🔨 Fix shrink_to_fit.

MyTinySTL/basic_string.h

@@ -420,7 +420,7 @@ class basic_string
   { return static_cast<size_type>(-1); }
 
   void      reserve(size_type n);
-  void      shrink_to_fit() noexcept;
+  void      shrink_to_fit();
 
   // 访问元素相关操作
   reference       operator[](size_type n) 
@@ -698,6 +698,9 @@ class basic_string
   // get raw pointer
   const_pointer to_raw_pointer() const;
 
+  // shrink_to_fit
+  void          reinsert(size_type size);
+
   // append
   template <class Iter>
   basic_string& append_range(Iter first, Iter last);
@@ -769,12 +772,11 @@ reserve(size_type n)
 // 减少不用的空间
 template <class CharType, class CharTraits>
 void basic_string<CharType, CharTraits>::
-shrink_to_fit() noexcept
+shrink_to_fit()
 {
   if (size_ != cap_)
   {
-    data_allocator::deallocate(buffer_ + size_, cap_ - size_);
-    cap_ = size_;
+    reinsert(size_);
   }
 }
 
@@ -1678,6 +1680,25 @@ to_raw_pointer() const
   return buffer_;
 }
 
+// reinsert 函数
+template <class CharType, class CharTraits>
+void basic_string<CharType, CharTraits>::
+reinsert(size_type size)
+{
+  auto new_buffer = data_allocator::allocate(size);
+  try
+  {
+    char_traits::move(new_buffer, buffer_, size);
+  }
+  catch (...)
+  {
+    data_allocator::deallocate(new_buffer);
+  }
+  buffer_ = new_buffer;
+  size_ = size;
+  cap_ = size;
+}
+
 // append_range，末尾追加一段 [first, last) 内的字符
 template <class CharType, class CharTraits>
 template <class Iter>

MyTinySTL/vector.h

@@ -69,10 +69,8 @@ class vector
 
 public:
   // 构造、复制、移动、析构函数
-  vector()
-  {
-    init_space(0, 16);
-  }
+  vector() noexcept
+  { try_init(); }
 
   explicit vector(size_type n)
   { fill_init(n, value_type()); }
@@ -164,7 +162,7 @@ class vector
   size_type capacity() const noexcept
   { return static_cast<size_type>(cap_ - begin_); }
   void      reserve(size_type n);
-  void      shrink_to_fit()  noexcept;
+  void      shrink_to_fit();
 
   // 访问元素相关操作
   reference operator[](size_type n)
@@ -284,6 +282,7 @@ class vector
   // helper functions
 
   // initialize / destroy
+  void      try_init() noexcept;
 
   void      init_space(size_type size, size_type cap);
 
@@ -318,6 +317,9 @@ class vector
   template <class IIter>
   void      copy_insert(iterator pos, IIter first, IIter last);
 
+  // shrink_to_fit
+
+  void      reinsert(size_type size);
 };
 
 /*****************************************************************************************/
@@ -367,21 +369,6 @@ vector<T>& vector<T>::operator=(vector&& rhs) noexcept
   return *this;
 }
 
-// 放弃多余的容量
-template <class T>
-void vector<T>::shrink_to_fit() noexcept
-{
-  if (end_ < cap_)
-  {
-    try
-    {
-      data_allocator::deallocate(end_ + 1, cap_ - end_);
-      cap_ = end_;
-    }
-    catch (...) {}
-  }
-}
-
 // 预留空间大小，当原容量小于要求大小时，才会重新分配
 template <class T>
 void vector<T>::reserve(size_type n)
@@ -400,6 +387,16 @@ void vector<T>::reserve(size_type n)
   }
 }
 
+// 放弃多余的容量
+template <class T>
+void vector<T>::shrink_to_fit()
+{
+  if (end_ < cap_)
+  {
+    reinsert(size());
+  }
+}
+
 // 在 pos 位置就地构造元素，避免额外的复制或移动开销
 template <class T>
 template <class ...Args>
@@ -553,6 +550,25 @@ void vector<T>::swap(vector<T>& rhs) noexcept
 /*****************************************************************************************/
 // helper function
 
+// try_init 函数，若分配失败则忽略，不抛出异常
+template <class T>
+void vector<T>::try_init() noexcept
+{
+  try
+  {
+    begin_ = data_allocator::allocate(16);
+    end_ = begin_;
+    cap_ = begin_ + 16;
+  }
+  catch (...)
+  {
+    begin_ = nullptr;
+    end_ = nullptr;
+    cap_ = nullptr;
+  }
+}
+
+// init_space 函数
 template <class T>
 void vector<T>::init_space(size_type size, size_type cap)
 {
@@ -848,6 +864,25 @@ copy_insert(iterator pos, IIter first, IIter last)
   }
 }
 
+// reinsert 函数
+template <class T>
+void vector<T>::reinsert(size_type size)
+{
+  auto new_begin = data_allocator::allocate(size);
+  try
+  {
+    mystl::uninitialized_move(begin_, end_, new_begin);
+  }
+  catch (...)
+  {
+    data_allocator::deallocate(new_begin, size);
+    throw;
+  }
+  begin_ = new_begin;
+  end_ = begin_ + size;
+  cap_ = begin_ + size;
+}
+
 /*****************************************************************************************/
 // 重载比较操作符