Hex converting

[luftwaffe]

Hello,

What is the fastest way to convert a string represents four hex values as a continuous flow (for example char*c = "10FF36CC") to convert to a string contains decimal values [and perhaps separator dots]? 16.255.54.204
?

[willchop]

luftwaffe,

The example I'm providing uses STL strings and streams to get
the job done. The code assumes the input string is comprised
of consecutive hex numbers that are two characters long. I
threw it together quickly as a starting place for you. You can
probably optimize it if you do some profiling.

bool make_decimal_ip_str(const std::string& in_str, std::string& out_str)
{
    out_str.erase();
    std::string::size_type pos = 0;
    
    while (pos < in_str.size()) {
	// Isolate two char hex 
	std::string hex_str = in_str.substr(pos, 2);

	// Extract integer val from hex string
	std::istringstream iss(hex_str);
	int val = 0;
	iss >> std::hex >> val;
	if (iss.fail())
	    return false;

	// Insert integer value to string as decimal
	std::ostringstream oss;
	oss << val;
	if (oss.fail())
	    return false;

	// Build result string
	out_str += oss.str() + ".";

	// Increment substring pos
	pos += 2;
    }

    // Remove last dot
    out_str.erase(out_str.end()-1);
    return true;
}

int main(int argc, char* argv[])
{
    std::string result_str;
    std::string input_str = "10FF36CC";

    make_decimal_ip_str(input_str, result_str);

    std::cout << "hex: " << input_str << "  dec: " << result_str << std::endl;
    return 0;
}

regards, willchop