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  1. #include <iostream>
  2.  
  3.     template <unsigned SIZE>
  4.     struct offset_size {
  5.         typedef typename offset_size<SIZE - 1>::type type;
  6.     };
  7.  
  8.     template <>
  9.     struct offset_size<0> {
  10.         typedef unsigned char type;
  11.     };
  12.  
  13.     template <>
  14.     struct offset_size<257> {
  15.         typedef unsigned int type;
  16.     };
  17.  
  18.     template<unsigned SIZE>
  19.     class circular_buffer {
  20.     public: // Added this line so we can inspect the sizes from main()
  21.        unsigned char buffer[SIZE];
  22.        typename offset_size<SIZE>::type head; // index
  23.        typename offset_size<SIZE>::type tail; // index
  24.     };
  25.  
  26. int main() {
  27.     std::cout << sizeof(circular_buffer<256>().head) << std::endl;
  28.     std::cout << sizeof(circular_buffer<257>().head) << std::endl;
  29. }
Success #stdin #stdout 0.01s 2680KB
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stdin 
Standard input is empty
stdout 
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https://ideone.com/vYPow
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
secret

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