Base32.cs

using System;
using System.IO;
 
namespace Waher.Content
{
    public static class Base32
    {
        private const string Base32Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
 
        public static byte[] Decode(string Base32)
        {
            MemoryStream ms = new MemoryStream();
            ushort Buffer = 0;
            int Offset = 0;
 
            foreach (char ch in Base32)
            {
                if (char.IsWhiteSpace(ch))
                    continue;
 
                Buffer <<= 5;
                Offset += 5;
 
                if (ch >= 'A' && ch <= 'Z')
                     Buffer |= (byte)(ch - 'A');
                else if (ch >= '2' && ch <= '7')
                    Buffer |= (byte)(ch - '2' + 26);
                else if (ch == '=')
                    break;
                else if (ch >= 'a' && ch <= 'z')
                    Buffer |= (byte)(ch - 'a'); // Support lower-case letters as well.
                else
                    throw new FormatException("Invalid Base32 character: " + ch.ToString());
 
                if (Offset >= 8)
                {
                    ms.WriteByte((byte)(Buffer >> (Offset - 8)));
                    Offset -= 8;
                }
            }
 
            return ms.ToArray();
        }
 
        public static string Encode(byte[] Data)
        {
            if (Data == null || Data.Length == 0)
                return string.Empty;
 
            int Nr8CharBlocks = ((Data.Length << 3) + 39) / 40;
            int Len = Nr8CharBlocks << 3;
            char[] Result = new char[Len];
            ushort Buffer = 0;
            int NrBits = 0;
            int Pos = 0;
            byte b;
 
            for (int i = 0; i < Data.Length; i++)
            {
                Buffer <<= 8;
                Buffer |= Data[i];
                NrBits += 8;
 
                while (NrBits >= 5)
                {
                    NrBits -= 5;
                    b = (byte)(Buffer >> NrBits);
                    Result[Pos++] = Base32Chars[b & 0x1f];
                }
            }
 
            if (NrBits > 0)
            {
                b = (byte)(Buffer << (5 - NrBits));
                Result[Pos++] = Base32Chars[b & 0x1f];
            }
 
            while (Pos < Len)
                Result[Pos++] = '=';
 
            return new string(Result);
        }
    }
}