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  1. #include <functional>
  2. #include <ios>
  3. #include <streambuf>
  4.  
  5. template <typename CharT, class Traits = std::char_traits<CharT>>
  6. class encrypted_basic_streambuf : public std::basic_streambuf<CharT, Traits>
  7. {
  8. public:
  9.     // Irgendwie notwendig. Bug?
  10.     using char_type   = typename std::basic_streambuf<CharT, Traits>::char_type;
  11.     using traits_type = typename std::basic_streambuf<CharT, Traits>::traits_type;
  12.     using int_type    = typename std::basic_streambuf<CharT, Traits>::int_type;
  13.  
  14.     using encryption_function = std::function<char_type(char_type)>;
  15.  
  16.     encrypted_basic_streambuf(std::basic_ios<char_type, traits_type> &stream,
  17.                               encryption_function function)
  18.     : stream_(stream), streambuf_(stream.rdbuf()), function_(function)
  19.     {
  20.         stream_.rdbuf(this);
  21.     }
  22.  
  23.     ~encrypted_basic_streambuf()
  24.     {
  25.         stream_.rdbuf(streambuf_);
  26.     }
  27.  
  28. protected:
  29.     int_type underflow() override
  30.     {
  31.         auto c = streambuf_->sgetc();
  32.         return traits_type::eq_int_type(c, traits_type::eof()) ? c : function_(c);
  33.     }
  34.  
  35.     int_type uflow() override
  36.     {
  37.         auto c = streambuf_->sbumpc();
  38.         return traits_type::eq_int_type(c, traits_type::eof()) ? c : function_(c);
  39.     }
  40.  
  41.     int_type overflow(int_type c) override
  42.     {
  43.         streambuf_->sputc(function_(c));
  44.         return c;
  45.     }
  46.  
  47. private:
  48.     std::basic_ios<char_type, traits_type>       &stream_;
  49.     std::basic_streambuf<char_type, traits_type> *streambuf_;
  50.     encryption_function function_;
  51. };
  52.  
  53. #include <iostream>
  54.  
  55. int main()
  56. {
  57.     {
  58.         encrypted_basic_streambuf<char> encrypter(std::cout, [](char c){return c ^ 'a';});
  59.         std::cout << "Hallo Welt";
  60.     }
  61.     std::cout << "\n Test 2: \n";
  62.     {
  63.         class xor_encrypter
  64.         {
  65.         public:
  66.             xor_encrypter(char key)
  67.             : key_(key) {}
  68.  
  69.             char operator() (char c)
  70.             {
  71.                 return c ^ key_++;
  72.             }
  73.  
  74.         private:
  75.             char key_;
  76.         };
  77.  
  78.         encrypted_basic_streambuf<char> encrypter(std::cout, xor_encrypter('a'));
  79.         std::cout << "Hallo Welt";
  80.     }
  81. }
  82.  
Success #stdin #stdout 0s 2988KB
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A6

 Test 2: 
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F0

https://ideone.com/9litLY
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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