Class Base64

payload.cpp:683–774

#pragma comment(lib, "Ws2_32.lib")

class Base64 {
private:
    static const std::string BASE64_CHARS;

    static inline bool is_base64(unsigned char c) {
        return (isalnum(c) || (c == '+') || (c == '/'));
    }

public:
    static std::string encode(const std::string& input) {
        std::string ret;
        int i = 0;
        unsigned char char_array_3[3], char_array_4[4];

        for (size_t n = 0; n < input.size(); n++) {
            char_array_3[i++] = input[n];
            if (i == 3) {
                char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
                char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
                char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
                char_array_4[3] = char_array_3[2] & 0x3f;

                for (i = 0; i < 4; i++) {
                    ret += BASE64_CHARS[char_array_4[i]];
                }
                i = 0;
            }
        }

        if (i) {
            for (int j = i; j < 3; j++) {
                char_array_3[j] = '\0';
            }

            char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
            char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
            char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
            char_array_4[3] = char_array_3[2] & 0x3f;

            for (int j = 0; j < i + 1; j++) {
                ret += BASE64_CHARS[char_array_4[j]];
            }

            while (i++ < 3) {
                ret += '=';
            }
        }

        return ret;
    }

    static std::string decode(const std::string& encoded_string) {
        int in_len = encoded_string.size();
        int i = 0;
        int j = 0;
        int in_ = 0;
        unsigned char char_array_4[4], char_array_3[3];
        std::string ret;