Convert C# Code to C++ : Hex to Binary

Question

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Hello All,

I have some C# code and would like to convert it to C++. I have been trying and googling for several different ways, however is there just some easy fixes to this code snippet to make it C++ compatible? I am a novice is C++:

static std::string Hex2Bin(std::string sHexavalue)
    {

        std::string binaryValue = "";
        char charArray[] = sHexavalue::toupper.ToCharArray();

        for( int n=0; n < sHexavalue.length(); n++)
        {
            switch (charArray[n])
            {

                        case '0':
                            binaryValue += "0000";break;
                        case '1':
                            binaryValue += "0001";break;
                        case '2':
                            binaryValue += "0010";break;
                        case '3':
                            binaryValue += "0011";break;
                        case '4':
                            binaryValue += "0100";break;
                        case '5':
                            binaryValue += "0101";break;
                        case '6':
                            binaryValue += "0110";break;
                        case '7':
                            binaryValue += "0111";break;
                        case '8':
                            binaryValue += "1000";break;
                        case '9':
                            binaryValue += "1001";break;
                        case 'A':
                            binaryValue += "1010";break;
                        case 'B':
                            binaryValue += "1011";break;
                        case 'C':
                            binaryValue += "1100";break;
                        case 'D':
                            binaryValue += "1101";break;
                        case 'E':
                            binaryValue += "1110";break;
                        case 'F':
                            binaryValue += "1111";break;

            }

        }


        return binaryValue;



    }

My Error occurs when I have sHexavalue to be changed to uppercase and ToCharArray. I receieve this error: IntelliSense: initialization with '{...}' expected for aggregate object

So I know there is still lots of "conversion" from C# to C++ but I just need to know if it is possible to have the snippet converted in a quick simple way.

EDIT: Here is the original source:

//convert a Hexa value string to a binary value string
public static string Hex2Bin(string sHexavalue)
    {
        string binaryValue = "";
        char[] charArray = sHexavalue.ToUpper().ToCharArray();  

            for( int n=0; n < sHexavalue.Length; n++)
            {
                switch (charArray[n])
                {
                    case '0':
                        binaryValue += "0000";break;
                    case '1':
                        binaryValue += "0001";break;
                    case '2':
                        binaryValue += "0010";break;
                    case '3':
                        binaryValue += "0011";break;
                    case '4':
                        binaryValue += "0100";break;
                    case '5':
                        binaryValue += "0101";break;
                    case '6':
                        binaryValue += "0110";break;
                    case '7':
                        binaryValue += "0111";break;
                    case '8':
                        binaryValue += "1000";break;
                    case '9':
                        binaryValue += "1001";break;
                    case 'A':
                        binaryValue += "1010";break;
                    case 'B':
                        binaryValue += "1011";break;
                    case 'C':
                        binaryValue += "1100";break;
                    case 'D':
                        binaryValue += "1101";break;
                    case 'E':
                        binaryValue += "1110";break;
                    case 'F':
                        binaryValue += "1111";break;

                }

            }
        return binaryValue;
    }

Answer 1

Consider some suggestions:

1. Since the sHexValue is a read-only input parameter, pass by const reference (const &):

   std::string Hex2Bin(const std::string & sHexValue)
   

   (It's more efficient than passing the std::string by value.)

2. No need to do the ToCharArray() C# conversion in C++.
   You can access single chars in a std::string using operator[].

3. You can manage the upper and lower case for A-F using multiple case fall-through:

   case 'A': case 'a': .... break; // valid for both 'A' and 'a'
   

Here's a possible rewrite in C++:

// Convert a hex value string to a binary value string.
std::string Hex2Bin(const std::string & sHexValue)
{
    std::string binaryValue;   // automatically initialized to empty string

    for (int n = 0; n < sHexValue.size(); ++n)
    {
        switch (sHexValue[n])
        {
            case '0':
                binaryValue += "0000"; break;
            case '1':
                binaryValue += "0001"; break;
            case '2':
                binaryValue += "0010"; break;
            case '3':
                binaryValue += "0011"; break;
            case '4':
                binaryValue += "0100"; break;
            case '5':
                binaryValue += "0101"; break;
            case '6':
                binaryValue += "0110"; break;
            case '7':
                binaryValue += "0111"; break;
            case '8':
                binaryValue += "1000"; break;
            case '9':
                binaryValue += "1001"; break;
            case 'A': case 'a':
                binaryValue += "1010"; break;
            case 'B': case 'b':
                binaryValue += "1011"; break;
            case 'C': case 'c':
                binaryValue += "1100"; break;
            case 'D': case 'd':
                binaryValue += "1101"; break;
            case 'E': case 'e':
                binaryValue += "1110"; break;
            case 'F': case 'f':
                binaryValue += "1111"; break;
        }
    }

    return binaryValue;
}