STL源码剖析 容器 stl_deque.h

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deque

------------------------------------------------------------------------

??一直看不懂 operator->() ，不明白它为什么不用接受参数，直接 return &(operator*())

好像我们用迭代器的时候也不没怎么用到这个函数，甚至我都不会用

1.概述

vector 是单向开口的连续线性空间，deque 则是一种双向开口的连续线性空间

允许常数时间内对起头端进行元素的插入和移除操作

没有容量概念，因为它是动态地以分段连续空间组合而成，随时可以增加一段新的空间并链接起来

deque 的迭代器不是普通指针，如非必要，应选择 vector 而非 deque

对deque 排序，可将 deque 先完整复制到一个 vector 身上，将 vector 排序后，再复制回 deque
图 4-9

2.deque 的中控器

map (不是 STL 里的 map 容器) --> 主控，是一小块连续空间，每个元素指向另一段较大的连续空间 node-buffer

node-buffer --> 存储空间主体
图 4-10

3.迭代器

cur --> 指出分段连续空间在哪里 

first, last --> 判断自己是否已经处于缓冲区的边缘

node --> 在缓冲区边缘前进或后退时必须知道中控器在哪
图4-11

图4-12

#ifndef __SGI_STL_INTERNAL_DEQUE_H
#define __SGI_STL_INTERNAL_DEQUE_H

__STL_BEGIN_NAMESPACE

#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1174
#endif

// Note: this function is simply a kludge to work around several compilers'
//  bugs in handling constant expressions.
// 决定缓冲区大小
// 如果 n 不为 0，传回n ，表示 buffer size 由用户自定义
// 如果 n 为 0，表示 buffer size 使用默认值，那么
// 	 如果 sz(元素大小，sizeof(value_type))小于512，返回 512/sz,
//	 如果 sz不小于 512，返回 1
inline size_t __deque_buf_size(size_t n, size_t sz)
{
return n != 0 ? n : (sz < 512 ? size_t(512 / sz) : size_t(1));
}

#ifndef __STL_NON_TYPE_TMPL_PARAM_BUG
template <class T, class Ref, class Ptr, size_t BufSiz>
struct __deque_iterator {
typedef __deque_iterator<T, T&, T*, BufSiz>             iterator;
typedef __deque_iterator<T, const T&, const T*, BufSiz> const_iterator;
static size_t buffer_size() {return __deque_buf_size(BufSiz, sizeof(T)); }
#else /* __STL_NON_TYPE_TMPL_PARAM_BUG */
template <class T, class Ref, class Ptr>
struct __deque_iterator {
typedef __deque_iterator<T, T&, T*>             iterator;
typedef __deque_iterator<T, const T&, const T*> const_iterator;
static size_t buffer_size() {return __deque_buf_size(0, sizeof(T)); }
#endif

typedef random_access_iterator_tag iterator_category;
typedef T value_type;
typedef Ptr pointer;
typedef Ref reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef T** map_pointer;

typedef __deque_iterator self;

T* cur; //指向缓冲区的现行元素
T* first; //指向缓冲区的头
T* last; // 指向缓冲区的尾

map_pointer node; //指向中控器

__deque_iterator(T* x, map_pointer y)
: cur(x), first(*y), last(*y + buffer_size()), node(y) {}
__deque_iterator() : cur(0), first(0), last(0), node(0) {}
__deque_iterator(const iterator& x)
: cur(x.cur), first(x.first), last(x.last), node(x.node) {}
//解引用
reference operator*() const { return *cur; }
#ifndef __SGI_STL_NO_ARROW_OPERATOR
//？？好像没用过这东西
pointer operator->() const { return &(operator*()); }
#endif /* __SGI_STL_NO_ARROW_OPERATOR */
//两个迭代器之间的距离
difference_type operator-(const self& x) const {
return difference_type(buffer_size()) * (node - x.node - 1) +
(cur - first) + (x.last - x.cur);
}
//前置++
self& operator++() {
++cur;					//切换至下一个元素
if (cur == last) {		//如果已达到所在缓冲区的尾端
set_node(node + 1);	//就切换至下一缓冲区的第一个元素
cur = first;
}
return *this;
}
//后置++
self operator++(int)  {
self tmp = *this;
++*this;				//调用前置++ 完成前进 ? --> yes
return tmp;
}
//前置--
self& operator--() {
if (cur == first) {
set_node(node - 1);
cur = last;
}
--cur;
return *this;
}
//后置--
self operator--(int) {
self tmp = *this;
--*this;
return tmp;
}
//随机存取
self& operator+=(difference_type n) {
difference_type offset = n + (cur - first);
//目标位置在同一缓冲区
if (offset >= 0 && offset < difference_type(buffer_size()))
cur += n;
//目标位置在不同缓冲区
else {
difference_type node_offset =
offset > 0 ? offset / difference_type(buffer_size())
: -difference_type((-offset - 1) / buffer_size()) - 1;
//切换至正确的节点(缓冲区)
set_node(node + node_offset);
//切换至正确的元素
cur = first + (offset - node_offset * difference_type(buffer_size()));
}
return *this;
}

