Tag Archives: C#

Converting a string of binary to ASCII

I was recently going through the Toughest Developer Puzzle Ever. In one of the puzzles, it required the conversion of two binary strings for the username and password combination.

While I could have just as easily searched for some page with sample code or even a built-in converter, I decide to challenge myself a little more by writing some code.

Here’s the code that I came up with in C#:

//Usage examples:
string binaryString = "0111001101101111011001100111010001110111011000010111001001100101";
string textString = binaryString.BitStringToText(); //results in the word "software"

binaryString = "good stuff".TextToBitString();
//produces: 01100111011011110110111101100100001000000111001101110100011101010110011001100110
public static class BinaryConverterStringExtensions
{
	private const int BITS_PER_BYTE = 8;
	public static string BitStringToText(this string bits)
	{
		var asciiText = new StringBuilder();
		int paddingDifference = BITS_PER_BYTE - (bits.Length % BITS_PER_BYTE);

		if(paddingDifference < BITS_PER_BYTE)
		{
			bits = bits.PadLeft(paddingDifference + bits.Length, '0');
		}

		for(int i = 0; i < bits.Length; i += BITS_PER_BYTE)
		{
			asciiText.Append(ConvertBinaryToChar(bits.Substring(i, BITS_PER_BYTE)));
		}
		return asciiText.ToString();
	}

	public static string TextToBitString(this string text)
	{
		var binaryString = new StringBuilder();
		foreach(char c in text)
		{
			byte num = (byte)c;
			string bits = string.Empty;
			while(num > 0)
			{
				byte rem = (byte)(num % 2);
				bits += rem.ToString();
				num /= 2;
			}
			string reversedBits = new string(bits.Reverse().ToArray());
			binaryString.Append(reversedBits.PadLeft(BITS_PER_BYTE, '0'));
		}
		return binaryString.ToString();
	}

	private static char ConvertBinaryToChar(IEnumerable<char> binaryChars)
	{
		byte result = 0;
		if(IsValid(binaryChars))
		{
			var reversedBinary = binaryChars.Reverse().ToArray();
			for(int pos = 0, len = reversedBinary.Count(); pos < len; pos++)
			{
				byte n = byte.Parse(reversedBinary[pos].ToString());
				result += (byte)(n * (byte)Math.Pow(2, pos));
			}
		}
		return (char)result;
	}

	//Validation Logic: Throw an exception string is does not contain binary chars or is longer than 8 chars.
	private static bool IsValid(IEnumerable<char> binaryChars)
	{
		bool isBinary = binaryChars.All(b => b.Equals('0') || b.Equals('1'));
		byte result = 0;
		if(!isBinary)
		{
			throw new ArgumentException("Non-binary characters detected");
		}
		else if(binaryChars.Count() > BITS_PER_BYTE)
		{
			throw new ArgumentException("Invalid string length. Needs to be 8 characters or less");
		}
		return true;
	}
}
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