NumericEncoder.cs

namespace Waher.Content.QR.Serialization
{
    public class NumericEncoder : ITextEncoder
    {
        private readonly BitWriter output;
 
        public NumericEncoder(BitWriter Output)
        {
            this.output = Output;
        }
 
        public static bool CanEncode(string Text)
        {
            foreach (char ch in Text)
            {
                if (ch < '0' || ch > '9')
                    return false;
            }
 
            return true;
        }
 
        public void Encode(string Text)
        {
            int i = 0;
            int c = 0;
 
            foreach (char ch in Text)
            {
                if (ch < '0' || ch > '9')
                    continue;
 
                i *= 10;
                i += ch - '0';
 
                if (++c >= 3)
                {
                    this.output.WriteBits((uint)i, 10);
                    i = c = 0;
                }
            }
 
            switch (c)
            {
                case 1:
                    this.output.WriteBits((uint)i, 4);
                    break;
 
                case 2:
                    this.output.WriteBits((uint)i, 7);
                    break;
            }
        }
 
        public static int GetByteLength(int NrCharacters)
        {
            int NrBits = 10 * (NrCharacters / 3);
 
            switch ((NrCharacters & 3))
            {
                case 1:
                    NrBits += 4;
                    break;
 
                case 2:
                    NrBits += 7;
                    break;
            }
 
            return (NrBits + 7) / 8;
        }
 
    }
}