self operator+(difference_type n) const {
self tmp = *this;
return tmp += n; //? 不懂为什么是对 临时变量 调用 operator+= --> 因为是 operator+，本来就不用改变 this 指向的对象
}

self& operator-=(difference_type n) { return *this += -n; }

self operator-(difference_type n) const {
self tmp = *this;
return tmp -= n;
}

reference operator[](difference_type n) const { return *(*this + n); }

bool operator==(const self& x) const { return cur == x.cur; }
bool operator!=(const self& x) const { return !(*this == x); }
bool operator<(const self& x) const {
return (node == x.node) ? (cur < x.cur) : (node < x.node);
}
//使用 set_node 来跳一个缓冲区
void set_node(map_pointer new_node) {
node = new_node;
first = *new_node;
last = first + difference_type(buffer_size());
}
};

#ifndef __STL_CLASS_PARTIAL_SPECIALIZATION

#ifndef __STL_NON_TYPE_TMPL_PARAM_BUG

template <class T, class Ref, class Ptr, size_t BufSiz>
inline random_access_iterator_tag
iterator_category(const __deque_iterator<T, Ref, Ptr, BufSiz>&) {
return random_access_iterator_tag();
}

template <class T, class Ref, class Ptr, size_t BufSiz>
inline T* value_type(const __deque_iterator<T, Ref, Ptr, BufSiz>&) {
return 0;
}

template <class T, class Ref, class Ptr, size_t BufSiz>
inline ptrdiff_t* distance_type(const __deque_iterator<T, Ref, Ptr, BufSiz>&) {
return 0;
}

#else /* __STL_NON_TYPE_TMPL_PARAM_BUG */

template <class T, class Ref, class Ptr>
inline random_access_iterator_tag
iterator_category(const __deque_iterator<T, Ref, Ptr>&) {
return random_access_iterator_tag();
}

template <class T, class Ref, class Ptr>
inline T* value_type(const __deque_iterator<T, Ref, Ptr>&) { return 0; }

template <class T, class Ref, class Ptr>
inline ptrdiff_t* distance_type(const __deque_iterator<T, Ref, Ptr>&) {
return 0;
}

#endif /* __STL_NON_TYPE_TMPL_PARAM_BUG */

#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */

// See __deque_buf_size().  The only reason that the default value is 0
//  is as a workaround for bugs in the way that some compilers handle
//  constant expressions.

// deque 类
template <class T, class Alloc = alloc, size_t BufSiz = 0>
class deque {
public:                         // Basic types
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 size_t size_type;
typedef ptrdiff_t difference_type;

public:                         // Iterators
#ifndef __STL_NON_TYPE_TMPL_PARAM_BUG
typedef __deque_iterator<T, T&, T*, BufSiz>              iterator;
typedef __deque_iterator<T, const T&, const T&, BufSiz>  const_iterator;
#else /* __STL_NON_TYPE_TMPL_PARAM_BUG */
typedef __deque_iterator<T, T&, T*>                      iterator;
typedef __deque_iterator<T, const T&, const T*>          const_iterator;
#endif /* __STL_NON_TYPE_TMPL_PARAM_BUG */

#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_iterator<const_iterator, value_type, const_reference,
difference_type>
const_reverse_iterator;
typedef reverse_iterator<iterator, value_type, reference, difference_type>
reverse_iterator;
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */

protected:                      // Internal typedefs
//元素指针的指针，即指向 map 中元素的指针
typedef pointer* map_pointer;
//空间配置器，每次配置一个元素大小
typedef simple_alloc<value_type, Alloc> data_allocator;
//空间配置器，每次配置一个指针大小
typedef simple_alloc<pointer, Alloc> map_allocator;

static size_type buffer_size() {
return __deque_buf_size(BufSiz, sizeof(value_type));
}
static size_type initial_map_size() { return 8; }

protected:                      // Data members
iterator start;				//第一缓冲区的第一个元素
iterator finish;				//最后缓冲区的最后一个元素

map_pointer map; //指向 map
size_type map_size; // map 内可容纳多少指针

public:                         // Basic accessors
iterator begin() { return start; }
iterator end() { return finish; }
const_iterator begin() const { return start; }
const_iterator end() const { return finish; }

reverse_iterator rbegin() { return reverse_iterator(finish); }
reverse_iterator rend() { return reverse_iterator(start); }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(finish);
}
const_reverse_iterator rend() const {
return const_reverse_iterator(start);
}

reference operator[](size_type n) { return start[difference_type(n)]; }
const_reference operator[](size_type n) const {
return start[difference_type(n)];
}

reference front() { return *start; }
reference back() {
//? 以下三行为什么不改为： return *(finish - 1);
iterator tmp = finish;
--tmp;
return *tmp;
}
const_reference front() const { return *start; }
const_reference back() const {
const_iterator tmp = finish;
--tmp;
return *tmp;
}

