C/C++

C++에서 base64로 인코딩

by Naya posted Nov 15, 2012
?

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void wstrToUtf8(string& dest, const wstring& src){
    dest.clear();
    for (size_t i = 0; i < src.size(); i++){
        wchar_t w = src[i];
        if (w <= 0x7f)
            dest.push_back((char)w);
        else if (w <= 0x7ff){
            dest.push_back(0xc0 | ((w >> 6)& 0x1f));
            dest.push_back(0x80| (w & 0x3f));
        }
        else if (w <= 0xffff){
            dest.push_back(0xe0 | ((w >> 12)& 0x0f));
            dest.push_back(0x80| ((w >> 6) & 0x3f));
            dest.push_back(0x80| (w & 0x3f));
        }
        else if (w <= 0x10ffff){
            dest.push_back(0xf0 | ((w >> 18)& 0x07));
            dest.push_back(0x80| ((w >> 12) & 0x3f));
            dest.push_back(0x80| ((w >> 6) & 0x3f));
            dest.push_back(0x80| (w & 0x3f));
        }
        else
            dest.push_back('?');
    }
}
 
 
string wstrToUtf8(const wstring& str){
    string result;
    wstrToUtf8(result, str);
    return result;
}
 
 
//===========================================================
// base64
//===========================================================
std::wstring base64Encode(const wstring input){
    string utf8_input = wstrToUtf8(input);
 
    unsigned char const* buffer = (unsigned const char*)(utf8_input.c_str());
    size_t size = utf8_input.length();
 
    using std::wstring;
    static wchar_t const* base64Table =
        L"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
     
    // for =
    // size_t base64Size = (size + 2 - ((size + 2) % 3)) / 3 * 4;
    // wstring result(base64Size, L'=');
 
    size_t base64Size = ceil(size * 4.0 / 3);
    wstring result(base64Size, L'');
 
    unsigned char const* s = buffer;  // source pointer
    size_t di = 0;                    // destination index
    for(size_t i = 0; i < size / 3; i++){
        // input: 0000_0000 0000_0000 0000_0000
        // 
        // out1:  0000_00
        // out2:         00 0000
        // out3:                _0000 00
        // out4:                        00_0000
         
        result[di++] = base64Table[s[0] >> 2];
        result[di++] = base64Table[((s[0] << 4) | (s[1] >> 4)) & 0x3f];
        result[di++] = base64Table[((s[1] << 2) | (s[2] >> 6)) & 0x3f];
        result[di++] = base64Table[s[2] & 0x3f];
        s += 3;
    }
 
    size_t remainSize = size % 3;
    switch(remainSize){
    case 0:
        break;
    case 1:
        result[di++] = base64Table[s[0] >> 2];
        result[di++] = base64Table[(s[0] << 4) & 0x3f];
        break;
    case 2:
        result[di++] = base64Table[s[0] >> 2];
        result[di++] = base64Table[((s[0] << 4) | (s[1] >> 4)) & 0x3f];
        result[di++] = base64Table[(s[1] << 2) & 0x3f];
        break;
    default:
        throw std::logic_error("Should not happen.");
    }
    return result;
}
 
 
 
int main() {
    wcout.imbue(locale("korean"));
 
    wstring plain(L"대한민국");
    wcout << base64Encode(plain).c_str() << endl;
 
    return 0;
}


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