STL 源码注释（2）——Vector
(为了保证代码的简洁性，源码中若干地方省去了异常处理环节，后续还有其他容器的源码注释)
1、vector的初始化和回收机制：
2、vector内存的动态增长
3、vector的API如下：
构造函数：
vector() : start(0), finish(0), end_of_storage(0) {}"初始化的vector为空"
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) {"把另一个vector中每一个元素都拷贝到新的vector（先分配空间再拷贝容器中元素）"
start = allocate_and_copy(x.end() - x.begin(), x.begin(), x.end());"见初始位置"
finish = start + (x.end() - x.begin());
end_of_storage = finish;
}
template <class InputIterator>
vector(InputIterator first, InputIterator last) :"按迭代器所指的范围拷贝，注意：迭代器的类型应覆盖所有迭代器的类型"
start(0), finish(0), end_of_storage(0)
{
range_initialize(first, last, iterator_category(first));"见初始位置"
}
内部函数： fill_initialize（赋初值初始化方式）
allocate_and_fill
range_initialize（拷贝元素初始化方式）
allocate_and_copy
void fill_initialize(size_type n, const T& value) {"批量分配并初始化，然后修改vector的位置元素"
start = allocate_and_fill(n, value);
finish = start + n;
end_of_storage = finish;
}
iterator allocate_and_fill(size_type n, const T& x) {"批量分配n个value_type大小的空间，并赋值初始化"
iterator result = data_allocator::allocate(n);
uninitialized_fill_n(result, n, x);
return result;
}
template <class InputIterator>
void range_initialize(InputIterator first, InputIterator last,"一次分配一个空间并初始化（重复n次），每一次都修改vector的位置元素"
input_iterator_tag) {
for ( ; first != last; ++first)
push_back(*first);""
}
template <class ForwardIterator>
void range_initialize(ForwardIterator first, ForwardIterator last,"批量分配n个空间并初始化，再修改vector的位置元素"
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 ForwardIterator>
iterator allocate_and_copy(size_type n,"批量分配n个value_type大小的空间，并进行拷贝初始化"
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));
}
析构函数：
~vector() { "析构函数"
destroy(start, finish);""
deallocate();
}
内部函数：destroy（析构函数）
deallocate（释放空间）
template <class T>
inline void destroy(T* pointer) {
pointer->~T();
}
template <class ForwardIterator>
inline void
__destroy_aux(ForwardIterator first, ForwardIterator last, __false_type) {
for ( ; first < last; ++first)
destroy(&*first);
}
template <class ForwardIterator>
inline void __destroy_aux(ForwardIterator, ForwardIterator, __true_type) {}
template <class ForwardIterator, class T>
inline void __destroy(ForwardIterator first, ForwardIterator last, T*) {
typedef typename __type_traits<T>::has_trivial_destructor trivial_destructor;
__destroy_aux(first, last, trivial_destructor());
}
template <class ForwardIterator>"依次调用每一个迭代器指向元素的析构函数"
inline void destroy(ForwardIterator first, ForwardIterator last) {
__destroy(first, last, value_type(first));
}
void deallocate() {"空间释放"
if (start) data_allocator::deallocate(start, end_of_storage - start);
}
重载操作符：=、==、!=、>、<、>=、<=、[]
template <class T, class Alloc>
vector<T, Alloc>& vector<T, Alloc>::operator=(const vector<T, Alloc>& x) {
if (&x != this) {
if (x.size() > capacity()) {"自身容量不足，需重新分配更大的内存"
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()) {"自身空间足够"
iterator i = copy(x.begin(), x.end(), begin());
destroy(i, finish);
}
else {"自身空间不足，但自身容量足够"
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>
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());
}
内部函数：equal
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());
}
内部函数：lexicographical_compare
reference operator[](size_type n) { return *(begin() + n); }"下标操作"
const_reference operator[](size_type n) const { return *(begin() + n); }
begin():
iterator begin() { return start; }"begin函数"
const_iterator begin() const { return start; }
end():
iterator end() { return finish; }"end函数"
const_iterator end() const { return finish; }
rbegin():
reverse_iterator rbegin() { return reverse_iterator(end()); }"rbegin函数"
const_reverse_iterator rbegin() const {
