C++标准库STL部分代码学习（源码之前，了无秘密）

#include<iostream>
using namespace std;
#include<memory.h>  

// alloc是SGI STL的空间配置器
template <class T, class Alloc = alloc>
class vector
{
public:
    // vector的嵌套类型定义,typedef用于提供iterator_traits<I>支持
    typedef T value_type;
    typedef value_type* pointer;
    typedef value_type* iterator;
    typedef value_type& reference;
    typedef size_t size_type;
    typedef ptrdiff_t difference_type;
protected:
    // 这个提供STL标准的allocator接口
    typedef simple_alloc <value_type, Alloc> data_allocator;

    iterator start;               // 表示目前使用空间的头
    iterator finish;              // 表示目前使用空间的尾
    iterator end_of_storage;      // 表示实际分配内存空间的尾

    void insert_aux(iterator position, const T& x);

    // 释放分配的内存空间
    void deallocate()
    {
        // 由于使用的是data_allocator进行内存空间的分配,
        // 所以需要同样使用data_allocator::deallocate()进行释放
        // 如果直接释放, 对于data_allocator内部使用内存池的版本
        // 就会发生错误
        if (start)
            data_allocator::deallocate(start, end_of_storage - start);
    }

    void fill_initialize(size_type n, const T& value)
    {
        start = allocate_and_fill(n, value);
        finish = start + n;                         // 设置当前使用内存空间的结束点
        // 构造阶段, 此实作不多分配内存,
        // 所以要设置内存空间结束点和, 已经使用的内存空间结束点相同
        end_of_storage = finish;
    }

public:
    // 获取几种迭代器
    iterator begin() { return start; }	
    iterator end() { return finish; }

    // 返回当前对象个数
    size_type size() const { return size_type(end() - begin()); }	//我想，这里的size()花费的应该是常数时间吧
    size_type max_size() const { return size_type(-1) / sizeof(T); }
    // 返回重新分配内存前最多能存储的对象个数
    size_type capacity() const { return size_type(end_of_storage - begin()); }
    bool empty() const { return begin() == end(); }	//其实这里的empty和size花费相差不会很大吧
    reference operator[](size_type n) { return *(begin() + n); }

    // 本实作中默认构造出的vector不分配内存空间
    vector() : start(0), finish(0), end_of_storage(0) {}

    vector(size_type n, const T& value) { fill_initialize(n, value); }
    vector(int n, const T& value) { fill_initialize(n, value); }
    vector(long n, const T& value) { fill_initialize(n, value); }

    // 需要对象提供默认构造函数
    explicit vector(size_type n) { fill_initialize(n, T()); }

    vector(const vector<T, Alloc>& x)
    {
        start = allocate_and_copy(x.end() - x.begin(), x.begin(), x.end());
        finish = start + (x.end() - x.begin());
        end_of_storage = finish;
    }

	//没有纯虚析构函数哦
    ~vector()
    {
        // 析构对象
        destroy(start, finish);
        // 释放内存
        deallocate();
    }

    vector<T, Alloc>& operator=(const vector<T, Alloc>& x);

    // 提供访问函数
    reference front() { return *begin(); }
    reference back() { return *(end() - 1); }

    
    // 向容器尾追加一个元素, 可能导致内存重新分配
    
    //                          push_back(const T& x)
    //                                   |
    //                                   |---------------- 容量已满?
    //                                   |
    //               ----------------------------
    //           No  |                          |  Yes
    //               |                          |
    //               ↓                          ↓
    //      construct(finish, x);       insert_aux(end(), x);
    //      ++finish;                           |
    //                                          |------ 内存不足, 重新分配
    //                                          |       大小为原来的2倍
    //      new_finish = data_allocator::allocate(len);       <stl_alloc.h>
    //      uninitialized_copy(start, position, new_start);   <stl_uninitialized.h>
    //      construct(new_finish, x);                         <stl_construct.h>
    //      ++new_finish;
    //      uninitialized_copy(position, finish, new_finish); <stl_uninitialized.h>
    

    void push_back(const T& x)
    {
        // 内存满足条件则直接追加元素, 否则需要重新分配内存空间
        if (finish != end_of_storage)
        {
            construct(finish, x);
            ++finish;
        }
        else
            insert_aux(end(), x);
    }


    
    // 在指定位置插入元素
    
    //                   insert(iterator position, const T& x)
    //                                   |
    //                                   |------------ 容量是否足够 && 是否是end()?
    //                                   |
    //               -------------------------------------------
    //            No |                                         | Yes
    //               |                                         |
    //               ↓                                         ↓
    //    insert_aux(position, x);                  construct(finish, x);
    //               |                              ++finish;
    //               |-------- 容量是否够用?
    //               |
    //        --------------------------------------------------
    //    Yes |                                                | No
    //        |                                                |
    //        ↓                                                |
    // construct(finish, *(finish - 1));                       |
    // ++finish;                                               |
    // T x_copy = x;                                           |
    // copy_backward(position, finish - 2, finish - 1);        |
    // *position = x_copy;                                     |
    //                                                         ↓
    // data_allocator::allocate(len);                       <stl_alloc.h>
    // uninitialized_copy(start, position, new_start);      <stl_uninitialized.h>
    // construct(new_finish, x);                            <stl_construct.h>
    // ++new_finish;
    // uninitialized_copy(position, finish, new_finish);    <stl_uninitialized.h>
    // destroy(begin(), end());                             <stl_construct.h>
    // deallocate();
    

