encoding_utils.cc

/*
 * Copyright (c) 2023 by Mark Tarrabain All rights reserved. Redistribution and use in source and binary forms,
 * with or without modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this list of conditions and the following
 * disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
 * disclaimer in the documentation and/or other materials provided with the distribution.
 * Neither the name of the nor the names of its contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include "encoding_utils.h"

static std::string base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                  "abcdefghijklmnopqrstuvwxyz"
                                  "0123456789+/";

namespace base64 {
static auto constexpr fillchar = '=';

static std::string cvt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                         "abcdefghijklmnopqrstuvwxyz"
                         "0123456789+/";

std::vector<uint8_t> decode(const std::string &data)
{
    std::string::size_type i;
    char c;
    char c1;
    std::string::size_type len = data.length();
    std::vector<uint8_t> ret;

    for (i = 0; i < len; ++i) {
        c = (char)cvt.find(data[i]);
        ++i;
        c1 = (char)cvt.find(data[i]);
        c = (c << 2) | ((c1 >> 4) & 0x3);
        ret.push_back(c);
        if (++i < len) {
            c = data[i];
            if (fillchar == c) {
                break;
            }
            c = (char)cvt.find(c);
            c1 = ((c1 << 4) & 0xf0) | ((c >> 2) & 0xf);
            ret.push_back(c1);
        }
        if (++i < len) {
            c1 = data[i];
            if (fillchar == c1) {
                break;
            }
            c1 = (char)cvt.find(c1);
            c = ((c << 6) & 0xc0) | c1;
            ret.push_back(c);
        }
    }
    return (ret);
}

} // namespace base64