stl源码剖析 详细学习笔记deque（3）
protected:
typedef simple_alloc<value_type,Alloc> data_allocator;
//用来配置元素的alloc
typedef simple_alloc<pointer,Alloc> map_allocator;
//用来配置指针的alloc
deque(int n,const value_type& value)
:start(),finish(),map(0),map_size(0)
{
fill_initialize(n,value);
}
//fill_initialize
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::fill_initialize(size_t n,
const value_type& value)
{
//可以分配一定数量(略大于需求量)的内存
create_map_and_nodes(n);
map_pointer cur;
__STL_TRY
{
//这里初始化start之后finish之前的所有元素
//这里的cur不是元素，而是一个map_ponter,*cur才是node (*cur).cur才是元素
for(cur=start.node;cur<finish.node;++cur)
uninitialized_fill(*cur,*cur+buffer_size(),value);
//最后一块缓存区(finish)不一定全部有元素，所以只要初始化到finish.cur前面一个的位置
uninitialized_fill(finish.first,finish.cur,value);
}
catch(...)
{
...
}
}
//create_map_and_nodes
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::create_map_and_nodes(size_type num_elements)
{
//得到缓存区的数量
size_type num_nodes=num_elements / buffer_size() + 1;
//取 8 或 缓存区数量+2
map_size = max(initial_map_size(),num_nodes + 2);
//分配map_size大小(所以node)的内存
map=map_allocator::allocate(map_size);
// map_size - num_nodes == 已经分配的内存中 不需要初始化的部分
// (map_size - num_nodes) / 2 表示前后各一半
map_pointer nstart = map + (map_size - num_nodes) / 2;
map_pointer nfinish = nstart + num_nodes -1;
//cur:{T**}
map_pointer cur;
__STL_TRY
{
//pointer allocate_node(){return data_allocator::allocate(buffer_size());}
//分配buffer_size()大小(一个缓存区大小)的内存
for(cur=nstart;cur <= nfinish;++cur)
{
*cur=allocate_node();
}
}
catch(...)
{
...
}
start.set_node(nstart);
finish.set_node(nfinish);
start.cur=start.first;
finish.cur=finish.first + num_elements % buffer_size();
}
//push_back
public:
void push_back(const value_type& t)
{
if( finish.cur != finish.last -1)
{
//使用finish缓存区的未使用空间，构造元素
//如果是必要的 会一个个调用构造函数，不然就一起构造了
construct(finish.cur , t);
++finish.cur;
}
else
//当finish只剩下 一个一下 的空间时调用(最后一个使last不能存数据,
//使finish能指向一个空的缓存区
push_back_aux(t);
}
//push_back_aux
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::push_back_aux(const value_type& t)
{
value_type t_copy=t;
reserve_map_at_back();
*(finish.node + 1) = allocate_node();
__STL_TRY
{
construct(finish.cur , t_copy);
finish.set_node(finish.node + 1);
finish.cur = finish.first;
}
//deallocate_node(pointer n){ data_allocator::deallocate(n,buffer_size());}
__STL_UNWIND(deallocate_node(*(finish.node + 1)));
}
//push_front
void push_front(const value_type& t)
{
if(start.cur != start.first)
{
construct(start.cur-1,t);
--start.cur;
}
else
push_front_aux(t);
}
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::push_front_aux(const value_type& t)
{
value_type t_copy =t;
reserve_map_at_front();
*(start.node - 1) = allocate_node();
__STL_TRY
{
start.set_node(start.node - 1);
start.cur=start.last - 1;
construct(start.cur , t_copy);
}
catch(..)
