t                     difference_type;
            typedef bidirectional_iterator_tag    iterator_category;
            typedef _Tp                           value_type;
            typedef _Tp*                          pointer;
            typedef _Tp&                          reference;

            _List_iterator() { }

            _List_iterator(_List_node_base* __x)
                : _M_node(__x) { }

            // Must downcast from List_node_base to _List_node to get to _M_data.
            reference
                operator*() const
                { return static_cast<_Node*>(_M_node)->_M_data; }

            pointer
                operator->() const
                { return &static_cast<_Node*>(_M_node)->_M_data; }

            _Self&
                operator++()
                {
                    _M_node = _M_node->_M_next;
                    return *this;
                }

            _Self
                operator++(int)
                {
                    _Self __tmp = *this;
                    _M_node = _M_node->_M_next;
                    return __tmp;
                }

            _Self&
                operator--()
                {
                    _M_node = _M_node->_M_prev;
                    return *this;
                }

            _Self
                operator--(int)
                {
                    _Self __tmp = *this;
                    _M_node = _M_node->_M_prev;
                    return __tmp;
                }

            bool
                operator==(const _Self& __x) const
                { return _M_node == __x._M_node; }

            bool
                operator!=(const _Self& __x) const
                { return _M_node != __x._M_node; }

            // The only member points to the %list element.
            _List_node_base* _M_node;
        };

    /**
     *  @brief A list::const_iterator.
     *
     *  @if maint
     *  All the functions are op overloads.
     *  @endif
     */
    template<typename _Tp>
        struct _List_const_iterator
        {
            typedef _List_const_iterator<_Tp>     _Self;
            typedef const _List_node<_Tp>         _Node;
            typedef _List_iterator<_Tp>           iterator;

            typedef ptrdiff_t                     difference_type;
            typedef bidirectional_iterator_tag    iterator_category;
            typedef _Tp                           value_type;
            typedef const _Tp*                    pointer;
            typedef const _Tp&                    reference;

            _List_const_iterator() { }

            _List_const_iterator(const _List_node_base* __x)
                : _M_node(__x) { }

            _List_const_iterator(const iterator& __x)
                : _M_node(__x._M_node) { }

            // Must downcast from List_node_base to _List_node to get to
            // _M_data.
            reference
                operator*() const
                { return static_cast<_Node*>(_M_node)->_M_data; }

            pointer
                operator->() const
                { return &static_cast<_Node*>(_M_node)->_M_data; }

            _Self&
                operator++()
                {
                    _M_node = _M_node->_M_next;
                    return *this;
                }

            _Self
                operator++(int)
                {
                    _Self __tmp = *this;
                    _M_node = _M_node->_M_next;
                    return __tmp;
                }

            _Self&
                operator--()
                {
                    _M_node = _M_node->_M_prev;
                    return *this;
                }

            _Self
                operator--(int)
                {
                    _Self __tmp = *this;
                    _M_node = _M_node->_M_prev;
                    return __tmp;
                }

            bool
                operator==(const _Self& __x) const
                { return _M_node == __x._M_node; }

            bool
                operator!=(const _Self& __x) const
                { return _M_node != __x._M_node; }

            // The only member points to the %list element.
            const _List_node_base* _M_node;
        };

    template<typename _Val>
        inline bool
        operator==(const _List_iterator<_Val>& __x,
                const _List_const_iterator<_Val>& __y)
        { return __x._M_node == __y._M_node; }

    template<typename _Val>
        inline bool
        operator!=(const _List_iterator<_Val>& __x,
                const _List_const_iterator<_Val>& __y)
        { return __x._M_node != __y._M_node; }


    /**
     *  @if maint
     *  See bits/stl_deque.h's _Deque_base for an explanation.
     *  @endif
     */
    template<typename _Tp, typename _Alloc>
        class _List_base
        {
            protected:
                // NOTA BENE
                // The stored instance is not actually of "allocator_type"'s
                // type.  Instead we rebind the type to
                // Allocator<List_node<Tp>>, which according to [20.1.5]/4
                // should probably be the same.  List_node<Tp> is not the same
                // size as Tp (it's two pointers larger), and specializations on
                // Tp may go unused because List_node<Tp> is being bound
                // instead.
                //
                // We put this to the test in the constructors and in
                // get_allocator, where we use conversions between
                // allocator_type and _Node_Alloc_type. The conversion is
                // required by table 32 in [20.1.5].
                typedef typename _Alloc::template rebind<_List_node<_Tp> >::other

                    _Node_Alloc_type;

                struct _List_impl 
                    : public _Node_Alloc_type {
                        _List_node_base _M_node;
                        _List_impl (const _Node_Alloc_type& __a)
                            : _Node_Alloc_type(__a)
                        { }
                    };

                _List_impl _M_impl;

                _List_node<_Tp>*
                    _M_get_node()
                    { return _M_impl._Node_Alloc_type::allocate(1); }

                void
                    _M_put_node(_List_node<_Tp>* __p)
                    { _M_impl._Node_Alloc_type::deallocate(__p, 1); }

            public:
                typedef _Alloc allocator_type;

                allocator_type
                    get_allocator() const
                    { return allocator_type(*static_cast<const _Node_Alloc_type*>(&this->_M_impl)); }

                _List_base(const allocator_type& __a)
                    : _M_impl(__a)
                { _M_init(); }

                // This is what actually destroys the list.
                ~_List_base()
                { _M_clear(); }

                void
                    _M_clear();

                void
                    _M_init()
                    {
                        this->_M_impl._M_node._M_next = &this->_M_impl._M_node;
                        this->_M_impl._M_node._M_prev = &this->_M_impl._M_node;
                    }
        };

    /**
     *  @brief A standard container with linear time access to elements,
     *  and fixed time insertion/deletion at any point in the sequence.
     *
     *  @ingroup Containers
     *  @ingroup Sequences
     *
     *  Meets the requirements of a <a href="tables.html#65">container</a>, a
     *  <a href="tables.html#66">reversible container</a>, and a
     *  <a href="tables.html#67">sequence</a>, including the
     *  <a href="tables.html#68">optional sequence requirements</a> with the
     *  %exception of @c at and @c operator[].
     *
     *  This is a @e doubly @e linked %list.  Traversal up and down the
     *  %list requires linear time, but adding and removing elements (or
     *  @e nodes) is done in constant time, regardless of where the
     *  change takes place.  Unlike std::vector and std::deque,
     *  random-access iterators are not provided, so subscripting ( @c
     *  [] ) access is not allowed.  For algorithms which only need
     *  sequential access, this lack makes no difference.
     *
     *  Also unlike the other standard containers, std::list provides
     *  specialized algorithms %unique to linked lists, such as
     *  splicing, sorting, and in-place reversal.
     *
     *  @if maint
     *  A couple points on memory allocation for list<Tp>:
     *
     *  First, we never actually allocate a Tp, we allocate
     *  List_node<Tp>'s and trust [20.1.5]/4 to DTRT.  This is to ensure
     *  that after elements from %list<X,Alloc1> are spliced into
     *  %list<X,Alloc2>, destroying the memory of the second %list is a
     *  valid operation, i.e., Alloc1 giveth and Alloc2 taketh away.
     *
     *  Second, a %list conceptually represented as
     *  @code
     *    A <---> B <---> C <---> D
     *  @endcode
     *  is actually circular; a link exists between A and D.  The %list
     *  class holds (as its only data member) a private list::iterator
     *  pointing to @e D, not to @e A!  To get to the head of the %list,
     *  we start at the tail and move forward by one.  When this member
     *  iterator's next/previous pointers refer to itself, the %list is
     *  %empty.  @endif
     */
    template<typename _Tp, typename _Alloc = allocator<_Tp> >
        class list : protected _List_base<_Tp, _Alloc>
    {
        // concept requirements
        __glibcxx_class_requires(_Tp, _SGIAssignableConcept)

            typedef _List_base<_Tp, _Alloc>                   _Base;

        public:
        typedef _Tp                                        value_type;
        typedef typename _Alloc::pointer                   pointer;
        typedef typename _Alloc::const_pointer             const_pointer;
        typedef typename _Alloc::reference                 reference;
        typedef typename _Alloc::const_reference           const_reference;
        typedef _List_iterator<_Tp>                        iterator;
        typedef _List_const_iterator<_Tp>                  const_iterator;
        typedef std::reverse_iterator<const_iterator>      const_reverse_iterator;
        typedef std::reverse_iterator<iterator>            reverse_iterator;
        typedef size_t                                     size_type;
        typedef ptrdiff_t                                  difference_type;
        typedef typename _Base::allocator_type             allocator_type;

        protected:
        // Note that pointers-to-_Node's can be ctor-converted to
        // iterator types.
        typedef _List_node<_Tp>				_Node;

        /** @if maint
         *  One data member plus two memory-handling functions.  If the
         *  _Alloc type requires separate instances, then one of those
         *  will also be included, accumulated from the topmost parent.
         *  @endif
         */