size_type size() const { return finish - start;; }
size_type max_size() const { return size_type(-1); }
bool empty() const { return finish == start; }

public:                         // Constructor, destructor.
deque()
: start(), finish(), map(0), map_size(0)
{
create_map_and_nodes(0);
}

deque(const deque& x)
: start(), finish(), map(0), map_size(0)
{
create_map_and_nodes(x.size());
__STL_TRY {
uninitialized_copy(x.begin(), x.end(), start);
}
__STL_UNWIND(destroy_map_and_nodes());
}

deque(size_type n, const value_type& value)
: start(), finish(), map(0), map_size(0)
{
fill_initialize(n, value);
}

deque(int n, const value_type& value)
: start(), finish(), map(0), map_size(0)
{
fill_initialize(n, value);
}

deque(long n, const value_type& value)
: start(), finish(), map(0), map_size(0)
{
fill_initialize(n, value);
}

explicit deque(size_type n)
: start(), finish(), map(0), map_size(0)
{
fill_initialize(n, value_type());
}

#ifdef __STL_MEMBER_TEMPLATES

template <class InputIterator>
deque(InputIterator first, InputIterator last)
: start(), finish(), map(0), map_size(0)
{
range_initialize(first, last, iterator_category(first));
}

#else /* __STL_MEMBER_TEMPLATES */

deque(const value_type* first, const value_type* last)
: start(), finish(), map(0), map_size(0)
{
create_map_and_nodes(last - first);
__STL_TRY {
uninitialized_copy(first, last, start);
}
__STL_UNWIND(destroy_map_and_nodes());
}

deque(const_iterator first, const_iterator last)
: start(), finish(), map(0), map_size(0)
{
create_map_and_nodes(last - first);
__STL_TRY {
uninitialized_copy(first, last, start);
}
__STL_UNWIND(destroy_map_and_nodes());
}

#endif /* __STL_MEMBER_TEMPLATES */

~deque() {
destroy(start, finish);
destroy_map_and_nodes();
}

deque& operator= (const deque& x) {
const size_type len = size();
if (&x != this) {
if (len >= x.size())
erase(copy(x.begin(), x.end(), start), finish);
else {
const_iterator mid = x.begin() + difference_type(len);
copy(x.begin(), mid, start);
insert(finish, mid, x.end());
}
}
return *this;
}

void swap(deque& x) {
__STD::swap(start, x.start);
__STD::swap(finish, x.finish);
__STD::swap(map, x.map);
__STD::swap(map_size, x.map_size);
}

public:                         // push_* and pop_*

void push_back(const value_type& t) {
//最后缓冲区尚有一个以上的备用空间
if (finish.cur != finish.last - 1) {
construct(finish.cur, t);
++finish.cur;
}
//只剩一个备用空间
else
push_back_aux(t);
}

void push_front(const value_type& t) {
//第一缓冲区尚有备用空间
if (start.cur != start.first) {
construct(start.cur - 1, t);
--start.cur;
}
//尚有备用空间
else
push_front_aux(t);
}

void pop_back() {
//最后缓冲区有一个或更多的元素
if (finish.cur != finish.first) {
--finish.cur; //指针前移，相当于排除了最后的元素
destroy(finish.cur); //析构并释放最后的元素
}
//最后缓冲区没有任何元素
else
pop_back_aux();
}

void pop_front() {
//第一缓冲区有一个或更多个元素
if (start.cur != start.last - 1) {
destroy(start.cur);
++start.cur;
}
//第一缓冲区且有一个元素
else
pop_front_aux();
}

public:                         // Insert

iterator insert(iterator position, const value_type& x) {
//如果插入点是 deque 最前端，交给 push_front 去做
if (position.cur == start.cur) {
push_front(x);
return start;
}
//如果插入点是 deque 最后端，交给 push_back 去做
else if (position.cur == finish.cur) {
push_back(x);
iterator tmp = finish;
--tmp;
return tmp;
}
//其他情况交给 insert_aux 去做
else {
return insert_aux(position, x);
}
}

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

void insert(iterator pos, size_type n, const value_type& x);

void insert(iterator pos, int n, const value_type& x) {
insert(pos, (size_type) n, x);
}
void insert(iterator pos, long n, const value_type& x) {
insert(pos, (size_type) n, x);
}

#ifdef __STL_MEMBER_TEMPLATES

template <class InputIterator>
void insert(iterator pos, InputIterator first, InputIterator last) {
insert(pos, first, last, iterator_category(first));
}

#else /* __STL_MEMBER_TEMPLATES */

void insert(iterator pos, const value_type* first, const value_type* last);
void insert(iterator pos, const_iterator first, const_iterator last);

