libxrpl/basics/base64.cpp

// 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)
//
 
/*
   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
 
*/
 
#include <xrpl/basics/base64.h>
 
#include <cstddef>
#include <cstdint>
#include <string>
#include <string_view>
#include <utility>
 
namespace xrpl {
 
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) + 2;
}
 
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);
}
 
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)};
}
 
}  // namespace base64
 
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;
}
 
std::string
base64_decode(std::string_view 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;
}
 
}  // namespace xrpl