1 // Copyright (c) 2015-2022 The Limenka 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 std::string UrlDecode(std::string_view url_encoded)
13 {
14 std::string res;
15 res.reserve(url_encoded.size());
16 17 for (size_t i = 0; i < url_encoded.size(); ++i) {
18 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 if (c == '%' && i + 2 < url_encoded.size()) {
22 unsigned int decoded_value{0};
23 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 if (ec == std::errc{} && p == url_encoded.data() + i + 3) {
28 res += static_cast<char>(decoded_value);
29 // Next two characters are part of the percent encoding
30 i += 2;
31 continue;
32 }
33 // In case of invalid percent encoding, add the '%' and continue
34 }
35 res += c;
36 }
37 38 return res;
39 }
40