#endif /* __STL_MEMBER_TEMPLATES */

void resize(size_type new_size, const value_type& x) {
const size_type len = size();
if (new_size < len)
erase(start + new_size, finish);
else
insert(finish, new_size - len, x);
}

void resize(size_type new_size) { resize(new_size, value_type()); }

public:                         // Erase
//清除 pos 所指的元素
iterator erase(iterator pos) {
iterator next = pos;
++next;
difference_type index = pos - start; // 清除点前的元素个数
if (index < (size() >> 1)) { // 如果清除点之前的元素比较少，则移动清除点之前的元素
copy_backward(start, pos, next);
pop_front();
}
else { //如果清除点之后的元素比较少，则移动清除点之后的元素
copy(next, finish, pos);
pop_back();
}
return start + index;
}

iterator erase(iterator first, iterator last);
void clear();

protected:                        // Internal construction/destruction

void create_map_and_nodes(size_type num_elements);
void destroy_map_and_nodes();
void fill_initialize(size_type n, const value_type& value);

#ifdef __STL_MEMBER_TEMPLATES

template <class InputIterator>
void range_initialize(InputIterator first, InputIterator last,
input_iterator_tag);

template <class ForwardIterator>
void range_initialize(ForwardIterator first, ForwardIterator last,
forward_iterator_tag);

#endif /* __STL_MEMBER_TEMPLATES */

protected:                        // Internal push_* and pop_*

void push_back_aux(const value_type& t);
void push_front_aux(const value_type& t);
void pop_back_aux();
void pop_front_aux();

protected:                        // Internal insert functions

#ifdef __STL_MEMBER_TEMPLATES

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

template <class ForwardIterator>
void insert(iterator pos, ForwardIterator first, ForwardIterator last,
forward_iterator_tag);

#endif /* __STL_MEMBER_TEMPLATES */

iterator insert_aux(iterator pos, const value_type& x);
void insert_aux(iterator pos, size_type n, const value_type& x);

#ifdef __STL_MEMBER_TEMPLATES

template <class ForwardIterator>
void insert_aux(iterator pos, ForwardIterator first, ForwardIterator last,
size_type n);

#else /* __STL_MEMBER_TEMPLATES */

void insert_aux(iterator pos,
const value_type* first, const value_type* last,
size_type n);

void insert_aux(iterator pos, const_iterator first, const_iterator last,
size_type n);

#endif /* __STL_MEMBER_TEMPLATES */

iterator reserve_elements_at_front(size_type n) {
size_type vacancies = start.cur - start.first;
if (n > vacancies)
new_elements_at_front(n - vacancies);
return start - difference_type(n);
}

iterator reserve_elements_at_back(size_type n) {
size_type vacancies = (finish.last - finish.cur) - 1;
if (n > vacancies)
new_elements_at_back(n - vacancies);
return finish + difference_type(n);
}

void new_elements_at_front(size_type new_elements);
void new_elements_at_back(size_type new_elements);

void destroy_nodes_at_front(iterator before_start);
void destroy_nodes_at_back(iterator after_finish);

protected:                      // Allocation of map and nodes

// Makes sure the map has space for new nodes.  Does not actually
//  add the nodes.  Can invalidate map pointers.  (And consequently,
//  deque iterators.)

void reserve_map_at_back (size_type nodes_to_add = 1) {
if (nodes_to_add + 1 > map_size - (finish.node - map))
reallocate_map(nodes_to_add, false);
}

void reserve_map_at_front (size_type nodes_to_add = 1) {
if (nodes_to_add > start.node - map)
reallocate_map(nodes_to_add, true);
}

void reallocate_map(size_type nodes_to_add, bool add_at_front);

pointer allocate_node() { return data_allocator::allocate(buffer_size()); }
void deallocate_node(pointer n) {
data_allocator::deallocate(n, buffer_size());
}

#ifdef __STL_NON_TYPE_TMPL_PARAM_BUG
public:
bool operator==(const deque<T, Alloc, 0>& x) const {
return size() == x.size() && equal(begin(), end(), x.begin());
}
bool operator!=(const deque<T, Alloc, 0>& x) const {
return size() != x.size() || !equal(begin(), end(), x.begin());
}
bool operator<(const deque<T, Alloc, 0>& x) const {
return lexicographical_compare(begin(), end(), x.begin(), x.end());
}
#endif /* __STL_NON_TYPE_TMPL_PARAM_BUG */
};

// Non-inline member functions

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::insert(iterator pos,
size_type n, const value_type& x) {
if (pos.cur == start.cur) {
iterator new_start = reserve_elements_at_front(n);
uninitialized_fill(new_start, start, x);
start = new_start;
}
else if (pos.cur == finish.cur) {
iterator new_finish = reserve_elements_at_back(n);
uninitialized_fill(finish, new_finish, x);
finish = new_finish;
}
else
insert_aux(pos, n, x);
}

#ifndef __STL_MEMBER_TEMPLATES

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::insert(iterator pos,
const value_type* first,
const value_type* last) {
size_type n = last - first;
if (pos.cur == start.cur) {
iterator new_start = reserve_elements_at_front(n);
__STL_TRY {
uninitialized_copy(first, last, new_start);
start = new_start;
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else if (pos.cur == finish.cur) {
iterator new_finish = reserve_elements_at_back(n);
__STL_TRY {
uninitialized_copy(first, last, finish);
finish = new_finish;
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
else
insert_aux(pos, first, last, n);
}

