/// <summary>
/// Converts a hexadecimal string into its binary representation.
/// </summary>
/// <param name="hexString">The hex string</param>
/// <returns>The byte array corresponding to the contents of the hex string,
/// or null if the input string is not a valid hex string.</returns>
public static byte[] HexToBinary(this string hexString)
{
if (hexString == null || hexString.Length % 2 != 0)
{
// input string length is not evenly divisible by 2
return(null);
}
var binary = new byte[hexString.Length / 2];
for (var i = 0; i < binary.Length; i++)
{
var highNibble = NumberUtil.HexToInt(hexString[2 * i]);
var lowNibble = NumberUtil.HexToInt(hexString[2 * i + 1]);
if (highNibble == -1 || lowNibble == -1)
{
return(null); // bad hex data
}
binary[i] = (byte)((highNibble << 4) | lowNibble);
}
return(binary);
}
