《STL源代码分析》---stl_list.h读书笔记

STL在列表list它是一种经常使用的容器。list不连续双向链表在内存，而且是环形。

理解列表如何操作的详细信息，然后。阅读STL名单上的代码是最好的方法。

G++ 2.91.57。cygnus\cygwin-b20\include\g++\stl_list.h 完整列表
 
/*
 *
 * 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.
 */
 
/* NOTE: This is an internal header file, included by other STL headers.
 *   You should not attempt to use it directly.
 */
 
#ifndef __SGI_STL_INTERNAL_LIST_H
#define __SGI_STL_INTERNAL_LIST_H
 
__STL_BEGIN_NAMESPACE
 
#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1174
#endif
 
// List结点结构，List是双向的
template <class T>
struct __list_node {
  typedef void* void_pointer;
  void_pointer next;  // 事实上能够设为 __list_node<T>*
  void_pointer prev;
  T data;
};
 
 
//list是一个双向链表，其迭代器能够向前移、向后移
//因此迭代器类型为bidirectional_iterator_tag
template<class T, class Ref, class Ptr>
struct __list_iterator { // 没有继承 std::iterator
  typedef __list_iterator<T, T&, T*>             iterator;
  typedef __list_iterator<T, const T&, const T*> const_iterator;
  typedef __list_iterator<T, Ref, Ptr>           self;
 
  // 没有继承 std::iterator，自定义迭代器5个类别
  typedef bidirectional_iterator_tag iterator_category;	 // (1)
  typedef T value_type; 			// (2)
  typedef Ptr pointer; 			// (3)
  typedef Ref reference; 			// (4)
  typedef __list_node<T>* link_type;
  typedef size_t size_type;
  typedef ptrdiff_t difference_type; // (5)
 
  link_type node;  // 原生态指针，指向实际的List结点
 
  //迭代器的构造函数
  __list_iterator(link_type x) : node(x) {}
  __list_iterator() {}
  __list_iterator(const iterator& x) : node(x.node) {}
 
  // 迭代器须要重载的运算符，为了支持标准算法STL
  bool operator==(const self& x) const { return node == x.node; }
  bool operator!=(const self& x) const { return node != x.node; }
  
  //对迭代器dereference。取的是迭代器所维护的结点的值
  reference operator*() const { return (*node).data; }	
 
#ifndef __SGI_STL_NO_ARROW_OPERATOR //假设支持->操作
  /*
  返回的是所维护结点的地址（能够理解为指针）。
  这时，能够把迭代器当作原生态指针来调用结点的函数
  */
  pointer operator->() const { return &(operator*()); }
#endif /* __SGI_STL_NO_ARROW_OPERATOR */
 
 
  //迭代器前进、后退的支持
  self& operator++() { 
    node = (link_type)((*node).next);  	
    return *this;
  }
  self operator++(int) { 
    self tmp = *this;
    ++*this;
    return tmp;
  }
  
  self& operator--() { 
    node = (link_type)((*node).prev); 
    return *this;
  }
  self operator--(int) { 
    self tmp = *this;
    --*this;
    return tmp;
  }
};
//假设编译器不支持partial specialization偏特性化
#ifndef __STL_CLASS_PARTIAL_SPECIALIZATION
template <class T, class Ref, class Ptr>
inline bidirectional_iterator_tag
iterator_category(const __list_iterator<T, Ref, Ptr>&) {
  return bidirectional_iterator_tag();
}
 
template <class T, class Ref, class Ptr>
inline T*
value_type(const __list_iterator<T, Ref, Ptr>&) {
  return 0;
}
 
template <class T, class Ref, class Ptr>
inline ptrdiff_t*
distance_type(const __list_iterator<T, Ref, Ptr>&) {
  return 0;
}
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
 
//以下是List的定义
template <class T, class Alloc = alloc> // 默觉得 alloc 为配置器
class list {
protected:
  typedef void* void_pointer;
  typedef __list_node<T> list_node;
  // List的空间配置器。每次仅仅配置一个结点
  typedef simple_alloc<list_node, Alloc> list_node_allocator;
public:      
  typedef T value_type;
  typedef value_type* pointer;
  typedef const value_type* const_pointer;
  typedef value_type& reference;
  typedef const value_type& const_reference;
  typedef list_node* link_type;
  typedef size_t size_type;
  typedef ptrdiff_t difference_type;
 
public:
/*
当开发人员定义一个迭代器时list<T>::iterator。首先调用的是
 __list_iterator<T, T&, T*>的构造函数。假设有初始值，便会
 因此设定迭代器和容器的联结关系
*/
  typedef __list_iterator<T, T&, T*>             iterator;
  typedef __list_iterator<T, const T&, const T*> const_iterator;
 
