//
// Copyright (c) 2016-2019 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
//

#include "base64.h"

NS_AX_BEGIN

namespace base64 {

AX_DLL char const*
get_alphabet()
{
    static char constexpr tab[] = {
        "ABCDEFGHIJKLMNOP"
        "QRSTUVWXYZabcdef"
        "ghijklmnopqrstuv"
        "wxyz0123456789+/"
    };
    return &tab[0];
}

AX_DLL 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];
}

AX_DLL 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);
}

AX_DLL 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] = {0,0,0,0};
    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);
}

} // base64

NS_AX_END