BitWriter.cs

using System;
using System.IO;
 
namespace Waher.Content.QR.Serialization
{
    public class BitWriter : IDisposable
    {
        private MemoryStream output;
        private byte current;
        private int bits;
        private int length;
 
        public BitWriter()
        {
            this.output = new MemoryStream();
            this.current = 0;
            this.bits = 0;
            this.length = 0;
        }
 
        public void Dispose()
        {
            this.output?.Dispose();
            this.output = null;
        }
 
        public void WriteBit(bool Bit)
        {
            if (Bit)
                this.current |= (byte)(1 << (7 - this.bits));
 
            if (++this.bits >= 8)
            {
                this.output.WriteByte(this.current);
                this.length++;
                this.bits = 0;
                this.current = 0;
            }
        }
 
        public void WriteBits(uint Value, int NrBits)
        {
            if (NrBits < 32)
                Value <<= (32 - NrBits);
 
            int c;
 
            while (NrBits > 0)
            {
                c = 8 - this.bits;
                if (c > NrBits)
                    c = NrBits;
 
                this.current |= (byte)(Value >> (24 + this.bits));
                Value <<= c;
                NrBits -= c;
                this.bits += c;
 
                if (this.bits >= 8)
                {
                    this.output.WriteByte(this.current);
                    this.length++;
                    this.bits = 0;
                    this.current = 0;
                }
            }
        }
 
        public void Flush()
        {
            if (this.bits > 0)
            {
                this.output.WriteByte(this.current);
                this.length++;
                this.bits = 0;
                this.current = 0;
            }
        }
 
        public void Pad(int MaxLength, params byte[] PaddingBytes)
        {
            int i = 0;
            int c = PaddingBytes.Length;
 
            if (c == 0)
                throw new ArgumentException("Missing padding bytes.", nameof(PaddingBytes));
 
            this.Flush();
            while (this.length < MaxLength)
            {
                this.output.WriteByte(PaddingBytes[i++]);
                this.length++;
                if (i >= c)
                    i = 0;
            }
        }
 
        public byte[] ToArray()
        {
            this.Flush();
            return this.output.ToArray();
        }
 
        public int TotalBits => (this.length << 3) + this.bits;
    }
}