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  1. #include <cctype>
  2. #include <iostream>
  3.  
  4. namespace {
  5.   int to_int(int c) {
  6.     if (not isxdigit(c)) return -1; // error: non-hexadecimal digit found
  7.     if (isdigit(c)) return c - '0';
  8.     if (isupper(c)) c = tolower(c);
  9.     return c - 'a' + 10;
  10.   }
  11.  
  12.   template<class InputIterator, class OutputIterator> int
  13.   unhexlify(InputIterator first, InputIterator last, OutputIterator ascii) {
  14.     while (first != last) {
  15.       int top = to_int(*first++);
  16.       int bot = to_int(*first++);
  17.       if (top == -1 or bot == -1)
  18. 	return -1; // error
  19.       *ascii++ = (top << 4) + bot;
  20.     }
  21.     return 0;
  22.   }
  23. }
  24.  
  25. int main() {
  26.   char hex[] = "7B5a7D";
  27.   size_t len = sizeof(hex) - 1; // strlen
  28.   char ascii[len/2+1];
  29.   ascii[len/2] = '\0';
  30.  
  31.   if (unhexlify(hex, hex+len, ascii) < 0) return 1; // error
  32.   std::cout << hex << " -> " << ascii << std::endl;
  33. }
  34.  
Success #stdin #stdout 0s 2828KB
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stdin
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Standard input is empty
stdout
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7B5a7D -> {Z}
https://ideone.com/o4boW
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
secret

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