AlphanumericEncoder.cs

namespace Waher.Content.QR.Serialization
{
    public class AlphanumericEncoder : ITextEncoder
    {
        public const string AlphanumericCharacters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
 
        private readonly BitWriter output;
 
        public AlphanumericEncoder(BitWriter Output)
        {
            this.output = Output;
        }
 
        public static bool CanEncode(string Text)
        {
            foreach (char ch in Text)
            {
                if (AlphanumericCharacters.IndexOf(ch) < 0)
                    return false;
            }
 
            return true;
        }
 
        public void Encode(string Text)
        {
            int i = 0;
            int j;
            int c = 0;
 
            foreach (char ch in Text)
            {
                j = AlphanumericCharacters.IndexOf(ch);
                if (j < 0)
                    continue;
 
                i *= 45;
                i += j;
 
                if (++c >= 2)
                {
                    this.output.WriteBits((uint)i, 11);
                    i = c = 0;
                }
            }
 
            if (c == 1)
                this.output.WriteBits((uint)i, 6);
        }
 
        public static int GetByteLength(int NrCharacters)
        {
            int NrBits = 11 * (NrCharacters / 2);
            if ((NrCharacters & 1) != 0)
                NrBits += 6;
 
            return (NrBits + 7) / 8;
        }
    }
}