STL源代碼剖析 容器 stl_vector.h
本文為senlie原創。轉載請保留此地址：http://blog.csdn.net/zhengsenlie
vector
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描寫敘述：
1.叠代器
vector 維護的是一個連續線性空間。它的叠代器是普通指針。
能滿足 RandomAccessIterator 全部必要條件：operator*, operator->,operator++,operator--,operator+,
operator-,operator+=,operator-=,operator[]
2.數據結構
vector所採用的數據結構是線性連續空間。
叠代器 start、finish分別表示配置得來的連續空間中眼下已經被使用的範圍
叠代器 end_of_storage 指向整塊連續空間的尾端
添加新元素時。假設走過當時的容量，則容量會擴充至兩倍。
假設兩倍容量仍不足，就擴張至足夠大的容量。
擴充容量的過程為：又一次配置、元素移動、釋放原空間
所謂動態添加大小，並非在原空間之後接續新空間，由於無法保證原空間之後
尚有可供配置的空間。因此。對 vector 的不論什麽操作。一旦引起空間又一次配置，
指向原 vector 的全部叠代器就失效了。
演示樣例：
vector<int> V; V.insert(V.begin(), 3); assert(V.size() == 1 && V.capacity() >= 1 && V[0] == 3);
源代碼：
#ifndef __SGI_STL_INTERNAL_VECTOR_H
#define __SGI_STL_INTERNAL_VECTOR_H
__STL_BEGIN_NAMESPACE
#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1174
#endif
template <class T, class Alloc = alloc>
class vector {
public:
typedef T value_type;
typedef value_type* pointer;
typedef const value_type* const_pointer;
typedef value_type* iterator; //vector 的叠代器是個原生的指針
typedef const value_type* const_iterator;
typedef value_type& reference;
typedef const value_type& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
#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:
typedef simple_alloc<value_type, Alloc> data_allocator; //連續空間？
iterator start; //表示眼下使用空間的頭
iterator finish; //表示眼下使用空間的尾
iterator end_of_storage; //表示眼下可用空間的尾
void insert_aux(iterator position, const T& x);
void deallocate() {
if (start) data_allocator::deallocate(start, end_of_storage - start);
}
// 填充並予以初始化
void fill_initialize(size_type n, const T& value) {
start = allocate_and_fill(n, value);
finish = start + n;
end_of_storage = finish;
}
public:
iterator begin() { return start; }
const_iterator begin() const { return start; }
iterator end() { return finish; }
const_iterator end() const { return finish; }
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());
}
size_type size() const { return size_type(end() - begin()); }
size_type max_size() const { return size_type(-1) / sizeof(T); }
size_type capacity() const { return size_type(end_of_storage - begin()); }
bool empty() const { return begin() == end(); }
reference operator[](size_type n) { return *(begin() + n); }
const_reference operator[](size_type n) const { return *(begin() + n); }
vector() : start(0), finish(0), end_of_storage(0) {}
//構造函數，同意指定 vector 大小 n 和初值 value
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); }
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;
}
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
vector(InputIterator first, InputIterator last) :
start(0), finish(0), end_of_storage(0)
{
range_initialize(first, last, iterator_category(first));
}
#else /* __STL_MEMBER_TEMPLATES */
vector(const_iterator first, const_iterator last) {
size_type n = 0;
distance(first, last, n);
start = allocate_and_copy(n, first, last);
finish = start + n;
end_of_storage = finish;
}
#endif /* __STL_MEMBER_TEMPLATES */
~vector() {
destroy(start, finish);
deallocate();
}
vector<T, Alloc>& operator=(const vector<T, Alloc>& x);
void reserve(size_type n) {
if (capacity() < n) {
const size_type old_size = size();
iterator tmp = allocate_and_copy(n, start, finish);
destroy(start, finish);
deallocate();
start = tmp;
finish = tmp + old_size;
end_of_storage = start + n;
}
}
reference front() { return *begin(); }
const_reference front() const { return *begin(); }
reference back() { return *(end() - 1); }
const_reference back() const { return *(end() - 1); }
//
void push_back(const T& x) {
if (finish != end_of_storage) { //檢查是否還有備用空間
construct(finish, x); //有，直接在備用空間上構造元素
++finish; //調整叠代器 finish
}
else
insert_aux(end(), x); //沒有，擴充空間(又一次配置、元素移動、釋放原空間)
}
void swap(vector<T, Alloc>& x) {
__STD::swap(start, x.start);
__STD::swap(finish, x.finish);
__STD::swap(end_of_storage, x.end_of_storage);
}
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()); }
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
void insert(iterator position, InputIterator first, InputIterator last) {
range_insert(position, first, last, iterator_category(first));
}
#else /* __STL_MEMBER_TEMPLATES */
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);
}
void pop_back() {
--finish; //將尾端標記往前移一格，表示將放棄尾端元素
destroy(finish); //析構尾端元素
}
//清除 position 指向的元素
iterator erase(iterator position) {
if (position + 1 != end())
copy(position + 1, finish, position);
--finish;