#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
  typedef reverse_iterator<const_iterator> const_reverse_iterator;
  typedef reverse_iterator<iterator> reverse_iterator;
#else /* __STL_CLASS_PARTIAL_SPECIALIZATION */
  typedef reverse_bidirectional_iterator<const_iterator, value_type,
  const_reference, difference_type>
  const_reverse_iterator;
  typedef reverse_bidirectional_iterator<iterator, value_type, reference,
  difference_type>
  reverse_iterator; 
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
 
protected:
  // 配置一个结点（未初始化）。返回其指针
  link_type get_node() { return list_node_allocator::allocate(); }
  // 释放一个结点
  void put_node(link_type p) { list_node_allocator::deallocate(p); }
 
  // 配置一个结点，并用x初始化
  link_type create_node(const T& x) {
    link_type p = get_node();
    __STL_TRY {
      construct(&p->data, x);	// 全局函数
    }
    __STL_UNWIND(put_node(p));
    return p;
  }
  // 销毁一个结点
  void destroy_node(link_type p) {
    destroy(&p->data); 		//全局函数
    put_node(p);
  }
 
protected:
	//初始化一个空链表。首尾相连
  void empty_initialize() { 
    node = get_node();	
    node->next = node;	
    node->prev = node;
  }
  //初始化长为n的链表。值都为value
  void fill_initialize(size_type n, const T& value) {
    empty_initialize();
    __STL_TRY {
      insert(begin(), n, value);
    }
    __STL_UNWIND(clear(); put_node(node));
  }
 
#ifdef __STL_MEMBER_TEMPLATES
  //以迭代器的区间初始化一个链表
  template <class InputIterator>
  void range_initialize(InputIterator first, InputIterator last) {
    empty_initialize();
    __STL_TRY {
      insert(begin(), first, last);
    }
	//commit or rollback
    __STL_UNWIND(clear(); put_node(node));
  }
#else  /* __STL_MEMBER_TEMPLATES */
  void range_initialize(const T* first, const T* last) {
    empty_initialize();
    __STL_TRY {
      insert(begin(), first, last);
    }
    __STL_UNWIND(clear(); put_node(node));
  }
  void range_initialize(const_iterator first, const_iterator last) {
    empty_initialize();
    __STL_TRY {
      insert(begin(), first, last);
    }
    __STL_UNWIND(clear(); put_node(node));
  }
#endif /* __STL_MEMBER_TEMPLATES */
 
protected:
  /*
  List仅仅维护这一个结点。它指向List未结点的下一个位置。即头结点。由于List是一个
  环形的双向链表。
  该结点是空结点，next指向头结点。

*/ link_type node; // 能够觉得它是哨兵结点（在算法导论中有讲哨兵结点） public: list() { empty_initialize(); } // 默认构造函数，空链表。 //指向头结点的迭代器 iterator begin() { return (link_type)((*node).next); } const_iterator begin() const { return (link_type)((*node).next); } //指向尾结点下一个位置的迭代器。所以返回node iterator end() { return node; } const_iterator end() const { return node; } reverse_iterator rbegin() { return reverse_iterator(end()); } const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); } reverse_iterator rend() { return reverse_iterator(begin()); } const_reverse_iterator rend() const { return const_reverse_iterator(begin()); } //链表仅仅有node结点时为空链表 bool empty() const { return node->next == node; } size_type size() const { size_type result = 0; distance(begin(), end(), result); // 在<stl_iterator.h>定义，result是引用传递 return result; } //链表最大容量。没什么意义吧？ size_type max_size() const { return size_type(-1); } // 取链表头结点的内容 reference front() { return *begin(); } const_reference front() const { return *begin(); } // 取链表尾结点的内容 reference back() { return *(--end()); } const_reference back() const { return *(--end()); } //交换两个链表 void swap(list<T, Alloc>& x) { __STD::swap(node, x.node); } // 在迭代器 position 所指位置前插入一个结点。其值为x。

