在c++中编码已解码的urls

#include <iostream>
#include <iomanip>
#include <sstream>
#include <string>
#include <cctype>

// URL 编码函数
std::string url_encode(const std::string &value) {
    std::ostringstream escaped;
    escaped.fill('0');
    escaped << std::hex;

    for (char c : value) {
        // 保留字母、数字和某些特殊字符
        if (isalnum(static_cast<unsigned char>(c)) || c == '-' || c == '_' || c == '.' || c == '~') {
            escaped << c;
        } else {
            // 将其他字符转换为 % 后跟两个十六进制数字
            escaped << '%' << std::setw(2) << int(static_cast<unsigned char>(c));
        }
    }

    return escaped.str();
}

// URL 解码函数
std::string url_decode(const std::string &value) {
    std::string result;
    result.reserve(value.size());

    for (size_t i = 0; i < value.size(); ++i) {
        if (value[i] == '%' && i + 2 < value.size()) {
            // 将 % 后跟的两个十六进制数字转换为字符
            std::istringstream hex_stream(value.substr(i + 1, 2));
            int hex_value;
            if (hex_stream >> std::hex >> hex_value) {
                result += static_cast<char>(hex_value);
                i += 2;
            } else {
                result += '%';
            }
        } else if (value[i] == '+') {
            // 将 + 转换为空格
            result += ' ';
        } else {
            result += value[i];
        }
    }

    return result;
}

int main() {
    std::string original = "Hello, World! 你好，世界！";
    std::string encoded = url_encode(original);
    std::string decoded = url_decode(encoded);

    std::cout << "Original: " << original << std::endl;
    std::cout << "Encoded: " << encoded << std::endl;
    std::cout << "Decoded: " << decoded << std::endl;

    return 0;
}