destroy(finish);
return position;
}
//清除[first, last)中的全部元素
iterator erase(iterator first, iterator last) {
iterator i = copy(last, finish, first); //將 [last, finish) 指示的元素拷貝至 first 叠代器開頭的地方
destroy(i, finish); //析構[i, finish) 裏的元素
finish = finish - (last - first); //調整 finish 指示的位置 last - first 表示清除掉了的元素個數
return first;
}
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()); }
//調用 erase 清除全部元素
void clear() { erase(begin(), end()); }
protected:
//配置而後填充
iterator allocate_and_fill(size_type n, const T& x) {
iterator result = data_allocator::allocate(n); //配置 n 個元素空間
__STL_TRY {
uninitialized_fill_n(result, n, x); //全局函數。全依據 result 的類型特性(type traits)決定使用算法 fill_n() 或重復調用 construct() 來完畢任務
return result;
}
__STL_UNWIND(data_allocator::deallocate(result, n));
}
#ifdef __STL_MEMBER_TEMPLATES
template <class ForwardIterator>
iterator allocate_and_copy(size_type n,
ForwardIterator first, ForwardIterator last) {
iterator result = data_allocator::allocate(n);
__STL_TRY {
uninitialized_copy(first, last, result);
return result;
}
__STL_UNWIND(data_allocator::deallocate(result, n));
}
#else /* __STL_MEMBER_TEMPLATES */
iterator allocate_and_copy(size_type n,
const_iterator first, const_iterator last) {
iterator result = data_allocator::allocate(n);
__STL_TRY {
uninitialized_copy(first, last, result);
return result;
}
__STL_UNWIND(data_allocator::deallocate(result, n));
}
#endif /* __STL_MEMBER_TEMPLATES */
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
void range_initialize(InputIterator first, InputIterator last,
input_iterator_tag) {
for ( ; first != last; ++first)
push_back(*first);
}
// This function is only called by the constructor. We have to worry
// about resource leaks, but not about maintaining invariants.
template <class ForwardIterator>
void range_initialize(ForwardIterator first, ForwardIterator last,
forward_iterator_tag) {
size_type n = 0;
distance(first, last, n);
start = allocate_and_copy(n, first, last);
finish = start + n;
end_of_storage = finish;
}
template <class InputIterator>
void range_insert(iterator pos,
InputIterator first, InputIterator last,
input_iterator_tag);
template <class ForwardIterator>
void range_insert(iterator pos,
ForwardIterator first, ForwardIterator last,
forward_iterator_tag);
#endif /* __STL_MEMBER_TEMPLATES */
};
template <class T, class Alloc>
inline bool operator==(const vector<T, Alloc>& x, const vector<T, Alloc>& y) {
return x.size() == y.size() && equal(x.begin(), x.end(), y.begin());
}
template <class T, class Alloc>
inline bool operator<(const vector<T, Alloc>& x, const vector<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>
inline void swap(vector<T, Alloc>& x, vector<T, Alloc>& y) {
x.swap(y);
}
#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER */
template <class T, class Alloc>
vector<T, Alloc>& vector<T, Alloc>::operator=(const vector<T, Alloc>& x) {
if (&x != this) {
if (x.size() > capacity()) {
iterator tmp = allocate_and_copy(x.end() - x.begin(),
x.begin(), x.end());
destroy(start, finish);
deallocate();
start = tmp;
end_of_storage = start + (x.end() - x.begin());
}
else if (size() >= x.size()) {
iterator i = copy(x.begin(), x.end(), begin());
destroy(i, finish);
}
else {
copy(x.begin(), x.begin() + size(), start);
uninitialized_copy(x.begin() + size(), x.end(), finish);
}
finish = start + x.size();
}
return *this;
}
template <class T, class Alloc>
void vector<T, Alloc>::insert_aux(iterator position, const T& x) {
if (finish != end_of_storage) { // 不是備用空間不夠才會調用 insert_aux 來插入元素嗎？ 為什麽還會出現 finish != end_of_storage 的情況 ？
// --> 除了 push_back 不夠空間時會調用 insert_aux，正常的 insert 也是調用 insert_aux 實現的。
//為什麽不直接 copy_backward(position, finish - 1, finish)。 然後 *position = x_copy 呢？
construct(finish, *(finish - 1));
++finish;
T x_copy = x;
copy_backward(position, finish - 2, finish - 1);
*position = x_copy;
}
else { //無備用空間 position == finish
const size_type old_size = size();
const size_type len = old_size != 0 ? 2 * old_size : 1;
//假設原大小為0。則配置1個元素大小的空間，否則配置原大小兩倍的空間
iterator new_start = data_allocator::allocate(len); //實際配置
iterator new_finish = new_start;
__STL_TRY {
//將原空間的全部內容拷貝到新空間 positition
new_finish = uninitialized_copy(start, position, new_start);
//為新元素設定初值 x
construct(new_finish, x);
//調整叠代器 finish
++new_finish;
//？？我認為以下這行代碼沒用。由於無備用空間的情況，position == finish
new_finish = uninitialized_copy(position, finish, new_finish);
}
# ifdef __STL_USE_EXCEPTIONS
catch(...) { //異常居然能夠用三個小點 ... ?
