/// <summary>
/// Converts a base-32 encoded string to a byte array.
/// </summary>
/// <param name="base32">A base-32 encoded string.</param>
/// <returns>The data represented by the base-32 string.</returns>
/// <exception cref="ArgumentException">The argument is not a valid base32-encoded string.</exception>
public static byte[] ToBinary(string base32)
{
base32 = base32.ToUpper();
if (base32.Any(c => !Alphabet.Contains(c) && c != Padding))
{
throw new ArgumentException("String contains invalid characters.");
}
var fullSegments = base32.Length / 8;
var finalSegmentLength = base32.Length % 8;
var segments = fullSegments + (finalSegmentLength == 0 ? 0 : 1);
IEnumerable <byte> result = new byte[0];
for (int i = 0; i < segments; i++)
{
var segment = base32.Skip(i * 8).Take(8).ToArray();
var slice = Base32.ConvertSegmentToBinary(segment);
result = result.Concat(slice);
}
return(result.ToArray());
}