return const_reverse_iterator(end());
}
rend():
reverse_iterator rend() { return reverse_iterator(begin()); }"rend函数"
const_reverse_iterator rend() const {
return const_reverse_iterator(begin());
}
front():
reference front() { return *begin(); }"返回第一个元素的值"
const_reference front() const { return *begin(); }
back():
reference back() { return *(end() - 1); }"返回最后一个元素的值"
const_reference back() const { return *(end() - 1); }
insert():
iterator insert(iterator position, const T& x) {"在指定的位置插入一个新元素，值为x"
size_type n = position - begin();
if (finish != end_of_storage && position == end()) {"恰好插入位置是end位置"
construct(finish, x);
++finish;
}
else
insert_aux(position, x);
return begin() + n;
}
iterator insert(iterator position) { return insert(position, T()); }"在指定的位置插入一个新元素，值为默认"
template <class InputIterator>
void insert(iterator position, InputIterator first, InputIterator last) {"从指定的位置开始插入一段新元素"
range_insert(position, first, last, iterator_category(first));
}
内部函数：range_insert
void insert (iterator pos, size_type n, const T& x){"在指定的位置插入n个值为x的新元素"
if (n != 0) {
if (size_type(end_of_storage - finish) >= n) {"剩余空间足够用于插入n个元素"
T x_copy = x;
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);
fill(position, position + n, x_copy);
}
else {
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 {
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_fill_n(new_finish, n, x);
new_finish = uninitialized_copy(position, finish, new_finish);
}
destroy(start, finish);
deallocate();
start = new_start;
finish = new_finish;
end_of_storage = new_start + len;
}
}
}
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);
}
内部函数：range_insert
template <class InputIterator>"range_insert函数"
void range_insert(iterator pos,
InputIterator first, InputIterator last,
input_iterator_tag) {
for ( ; first != last; ++first) {
pos = insert(pos, *first);
++pos;
}
}
template <class ForwardIterator>
void 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);
}
destroy(start, finish);
deallocate();
start = new_start;
finish = new_finish;
end_of_storage = new_start + len;
}
}
}
push_back():
void push_back(const T& x) {"push_back函数"
if (finish != end_of_storage) {
construct(finish, x);"调用元素的构造函数并初始化"
++finish;
}
else
insert_aux(end(), x);
}
pop_back():
void pop_back() {"pop_back函数"
--finish;
destroy(finish);
}
clear():
void clear() { erase(begin(), end()); }"clear函数"
at():
assign():
erase():
iterator erase(iterator position) {"释放某个位置的元素"
if (position + 1 != end())
copy(position + 1, finish, position);
--finish;
destroy(finish);
return position;
}
iterator erase(iterator first, iterator last) {"释放一段区间的元素"
iterator i = copy(last, finish, first);
destroy(i, finish);
finish = finish - (last - first);
return first;
}
capacity():
size_type capacity() const { return size_type(end_of_storage - begin()); }"capacity函数"
size():
size_type size() const { return size_type(end() - begin()); }"size函数"
resize():
void resize(size_type new_size, const T& x) {"resize改变了vector的capacity同时也增加了它的size"
if (new_size < size())
erase(begin() + new_size, end());//并不做赋值初始化动作
else
insert(end(), new_size - size(), x);
}
max_size():
size_type max_size() const { return size_type(-1) / sizeof(T); }"max_size函数"（疑惑）
empty():
bool empty() const { return begin() == end(); }"empty函数"
swap():
template <class T, class Alloc>
inline void swap(vector<T, Alloc>& x, vector<T, Alloc>& y) {"只交换位置元素而已"
x.swap(y);
}
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);
}
reserve():
void reserve(size_type n) {"reserve增加了vector的capacity，但是它的size没有改变"
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;
}
}
注：由于本人水平有限，若有不对的地方，欢迎指正！谢谢