BitConverter.ToString() in reverse? [duplicate]

Answer 1

You can parse the string yourself:

byte[] data = new byte[(s.Length + 1) / 3];
for (int i = 0; i < data.Length; i++) {
   data[i] = (byte)(
      "0123456789ABCDEF".IndexOf(s[i * 3]) * 16 +
      "0123456789ABCDEF".IndexOf(s[i * 3 + 1])
   );
}

The neatest solution though, I believe, is using extensions:

byte[] data = s.Split('-').Select(b => Convert.ToByte(b, 16)).ToArray();

Answer 2

byte[] data = Array.ConvertAll<string, byte>(str.Split('-'), s => Convert.ToByte(s, 16));

Answer 3

If you don't need that specific format, try using Base64, like this:

var bytes = new byte[] { 0x12, 0x34, 0x56 };
var base64 = Convert.ToBase64String(bytes);
bytes = Convert.FromBase64String(base64);

Base64 will also be substantially shorter.

If you need to use that format, this obviously won't help.

Answer 4

I believe the following will solve this robustly.

public static byte[] HexStringToBytes(string s)
{
    const string HEX_CHARS = "0123456789ABCDEF";

    if (s.Length == 0)
        return new byte[0];

    if ((s.Length + 1) % 3 != 0)
        throw new FormatException();

    byte[] bytes = new byte[(s.Length + 1) / 3];

    int state = 0; // 0 = expect first digit, 1 = expect second digit, 2 = expect hyphen
    int currentByte = 0;
    int x;
    int value = 0;

    foreach (char c in s)
    {
        switch (state)
        {
            case 0:
                x = HEX_CHARS.IndexOf(Char.ToUpperInvariant(c));
                if (x == -1)
                    throw new FormatException();
                value = x << 4;
                state = 1;
                break;
            case 1:
                x = HEX_CHARS.IndexOf(Char.ToUpperInvariant(c));
                if (x == -1)
                    throw new FormatException();
                bytes[currentByte++] = (byte)(value + x);
                state = 2;
                break;
            case 2:
                if (c != '-')
                    throw new FormatException();
                state = 0;
                break;
        }
    }

    return bytes;
}

Answer 5

it seems like a nasty workaround to break the string into an array of strings and then convert each of them.

I don't think there's another way... the format produced by BitConverter.ToString is quite specific, so if there is no existing method to parse it back to a byte[], I guess you have to do it yourself

Answer 6

Not a built in method, but an implementation. (It could be done without the split though).

String[] arr=str.Split('-');
byte[] array=new byte[arr.Length];
for(int i=0; i<arr.Length; i++) array[i]=Convert.ToByte(arr[i],16);

Method without Split: (Makes many assumptions about string format)

int length=(s.Length+1)/3;
byte[] arr1=new byte[length];
for (int i = 0; i < length; i++)
    arr1[i] = Convert.ToByte(s.Substring(3 * i, 2), 16);

And one more method, without either split or substrings. You may get shot if you commit this to source control though. I take no responsibility for such health problems.

int length=(s.Length+1)/3;
byte[] arr1=new byte[length];
for (int i = 0; i < length; i++)
{
    char sixteen = s[3 * i];
    if (sixteen > '9') sixteen = (char)(sixteen - 'A' + 10);
    else sixteen -= '0';

    char ones = s[3 * i + 1];
    if (ones > '9') ones = (char)(ones - 'A' + 10);
    else ones -= '0';

    arr1[i] = (byte)(16*sixteen+ones);
}

(basically implementing base16 conversion on two chars)