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  1. template <typename T>
  2. T* dup(T* begin, T* end)
  3. {
  4.   class mem_guard {
  5.     void *p;
  6.   public:
  7.     mem_guard(std::size_t n) { p = std::malloc(n*sizeof(T)); }
  8.    ~mem_guard() { if (p) std::free(p); }
  9.  
  10.     T* get()     { return static_cast<T*>(p); }
  11.     T* release() { T *ptr=get(); p=0; return ptr; }
  12.   };
  13.  
  14.   class unroll_guard {
  15.     T *start, *curr;
  16.   public:
  17.     unroll_guard(T *p) : start(p), curr(p) {}
  18.    ~unroll_guard() { if (start) while (curr-- != start) curr->~T(); }
  19.     void emplace_back(T const& t) { new (curr) T(t); ++curr; }
  20.     void release() { start = 0; }
  21.   };
  22.  
  23.   std::ptrdiff_t n = end - begin;
  24.   assert(n > 0);
  25.  
  26.   // guard the memory
  27.   mem_guard memory(n);
  28.   if (!memory.get())
  29.     return 0;
  30.  
  31.   // guard the items
  32.   unroll_guard data(memory.get());
  33.   for (; begin != end; ++begin)
  34.     data.emplace_back(*begin);
  35.  
  36.   // everything ok, release the resources
  37.   data.release();
  38.   return memory.release();
  39. }
  40.  
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https://ideone.com/zIE58c
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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