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  1. #include <vector>
  2. #include <iostream>
  3.  
  4. class String
  5. {
  6. public:
  7.     //! default constructor
  8.     String();
  9.  
  10.     //! constructor taking C-style string i.e. a char array terminated with'\0'.
  11.     explicit String(const char * const c);
  12.  
  13.     //! copy constructor
  14.     explicit String(const String& s);
  15.  
  16.     //! move constructor    
  17.     String(String&& s) noexcept;
  18.  
  19.     //! operator =
  20.     String& operator = (const String& rhs);
  21.  
  22.     //! move operator =     
  23.     String& operator = (String&& rhs) noexcept;
  24.  
  25.     //! destructor
  26.     ~String();
  27.  
  28.     //! members
  29.     char* begin() const  { return elements;   }
  30.     char* end()   const  { return first_free; }
  31.  
  32.     std::size_t size()     const {return first_free - elements;  }
  33.     std::size_t capacity() const {return cap - elements;         }
  34.  
  35. private:
  36.  
  37.     //! data members
  38.     char* elements;
  39.     char* first_free;
  40.     char* cap;
  41.  
  42.     std::allocator<char> alloc;
  43.  
  44.     //! utillities for big 3
  45.     void free();
  46.  
  47. };
  48.  
  49. //! default constructor
  50. String::String():
  51.     elements    (nullptr),
  52.     first_free  (nullptr),
  53.     cap         (nullptr)
  54. {}
  55.  
  56. //! copy constructor
  57. String::String(const String &s)
  58. {
  59.     char* newData = alloc.allocate(s.size());
  60.     std::uninitialized_copy(s.begin(), s.end(), newData);
  61.  
  62.     elements = newData;
  63.     cap = first_free = newData + s.size();
  64.  
  65.     std::cout << "Copy constructing......\n";
  66. }
  67.  
  68. //! move constructor    
  69. String::String(String &&s) noexcept :
  70.     elements(s.elements), first_free(s.first_free), cap(s.cap)
  71. {
  72.     s.elements = s.first_free = s.cap = nullptr;
  73.     std::cout << "Move constructing......\n";
  74. }
  75.  
  76. String::~String()
  77. {
  78.     // leaky leaky
  79. }
  80.  
  81. String& String::operator = (String&& rhs) noexcept
  82. {
  83.     String temp(rhs);
  84.     std::swap(elements, temp.elements);
  85.     std::swap(first_free, temp.first_free);
  86.     std::swap(cap, temp.cap);
  87.     return *this;
  88. }
  89.  
  90. int main()
  91. {
  92.     std::vector<String> v;
  93.     String s;
  94.     for (unsigned i = 0; i != 4; ++i)
  95.         v.push_back(s);
  96.  
  97.     return 0;
  98. }
  99.  
Success #stdin #stdout 0s 3472KB
comments (?)
stdin
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Standard input is empty
stdout
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Copy constructing......
Copy constructing......
Move constructing......
Copy constructing......
Move constructing......
Move constructing......
Copy constructing......
https://ideone.com/9YaaZ0
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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