openVCB/openVCBBlueprint.cpp at main · roflcopter4/openVCB · GitHub

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#include "openVCB.h"


namespace openVCB {

static constexpr uint32_t B64index[256] = {
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 62, 63, 62, 62, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0,
      0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
      19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 63, 0, 26, 27, 28, 29, 30, 31, 32, 33,
      34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
};

static std::vector<uint8_t> b64decode(std::string const &data)
{
    size_t   len    = data.length();
    uint32_t pad    = len > 0 && (len % 4 || data[len - 1] == '=');
    size_t   size   = ((len + 3) / 4 - pad) * 4;
    auto     result = std::vector<uint8_t>(size / 4 * 3 + pad);

    for (size_t i = 0, j = 0; i < size; i += 4) {
        uint32_t n = B64index[static_cast<uint8_t>(data[i + 0])] << 18 |
                     B64index[static_cast<uint8_t>(data[i + 1])] << 12 |
                     B64index[static_cast<uint8_t>(data[i + 2])] <<  6 |
                     B64index[static_cast<uint8_t>(data[i + 3])] <<  0;

        result[j++] = (n >> 16) & 0xFF;
        result[j++] = (n >> 8) & 0xFF;
        result[j++] = n & 0xFF;
    }

    if (pad) {
        uint32_t n = B64index[static_cast<uint8_t>(data[size])]     << 18 |
                     B64index[static_cast<uint8_t>(data[size + 1])] << 12;
        result[result.size() - 1] = static_cast<uint8_t>(n >> 16);

        if (len > size + 2 && data[size + 2] != '=') {
            n |= B64index[static_cast<uint8_t>(data[size + 2])] << 6;
            result.push_back(n >> 8 & 0xFF);
        }
    }

    return result;
}

static bool isBase64(std::string const &text)
{
    size_t const len = text.length();
    size_t       i   = 0;

    // must be multiple of 4
    if (len % 4 != 0)
        return false;

    /* It wouldn't surprise me if this were actually slower. */
    return std::ranges::all_of(text, [len, &i](char ch) {
        bool ret = ::isalnum(ch) || ch == '/' || ch == '+' || (i >= len - 3 && ch == '=');
        ++i;
        return !ret;
    });

#if 0
    // valid characters only
    for (size_t i = 0; i < len; i++) {
        char ch = text[i];
        if (!(::isalnum(ch) || ch == '/' || ch == '+' || (i >= len - 3 && ch == '=')))
            return false;
    }

    return true;
#endif
}

static std::string removeWhitespace(std::string str)
{
    str.erase(std::ranges::remove_if(str, ::isspace).begin(), str.end());
    return str;
}

bool Project::readFromBlueprint(std::string clipboardData) // XXX: Does this need to be a copy?
{
    clipboardData = removeWhitespace(clipboardData);

    if (!isBase64(clipboardData))
        return false;

    std::vector<uint8_t> logicData = b64decode(clipboardData);

    // check minimum size: zstd magic number [4] + vcb header [32]
    if (logicData.size() <= 36)
        return false;

    union char2int {
        uint8_t const  *ch;
        uint32_t const *i;
    };
    char2int dummy = {.ch = logicData.data()};

    // Check zstd magic number, and do it in a way that doesn't invoke
    // undefined behavior.
    if (dummy.i[0] != 0xFD2FB528U)
        return false;

    return processLogicData(logicData, 32);
}

} // namespace openVCB