    iterator insert(iterator position, const T& x)
    {
        size_type n = position - begin();
        if (finish != end_of_storage && position == end())
        {
            construct(finish, x);
            ++finish;
        }
        else
            insert_aux(position, x);
        return begin() + n;
    }

    iterator insert(iterator position) { return insert(position, T()); }

    void pop_back()
    {
        --finish;
        destroy(finish);
    }

    iterator erase(iterator position)
    {
        if (position + 1 != end())
            copy(position + 1, finish, position);
        --finish;
        destroy(finish);
        return position;
    }


    iterator erase(iterator first, iterator last)
    {
        iterator i = copy(last, finish, first);
        // 析构掉需要析构的元素
        destroy(i, finish);
        finish = finish - (last - first);
        return first;
    }

    // 调整size, 但是并不会重新分配内存空间
    void resize(size_type new_size, const T& x)
    {
        if (new_size < size())
            erase(begin() + new_size, end());
        else
            insert(end(), new_size - size(), x);
    }
    void resize(size_type new_size) { resize(new_size, T()); }

    void clear() { erase(begin(), end()); }

protected:
    // 分配空间, 并且复制对象到分配的空间处
    iterator allocate_and_fill(size_type n, const T& x)
    {
        iterator result = data_allocator::allocate(n);
        uninitialized_fill_n(result, n, x);
        return result;
    }

    // 提供插入操作
    
    //                 insert_aux(iterator position, const T& x)
    //                                   |
    //                                   |---------------- 容量是否足够?
    //                                   ↓
    //              -----------------------------------------
    //        Yes   |                                       | No
    //              |                                       |
    //              ↓                                       |
    // 从opsition开始, 整体向后移动一个位置                     |
    // construct(finish, *(finish - 1));                    |
    // ++finish;                                            |
    // T x_copy = x;                                        |
    // copy_backward(position, finish - 2, finish - 1);     |
    // *position = x_copy;                                  |
    //                                                      ↓
    //                            data_allocator::allocate(len);
    //                            uninitialized_copy(start, position, new_start);
    //                            construct(new_finish, x);
    //                            ++new_finish;
    //                            uninitialized_copy(position, finish, new_finish);
    //                            destroy(begin(), end());
    //                            deallocate();
    

    template <class T, class Alloc>
    void insert_aux(iterator position, const T& x)
    {
        if (finish != end_of_storage)    // 还有备用空间
        {
            // 在备用空间起始处构造一个元素，并以vector最后一个元素值为其初值
            construct(finish, *(finish - 1));
            ++finish;
            T x_copy = x;
            copy_backward(position, finish - 2, finish - 1);
            *position = x_copy;
        }
        else   // 已无备用空间
        {
            const size_type old_size = size();
            const size_type len = old_size != 0 ? 2 * old_size : 1;
            // 以上配置元素：如果大小为0，则配置1（个元素大小）
            // 如果大小不为0，则配置原来大小的两倍
            // 前半段用来放置原数据，后半段准备用来放置新数据

            iterator new_start = data_allocator::allocate(len);  // 实际配置
            iterator new_finish = new_start;
            // 将内存重新配置
            try
            {
                // 将原vector的安插点以前的内容拷贝到新vector
                new_finish = uninitialized_copy(start, position, new_start);
                // 为新元素设定初值 x
                construct(new_finish, x);
                // 调整水位
                ++new_finish;
                // 将安插点以后的原内容也拷贝过来
                new_finish = uninitialized_copy(position, finish, new_finish);
            }
            catch(...)
            {
                // 回滚操作
                destroy(new_start, new_finish);
                data_allocator::deallocate(new_start, len);
                throw;
            }
            // 析构并释放原vector
            destroy(begin(), end());
            deallocate();

            // 调整迭代器，指向新vector
            start = new_start;
            finish = new_finish;
            end_of_storage = new_start + len;
        }
    }

    
    // 在指定位置插入n个元素
    
    //             insert(iterator position, size_type n, const T& x)
    //                                   |
    //                                   |---------------- 插入元素个数是否为0?
    //                                   ↓
    //              -----------------------------------------
    //        No    |                                       | Yes
    //              |                                       |
    //              |                                       ↓
    //              |                                    return;
    //              |----------- 内存是否足够?
    //              |
    //      -------------------------------------------------
    //  Yes |                                               | No
    //      |                                               |
    //      |------ (finish - position) > n?                |
    //      |       分别调整指针                              |
    //      ↓                                               |
    //    ----------------------------                      |
    // No |                          | Yes                  |
    //    |                          |                      |
    //    ↓                          ↓                      |
    // 插入操作, 调整指针           插入操作, 调整指针           |
    //                                                      ↓
    //            data_allocator::allocate(len);
    //            new_finish = uninitialized_copy(start, position, new_start);
    //            new_finish = uninitialized_fill_n(new_finish, n, x);
    //            new_finish = uninitialized_copy(position, finish, new_finish);
    //            destroy(start, finish);
    //            deallocate();
    

    template <class T, class Alloc>
    void insert(iterator position, size_type n, const T& x)	//注意看，这里传进来的是拷贝
    {
        // 如果n为0则不进行任何操作
        if (n != 0)
        {
            if (size_type(end_of_storage - finish) >= n)
            {      // 剩下的备用空间大于等于“新增元素的个数”
                T x_copy = x;
                // 以下计算插入点之后的现有元素个数
                const size_type elems_after = finish - position;
                iterator old_finish = finish;
                if (elems_after > n)
                {
                    // 插入点之后的现有元素个数 大于 新增元素个数
                    uninitialized_copy(finish - n, finish, finish);
                    finish += n;    // 将vector 尾端标记后移
                    copy_backward(position, old_finish - n, old_finish);
                    fill(position, position + n, x_copy); // 从插入点开始填入新值
                }
                else
                {
                    // 插入点之后的现有元素个数 小于等于 新增元素个数
                    uninitialized_fill_n(finish, n - elems_after, x_copy);
                    finish += n - elems_after;
                    uninitialized_copy(position, old_finish, finish);
                    finish += elems_after;
                    fill(position, old_finish, x_copy);
                }
            }
            else
            {   // 剩下的备用空间小于“新增元素个数”（那就必须配置额外的内存）
                // 首先决定新长度：就长度的两倍 ， 或旧长度+新增元素个数
                const size_type old_size = size();
                const size_type len = old_size + max(old_size, n);
                // 以下配置新的vector空间
                iterator new_start = data_allocator::allocate(len);
                iterator new_finish = new_start;
                __STL_TRY
                {
                    // 以下首先将旧的vector的插入点之前的元素复制到新空间
                    new_finish = uninitialized_copy(start, position, new_start);
                    // 以下再将新增元素（初值皆为n）填入新空间
                    new_finish = uninitialized_fill_n(new_finish, n, x);
                    // 以下再将旧vector的插入点之后的元素复制到新空间
                    new_finish = uninitialized_copy(position, finish, new_finish);
                }
#         ifdef  __STL_USE_EXCEPTIONS
                catch(...)
                {
                    destroy(new_start, new_finish);
                    data_allocator::deallocate(new_start, len);
                    throw;
                }
#         endif /* __STL_USE_EXCEPTIONS */
                destroy(start, finish);
                deallocate();
                start = new_start;
                finish = new_finish;
                end_of_storage = new_start + len;
            }
        }
    }
};

template <class T, class Alloc = alloc>
class list {
···

public:
  list() { empty_initialize(); }

  iterator begin() { return (link_type)((*node).next); }
  const_iterator begin() const { return (link_type)((*node).next); }
  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());
  }
  
  bool empty() const { return node->next == node; }
  size_type size() const {
      size_type result = 0;
      distance(begin(), end(), result);
      return result;
    }
  size_type max_size() const { return size_type(-1); 
  
  reference front() { return *begin(); }
  const_reference front() const { return *begin(); }
  reference back() { return *(--end()); }
  const_reference back() const { return *(--end()); }
  void swap(list<T, Alloc>& x) { __STD::swap(node, x.node); }
  
  iterator insert(iterator position, const T& x) {
      link_type tmp = create_node(x);
      tmp->next = position.node;
      tmp->prev = position.node->prev;
      (link_type(position.node->prev))->next = tmp;
      position.node->prev = tmp;
      return tmp;
 }
 iterator insert(iterator position) { return insert(position, T()); }

 template <class InputIterator>
 void insert(iterator position, InputIterator first, InputIterator last);

 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);
 }

 void push_front(const T& x) { insert(begin(), x); }
 void push_back(const T& x) { insert(end(), x); }
      
 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();

 void pop_front() { erase(begin()); }
 void pop_back() {
      iterator tmp = end();
      erase(--tmp);
 }
      
 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()); }

    #ifdef __STL_MEMBER_TEMPLATES
      template <class InputIterator>
      list(InputIterator first, InputIterator last) {
        range_initialize(first, last);
      }

      list(const list<T, Alloc>& x) {
        range_initialize(x.begin(), x.end());
      }
      ~list() {
        clear();
        put_node(node);
      }
      list<T, Alloc>& operator=(const list<T, Alloc>& x);

   ···
   
    public:
      void splice(iterator position, list& x) {
        if (!x.empty())
          transfer(position, x.begin(), x.end());
      }
      void splice(iterator position, list&, iterator i) {
        iterator j = i;
        ++j;
        if (position == i || position == j) return;
        transfer(position, i, j);
      }
      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();

      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);

      friend bool operator== __STL_NULL_TMPL_ARGS (const list& x, const list& y);
    };