Converting a paragraph to hex notatation, then back to string

Question

Hi,

How would you convert a parapraph to hex notation, and then back again into its original string form?

(C#)

A side note: would putting the string into hex format shrink it the most w/o getting into hardcore shrinking algo's?

Answer 1

public string ConvertToHex(string asciiString)
{
    string hex = "";
    foreach (char c in asciiString)
    {
        int tmp = c;
        hex += String.Format("{0:x2}", (uint)System.Convert.ToUInt32(tmp.ToString()));
    }
    return hex;
}

Answer 2

What exactly do you mean by "hex notation"? That usually refers to encoding binary data, not text. You'd need to encode the text somehow (e.g. using UTF-8) and then encode the binary data as text by converting each byte to a pair of characters.

using System;
using System.Text;

public class Hex
{
    static void Main()
    {
        string original = "The quick brown fox jumps over the lazy dog.";

        byte[] binary = Encoding.UTF8.GetBytes(original);
        string hex = BytesToHex(binary);
        Console.WriteLine("Hex: {0}", hex);
        byte[] backToBinary = HexToBytes(hex);

        string restored = Encoding.UTF8.GetString(backToBinary);
        Console.WriteLine("Restored: {0}", restored);
    }

    private static readonly char[] HexChars = "0123456789ABCDEF".ToCharArray();

    public static string BytesToHex(byte[] data)
    {
        StringBuilder builder = new StringBuilder(data.Length*2);
        foreach(byte b in data)
        {
            builder.Append(HexChars[b >> 4]);
            builder.Append(HexChars[b & 0xf]);
        }
        return builder.ToString();
    }

    public static byte[] HexToBytes(string text)
    {
        if ((text.Length & 1) != 0)
        {
            throw new ArgumentException("Invalid hex: odd length");
        }
        byte[] ret = new byte[text.Length/2];
        for (int i=0; i < text.Length; i += 2)
        {
            ret[i/2] = (byte)(ParseNybble(text[i]) << 4 | ParseNybble(text[i+1]));
        }
        return ret;
    }

    private static int ParseNybble(char c)
    {
        if (c >= '0' && c <= '9')
        {
            return c-'0';
        }
        if (c >= 'A' && c <= 'F')
        {
            return c-'A'+10;
        }
        if (c >= 'a' && c <= 'f')
        {
            return c-'A'+10;
        }
        throw new ArgumentOutOfRangeException("Invalid hex digit: " + c);
    }
}

No, doing this would not shrink it at all. Quite the reverse - you'd end up with a lot more text! However, you could compress the binary form. In terms of representing arbitrary binary data as text, Base64 is more efficient than plain hex. Use Convert.ToBase64String and Convert.FromBase64String for the conversions.

Answer 3

While I can't help much on the C# implementation, I would highly recommend LZW as a simple-to-implement data compression algorithm for you to use.

Answer 4

Perhaps the answer can be more quickly reached if we ask: what are you really trying to do? Converting an ordinary string to a string of a hex representation seems like the wrong approach to anything, unless you are making a hexidecimal/encoding tutorial for the web.

Answer 5

static byte[] HexToBinary(string s) {
  byte[] b = new byte[s.Length / 2];
  for (int i = 0; i < b.Length; i++)
    b[i] = Convert.ToByte(s.Substring(i * 2, 2), 16);
  return b;
}
static string BinaryToHex(byte[] b) {
  StringBuilder sb = new StringBuilder(b.Length * 2);
  for (int i = 0; i < b.Length; i++)
    sb.Append(Convert.ToString(256 + b[i], 16).Substring(1, 2));
  return sb.ToString();
}