encoding.hpp

/** 
 * @file encoding.hpp
 * @brief Contains base64 encoder/decoder
 * @author Jari Ronkainen
 * @version 0.3
 * @date 2017-08-22
 */
#ifndef MUSH_ENCODING
#define MUSH_ENCODING

#include <cstdint>

#include "buffer.hpp"
#include "string.hpp"

namespace mush
{
    constexpr char base64_characters[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "abcdefghijklmnopqrstuvwxyz"
        "0123456789+/";

    namespace base64
    {
        uint32_t get_b64_id(char32_t c)
        {
            if (c == '+')
                return 62;
            else if (c == '/')
                return 63;
            else if (c < 'A')
                return c - '0' + 52;
            else if (c < 'a')
                return c - 'A';
            else
                return c - 'a' + 26;
        }

        bool valid_char(char32_t c)
        {
            return std::isalnum(c) || c == '+' || c == '/' || c == '=';
        }

        string encode(const mush::Buffer& in_buf)
        {
            string rval;

            int val = 0, valb = -6;
            for (uint8_t c : in_buf)
            {
                val = (val << 8) + c;
                valb += 8;
                while (valb >= 0)
                {
                    rval += string(base64_characters[(val>>valb) & 0x3f]);
                    valb -= 6;
                }
            }
            if (valb > -6)
                rval += base64_characters[((val<<8)>>(valb+8)) & 0x3f];
            while (rval.length() % 4)
                rval += '=';

            return rval;
        }

        Buffer decode(const mush::string& in_str)
        {
            Buffer rval;

            int val = 0;
            int valb = -8;

            for (char32_t c : in_str)
            {
                if (!valid_char(c))
                    break;

                val = (val << 6) + get_b64_id(c);
                valb += 6;
                if (valb > 0)
                {
                    rval.push_back((val >> valb) & 0xff);
                    valb -= 8;
                }
            }
            return rval;
        }
    }
}

#endif

/*
 Copyright (c) 2017 Jari Ronkainen

    This software is provided 'as-is', without any express or implied warranty.
    In no event will the authors be held liable for any damages arising from the
    use of this software.

    Permission is granted to anyone to use this software for any purpose, including
    commercial applications, and to alter it and redistribute it freely, subject to
    the following restrictions:

    1. The origin of this software must not be misrepresented; you must not claim
       that you wrote the original software. If you use this software in a product,
       an acknowledgment in the product documentation would be appreciated but is
       not required.

    2. Altered source versions must be plainly marked as such, and must not be
       misrepresented as being the original software.

    3. This notice may not be removed or altered from any source distribution.
*/