Skip to content

Commit

Permalink
修改扩容的 bug
Browse files Browse the repository at this point in the history
  • Loading branch information
@senlinzhan
senlinzhan committed Apr 29, 2017
1 parent 2620910 commit cb074a0
Showing 1 changed file with 48 additions and 59 deletions.
107 changes: 48 additions & 59 deletions vector.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ class vector
using const_reverse_iterator = std::reverse_iterator<const T*>;

private:
static constexpr size_type INIT_CAPACITY = 10;
static constexpr size_type FIRST_EXPAND_CAPACITY = 10;
static constexpr size_type EXPAND_RATE = 2;

pointer elem_ = nullptr; // pointer to the first element in the allocated space
Expand Down Expand Up @@ -212,11 +212,11 @@ class vector

void resize(size_type new_size, const value_type &value)
{
if(new_size < size())
if (new_size < size())
{
erase(begin() + new_size, end());
}
else if(new_size > size())
else if (new_size > size())
{
insert(end(), size() - new_size, value);
}
Expand All @@ -225,23 +225,21 @@ class vector
void push_back(const value_type &value)
{
check_expand_capacity();
alloc_.construct(free_, value);
++free_;
alloc_.construct(free_++, value);
}

void push_back(value_type &&value)
{
check_expand_capacity();
new (free_) value_type(std::move(value));
new (free_) value_type(std::move(value)); // placement new
++free_;
}

template<typename... Args>
void emplace_back(Args&&... args)
{
check_expand_capacity();
alloc_.construct(free_, std::forward<Args>(args)...);
++free_;
alloc_.construct(free_++, std::forward<Args>(args)...);
}

void shrink_to_fit()
Expand All @@ -262,20 +260,21 @@ class vector

void reserve(size_type n)
{
if(n > capacity())
{
expand_to(n);
}
expand_capacity(n);
}

reference operator[](size_type n)
{
return at(n);
if (n < size())
{
return elem_[n];
}
throw std::out_of_range("vector::operator[] - the specify index is out of bound");
}

const_reference operator[](size_type n) const
{
return at(n);
return const_cast<vector *>(this)->operator[](n);
}

reference at(size_type n)
Expand All @@ -284,10 +283,7 @@ class vector
{
return elem_[n];
}
else
{
throw std::out_of_range("vector::at() - the specify index is out of bound");
}
throw std::out_of_range("vector::at() - the specify index is out of bound");
}

const_reference at(size_type n) const
Expand All @@ -297,11 +293,11 @@ class vector

reference front()
{
if(!elem_)
if (elem_)
{
throw std::length_error("vector::front() - the vector is empty");
return *begin();
}
return *begin();
throw std::length_error("vector::front() - the vector is empty");
}

const_reference front() const
Expand All @@ -311,11 +307,11 @@ class vector

reference back()
{
if(!elem_)
if(elem_)
{
throw std::length_error("vector::back() - the vector is empty");
return *rbegin();
}
return *rbegin();
throw std::length_error("vector::back() - the vector is empty");
}

const_reference back() const noexcept
Expand All @@ -325,11 +321,11 @@ class vector

void pop_back()
{
if(!elem_)
if (!empty())
{
throw std::length_error("vector::pop_back() - the vector is empty");
alloc_.destroy(--free_);
}
alloc_.destroy(--free_);
throw std::length_error("vector::pop_back() - the vector is empty");
}

template<typename... Args>
Expand All @@ -339,36 +335,30 @@ class vector
{
throw std::out_of_range("vector::emplace() - parameter \"position\" is out of bound");
}

// if we expand vector's size, then position will be invalid
difference_type diff = position - cbegin();
check_expand_capacity();

if(position == cend())
// we use pos instead of position
auto pos = elem_ + diff;

if (pos == cend())
{
emplace_back(std::forward<Args>(args)...);
alloc_.construct(free_++, std::forward<Args>(args)...);
return free_ - 1;
}

difference_type diff = position - cbegin();

// if we expand vector's size, then position will be invalid
if(free_ == last_)
{
check_expand_capacity();
}

// Note: we can't use position now, because position may be invalid, we use pos instead
auto pos = elem_ + diff;

// we construct a new element as the last element
alloc_.construct(free_, *(free_ - 1));
// move construct a new element
new (free_) value_type(std::move(*(free_ - 1)));
++free_;

// move elements
for(auto iter = free_ - 2; iter != pos; --iter)

for (auto iter = free_ - 2; iter != pos; --iter)
{
*iter = std::move(*(iter - 1));
}

*pos = value_type(std::forward<Args>(args)...);

return pos;
}

Expand Down Expand Up @@ -498,24 +488,23 @@ class vector
}

private:

void check_expand_capacity()
{
if (free_ == last_)
{
size_type new_size = empty() ? INIT_CAPACITY : size() * EXPAND_RATE;
expand_to(new_size);
size_type new_capacity = empty() ? FIRST_EXPAND_CAPACITY : size() * EXPAND_RATE;
expand_capacity(new_capacity);
}
}

void expand_to(size_type new_size)
void expand_capacity(size_type new_capacity)
{
if(new_size <= size())
if (new_capacity <= capacity())
{
return;
}
auto new_elem = alloc_.allocate(new_size);

auto new_elem = alloc_.allocate(new_capacity);
auto new_free = new_elem;

// if value_type's move constructor is noexcept, then move elements
Expand All @@ -524,7 +513,8 @@ class vector
{
for(auto iter = elem_; iter != free_; ++iter)
{
alloc_.construct(new_free++, std::move( *iter ));
new (new_free) value_type(std::move(*iter)); // placement new
++new_free;
}
}
else
Expand All @@ -533,9 +523,9 @@ class vector
{
new_free = std::uninitialized_copy(elem_, free_, new_elem);
}
catch(...) // catch the exception throw by value_type's copy constructor
catch(...) // catch the exception throw by value_type's copy constructor
{
alloc_.deallocate(new_elem, new_size);
alloc_.deallocate(new_elem, new_capacity);
throw;
}
}
Expand All @@ -545,10 +535,9 @@ class vector

elem_ = new_elem;
free_ = new_free;
last_ = new_elem + new_size;
last_ = new_elem + new_capacity;
}


// Note: before call this function, you must sure that the container is empty!
void create_elements(size_type n, const value_type &value)
{
Expand Down

0 comments on commit cb074a0

Please sign in to comment.