cpp_hex2bin

cpp_hex2bin.cpp

void Bin2Hex(const char* buf, size_t len, std::string& out)
{
    std::ostringstream ostr;
    ostr << std::hex;
    ostr.fill('0');
    for (size_t i = 0; i < len; i++)
    {
        unsigned char tmp = buf[i];
        ostr << std::setw(2) << static_cast<short>(tmp);
    }
    out = ostr.str();
}

void Hex2Bin(const std::string& hex, std::string& out)
{
    lightAssert(hex.length() % 2 == 0);

    std::string tmp;
    tmp.reserve(hex.length() / 2);

    std::string extract;
    for (std::string::const_iterator pos = hex.begin(); pos < hex.end(); pos += 2)
    {
        extract.assign(pos, pos + 2);
        tmp.push_back(strtol(extract.c_str(), NULL, 16));
    }

    out = tmp;
}

https://stackoverflow.com/questions/18906027/missing-punctuation-from-c-hex2bin