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::insert(iterator pos,
const_iterator first,
const_iterator last)
{
size_type n = last - first;
if (pos.cur == start.cur) {
iterator new_start = reserve_elements_at_front(n);
__STL_TRY {
uninitialized_copy(first, last, new_start);
start = new_start;
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else if (pos.cur == finish.cur) {
iterator new_finish = reserve_elements_at_back(n);
__STL_TRY {
uninitialized_copy(first, last, finish);
finish = new_finish;
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
else
insert_aux(pos, first, last, n);
}

#endif /* __STL_MEMBER_TEMPLATES */

template <class T, class Alloc, size_t BufSize>
deque<T, Alloc, BufSize>::iterator
//清除[first, last)区间内的所有元素
deque<T, Alloc, BufSize>::erase(iterator first, iterator last) {
//如果清除区间就是整个 deque ，直接调用 clear() 即可
if (first == start && last == finish) {
clear();
return finish;
}
else {
difference_type n = last - first;
difference_type elems_before = first - start;
//如果清除区间前面的元素较少，向后移动前方元素(覆盖清除区间)，然后析构冗余元素
if (elems_before < (size() - n) / 2) {
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());
start = new_start;
}
//如果清除区间后面的元素较少，向前移动后方元素，然后析构冗余元素
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;
}
}

//清除整个 deque ，需要保有一个缓冲区。
template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::clear() {
//针对头尾以外的每一个缓冲区，析构所有元素并释放缓冲区空间
for (map_pointer node = start.node + 1; node < finish.node; ++node) {
destroy(*node, *node + buffer_size());
data_allocator::deallocate(*node, buffer_size());
}
//还剩头尾两个缓冲区
if (start.node != finish.node) {
destroy(start.cur, start.last);
destroy(finish.first, finish.cur);
//只释放尾部缓冲区的空间，保留头缓冲区
data_allocator::deallocate(finish.first, buffer_size());
}
//只剩一个缓冲区
else
//不释放唯一的缓冲区空间
destroy(start.cur, finish.cur);

finish = start;
}
//产生并安排好 deque 的结构
template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::create_map_and_nodes(size_type num_elements) {
//需要的节点数 = (元素个数/每个缓冲区可容纳的元素个数) + 1
//如果刚好整除，会多配一个节点
size_type num_nodes = num_elements / buffer_size() + 1;
// initial_map_size 函数返回 8 ，所以这里是取 8 和 "所需节点数加2(前后预留一个，扩充时可用)" 的最大值
map_size = max(initial_map_size(), num_nodes + 2);
//配置出一个"具有 map_size 个节点"的 map
map = map_allocator::allocate(map_size);

//令 nstart 和 nfinish 指向 map 所拥有之全部节点的最中央区段
map_pointer nstart = map + (map_size - num_nodes) / 2;
map_pointer nfinish = nstart + num_nodes - 1;

map_pointer cur;
__STL_TRY {
//为 map 内的每个现用节点配置缓冲区。所有缓冲区加起来就是 deque 的可用空间(最后一个缓冲区可能留有一些余裕)
for (cur = nstart; cur <= nfinish; ++cur)
*cur = allocate_node();
}
#     ifdef  __STL_USE_EXCEPTIONS
catch(...) {
for (map_pointer n = nstart; n < cur; ++n)
deallocate_node(*n);
map_allocator::deallocate(map, map_size);
throw;
}
#     endif /* __STL_USE_EXCEPTIONS */
//为 deque 内的两个迭代器 start 和 end 设定正确内容
start.set_node(nstart);
finish.set_node(nfinish);
start.cur = start.first;
finish.cur = finish.first + num_elements % buffer_size();
}

// This is only used as a cleanup function in catch clauses.
template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::destroy_map_and_nodes() {
for (map_pointer cur = start.node; cur <= finish.node; ++cur)
deallocate_node(*cur);
map_allocator::deallocate(map, map_size);
}

//负责产生并安排好 deque 的结构，并元素的初值设定妥当
template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::fill_initialize(size_type n,
const value_type& value) {
create_map_and_nodes(n);//把 deque 的结构都产生并安排好
map_pointer cur;
__STL_TRY {
//为每个节点的缓冲区设定初值
for (cur = start.node; cur < finish.node; ++cur)
uninitialized_fill(*cur, *cur + buffer_size(), value);
//最后一个节点的设定稍有不同(因为尾端可能有备用空间，不必设初值)
uninitialized_fill(finish.first, finish.cur, value);
}
#       ifdef __STL_USE_EXCEPTIONS
catch(...) {
for (map_pointer n = start.node; n < cur; ++n)
destroy(*n, *n + buffer_size());
destroy_map_and_nodes();
throw;
}
#       endif /* __STL_USE_EXCEPTIONS */
}

