Base64 Library

#include <string>

std::string dict = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

std::string Base64EncodeString(const unsigned char *Buffer, int Length)
{
    std::string result;
    for (int i = 0; i < Length; i += 3)
    {
        result += dict[Buffer[i] >> 2];
        if (i == Length - 1)
        {
            result += dict[((Buffer[i] & 0x03) << 4)];
            result += "==";
        }
        else if (i == Length - 2)
        {
            result += dict[(Buffer[i] << 4) | (Buffer[i + 1] >> 4)];
            result += dict[(Buffer[i + 1] & 0x03) << 2];
            result += "=";
        }
        else
        {
            result += dict[(Buffer[i] << 4) | (Buffer[i + 1] & 0xF0) >> 4];
            result += dict[(Buffer[i + 1] & 0x0F << 2) | (Buffer[i + 2] & 0xC0) >> 6];
            result += dict[Buffer[i + 2] & 0x3F];
        }
    }
    return result;
}

std::string Base64DecodeString(const std::string& Buffer)
{
    std::string result;

    for (int i = 0; i < Buffer.size(); i += 4)
    {
        if (dict.find(Buffer[i]) == std::string::npos ||
            dict.find(Buffer[i + 1]) == std::string::npos ||
            dict.find(Buffer[i + 2]) == std::string::npos ||
            dict.find(Buffer[i + 3]) == std::string::npos)
            return nullptr;

        result += dict.find(Buffer[i]) << 2 | (dict.find(Buffer[i + 1]) & 0x30) >> 4;

        if (Buffer[i + 2] != '=')
        {
            result += ((dict.find(Buffer[i + 1]) & 0x0F) << 4 | (dict.find(Buffer[i + 2]) & 0x3C) >> 2);
            result += ((dict.find(Buffer[i + 2]) & 0x03) << 6) | dict.find(Buffer[i + 3]) - (i == Buffer.size() - 4 && Buffer[i + 3] == '=' ? dict.find(Buffer[i + 3]) : 0);
        }
    }
    return result;
}