//在函数中 tmp为指针。返回的却是迭代器 iterator insert(iterator position, const T& x) { link_type tmp = create_node(x); // 生成结点并用x初始化 // 调整指针 tmp->next = position.node; tmp->prev = position.node->prev; //prev和next指针都是void*，所以须要指针类型转换 (link_type(position.node->prev))->next = tmp; position.node->prev = tmp; return tmp; } //在迭代器 position 所指位置前插入一个结点，其值为T的默认值。这也说明List的元素要有默认构造函数 iterator insert(iterator position) { return insert(position, T()); } //在position所指位置前插入多个元素 #ifdef __STL_MEMBER_TEMPLATES template <class InputIterator> void insert(iterator position, InputIterator first, InputIterator last); #else /* __STL_MEMBER_TEMPLATES */ void insert(iterator position, const T* first, const T* last); void insert(iterator position, const_iterator first, const_iterator last); #endif /* __STL_MEMBER_TEMPLATES */ void insert(iterator pos, size_type n, const T& x); void insert(iterator pos, int n, const T& x) { insert(pos, (size_type)n, x); } void insert(iterator pos, long n, const T& x) { insert(pos, (size_type)n, x); } // 在头结点前插入元素 void push_front(const T& x) { insert(begin(), x); } // 在尾结点后插入元素 void push_back(const T& x) { insert(end(), x); } // 移除迭代器 position 所指结点 iterator erase(iterator position) { link_type next_node = link_type(position.node->next); link_type prev_node = link_type(position.node->prev); prev_node->next = next_node; next_node->prev = prev_node; destroy_node(position.node); return iterator(next_node); } iterator erase(iterator first, iterator last); void resize(size_type new_size, const T& x); void resize(size_type new_size) { resize(new_size, T()); } void clear(); // 移除头结点 void pop_front() { erase(begin()); } // 移除尾结点 void pop_back() { iterator tmp = end(); erase(--tmp); } //几个构造函数 list(size_type n, const T& value) { fill_initialize(n, value); } list(int n, const T& value) { fill_initialize(n, value); } list(long n, const T& value) { fill_initialize(n, value); } explicit list(size_type n) { fill_initialize(n, T()); } //用迭代器区间初始化List #ifdef __STL_MEMBER_TEMPLATES template <class InputIterator> list(InputIterator first, InputIterator last) { range_initialize(first, last); } #else /* __STL_MEMBER_TEMPLATES */ list(const T* first, const T* last) { range_initialize(first, last); } list(const_iterator first, const_iterator last) { range_initialize(first, last); } #endif /* __STL_MEMBER_TEMPLATES */ //用一个List初始化 list(const list<T, Alloc>& x) { range_initialize(x.begin(), x.end()); } ~list() { clear();//清除全部结点。哨兵结点除外 put_node(node);//释放唯一的一个结点 } list<T, Alloc>& operator=(const list<T, Alloc>& x); protected: // 将[first,last) 內的全部元素搬移到position 前，不包含last元素。

void transfer(iterator position, iterator first, iterator last) { if (position != last) { /* 要把[first,last)在原有链表去除，然后安接到position前 (1)-(7)步相应后面的图 */ (*(link_type((*last.node).prev))).next = position.node; // (1) (*(link_type((*first.node).prev))).next = last.node; // (2) (*(link_type((*position.node).prev))).next = first.node; // (3) link_type tmp = link_type((*position.node).prev); // (4) (*position.node).prev = (*last.node).prev; // (5) (*last.node).prev = (*first.node).prev; // (6) (*first.node).prev = tmp; // (7) } } public: // 將 x 链表插入到 position 所指位置之前。x 不是 *this。