{
start.set_node(start.node + 1);
start.cur=start.first;
//deallocate_node(pointer n){ data_allocator::deallocate(n,buffer_size());}
deallocate_node(*(start.node - 1));
}
}
void reserve_map_at_back (size_type nodes_to_add = 1)
{
// l= map + map_size ==最后的node之后一个越界的node
// l-finish.node -1 == 剩下的node个数
// nodes_to_add > l - finish.node -1 不需要重新分配内存
if(nodes_to_add + 1 > map_size - (finish.node - map))
reallocate_map(nodes_to_add,false);//false表示在尾部重分配
}
void reserve_map_at_front (size_type nodes_to_add = 1)
{
//同上
if(nodes_to_add >start.node - map)
reallocate_map(nodes_to_add,true);
}
//reallocate_map
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::reallocate_map(size_type nodes_to_add,
bool add_at_front)
{
size_type ole_num_nodes = finish.node - start.node + 1;
size_type new_num_nodes = ole_num_nodes + nodes_to_add;
map_pointer new_nstart;//T**类型
if(map_size > 2 * new_num_nodes)
{ //剩余的node内存数量是 两倍的 新的node数量 时调用
/*
最后要使头尾剩下的可分配(未使用)的node数量一样
如果是add_at_front 接下来会在头部添加 nodes_to_add数量的node
如果是add_at_front 接下来会在尾部添加
说到底 这个reallocate函数并不添加node,他的使命是确保有足够的
nodes给前面的aux函数使用
*/
new_nstart = map + (map_size - new_num_nodes) / 2
+ (add_at_front ? nodes_to_add : 0);
//防止覆盖问题
if(new_nstart < start.node)
copy(start.node , finish.node + 1, new_nstart);
else
copy_backward(start.node, finish.node + 1, new_nstart + ole_num_nodes);
}
else
{ //剩下的没有两倍就 重新分配一块nodes内存
//新的缓存区起码要留map_size+2 的大小
size_type new_map_size = map_size + max(map_size, nodes_to_add) + 2;
map_pointer new_map =map_allocator::allocate(new_map_size);
//同上
new_nstart = new_map + (new_map_size - new_num_nodes) / 2
+ (add_at_front ? nodes_to_add : 0);
copy(start.node, finish,node +1, new_nstart);
map_allocator::deallocate(map,map_size);
map=new_map;
map_size = new_map_size;
}
start.set_node(new_nstart);
finish.set_node(new_nstart + ole_num_nodes);
}
//pop_back
void pop_back()
{
if(finish.cur != finish.first)
{
--finish.cur;
destroy(finish.cur);
}
else
pop_back_aux();
}
//pop_back_aux
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::pop_back_aux()
{
//释放finish的缓存，使finish指向前一个node末尾
//deallocate_node(pointer n){ data_allocator::deallocate(n,buffer_size());}
deallocate_node(finish.first);
finish.set_node(finish.node - 1);
finish.cur = finish.last -1;
destroy(finish.cur);
}
//pop_front
void pop_front()
{
if(start.cur != start.last -1 )
{
destroy(start.cur)
++start.cur;
}
else
pop_front_aux();
}
//pop_front_aux
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::pop_front_aux()
{
destroy(start.cur);
deallocate_node(start.first);
start.set_node(start.node +1);
start.cur = start.first;
}
//clear
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::clear()
{
for(map_pointer node = start.node +1; node < finish.node; ++node)
{
//先析构，再清除内存
destroy(*node, *node + buffer_size());
data_allocator::deallocate(*node, buffer_size());
}
if(start.node != finish.node)
{//在clear之前有大于等于两个node时调用
destroy(start.cur, start.last);
destroy(finish.first, finish.cur);
data_allocator::deallocate(finish.first, buffer_size());
}
else
{//在clear之前finish 和start指向同一个node；
destroy(start.cur, finish.cur);
}
//前面都保存了一个node的内存,没有释放所有内存
finish = start;
}
//erase
iterator erase(iterator pos)
{
iterator next = pos;
++next;
diffenrence_type index = pos - start;
if(index < (size() >> 1))
{//如果前面元素少，就从前开始拷贝前面的元素来填充(覆盖)当前元素，反之就从后开始拷贝
copy_backward(start, pos, next);
pop_front();
}
else
{
copy(next, finish, pos);
pop_back();
}
return start + index;
}
//erase 区间
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::erase(iterator first, iterator last)
{
if(first == start && last == finish)
{//如果是全部删除 直接调用clear()
clear();
return finish;
}
else
{
diffenrence_type n = last - first;
//最开始的元素到要删除的迭代器的第一个元素的元素个数
diffenrence_type elems_before = first -start;
if(elems_before < (size() - n) / 2)
{//前面的元素比较少就调用
copy_backward(start, first, last)
iterator new_start = start + n;
destroy(start, new_start);
for(map_pointer cur =start.node; cur < new_start.node; ++cur)
data_allocator::deallocate(*cur, buffer_size());
setart = new_start;
}
else
{
copy(last, finish,first);
iterator new_finish = finish -n;
destroy(new_finish, finish);
for(map_pointer cur =new_finish.node + 1; cur< finish.node; ++cur)
data_allocator::deallocate(*cur, buffer_size());
finish = new_finish;
}
return start + elems_before;
}
}
iterator insert(iterator position, const value_type& x)
{
if(position.cur == start.cur)
{
push_front(x);
return start;
}
else if(position.cur == finish.cur)
{
push_back(x);
iterator tmp = finish;
--tmp;
return tmp;
}
else
{
return insert_aux(position,x);
}
}
//insert_aux
template<class T,class Alloc,size_t BufSize>
void deque<T,Alloc,BufSize>::insert_aux(iterator pos, const value_type& x)
{
diffenrence_type index = pos - start;
value_type x_copy = x;
if(index < size() / 2)
{//哪边元素少就移动哪边
//新加一个元素到头部
push_front(front());
//设置要移动的各项位置
iterator front1 = start;
++front1;
iterator front2 = front1;
++front2;
//由于新加了一个元素 内存结构发生变化 所以要重新给pos赋值
pos = start + index;
iterator pos1 = pos;
++pos1;
//把从原先第一个元素到原先pos的元素都往前移动一格的位置
copy(front2, pos1, front1);
}
else
{
//几乎同上
push_back(back());
iterator back1 = finish;
--back1;
iterator back2 = back1;
--back2;
pos = start + index;
copy_backward(pos, back2, back1);
}
*pos = x_copy;
return pos;
}