#ifdef __STL_MEMBER_TEMPLATES

template <class T, class Alloc, size_t BufSize>
template <class InputIterator>
void deque<T, Alloc, BufSize>::range_initialize(InputIterator first,
InputIterator last,
input_iterator_tag) {
create_map_and_nodes(0);
for ( ; first != last; ++first)
push_back(*first);
}

template <class T, class Alloc, size_t BufSize>
template <class ForwardIterator>
void deque<T, Alloc, BufSize>::range_initialize(ForwardIterator first,
ForwardIterator last,
forward_iterator_tag) {
size_type n = 0;
distance(first, last, n);
create_map_and_nodes(n);
__STL_TRY {
uninitialized_copy(first, last, start);
}
__STL_UNWIND(destroy_map_and_nodes());
}

#endif /* __STL_MEMBER_TEMPLATES */

// 只有当 finish.cur == finish.last - 1 时才会调用，即只剩一个备用空间
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();
//配置一个新缓冲区
*(finish.node + 1) = allocate_node();
__STL_TRY {
construct(finish.cur, t_copy); //设置元素值
finish.set_node(finish.node + 1); //改变 finish， 令其指向新节点
finish.cur = finish.first; //设定 finish 的状态
}
__STL_UNWIND(deallocate_node(*(finish.node + 1)));
}

// 只有当 start.cur == start.first 才会被调用，即第一个缓冲区尚有备用空间可用了
//--> 为什么 push_back 的时候是只有一个备用空间时调用，而 push_front 是没有备用空间时调用 ？？
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);
}
#     ifdef __STL_USE_EXCEPTIONS
catch(...) {
start.set_node(start.node + 1);
start.cur = start.first;
deallocate_node(*(start.node - 1));
throw;
}
#     endif /* __STL_USE_EXCEPTIONS */
}

// 只有当 finish.cur == finish.first 时才会调用
template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>:: pop_back_aux() {
deallocate_node(finish.first); //释放最后一个缓冲区
finish.set_node(finish.node - 1); //调整 finish 的状态，使指向上一个缓冲区的最后一个元素
finish.cur = finish.last - 1;
destroy(finish.cur); //将该元素析构
}

//只有当 start.cur == start.last - 1 时才会调用
template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::pop_front_aux() {
destroy(start.cur); //将第一缓冲区的第一个元素析构
deallocate_node(start.first); //释放第一缓冲区
start.set_node(start.node + 1); //调整 start 的状态，使指向下一个缓冲区的第一个元素
start.cur = start.first;
}

#ifdef __STL_MEMBER_TEMPLATES

template <class T, class Alloc, size_t BufSize>
template <class InputIterator>
void deque<T, Alloc, BufSize>::insert(iterator pos,
InputIterator first, InputIterator last,
input_iterator_tag) {
copy(first, last, inserter(*this, pos));
}

template <class T, class Alloc, size_t BufSize>
template <class ForwardIterator>
void deque<T, Alloc, BufSize>::insert(iterator pos,
ForwardIterator first,
ForwardIterator last,
forward_iterator_tag) {
size_type n = 0;
distance(first, last, n);
if (pos.cur == start.cur) {
iterator new_start = reserve_elements_at_front(n);
__STL_TRY {
uninitialized_copy(first, last, new_start);
start = new_start;
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else if (pos.cur == finish.cur) {
iterator new_finish = reserve_elements_at_back(n);
__STL_TRY {
uninitialized_copy(first, last, finish);
finish = new_finish;
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
else
insert_aux(pos, first, last, n);
}

#endif /* __STL_MEMBER_TEMPLATES */

template <class T, class Alloc, size_t BufSize>
typename deque<T, Alloc, BufSize>::iterator
deque<T, Alloc, BufSize>::insert_aux(iterator pos, const value_type& x) {
difference_type index = pos - start;
value_type x_copy = x;
//如果插入点之前的元素个数比较少，在最前端加入与第一个元素同值的元素，然后进行元素移动
if (index < size() / 2) {
push_front(front());
iterator front1 = start;
++front1;
iterator front2 = front1;
++front2;
pos = start + index;
iterator pos1 = pos;
++pos1;
copy(front2, pos1, front1);
}

//如果插入点之后的元素个数比较少，在最后端加入与最后一个元素同值的元素，然后进行元素移动
else {
push_back(back());
iterator back1 = finish;
--back1;
iterator back2 = back1;
--back2;
pos = start + index;
copy_backward(pos, back2, back1);
}
//在插入点上设定新值
*pos = x_copy;
return pos;
}