?
//回滾
destroy(new_start, new_finish);
data_allocator::deallocate(new_start, len);
throw;
}
# endif /* __STL_USE_EXCEPTIONS */
//析構並釋放原空間
destroy(begin(), end());
deallocate();
//調整叠代器。指向新 vector
start = new_start;
finish = new_finish;
end_of_storage = new_start + len;
}
}
template <class T, class Alloc>
//從 position 開始，插入 n 個元素，元素初值為 x
void vector<T, Alloc>::insert(iterator position, size_type n, const T& x) {
if (n != 0) { // 當 n != 0 才進行以下全部操作
if (size_type(end_of_storage - finish) >= n) { //備用空間大於新增元素個數
T x_copy = x;
const size_type elems_after = finish - position; //插入點之後的的現有元素個數
iterator old_finish = finish;
if (elems_after > n) { //"插入點之後的的現有元素個數"大於"新增元素個數"
//空間還沒初始化時用 uninitialized_copy 。 已經初始化了用 copy_backward
uninitialized_copy(finish - n, finish, finish);
finish += n;
copy_backward(position, old_finish - n, old_finish);
fill(position, position + n, x_copy); //從插入點開始填入新值
}
else { //"插入點之後的的現有元素個數"小於"新增元素個數"
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 {//備用空間小於新增元素個數
const size_type old_size = size();
// 首先決定新長度：舊長度的兩倍或舊長度+新元素個數，這兩個中取最大值
const size_type len = old_size + max(old_size, n);
iterator new_start = data_allocator::allocate(len);
iterator new_finish = new_start;
__STL_TRY {
//先用 uninitialized_copy 將舊 vector 的插入點之前的元素拷貝到新空間
new_finish = uninitialized_copy(start, position, new_start);
//再用 uninitialized_fill_n 將新增元素填入新空間
new_finish = uninitialized_fill_n(new_finish, n, x);
//最後再用 uninitialized_copy 將舊 vector 的插入點之後的元素拷貝到新空間
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 */
//清除並釋放舊的 vector
destroy(start, finish);
deallocate();
//調整標記
start = new_start;
finish = new_finish;
end_of_storage = new_start + len;
}
}
}
#ifdef __STL_MEMBER_TEMPLATES
template <class T, class Alloc> template <class InputIterator>
void vector<T, Alloc>::range_insert(iterator pos,
InputIterator first, InputIterator last,
input_iterator_tag) {
for ( ; first != last; ++first) {
pos = insert(pos, *first);
++pos;
}
}
template <class T, class Alloc> template <class ForwardIterator>
void vector<T, Alloc>::range_insert(iterator position,
ForwardIterator first,
ForwardIterator last,
forward_iterator_tag) {
if (first != last) {
size_type n = 0;
distance(first, last, n);
if (size_type(end_of_storage - finish) >= n) {
const size_type elems_after = finish - position;
iterator old_finish = finish;
if (elems_after > n) {
uninitialized_copy(finish - n, finish, finish);
finish += n;
copy_backward(position, old_finish - n, old_finish);
copy(first, last, position);
}
else {
ForwardIterator mid = first;
advance(mid, elems_after);
uninitialized_copy(mid, last, finish);
finish += n - elems_after;
uninitialized_copy(position, old_finish, finish);
finish += elems_after;
copy(first, mid, position);
}
}
else {
const size_type old_size = size();
const size_type len = old_size + max(old_size, n);
iterator new_start = data_allocator::allocate(len);
iterator new_finish = new_start;
__STL_TRY {
new_finish = uninitialized_copy(start, position, new_start);
new_finish = uninitialized_copy(first, last, new_finish);
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;
}
}
}
#else /* __STL_MEMBER_TEMPLATES */
template <class T, class Alloc>
void vector<T, Alloc>::insert(iterator position,
const_iterator first,
const_iterator last) {
if (first != last) {
size_type n = 0;
distance(first, last, n);
if (size_type(end_of_storage - finish) >= n) {
const size_type elems_after = finish - position;
iterator old_finish = finish;
if (elems_after > n) {
uninitialized_copy(finish - n, finish, finish);
finish += n;
copy_backward(position, old_finish - n, old_finish);
copy(first, last, position);
}
else {
uninitialized_copy(first + elems_after, last, finish);
finish += n - elems_after;
uninitialized_copy(position, old_finish, finish);
finish += elems_after;
copy(first, first + elems_after, position);
}
}
else {
const size_type old_size = size();
const size_type len = old_size + max(old_size, n);
iterator new_start = data_allocator::allocate(len);
iterator new_finish = new_start;
__STL_TRY {
new_finish = uninitialized_copy(start, position, new_start);
new_finish = uninitialized_copy(first, last, new_finish);
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;
}
}
}
#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_VECTOR_H */
// Local Variables:
// mode:C++
// End:
STL源代碼剖析 容器 stl_vector.h