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       1                 :             : // Copyright (c) 2015-2022 The Bitcoin Core developers
       2                 :             : // Distributed under the MIT software license, see the accompanying
       3                 :             : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
       4                 :             : 
       5                 :             : #include <common/url.h>
       6                 :             : 
       7                 :             : #include <charconv>
       8                 :             : #include <string>
       9                 :             : #include <string_view>
      10                 :             : #include <system_error>
      11                 :             : 
      12                 :          35 : std::string UrlDecode(std::string_view url_encoded)
      13                 :             : {
      14         [ +  - ]:          35 :     std::string res;
      15         [ +  - ]:          35 :     res.reserve(url_encoded.size());
      16                 :             : 
      17         [ +  + ]:         266 :     for (size_t i = 0; i < url_encoded.size(); ++i) {
      18         [ +  + ]:         231 :         char c = url_encoded[i];
      19                 :             :         // Special handling for percent which should be followed by two hex digits
      20                 :             :         // representing an octet values, see RFC 3986, Section 2.1 Percent-Encoding
      21   [ +  +  +  + ]:         231 :         if (c == '%' && i + 2 < url_encoded.size()) {
      22                 :          45 :             unsigned int decoded_value{0};
      23                 :          45 :             auto [p, ec] = std::from_chars(url_encoded.data() + i + 1, url_encoded.data() + i + 3, decoded_value, 16);
      24                 :             : 
      25                 :             :             // Only if there is no error and the pointer is set to the end of
      26                 :             :             // the string, we can be sure both characters were valid hex
      27   [ +  +  +  + ]:          45 :             if (ec == std::errc{} && p == url_encoded.data() + i + 3) {
      28         [ +  - ]:          26 :                 res += static_cast<char>(decoded_value);
      29                 :             :                 // Next two characters are part of the percent encoding
      30                 :          26 :                 i += 2;
      31                 :          26 :                 continue;
      32                 :             :             }
      33                 :             :             // In case of invalid percent encoding, add the '%' and continue
      34                 :             :         }
      35         [ +  - ]:         436 :         res += c;
      36                 :             :     }
      37                 :             : 
      38                 :          35 :     return res;
      39                 :           0 : }