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::insert_aux(iterator pos,
size_type n, const value_type& x) {
const difference_type elems_before = pos - start;
size_type length = size();
value_type x_copy = x;
if (elems_before < length / 2) {
iterator new_start = reserve_elements_at_front(n);
iterator old_start = start;
pos = start + elems_before;
__STL_TRY {
if (elems_before >= difference_type(n)) {
iterator start_n = start + difference_type(n);
uninitialized_copy(start, start_n, new_start);
start = new_start;
copy(start_n, pos, old_start);
fill(pos - difference_type(n), pos, x_copy);
}
else {
__uninitialized_copy_fill(start, pos, new_start, start, x_copy);
start = new_start;
fill(old_start, pos, x_copy);
}
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else {
iterator new_finish = reserve_elements_at_back(n);
iterator old_finish = finish;
const difference_type elems_after = difference_type(length) - elems_before;
pos = finish - elems_after;
__STL_TRY {
if (elems_after > difference_type(n)) {
iterator finish_n = finish - difference_type(n);
uninitialized_copy(finish_n, finish, finish);
finish = new_finish;
copy_backward(pos, finish_n, old_finish);
fill(pos, pos + difference_type(n), x_copy);
}
else {
__uninitialized_fill_copy(finish, pos + difference_type(n),
x_copy,
pos, finish);
finish = new_finish;
fill(pos, old_finish, x_copy);
}
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
}

#ifdef __STL_MEMBER_TEMPLATES

template <class T, class Alloc, size_t BufSize>
template <class ForwardIterator>
void deque<T, Alloc, BufSize>::insert_aux(iterator pos,
ForwardIterator first,
ForwardIterator last,
size_type n)
{
const difference_type elems_before = pos - start;
size_type length = size();
if (elems_before < length / 2) {
iterator new_start = reserve_elements_at_front(n);
iterator old_start = start;
pos = start + elems_before;
__STL_TRY {
if (elems_before >= difference_type(n)) {
iterator start_n = start + difference_type(n);
uninitialized_copy(start, start_n, new_start);
start = new_start;
copy(start_n, pos, old_start);
copy(first, last, pos - difference_type(n));
}
else {
ForwardIterator mid = first;
advance(mid, difference_type(n) - elems_before);
__uninitialized_copy_copy(start, pos, first, mid, new_start);
start = new_start;
copy(mid, last, old_start);
}
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else {
iterator new_finish = reserve_elements_at_back(n);
iterator old_finish = finish;
const difference_type elems_after = difference_type(length) - elems_before;
pos = finish - elems_after;
__STL_TRY {
if (elems_after > difference_type(n)) {
iterator finish_n = finish - difference_type(n);
uninitialized_copy(finish_n, finish, finish);
finish = new_finish;
copy_backward(pos, finish_n, old_finish);
copy(first, last, pos);
}
else {
ForwardIterator mid = first;
advance(mid, elems_after);
__uninitialized_copy_copy(mid, last, pos, finish, finish);
finish = new_finish;
copy(first, mid, pos);
}
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
}

#else /* __STL_MEMBER_TEMPLATES */

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::insert_aux(iterator pos,
const value_type* first,
const value_type* last,
size_type n)
{
const difference_type elems_before = pos - start;
size_type length = size();
if (elems_before < length / 2) {
iterator new_start = reserve_elements_at_front(n);
iterator old_start = start;
pos = start + elems_before;
__STL_TRY {
if (elems_before >= difference_type(n)) {
iterator start_n = start + difference_type(n);
uninitialized_copy(start, start_n, new_start);
start = new_start;
copy(start_n, pos, old_start);
copy(first, last, pos - difference_type(n));
}
else {
const value_type* mid = first + (difference_type(n) - elems_before);
__uninitialized_copy_copy(start, pos, first, mid, new_start);
start = new_start;
copy(mid, last, old_start);
}
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else {
iterator new_finish = reserve_elements_at_back(n);
iterator old_finish = finish;
const difference_type elems_after = difference_type(length) - elems_before;
pos = finish - elems_after;
__STL_TRY {
if (elems_after > difference_type(n)) {
iterator finish_n = finish - difference_type(n);
uninitialized_copy(finish_n, finish, finish);
finish = new_finish;
copy_backward(pos, finish_n, old_finish);
copy(first, last, pos);
}
else {
const value_type* mid = first + elems_after;
__uninitialized_copy_copy(mid, last, pos, finish, finish);
finish = new_finish;
copy(first, mid, pos);
}
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
}

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::insert_aux(iterator pos,
const_iterator first,
const_iterator last,
size_type n)
{
const difference_type elems_before = pos - start;
size_type length = size();
if (elems_before < length / 2) {
iterator new_start = reserve_elements_at_front(n);
iterator old_start = start;
pos = start + elems_before;
__STL_TRY {
if (elems_before >= n) {
iterator start_n = start + n;
uninitialized_copy(start, start_n, new_start);
start = new_start;
copy(start_n, pos, old_start);
copy(first, last, pos - difference_type(n));
}
else {
const_iterator mid = first + (n - elems_before);
__uninitialized_copy_copy(start, pos, first, mid, new_start);
start = new_start;
copy(mid, last, old_start);
}
}
__STL_UNWIND(destroy_nodes_at_front(new_start));
}
else {
iterator new_finish = reserve_elements_at_back(n);
iterator old_finish = finish;
const difference_type elems_after = length - elems_before;
pos = finish - elems_after;
__STL_TRY {
if (elems_after > n) {
iterator finish_n = finish - difference_type(n);
uninitialized_copy(finish_n, finish, finish);
finish = new_finish;
copy_backward(pos, finish_n, old_finish);
copy(first, last, pos);
}
else {
const_iterator mid = first + elems_after;
__uninitialized_copy_copy(mid, last, pos, finish, finish);
finish = new_finish;
copy(first, mid, pos);
}
}
__STL_UNWIND(destroy_nodes_at_back(new_finish));
}
}

