slist

gcc-you can use this code to learn something about gcc, and inquire further into linux,

// Singly-linked list implementation -*- C++ -*-

// Copyright (C) 2001, 2002 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) 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 ext/slist
 *  This file is a GNU extension to the Standard C++ Library (possibly
 *  containing extensions from the HP/SGI STL subset).  You should only
 *  include this header if you are using GCC 3 or later.
 */

#ifndef __SGI_STL_INTERNAL_SLIST_H
#define __SGI_STL_INTERNAL_SLIST_H

#include <bits/stl_algobase.h>
#include <bits/stl_alloc.h>
#include <bits/stl_construct.h>
#include <bits/stl_uninitialized.h>
#include <bits/concept_check.h>

namespace __gnu_cxx
{ 
using std::size_t;
using std::ptrdiff_t;
using std::_Alloc_traits;
using std::_Construct;
using std::_Destroy;
using std::allocator;

struct _Slist_node_base
{
  _Slist_node_base* _M_next;
};

inline _Slist_node_base*
__slist_make_link(_Slist_node_base* __prev_node,
                  _Slist_node_base* __new_node)
{
  __new_node->_M_next = __prev_node->_M_next;
  __prev_node->_M_next = __new_node;
  return __new_node;
}

inline _Slist_node_base* 
__slist_previous(_Slist_node_base* __head,
                 const _Slist_node_base* __node)
{
  while (__head && __head->_M_next != __node)
    __head = __head->_M_next;
  return __head;
}

inline const _Slist_node_base* 
__slist_previous(const _Slist_node_base* __head,
                 const _Slist_node_base* __node)
{
  while (__head && __head->_M_next != __node)
    __head = __head->_M_next;
  return __head;
}

inline void __slist_splice_after(_Slist_node_base* __pos,
                                 _Slist_node_base* __before_first,
                                 _Slist_node_base* __before_last)
{
  if (__pos != __before_first && __pos != __before_last) {
    _Slist_node_base* __first = __before_first->_M_next;
    _Slist_node_base* __after = __pos->_M_next;
    __before_first->_M_next = __before_last->_M_next;
    __pos->_M_next = __first;
    __before_last->_M_next = __after;
  }
}

inline void
__slist_splice_after(_Slist_node_base* __pos, _Slist_node_base* __head)
{
  _Slist_node_base* __before_last = __slist_previous(__head, 0);
  if (__before_last != __head) {
    _Slist_node_base* __after = __pos->_M_next;
    __pos->_M_next = __head->_M_next;
    __head->_M_next = 0;
    __before_last->_M_next = __after;
  }
}

inline _Slist_node_base* __slist_reverse(_Slist_node_base* __node)
{
  _Slist_node_base* __result = __node;
  __node = __node->_M_next;
  __result->_M_next = 0;
  while(__node) {
    _Slist_node_base* __next = __node->_M_next;
    __node->_M_next = __result;
    __result = __node;
    __node = __next;
  }
  return __result;
}

inline size_t __slist_size(_Slist_node_base* __node)
{
  size_t __result = 0;
  for ( ; __node != 0; __node = __node->_M_next)
    ++__result;
  return __result;
}

template <class _Tp>
struct _Slist_node : public _Slist_node_base
{
  _Tp _M_data;
};

struct _Slist_iterator_base
{
  typedef size_t                    size_type;
  typedef ptrdiff_t                 difference_type;
  typedef std::forward_iterator_tag iterator_category;

  _Slist_node_base* _M_node;

  _Slist_iterator_base(_Slist_node_base* __x) : _M_node(__x) {}
  void _M_incr() { _M_node = _M_node->_M_next; }

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

template <class _Tp, class _Ref, class _Ptr>
struct _Slist_iterator : public _Slist_iterator_base
{
  typedef _Slist_iterator<_Tp, _Tp&, _Tp*>             iterator;
  typedef _Slist_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;
  typedef _Slist_iterator<_Tp, _Ref, _Ptr>             _Self;

  typedef _Tp              value_type;
  typedef _Ptr             pointer;
  typedef _Ref             reference;
  typedef _Slist_node<_Tp> _Node;

  _Slist_iterator(_Node* __x) : _Slist_iterator_base(__x) {}
  _Slist_iterator() : _Slist_iterator_base(0) {}
  _Slist_iterator(const iterator& __x) : _Slist_iterator_base(__x._M_node) {}

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

  _Self& operator++()
  {
    _M_incr();
    return *this;
  }
  _Self operator++(int)
  {
    _Self __tmp = *this;
    _M_incr();
    return __tmp;
  }
};


// Base class that encapsulates details of allocators.  Three cases:
// an ordinary standard-conforming allocator, a standard-conforming
// allocator with no non-static data, and an SGI-style allocator.
// This complexity is necessary only because we're worrying about backward
// compatibility and because we want to avoid wasting storage on an 
// allocator instance if it isn't necessary.

// Base for general standard-conforming allocators.
template <class _Tp, class _Allocator, bool _IsStatic>
class _Slist_alloc_base {
public:
  typedef typename _Alloc_traits<_Tp,_Allocator>::allocator_type
          allocator_type;
  allocator_type get_allocator() const { return _M_node_allocator; }

  _Slist_alloc_base(const allocator_type& __a) : _M_node_allocator(__a) {}

protected:
  _Slist_node<_Tp>* _M_get_node() 
    { return _M_node_allocator.allocate(1); }
  void _M_put_node(_Slist_node<_Tp>* __p) 
    { _M_node_allocator.deallocate(__p, 1); }

protected:
  typename _Alloc_traits<_Slist_node<_Tp>,_Allocator>::allocator_type
           _M_node_allocator;
  _Slist_node_base _M_head;
};

// Specialization for instanceless allocators.
template <class _Tp, class _Allocator>
class _Slist_alloc_base<_Tp,_Allocator, true> {
public:
  typedef typename _Alloc_traits<_Tp,_Allocator>::allocator_type
          allocator_type;
  allocator_type get_allocator() const { return allocator_type(); }

  _Slist_alloc_base(const allocator_type&) {}

protected:
  typedef typename _Alloc_traits<_Slist_node<_Tp>, _Allocator>::_Alloc_type
          _Alloc_type;
  _Slist_node<_Tp>* _M_get_node() { return _Alloc_type::allocate(1); }
  void _M_put_node(_Slist_node<_Tp>* __p) { _Alloc_type::deallocate(__p, 1); }

protected:
  _Slist_node_base _M_head;
};


template <class _Tp, class _Alloc>
struct _Slist_base
  : public _Slist_alloc_base<_Tp, _Alloc,
                             _Alloc_traits<_Tp, _Alloc>::_S_instanceless>
{
  typedef _Slist_alloc_base<_Tp, _Alloc,
                            _Alloc_traits<_Tp, _Alloc>::_S_instanceless>
          _Base;
  typedef typename _Base::allocator_type allocator_type;

  _Slist_base(const allocator_type& __a)
    : _Base(__a) { this->_M_head._M_next = 0; }
  ~_Slist_base() { _M_erase_after(&this->_M_head, 0); }

protected:

  _Slist_node_base* _M_erase_after(_Slist_node_base* __pos)
  {
    _Slist_node<_Tp>* __next = (_Slist_node<_Tp>*) (__pos->_M_next);
    _Slist_node_base* __next_next = __next->_M_next;
    __pos->_M_next = __next_next;
    _Destroy(&__next->_M_data);
    _M_put_node(__next);
    return __next_next;
  }
  _Slist_node_base* _M_erase_after(_Slist_node_base*, _Slist_node_base*);
};

template <class _Tp, class _Alloc> 
_Slist_node_base*
_Slist_base<_Tp,_Alloc>::_M_erase_after(_Slist_node_base* __before_first,
                                        _Slist_node_base* __last_node) {
  _Slist_node<_Tp>* __cur = (_Slist_node<_Tp>*) (__before_first->_M_next);
  while (__cur != __last_node) {
    _Slist_node<_Tp>* __tmp = __cur;
    __cur = (_Slist_node<_Tp>*) __cur->_M_next;
    _Destroy(&__tmp->_M_data);
    _M_put_node(__tmp);
  }
  __before_first->_M_next = __last_node;
  return __last_node;
}

/**
 *  This is an SGI extension.
 *  @ingroup SGIextensions
 *  @doctodo
*/
template <class _Tp, class _Alloc = allocator<_Tp> >
class slist : private _Slist_base<_Tp,_Alloc>
{
  // concept requirements
  __glibcpp_class_requires(_Tp, _SGIAssignableConcept)

private:
  typedef _Slist_base<_Tp,_Alloc> _Base;
public:
  typedef _Tp               value_type;
  typedef value_type*       pointer;
  typedef const value_type* const_pointer;
  typedef value_type&       reference;
  typedef const value_type& const_reference;
  typedef size_t            size_type;
  typedef ptrdiff_t         difference_type;

  typedef _Slist_iterator<_Tp, _Tp&, _Tp*>             iterator;
  typedef _Slist_iterator<_Tp, const _Tp&, const _Tp*> const_iterator;

  typedef typename _Base::allocator_type allocator_type;
  allocator_type get_allocator() const { return _Base::get_allocator(); }

private:
  typedef _Slist_node<_Tp>      _Node;
  typedef _Slist_node_base      _Node_base;
  typedef _Slist_iterator_base  _Iterator_base;

  _Node* _M_create_node(const value_type& __x) {
    _Node* __node = this->_M_get_node();
    try {
      _Construct(&__node->_M_data, __x);
      __node->_M_next = 0;
    }
    catch(...)
      {
	this->_M_put_node(__node);
	__throw_exception_again;
      }
    return __node;
  }
  
  _Node* _M_create_node() {
    _Node* __node = this->_M_get_node();
    try {
      _Construct(&__node->_M_data);
      __node->_M_next = 0;
    }
    catch(...)
      {
	this->_M_put_node(__node);
	__throw_exception_again;
      }
    return __node;
  }

public:
  explicit slist(const allocator_type& __a = allocator_type()) : _Base(__a) {}

  slist(size_type __n, const value_type& __x,
        const allocator_type& __a =  allocator_type()) : _Base(__a)
    { _M_insert_after_fill(&this->_M_head, __n, __x); }

  explicit slist(size_type __n) : _Base(allocator_type())
    { _M_insert_after_fill(&this->_M_head, __n, value_type()); }

  // We don't need any dispatching tricks here, because _M_insert_after_range
  // already does them.
  template <class _InputIterator>
  slist(_InputIterator __first, _InputIterator __last,
        const allocator_type& __a =  allocator_type()) : _Base(__a)
    { _M_insert_after_range(&this->_M_head, __first, __last); }

  slist(const slist& __x) : _Base(__x.get_allocator())
    { _M_insert_after_range(&this->_M_head, __x.begin(), __x.end()); }

  slist& operator= (const slist& __x);

  ~slist() {}

public:
  // assign(), a generalized assignment member function.  Two
  // versions: one that takes a count, and one that takes a range.
  // The range version is a member template, so we dispatch on whether
  // or not the type is an integer.

  void assign(size_type __n, const _Tp& __val)
    { _M_fill_assign(__n, __val); }

  void _M_fill_assign(size_type __n, const _Tp& __val);

  template <class _InputIterator>
  void assign(_InputIterator __first, _InputIterator __last) {
    typedef typename _Is_integer<_InputIterator>::_Integral _Integral;
    _M_assign_dispatch(__first, __last, _Integral());
  }

  template <class _Integer>
  void _M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
    { _M_fill_assign((size_type) __n, (_Tp) __val); }

  template <class _InputIterator>
  void _M_assign_dispatch(_InputIterator __first, _InputIterator __last,
                          __false_type);

public:

  iterator begin() { return iterator((_Node*)this->_M_head._M_next); }
  const_iterator begin() const 
    { return const_iterator((_Node*)this->_M_head._M_next);}

  iterator end() { return iterator(0); }
  const_iterator end() const { return const_iterator(0); }

  // Experimental new feature: before_begin() returns a
  // non-dereferenceable iterator that, when incremented, yields
  // begin().  This iterator may be used as the argument to
  // insert_after, erase_after, etc.  Note that even for an empty 
  // slist, before_begin() is not the same iterator as end().  It 
  // is always necessary to increment before_begin() at least once to
  // obtain end().
  iterator before_begin() { return iterator((_Node*) &this->_M_head); }
  const_iterator before_begin() const
    { return const_iterator((_Node*) &this->_M_head); }

  size_type size() const { return __slist_size(this->_M_head._M_next); }
  
  size_type max_size() const { return size_type(-1); }

  bool empty() const { return this->_M_head._M_next == 0; }

  void swap(slist& __x)
    { std::swap(this->_M_head._M_next, __x._M_head._M_next); }

public:

  reference front() { return ((_Node*) this->_M_head._M_next)->_M_data; }
  const_reference front() const 
    { return ((_Node*) this->_M_head._M_next)->_M_data; }
  void push_front(const value_type& __x)   {
    __slist_make_link(&this->_M_head, _M_create_node(__x));
  }
  void push_front() { __slist_make_link(&this->_M_head, _M_create_node()); }
  void pop_front() {
    _Node* __node = (_Node*) this->_M_head._M_next;
    this->_M_head._M_next = __node->_M_next;
    _Destroy(&__node->_M_data);
    this->_M_put_node(__node);
  }

  iterator previous(const_iterator __pos) {
    return iterator((_Node*) __slist_previous(&this->_M_head, __pos._M_node));
  }
  const_iterator previous(const_iterator __pos) const {
    return const_iterator((_Node*) __slist_previous(&this->_M_head,
                                                    __pos._M_node));
  }

private:
  _Node* _M_insert_after(_Node_base* __pos, const value_type& __x) {
    return (_Node*) (__slist_make_link(__pos, _M_create_node(__x)));
  }

  _Node* _M_insert_after(_Node_base* __pos) {
    return (_Node*) (__slist_make_link(__pos, _M_create_node()));
  }

  void _M_insert_after_fill(_Node_base* __pos,
                            size_type __n, const value_type& __x) {
    for (size_type __i = 0; __i < __n; ++__i)
      __pos = __slist_make_link(__pos, _M_create_node(__x));
  }

  // Check whether it's an integral type.  If so, it's not an iterator.
  template <class _InIter>
  void _M_insert_after_range(_Node_base* __pos, 
                             _InIter __first, _InIter __last) {