void splice(iterator position, list& x) { if (!x.empty()) transfer(position, x.begin(), x.end()); } // 將 i 所指元素插入到 position 所指位置之前。position 和i 可在同一个list。 void splice(iterator position, list&, iterator i) { iterator j = i; ++j; if (position == i || position == j) return; transfer(position, i, j); } // 將 [first,last) 內的全部元素插入到 position 所指位置之前。 // position 和[first,last)可指在同一个list， // 但position不能位于[first,last)之內。 void splice(iterator position, list&, iterator first, iterator last) { if (first != last) transfer(position, first, last); } void remove(const T& value); void unique(); void merge(list& x); void reverse(); void sort(); #ifdef __STL_MEMBER_TEMPLATES template <class Predicate> void remove_if(Predicate); template <class BinaryPredicate> void unique(BinaryPredicate); template <class StrictWeakOrdering> void merge(list&, StrictWeakOrdering); template <class StrictWeakOrdering> void sort(StrictWeakOrdering); #endif /* __STL_MEMBER_TEMPLATES */ friend bool operator== __STL_NULL_TMPL_ARGS (const list& x, const list& y); }; //推断2个链表是否同样 template <class T, class Alloc> inline bool operator==(const list<T,Alloc>& x, const list<T,Alloc>& y) { typedef typename list<T,Alloc>::link_type link_type; link_type e1 = x.node; link_type e2 = y.node; link_type n1 = (link_type) e1->next; link_type n2 = (link_type) e2->next; for ( ; n1 != e1 && n2 != e2 ; n1 = (link_type) n1->next, n2 = (link_type) n2->next) if (n1->data != n2->data) return false; return n1 == e1 && n2 == e2; } //lexicographical_compare是STL算法 template <class T, class Alloc> inline bool operator<(const list<T, Alloc>& x, const list<T, Alloc>& y) { return lexicographical_compare(x.begin(), x.end(), y.begin(), y.end()); } #ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER template <class T, class Alloc> //交换两个链表 inline void swap(list<T, Alloc>& x, list<T, Alloc>& y) { x.swap(y); } #endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */ #ifdef __STL_MEMBER_TEMPLATES //在position之前插入迭代器区间的元素 template <class T, class Alloc> template <class InputIterator> void list<T, Alloc>::insert(iterator position, InputIterator first, InputIterator last) { for ( ; first != last; ++first) insert(position, *first); } #else /* __STL_MEMBER_TEMPLATES */ template <class T, class Alloc> void list<T, Alloc>::insert(iterator position, const T* first, const T* last) { for ( ; first != last; ++first) insert(position, *first); } template <class T, class Alloc> void list<T, Alloc>::insert(iterator position, const_iterator first, const_iterator last) { for ( ; first != last; ++first) insert(position, *first); } #endif /* __STL_MEMBER_TEMPLATES */ //在position位置之前插入n个元素x template <class T, class Alloc> void list<T, Alloc>::insert(iterator position, size_type n, const T& x) { for ( ; n > 0; --n) insert(position, x); } //擦除两个迭代器区间之间的元素 template <class T, class Alloc> list<T,Alloc>::iterator list<T, Alloc>::erase(iterator first, iterator last) { while (first != last) erase(first++); return last; } /* 又一次调整链表大小为 new_size 假设new_size大于原来的链表。则在链表末尾插入x 假设new_size小于原来的链表，则在末尾直接擦除多余的元素 */ template <class T, class Alloc> void list<T, Alloc>::resize(size_type new_size, const T& x) { iterator i = begin(); size_type len = 0; for ( ; i != end() && len < new_size; ++i, ++len) ; if (len == new_size) erase(i, end()); else // i == end() insert(end(), new_size - len, x); } // 清除全部结点，（哨兵结点除外） template <class T, class Alloc> void list<T, Alloc>::clear() { link_type cur = (link_type) node->next; // begin() while (cur != node) { link_type tmp = cur; cur = (link_type) cur->next; destroy_node(tmp); } // 恢复哨兵结点。链表此时为空链表 node->next = node; node->prev = node; } //重载赋值=操作符 template <class T, class Alloc> list<T, Alloc>& list<T, Alloc>::operator=(const list<T, Alloc>& x) { if (this != &x) {//防止自身赋值 iterator first1 = begin(); iterator last1 = end(); const_iterator first2 = x.begin(); const_iterator last2 = x.end(); //通过更改结点的值来赋值 while (first1 != last1 && first2 != last2) *first1++ = *first2++; /* 假设x链表小于this链表，擦除多余的。