#endif /* __STL_MEMBER_TEMPLATES */

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::new_elements_at_front(size_type new_elements) {
size_type new_nodes = (new_elements + buffer_size() - 1) / buffer_size();
reserve_map_at_front(new_nodes);
size_type i;
__STL_TRY {
for (i = 1; i <= new_nodes; ++i)
*(start.node - i) = allocate_node();
}
#       ifdef __STL_USE_EXCEPTIONS
catch(...) {
for (size_type j = 1; j < i; ++j)
deallocate_node(*(start.node - j));
throw;
}
#       endif /* __STL_USE_EXCEPTIONS */
}

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::new_elements_at_back(size_type new_elements) {
size_type new_nodes = (new_elements + buffer_size() - 1) / buffer_size();
reserve_map_at_back(new_nodes);
size_type i;
__STL_TRY {
for (i = 1; i <= new_nodes; ++i)
*(finish.node + i) = allocate_node();
}
#       ifdef __STL_USE_EXCEPTIONS
catch(...) {
for (size_type j = 1; j < i; ++j)
deallocate_node(*(finish.node + j));
throw;
}
#       endif /* __STL_USE_EXCEPTIONS */
}

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::destroy_nodes_at_front(iterator before_start) {
for (map_pointer n = before_start.node; n < start.node; ++n)
deallocate_node(*n);
}

template <class T, class Alloc, size_t BufSize>
void deque<T, Alloc, BufSize>::destroy_nodes_at_back(iterator after_finish) {
for (map_pointer n = after_finish.node; n > finish.node; --n)
deallocate_node(*n);
}

//重换一个 map (配置更大的，拷贝原来的，释放原来的)
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 old_num_nodes = finish.node - start.node + 1;//旧节点数
size_type new_num_nodes = old_num_nodes + nodes_to_add;//新节点数

map_pointer new_nstart;
//当前 map 的大小大于新节点数的两倍的情况
//即当前 map 足够大，则调整节点区间让它落在 map 的中间
if (map_size > 2 * new_num_nodes) {
new_nstart = map + (map_size - new_num_nodes) / 2
+ (add_at_front ? nodes_to_add : 0);
if (new_nstart < start.node)
copy(start.node, finish.node + 1, new_nstart);
else
copy_backward(start.node, finish.node + 1, new_nstart + old_num_nodes);
}
//否则，配置一块新的空间
else {
size_type new_map_size = map_size + max(map_size, nodes_to_add) + 2;

//配置一块新的空间
map_pointer new_map = map_allocator::allocate(new_map_size);
new_nstart = new_map + (new_map_size - new_num_nodes) / 2
+ (add_at_front ? nodes_to_add : 0);
//拷贝原 map
copy(start.node, finish.node + 1, new_nstart);
//释放原 map
map_allocator::deallocate(map, map_size);
//设定新 map 的起始地址和大小
map = new_map;
map_size = new_map_size;
}
//重新设定迭代器 start 和 finish
start.set_node(new_nstart);
finish.set_node(new_nstart + old_num_nodes - 1);
}

// Nonmember functions.

#ifndef __STL_NON_TYPE_TMPL_PARAM_BUG

template <class T, class Alloc, size_t BufSiz>
bool operator==(const deque<T, Alloc, BufSiz>& x,
const deque<T, Alloc, BufSiz>& y) {
return x.size() == y.size() && equal(x.begin(), x.end(), y.begin());
}

template <class T, class Alloc, size_t BufSiz>
bool operator<(const deque<T, Alloc, BufSiz>& x,
const deque<T, Alloc, BufSiz>& y) {
return lexicographical_compare(x.begin(), x.end(), y.begin(), y.end());
}

#endif /* __STL_NON_TYPE_TMPL_PARAM_BUG */

#if defined(__STL_FUNCTION_TMPL_PARTIAL_ORDER) && \
!defined(__STL_NON_TYPE_TMPL_PARAM_BUG)

template <class T, class Alloc, size_t BufSiz>
inline void swap(deque<T, Alloc, BufSiz>& x, deque<T, Alloc, BufSiz>& y) {
x.swap(y);
}

#endif

#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma reset woff 1174
#endif

__STL_END_NAMESPACE

#endif /* __SGI_STL_INTERNAL_DEQUE_H */

// Local Variables:
// mode:C++
// End: