base64.hpp

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//
// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// Official repository: https://github.com/boostorg/beast
//

/*
   Portions from http://www.adp-gmbh.ch/cpp/common/base64.html
   Copyright notice:

   base64.cpp and base64.h

   Copyright (C) 2004-2008 René Nyffenegger

   This source code is provided 'as-is', without any express or implied
   warranty. In no event will the author 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 source code must not be misrepresented; you must not
      claim that you wrote the original source code. If you use this source code
      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 source code.

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

   René Nyffenegger rene.nyffenegger@adp-gmbh.ch

*/

#ifndef BOOST_BEAST_DETAIL_BASE64_HPP
#define BOOST_BEAST_DETAIL_BASE64_HPP

#include <cctype>
#include <string>
#include <utility>

namespace boost {
namespace beast {
namespace detail {

namespace base64 {

inline
char const*
get_alphabet()
{
    static char constexpr tab[] = {
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    };
    return &tab[0];
}

inline
signed char const*
get_inverse()
{
    static signed char constexpr tab[] = {
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, //   0-15
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, //  16-31
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, //  32-47
         52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, //  48-63
         -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, //  64-79
         15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, //  80-95
         -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, //  96-111
         41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, // 112-127
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 128-143
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 144-159
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 160-175
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 176-191
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 192-207
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 208-223
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 224-239
         -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1  // 240-255
    };
    return &tab[0];
}


inline
std::size_t constexpr
encoded_size(std::size_t n)
{
    return 4 * ((n + 2) / 3);
}

inline
std::size_t constexpr
decoded_size(std::size_t n)
{
    return n / 4 * 3; // requires n&3==0, smaller
    //return 3 * n / 4;
}

template<class = void>
std::size_t
encode(void* dest, void const* src, std::size_t len)
{
    char*      out = static_cast<char*>(dest);
    char const* in = static_cast<char const*>(src);
    auto const tab = base64::get_alphabet();

    for(auto n = len / 3; n--;)
    {
        *out++ = tab[ (in[0] & 0xfc) >> 2];
        *out++ = tab[((in[0] & 0x03) << 4) + ((in[1] & 0xf0) >> 4)];
        *out++ = tab[((in[2] & 0xc0) >> 6) + ((in[1] & 0x0f) << 2)];
        *out++ = tab[  in[2] & 0x3f];
        in += 3;
    }

    switch(len % 3)
    {
    case 2:
        *out++ = tab[ (in[0] & 0xfc) >> 2];
        *out++ = tab[((in[0] & 0x03) << 4) + ((in[1] & 0xf0) >> 4)];
        *out++ = tab[                         (in[1] & 0x0f) << 2];
        *out++ = '=';
        break;

    case 1:
        *out++ = tab[ (in[0] & 0xfc) >> 2];
        *out++ = tab[((in[0] & 0x03) << 4)];
        *out++ = '=';
        *out++ = '=';
        break;

    case 0:
        break;
    }

    return out - static_cast<char*>(dest);
}

template<class = void>
std::pair<std::size_t, std::size_t>
decode(void* dest, char const* src, std::size_t len)
{
    char* out = static_cast<char*>(dest);
    auto in = reinterpret_cast<unsigned char const*>(src);
    unsigned char c3[3], c4[4];
    int i = 0;
    int j = 0;

    auto const inverse = base64::get_inverse();

    while(len-- && *in != '=')
    {
        auto const v = inverse[*in];
        if(v == -1)
            break;
        ++in;
        c4[i] = v;
        if(++i == 4)
        {
            c3[0] =  (c4[0]        << 2) + ((c4[1] & 0x30) >> 4);
            c3[1] = ((c4[1] & 0xf) << 4) + ((c4[2] & 0x3c) >> 2);
            c3[2] = ((c4[2] & 0x3) << 6) +   c4[3];

            for(i = 0; i < 3; i++)
                *out++ = c3[i];
            i = 0;
        }
    }

    if(i)
    {
        c3[0] = ( c4[0]        << 2) + ((c4[1] & 0x30) >> 4);
        c3[1] = ((c4[1] & 0xf) << 4) + ((c4[2] & 0x3c) >> 2);
        c3[2] = ((c4[2] & 0x3) << 6) +   c4[3];

        for(j = 0; j < i - 1; j++)
            *out++ = c3[j];
    }

    return {out - static_cast<char*>(dest),
        in - reinterpret_cast<unsigned char const*>(src)};
}

} // base64

template<class = void>
std::string
base64_encode (std::uint8_t const* data,
    std::size_t len)
{
    std::string dest;
    dest.resize(base64::encoded_size(len));
    dest.resize(base64::encode(&dest[0], data, len));
    return dest;
}

inline
std::string
base64_encode(std::string const& s)
{
    return base64_encode (reinterpret_cast <
        std::uint8_t const*> (s.data()), s.size());
}

template<class = void>
std::string
base64_decode(std::string const& data)
{
    std::string dest;
    dest.resize(base64::decoded_size(data.size()));
    auto const result = base64::decode(
        &dest[0], data.data(), data.size());
    dest.resize(result.first);
    return dest;
}

} // detail
} // beast
} // boost

#endif