否则在this后面插入 */ if (first2 == last2) erase(first1, last1); else insert(last1, first2, last2); } return *this; } // 将数值为value的结点移除 template <class T, class Alloc> void list<T, Alloc>::remove(const T& value) { iterator first = begin(); iterator last = end(); while (first != last) { // 巡访每一個節點 iterator next = first; ++next; if (*first == value) erase(first); // 找到就移除 first = next; } } // 移除数值同样的连续元素 template <class T, class Alloc> void list<T, Alloc>::unique() { iterator first = begin(); iterator last = end(); if (first == last) return; iterator next = first; while (++next != last) { if (*first == *next)//假设数值同样，则移除后面的那个 erase(next); else first = next; next = first; } } //将x合并到*this上面。两个链表都要先经过递增排序。相当于合并排序的最后一步 template <class T, class Alloc> void list<T, Alloc>::merge(list<T, Alloc>& x) { iterator first1 = begin(); iterator last1 = end(); iterator first2 = x.begin(); iterator last2 = x.end(); //注意：此时已经假设两个链表都已经非递减排序好了 while (first1 != last1 && first2 != last2) if (*first2 < *first1) { iterator next = first2; transfer(first1, first2, ++next); first2 = next; } else ++first1; if (first2 != last2) transfer(last1, first2, last2); } // 将 *this 的內容逆向重置 template <class T, class Alloc> void list<T, Alloc>::reverse() { //假设链表是空，或者仅仅有一个元素，就不做不论什么处理 //不是用size()==0或size()==1来推断。由于这样比較慢 if (node->next == node || link_type(node->next)->next == node) return; iterator first = begin(); ++first; while (first != end()) { iterator old = first; ++first; transfer(begin(), old, first); } } /* STL的sort算法仅仅能接受迭代器类型为RamdonAccessIterator的容器。所以list无法 使用，故自己重写排序算法。这里使用的是高速排序。详细能够參考这里：<a target=_blank href="http://blog.csdn.net/zhizichina/article/details/7538974">http://blog.csdn.net/zhizichina/article/details/7538974</a> */ template <class T, class Alloc> void list<T, Alloc>::sort() { if (node->next == node || link_type(node->next)->next == node) return; // carry作为tmp list<T, Alloc> carry; list<T, Alloc> counter[64]; int fill = 0; while (!empty()) { carry.splice(carry.begin(), *this, begin()); int i = 0; while(i < fill && !counter[i].empty()) { counter[i].merge(carry); carry.swap(counter[i++]); } carry.swap(counter[i]); if (i == fill) ++fill; } for (int i = 1; i < fill; ++i) counter[i].merge(counter[i-1]); swap(counter[fill-1]); } #ifdef __STL_MEMBER_TEMPLATES /* pred是一个函数，假设容器内的元素经过pred函数推断为真。则移除 */ template <class T, class Alloc> template <class Predicate> void list<T, Alloc>::remove_if(Predicate pred) { iterator first = begin(); iterator last = end(); while (first != last) { iterator next = first; ++next; if (pred(*first)) erase(first); first = next; } } /* 依据函数binary_pred来推断是否移除两个相邻的结点 */ template <class T, class Alloc> template <class BinaryPredicate> void list<T, Alloc>::unique(BinaryPredicate binary_pred) { iterator first = begin(); iterator last = end(); if (first == last) return; iterator next = first; while (++next != last) { if (binary_pred(*first, *next)) erase(next); else first = next; next = first; } } /* 假设两个链表均已经有序，用comp函数来推断怎样合并两个链表 */ template <class T, class Alloc> template <class StrictWeakOrdering> void list<T, Alloc>::merge(list<T, Alloc>& x, StrictWeakOrdering comp) { iterator first1 = begin(); iterator last1 = end(); iterator first2 = x.begin(); iterator last2 = x.end(); while (first1 != last1 && first2 != last2) if (comp(*first2, *first1)) { iterator next = first2; transfer(first1, first2, ++next); first2 = next; } else ++first1; if (first2 != last2) transfer(last1, first2, last2); } /* 用函数comp来推断怎样排序链表 */ template <class T, class Alloc> template <class StrictWeakOrdering> void list<T, Alloc>::sort(StrictWeakOrdering comp) { if (node->next == node || link_type(node->next)->next == node) return; list<T, Alloc> carry; list<T, Alloc> counter[64]; int fill = 0; while (!empty()) { carry.splice(carry.begin(), *this, begin()); int i = 0; while(i < fill && !counter[i].empty()) { counter[i].merge(carry, comp); carry.swap(counter[i++]); } carry.swap(counter[i]); if (i == fill) ++fill; } for (int i = 1; i < fill; ++i) counter[i].merge(counter[i-1], comp); swap(counter[fill-1]); } #endif /* __STL_MEMBER_TEMPLATES */ #if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32) #pragma reset woff 1174 #endif __STL_END_NAMESPACE #endif /* __SGI_STL_INTERNAL_LIST_H */ // Local Variables: // mode:C++ // End:

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